Networking ppt

SKILLS FOR INDIA

Overview of Networking

Basics of Networking

An overview of computer networking which introduces
many key concepts and terminology. Sets the stage for
future topics.
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A network consists of 2 or more computers connected
together, and they can communicate and share resources
(e.g. information)

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 Communications – activity associated with distributing or exchanging
information
 Telecommunications – technology of communications at a distance that
permits information to be created any where and used everywhere with
little delay
 A network is a way to get “stuff” between 2 or more “things”
 Examples: Mail, phone system, conversations, railroad system,
highways and roads

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
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

Must have a message
Message must have a transmitter
Message must have a medium
Message must be understood
Message must have some level of security

Destination System

Source System

Source  Transmitter  Transmission  Receiver  Destination
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Workstation/PC

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Medium

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Workstation/PC
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Essentials for Network

1.
2.
3.
4.
5.
6.

Text input information
Input data digital bit stream
Transmitted analog signal
Received analog signal
Output data digital bit stream
Text output information

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General Architecture of Computer Networks

External
nodes
(or stations)

Cloud

Internal nodes
(swithing devices)
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T H A N K Y O U. . .

All information, including graphical representations, etc provided in this presentation is for exclusive use of current Globsyn
Skills students and faculty. No part of the document may be reproduced in any form or by any means, electronic or otherwise,
without written permission of the owner.
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Bus Topology

 Bus: each node is daisy-chained (connected one right after the other)
along the same backbone. Information sent from a node travels along
the backbone until it reaches its destination node. Each end of a bus
network must be terminated with a resistor to keep the

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Ring Topology
 Similar to a bus network, rings have
nodes daisy chained, but the end of
the network in a ring topology comes
back around to the first node, creating
a complete circuit. Each node takes a
turn
sending
and
receiving
information through the use of a
token. The token along with any data
is sent from the first node to the
second node which extracts the data
addressed to it and adds any data it
wishes to send. Then second node
passes the token and data to the third
node, etc. until it comes back around
to the first node again. Only the node
with the token is allowed to send data
. All other nodes must wait for the
token to come to them.
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Star Topology
 In a star network, each node is
connected to a central device called a
hub. The hub takes a signal that comes
from any node and passes it along to all
the other nodes in the network
 A hub does not perform any type of
filtering or routing of the data
 A hub is a junction that joins all the
different nodes together

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Star-Bus Topology
 Prob. Most common topology
used today. Combines elements of
the star and bus topologies to
create a versatile network
environment
 Nodes in particular areas are
connected to hubs (and create star
topology), and hubs are connected
together along the network
backbone (like a bus network)
 Often you have stars nested
within stars

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Mesh Topology

 It is also called a point-to-point
topology
 Each device is connected
directly to all other network
devices
 It provides fault tolerance
 It is only found in wide area
networks

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Other network topologies


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Some basic network topologies not previously mentioned:
One-to-one
Hierarchical
Hybrid
Client-server
Multiple nodes

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SKILLS FOR INDIA

Types of Network

Network configuration

 Classification based on how computers behave in a network
 Two classifications are
 Peer-to-Peer network
 Server based network

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Peer-to-Peer network


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
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

Nodes provide and request services
User in each node administers resources
No extra investment
Easy to setup
Very weak security
Additional load on nodes

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Server based network

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
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

Designated computer to administer
Resources centralized
Supports larger networks
Strong security
Expensive

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 Advantages of peer-to-peer networks:
Low cost
Simple to configure
User has full accessibility of the computer
 Disadvantages of peer-to-peer networks:
May have duplication in resources
Difficult to uphold security policy
Difficult to handle uneven loading
 Where peer-to-peer network is appropriate:
10 or less users
No specialized services required
Security is not an issue
Only limited growth in the foreseeable future
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Clients and Servers
 Network Clients (Workstation)
Workstation
Computers that request network resources or services
Network Servers
Computers that manage and provide network resources and services to
clients
Usually have more processing power, memory and hard disk space than
clients
Run Network Operating System that can manage not only data, but also
users, groups, security, and applications on the network
Servers often have a more stringent requirement on its performance and
reliability

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 Advantages of client/server networks
Facilitate resource sharing – centrally administrate and control
Facilitate system backup and improve fault tolerance
Enhance security – only administrator can have access to Server
Support more users – difficult to achieve with peer-to-peer networks

 Disadvantages of client/server networks
High cost for Servers
Need expert to configure the network
Introduce a single point of failure to the system

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SKILLS FOR INDIA

Networking Media and Components

Coaxial cable
 Widely installed for use in business and corporation Ethernet and other
types of LANs.
 Consists of inter copper insulator covered by cladding material, and
then covered by an outer jacket
 Physical Descriptions:

 Inner conductor is solid copper metal
 Separated by insulating material
 Outer conductor is braided shielded (ground)
 Covered by sheath material
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 Applications:
 TV distribution (cable tv); long distance telephone transmission;
short run computer system links
 Local area networks
 Transmission characteristics:
 Can transmit analog and digital signals
 Usable spectrum for analog signaling is about 400 Mhz
 Amplifier needed for analog signals for less than 1 Km and less
distance for higher frequency
 Repeater needed for digital signals every Km or less distance for
higher data rates
 Operation of 100’s Mb/s over 1 Km
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Twisted Pair Cables
 Physical description:






Each wire with copper conductor
Separately insulated wires
Twisted together to reduce cross talk
Often bundled into cables of two or four twisted pairs
If enclosed in a sheath then is shielded twisted pair (STP) otherwise often
for home usage unshielded twisted pair (UTP). Must be shield from
voltage lines

 Application:
 Common in building for digital signaling used at speed of 10’s Mb/s
(CAT3) and 100Mb/s (CAT5) over 100s meters.
 Common for telephone interconnection at home and office buildings
 Less expensive medium; limited in distance, bandwidth, and data rate
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Categories of Twisted Pairs Cabling System
Category

Maximum
data rate

Usual application

CAT 1

Less than 1
Mbps

analog voice (plain old
telephone service)
Integrated Services Digital
Network Basic Rate
Interface in ISDN Doorbell
wiring

CAT 2

4 Mbps

Mainly used in the IBM
Cabling System for token
ring networks

CAT 3

16 Mbps

Voice and data on
10BASE-T Ethernet (certify
16Mhz signal)

CAT 4

20 Mbps

Used in 16Mbps Token
Ring

Specs describe cable
Material, type of
Connectors, and
Junction blocks to
Conform to a category

Otherwise not used much
CAT 5

100 Mbps

100 Mbps TPDDI
155 Mbps asynchronous
transfer mode (certify 100
Mhz signal)

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Optical Fibers
 Physical Description:
 Glass or plastic core of optical fiber = 2to125 µm
 Cladding is an insulating material
 Jacket is a protective cover
 Laser or light emitting diode provides transmission light source
 Applications:
 Long distance telecommunication
 Greater capacity; 2 Gb/s over 10’s of Km
 Smaller size and lighter weight
 Lower attenuation (reduction in strength of signal)
 Electromagnetic isolation – not effected by external electromagnetic
environment. Aka more privacy
 Greater repeater spacing – fewer repeaters, reduces line regeneration
cost
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 Multimode fiber is optical fiber that is designed to carry multiple light
rays or modes concurrently, each at a slightly different reflection angle
within the optical fiber core. used for relatively short distances because
the modes tend to disperse over longer lengths (this is called modal
dispersion)
 For longer distances, single mode fiber (sometimes called monomode)
fiber is used. In single mode fiber a single ray or mode of light act as a
carrier

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Wireless Transmission
 Frequency range (line of sight):
 26 GHz to 40 GHz: for microwave with highly directional beam as
possible
 30 MHz to 1 GHz: for omni directional applications
 300MHz to 20000 GHz: for infrared spectrum; used for point to
point and multiple point application (line of sight)
 Physical applications:
 Terrestrial microwave – long haul telecommunication service
(alternative to coaxial or optical fiber)
 Few amplifier and repeaters
 Propagation via towers located without blockage from trees, etc
(towers less than 60 miles apart)
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 Satellite is a microwave relay station
 Geostationary orbit (22,000 miles) and low orbit (12000 miles)
 Satellite ground stations are aligned to the space satellite, establishes a
link, broadcast at a specified frequency. Ground station normally
operate at a number of frequencies – full duplex
 Satellite space antenna is aligned to the ground station establishes a
link and transmits at the specified frequency. Satellite are capable of
transmitting at multiple frequencies simultaneously, full duplex.
 To avoid satellites from interfering with each other, a 4 degree
separation is required for 4/6 GHz band and 3 degree for 12/14 GHz
band. Limited to 90 satellites
 Disadvantage: not satellite repair capability; greater delay and
attenuation problems

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Wireless LAN
 Wireless LAN
 Hiper LAN (European standard; allow communication at up to 20
Mbps in 5 GHz range of the radio frequency (RF) spectrum
 Hiper LAN/2 operate at about 54 Mbps in the same RF band

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SKILLS FOR INDIA

Network Components

Hubs
 A hub is the place where data converges from one or more directions
and is forwarded out in one or more directions.
 Seen in local area networks

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Gateways

 A gateway is a network point that acts as an entrance to another
network. On the internet, in terms of routing, the network consists of
gateway nodes and host nodes
 Host nodes are computer of network users and the computers that serve
contents (such as Web pages)
 Gateway nodes are computers that control traffic within your
company’s network or at your local internet service provider (ISP)

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Routers
 A router is a device or a software in a computer that determines the next
network point to which a packet should be forwarded toward its
destination
 Allow different networks to communicate with each other
 A router creates and maintain a table of the available routes and their
conditions and uses this information along with distance and cost
algorithms to determine the best route for a given packet
 A packet will travel through a number of network points with routers
before arriving at its destination

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Bridge
 A bridge is a product that connects a local area network (LAN) to
another local area network that uses the same protocol (for example,
Ethernet or token ring)
 A bridge examines each message on a LAN, "passing" those known to
be within the same LAN, and forwarding those known to be on the
other interconnected LAN (or LANs)

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Differences
 Bridge: device to interconnect two LANs that use the SAME logical
link control protocol but may use different medium access control
protocols
 Router: device to interconnect SIMILAR networks, e.g. similar
protocols and workstations and servers
 Gateway: device to interconnect DISSIMILAR protocols and servers,
and Macintosh and IBM LANs and equipment

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Switches
 Allow different nodes of a network to communicate directly with each
other
 Allow several users to send information over a network at the same time
without slowing each other down

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SKILLS FOR INDIA

IEEE Standards

Introduction
 IEEE 802 refers to a family of IEEE standards
 Dealing with local area network and metropolitan area network
 Restricted to networks carrying variable-size packets
 Specified in IEEE 802 map to the lower two layers
• Data link layer
– LLC sub layer
– MAC sub layer
• Physical layer
 The most widely used standards
 The Ethernet family, Token Ring, Wireless LAN
 Bridging and Virtual Bridged LANs
 An individual Working Group provides the focus for each area
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IEEE 802 Working Groups
Active working groups
802.1

Inactive or disbanded working groups
802.2

Logical Link Control Working Group

Group
802.3

Higher Layer LAN Protocols Working

802.4

Token Bus Working Group

Ethernet Working Group

802.5

Token Ring Working Group

802.7

Broadband Area Network Working

802.11 Wireless LAN Working Group
802.15 Wireless Personal Area Network
(WPAN) Working Group
802.16 Broadband Wireless Access Working
Group

Group
802.8

Fiber Optic TAG

802.9

Integrated Service LAN Working
Group

802.17 Resilient Packet Ring Working Group

802.10 Security Working Group

802.18 Radio Regulatory TAG

802.12 Demand Priority Working Group

802.19 Coexistence TAG

802.14 Cable Modem Working Group

802.20 Mobile Broadband Wireless Access
(MBWA) Working Group
802.21 Media Independent Handoff Working Group

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 Types
 Infrastructure based
 Ad-hoc
AP

 Advantages
 Flexible deployment
 Minimal wiring difficulties
 More robust against disasters
(earthquake etc)

AP

wired network

 Disadvantages
 Low bandwidth compared to wired networks (1-10 Mbit/s)
 Need to follow wireless spectrum regulations
 Not support mobility

AP: Access Point
AP

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802.11

802.11

802.11a

802.11b

Protocol

Release
date

Op. Frequency

Legacy

1997

2.5~2.5 GHz

802.11a

1999

802.11b

802.11g

802.11n

Data rate
(Max)
2 Mbit/s

Range
(indoor)

Range
(outdoor)

5.15~5.35/5.47~5.725
/5.725~5.875 GHz

54 Mbit/s

~25 m

~75 m

1999

2.4~2.5GHz

11 Mbit/s

~35 m

~100 m

802.11g

2003

2.4~2.5GHz

54 Mbit/s

~25 m

~75 m

802.11n

2007

2.4GHz or 5GHz

540 Mbit/s

~50 m

~125 m
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802.11n Working Group
 What is the 802.11n?
 Uses MIMO radio technology and OFDM as a basis
 Anywhere from 100Mbps to 600Mbps depending on implementation
 Support both 2.4 GHz and 5 GHz
 Use multiple stream

 802.11n increase transmission efficiency of MAC
 Cutting guard band time in half
 Reducing the number of pilot carrier, for data
 Aggregating frames and bursting
 Using a 40MHz instead of a 20MHz channel

30~50% => 70%

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802.11n Working Group
Timeline

Draft 1.0 failed IEEE meeting ballot
IEEE record – 12,000 comments received
Draft 2.0 is now required – Orlando March 2007 IEEE
Meeting
Pre-N certification program start March 2007
Result – expect ratification in early 2008

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802.15 Wireless Personal Area
Network(WPAN)
Working Groups summary
802.15

802.15.1

802.15.2

802.15.3

 802.15.1 : WPAN/Bluetooth
 802.15.2 : Coexistence Group
802.15.3a
 802.15.3 : High Rate(HR) WPAN Group
 802.15.3a : WPAN HR Alternative PHY Task
Group
 802.15.3b : MAC Amendment Task Group
 802.15.4 : Low Rate(LW) WPAN Group(Zigbee)
 802.15.4a : WPAN Low Rate Alternative PHY
 802.15.4b : Revisions and Enhancements
 UWB Forum

802.15.3b

802.15.4

802.15.4a

802.15.4b

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802.16 Broadband Wireless Access(BWA)
 IEEE 802.16
 Be was established by IEEE Standards Board in 1999, aims to prepare
formal specifications for the global deployment of broadband Wireless
Metropolitan Area Network.
 A unit of the IEEE 802 LAN/MAN Standards Committee.
 A related technology Mobile Broadband Wireless Access(MBWA)
Mobile
(Vehicular)

WWAN
(IMT-2000)
cdma2000® 1xEV-DO,
cdma2000® 1xEV-DV
2G/2.5G

802.16e

Pedestrian
(Nomadic) Cellular
WCDMA HSDPA
802.15.1
(Bluetooth)

0.1

802.16a
(WiMAX)
802.15.3a
(UWB)

802.11
(WLAN)

1.0 3.1

10

100

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802.16 Broadband Wireless Access
(BWA)
802.16

802.16.f

802.15.g

802.15.h

802.15.i

802.15.j

802.15.m

802.15.k

 802.16f : Management Information Base
 802.16g : Management Plane Procedures and Services
 802.16h : Improved Coexistence Mechanisms for License-Exempt
Operation
 802.16i : Mobile Management Information Base
 802.16j : Multihop Relay Specification
 802.16k : Bridging of 802.16
 802.16m : Advanced Air Interface.

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Major Categories of Networks

Local Area Network
Metropolitan Area network
Wide area network
The internet
Personal Area Network

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Local Area Network
A Local Area Network (LAN) is a relatively small network that is
confined to a small geographic area, such as a single office or a building.
Laptops, desktops, servers, printers, and other networked devices that
make up a LAN are located relatively close to each other. A key
characteristic is that all of the equipment that comprises a LAN, is owned
by a single entity.

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Metropolitan Area Network

The term Metropolitan Area Network (MAN) is typically used to describe a
network that spans a citywide area or a town. MANs are larger than
traditional LANs and predominantly use high-speed media, such as fiber
optic cable, for their backbones. MANs are common in organizations that
need to connect several smaller facilities together for information sharing.
This is often the case for hospitals that need to connect treatment facilities,
outpatient facilities, doctor's offices, labs, and research offices for access to
centralized patient and treatment information. MANs share many of the
same security threats as LANs, but on a larger scale. The plight of an
administrator in a central location granting access to countless offices that
are scattered within a city is a difficult one that demands strict access
control mechanisms to protect against unauthorized information access.

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Wide Area Network

A Wide Area Network (WAN) covers a significantly larger geographic area
than LANs or MANs. A WAN uses public networks, telephone lines, and
leased lines to tie together smaller networks such as LANs and MANs over
a geographically dispersed area. Connecting devices in different geographic
areas together for information sharing, WANs are an important piece of
enterprise networks. For example, consider the VisaNet global network used
by Visa International. The VisaNet network connects locations throughout
150 countries to validate and debit credit-card transactions at over 24
million locations. By providing security and simplicity over a standardbased WAN architecture, Visa International relies on their network
infrastructure to provide reliable access to merchants who accept Visa credit
cards for transactions.

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Personal Area Network

A more recent term used to describe a type of network is a Personal Area
Network (PAN). PAN networks are usually wireless, established in an ondemand or ad-hoc fashion when needed to communicate between two or
more devices. PAN networks can be used between devices owned by two
different parties, or between two devices owned by one person, such as a
PDA and a laptop or mobile phone. These networks are usually characterized
as short-range, often limited to 10 meters or less in range.
An example of a PAN technology is Bluetooth wireless networking.
Bluetooth is designed as a cable-replacement technology, allowing users to
discard the serial and USB cables used by many of today's peripheral devices
and rely on a Bluetooth PAN for communication. Bluetooth PANs support up
to 7 devices in a single network and can be used for proprietary protocols
(such as PDA synchronization) or standards-based protocols, including
Internet access over IP and the Bluetooth Network Encapsulation Protocol
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(BNEP).

Data Communications Through WANs
 WANs were developed to communicate over a large geographical area
(e.g. lab-to-lab; city-to-city; east coast-to-west coast; North America-toSouth America etc)
 WANs require the crossing of public right of ways (under control and
regulations of the interstate commerce and institute of telephone and data
communications established by the gov’t and international treaties).
 WANs around the world relies on the infrastructure established by the
telephone companies (“common carrier”) or public switched telephone
network (PSTN)
 WANs consists of a number of interconnected switching nodes (today =
computers). Transmission signals are routed across the network
automatically by software control to the specified destination. The
purpose of these nodes are to route messages through switching facilities
to move data from node to node to its destination
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 WANs originally implemented circuit switching and packet switching
technologies. Recently, frame relay and asynchronous transfer mode
(ATM) networks have been implemented to achieve higher operating
and processing speeds for the message
 WAN are owned by the common carrier in the U.S. and government in
most foreign countries
 Interconnected devices, I.e. LANs or Personal Computers (PC) or
Workstation or Servers can be (usually are) privately owned by
companies

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ISO/OSI Reference Model





Open Systems Interconnection
No one really uses this in the real world.
A reference model so others can develop detailed interfaces
Value: The reference model defines 7 layers of functions that take place
at each end of communication and with each layer adding its own set of
special related functions
 Flow of data through each layer at one

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ISO/OSI Reference Model
File Transfer, Email, Remote Login 

ASCII Text, Sound (syntax layer) 

Establish/manage connection 
End-to-end control & error checking
(ensure complete data transfer): TCP 
Routing and Forwarding Address: IP 

Two party communication: Ethernet 
How to transmit signal; coding Hardware
means of sending an receiving data on a carrier
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Layer 1: Physical layer
The physical layer defines electrical and physical specifications for devices.
In particular, it defines the relationship between a device and a transmission
medium, such as a copper or fiber optical cable.
The major functions and services performed by the physical layer are:
Establishment and termination of a connection to
a communications medium
Participation in the process whereby the communication resources are
effectively shared among multiple users. For example,
contention resolution and flow control

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Modulation, or conversion between the representation of digital data in
user equipment and the corresponding signals transmitted over a
communications channel. These are signals operating over the physical
cabling (such as copper and optical fiber) or over aradio link
Parallel SCSI buses operate in this layer, although it must be remembered
that the logical SCSI protocol is a transport layer protocol that runs over this
bus. Various physical-layer Ethernet standards are also in this layer;
Ethernet incorporates both this layer and the data link layer. The same
applies to other local-area networks, such as token ring, FDDI, ITUT G.hn and IEEE 802.11, as well as personal area networks such
as Bluetooth and IEEE 802.15.4.

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Layer 2: Data link layer
The data link layer provides the functional and procedural means to transfer
data between network entities and to detect and possibly correct errors that
may occur in the physical layer. Originally, this layer was intended for
point-to-point and point-to-multipoint media, characteristic of wide area
media in the telephone system. Local area network architecture, which
included broadcast-capable multi access media, was developed
independently of the ISO work in IEEE Project 802. IEEE work
assumed sub-layering and management functions not required for WAN
use. In modern practice, only error detection, not flow control using sliding
window, is present in data link protocols such as Point-to-Point
Protocol (PPP), and, on local area networks, the IEEE 802.2 LLC layer is
not used for most protocols on the Ethernet, and on other local area
networks, its flow control and acknowledgment mechanisms are rarely used.
Sliding window flow control and acknowledgment is used at the transport
layer by protocols such as TCP, but is still used in niches where X.25 offers
performance advantages.
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The ITU-T G.hn standard, which provides high-speed local area
networking over existing wires (power lines, phone lines and coaxial
cables), includes a complete data link layer which provides both error
correction and flow control by means of a selective repeat Sliding
Window Protocol.
Both WAN and LAN service arrange bits, from the physical layer, into
logical sequences called frames. Not all physical layer bits necessarily
go into frames, as some of these bits are purely intended for physical
layer functions. For example, every fifth bit of the FDDI bit stream is
not used by the layer.

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Layer 3: Network layer
The network layer provides the functional and procedural means of
transferring variable length data sequences from a source host on one network
to a destination host on a different network (in contrast to the data link layer
which connects hosts within the same network), while maintaining the quality
of service requested by the transport layer. The network layer performs
network routing functions, and might also perform fragmentation and
reassembly, and report delivery errors. Routers operate at this layer, sending
data throughout the extended network and making the Internet possible. This
is a logical addressing scheme – values are chosen by the network engineer.
The addressing scheme is not hierarchical.

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Layer 3: Network layer
The network layer may be divided into three sub layers:
Sub network access – that considers protocols that deal with the interface to
networks, such as X.25;
Sub network-dependent convergence – when it is necessary to bring the
level of a transit network up to the level of networks on either side
Sub network-independent convergence – handles transfer across multiple
networks

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An example of this latter case is CLNP, or IPv6 ISO 8473. It manages
the connectionless transfer of data one hop at a time, from end system
to ingress router, router to router, and from egress router to destination end
system. It is not responsible for reliable delivery to a next hop, but only for
the detection of erroneous packets so they may be discarded. In this scheme,
IPv4 and IPv6 would have to be classed with X.25 as subnet access
protocols because they carry interface addresses rather than node addresses.
A number of layer-management protocols, a function defined in the
Management Annex, ISO 7498/4, belong to the network layer. These
include routing protocols, multicast group management, network-layer
information and error, and network-layer address assignment. It is the
function of the payload that makes these belong to the network layer, not the
protocol that carries
84

Layer 4: Transport layer
The transport layer provides transparent transfer of data between end users,
providing reliable data transfer services to the upper layers. The transport
layer controls the reliability of a given link through flow control,
segmentation/desegmentation, and error control. Some protocols are stateand connection-oriented. This means that the transport layer can keep track
of the segments and retransmit those that fail. The transport layer also
provides the acknowledgement of the successful data transmission and
sends the next data if no errors occurred.

85

OSI defines five classes of connection-mode transport protocols ranging
from class 0 (which is also known as TP0 and provides the least features)
to class 4 (TP4, designed for less reliable networks, similar to the Internet).
Class 0 contains no error recovery, and was designed for use on network
layers that provide error-free connections. Class 4 is closest to TCP,
although TCP contains functions, such as the graceful close, which OSI
assigns to the session layer. Also, all OSI TP connection-mode protocol
classes provide expedited data and preservation of record boundaries.
Although not developed under the OSI Reference Model and not strictly
conforming to the OSI definition of the transport layer, the Transmission
Control Protocol (TCP) and the User Datagram Protocol (UDP) of the
Internet Protocol Suite are commonly categorized as layer-4 protocols
within OSI.
86

Layer 5: Session layer
The session layer controls the dialogues (connections) between computers.
It establishes, manages and terminates the connections between the local
and remote application. It provides for full-duplex, half-duplex,
or simplex operation, and establishes checkpointing, adjournment,
termination, and restart procedures. The OSI model made this layer
responsible for graceful close of sessions, which is a property of
the Transmission Control Protocol, and also for session check pointing and
recovery, which is not usually used in the Internet Protocol Suite. The
session layer is commonly implemented explicitly in application
environments that use remote procedure calls. On this level, InterProcess_(computing) communication happen (SIGHUP, SIGKILL, End
Process, etc.).

87

Layer 6: Presentation layer
The presentation layer establishes context between application-layer entities,
in which the higher-layer entities may use different syntax and semantics if
the presentation service provides a mapping between them. If a mapping is
available, presentation service data units are encapsulated into session
protocol data units, and passed down the stack.
This layer provides independence from data representation (e.g., encryption)
by translating between application and network formats. The presentation
layer transforms data into the form that the application accepts. This layer
formats and encrypts data to be sent across a network. It is sometimes called
the syntax layer.
The original presentation structure used the basic encoding rules of Abstract
Syntax Notation One (ASN.1), with capabilities such as converting
an EBCDIC-coded
text file to
an ASCII-coded
file,
or serialization of objects and other data structures from and to XML.
88

Layer 7: Application layer
The application layer is the OSI layer closest to the end user, which means
that both the OSI application layer and the user interact directly with the
software application. This layer interacts with software applications that
implement a communicating component. Such application programs fall
outside the scope of the OSI model. Application-layer functions typically
include identifying communication partners, determining resource
availability, and synchronizing communication. When identifying
communication partners, the application layer determines the identity and
availability of communication partners for an application with data to
transmit. When determining resource availability, the application layer must
decide whether sufficient network or the requested communication exist. In
synchronizing communication, all communication between applications
requires cooperation that is managed by the application layer.
89

Comparison with TCP/IP Model
In the TCP/IP model of the Internet, protocols are deliberately not as rigidly
designed into strict layers as in the OSI model. [10] RFC 3439 contains a
section entitled "Layering considered harmful (section link here )."
However, TCP/IP does recognize four broad layers of functionality which
are derived from the operating scope of their contained protocols, namely
the scope of the software application, the end-to-end transport connection,
the internetworking range, and the scope of the direct links to other nodes
on the local network.
Even though the concept is different from the OSI model, these layers are
nevertheless often compared with the OSI layering scheme in the following
way: The Internet application layer includes the OSI application layer,
presentation layer, and most of the session layer. Its end-to-end transport
layer includes the graceful close function of the OSI session layer as well as
the OSI transport layer.
90

The internetworking layer (Internet layer) is a subset of the OSI network
layer (see above), while the link layer includes the OSI data link and
physical layers, as well as parts of OSI's network layer. These comparisons
are based on the original seven-layer protocol model as defined in ISO
7498, rather than refinements in such things as the internal organization of
the network layer document.
The presumably strict peer layering of the OSI model as it is usually
described does not present contradictions in TCP/IP, as it is permissible that
protocol usage does not follow the hierarchy implied in a layered model.
Such examples exist in some routing protocols (e.g., OSPF), or in the
description of tunneling protocols, which provide a link layer for an
application, although the tunnel host protocol may well be a transport or
even an application layer protocol in its own right.
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SKILLS FOR INDIA

Understanding Network Protocols

Protocols of Computer Communications and
Networks
 Protocol are used for communication between computers in different
computer networks. Protocol achieves:
 What is communicated between computers?
 How it is communicated?
 When it is communicated?
 What conformance (bit sequence) between computers?
 Key elements of a protocol are:
 SYNTAC: Data format and signal levels
 SEMANTICS: Control information for coordination and error
handling
 TIMING: Synchronization, speed matching, and sequencing
 Examples of protocols:
 WAN Protocol: TCP/IP
95

The Internet Protocol Suite and the OSI
Reference Model

96

TCP
The Transmission Control Protocol (TCP) is one of the core protocols of
the Internet Protocol Suite. TCP is one of the two original components of
the suite, complementing the Internet Protocol (IP), and therefore the entire
suite is commonly referred to as TCP/IP. TCP provides reliable, ordered
delivery of a stream of bytes from a program on one computer to another
program on another computer. TCP is the protocol used by major Internet
applications such as the World Wide Web, email, remote
administration and file transfer. Other applications, which do not require
reliable data stream service, may use the User Datagram Protocol (UDP),
which provides datagram service that emphasizes reduced latency over
reliability.

97

User Datagram Protocol
The User Datagram Protocol (UDP) is one of the core members of
the Internet Protocol Suite, the set of network protocols used for
the Internet. With UDP, computer applications can send messages, in this
case referred to as datagram, to other hosts on an Internet Protocol (IP)
network without requiring prior communications to set up special
transmission channels or data paths. The protocol was designed by David
P. Reed in 1980 and formally defined in RFC 768 .
UDP
uses
a
simple
transmission
model
without
implicit handshaking dialogues for providing reliability, ordering, or data
integrity. Thus, UDP provides an unreliable service and datagram may
arrive out of order, appear duplicated, or go missing without notice. UDP
assumes that error checking and correction is either not necessary or
performed in the application, avoiding the overhead of such processing at
the network interface level. Time-sensitive applications often use UDP
because dropping packets is preferable to waiting for delayed packets,
which may not be an option in a real-time system.
98

Internet Control Message Protocol

The Internet Control Message Protocol (ICMP) is one of the core
protocols of the Internet Protocol Suite. It is chiefly used by the operating
systems of networked computers to send error messages indicating, for
example, that a requested service is not available or that a host or router
could not be reached. ICMP can also be used to relay query messages. It is
assigned protocol number 1.
ICMP differs from transport protocols such as TCP and UDP in that it is
not typically used to exchange data between systems, nor is it regularly
employed by end-user network applications (with the exception of some
diagnostic tools like ping and trace route).
ICMP for Internet Protocol version 4 (IPv4) is also known as
ICMPv4. IPv6 has a similar protocol, ICMPv6.
99

Hypertext Transfer Protocol

Hypertext Transfer Protocol (HTTP) is an application protocol for
distributed, collaborative, hypermedia information systems. HTTP is the
foundation of data communication for the World Wide Web.
Hypertext is a multi-linear set of objects, building a network by using
logical links (the so-called hyperlinks) between the nodes (e.g. text or
words). HTTP is the protocol to exchange or transfer hypertext.
The standards development of HTTP was coordinated by the Internet
Engineering Task Force (IETF) and the World Wide Web
Consortium (W3C), culminating in the publication of a series of Requests
for Comments (RFCs), most notably RFC 2616 (June 1999), which defines
HTTP/1.1, the version of HTTP in common use.

100

Post Office Protocol
In computing, the Post Office Protocol (POP) is an applicationlayer Internet standard protocol used by locale-mail clients to retrieve email from
a
remote server over
a TCP/IP connection. POP
and IMAP (Internet Message Access Protocol) are the two most
prevalent Internet standard protocols for e-mail retrieval. Virtually all
modern e-mail clients and servers support both. The POP protocol has been
developed through several versions, with version 3 (POP3) being the current
standard.
Most webmail service
providers
such
as
Hotmail, Gmail and Yahoo! Mail also provide IMAP and POP3 service.

101

File
Protocol

Transfer

File Transfer Protocol (FTP) is a standard network protocol used to
transfer files from one host to another host over a TCP-based network,
such as the Internet. It is often used to upload web pages and other
documents from a private development machine to a public web-hosting
server. FTP is built on a client-server architecture and uses separate
control and data connections between the client and the server. FTP users
may authenticate themselves using a clear-text sign-in protocol, normally
in the form of a username and password, but can connect anonymously if
the server is configured to allow it. For secure transmission that hides
(encrypts) the username and password, and encrypts the content, SSH File
Transfer Protocol may be used.

102

Internet Message Control Protocol
Internet message access protocol (IMAP) is one of the two most
prevalent Internet standard protocols for email retrieval, the other
being the Post Office Protocol (POP). Virtually all modern e-mail
clients and mail servers support both protocols as a means of transferring
e-mail messages from a server.
The Internet Message Access Protocol (commonly known as IMAP) is
an Application Layer Internet protocol that allows a client to access email on a remote mail server. The current version, IMAP version 4
revision 1 (IMAP4rev1), is defined by RFC 3501. An IMAP server
typically listens on well-known port 143. IMAP over SSL (IMAPS) is
assigned well-known port number 993.

103

IPX/SP
X

IPX/SPX is a routable protocol and can be used for small and large
networks. It was created by Novell primarily for Novell NetWare networks,
but is popular enough that it is used on products that are not from Novell.
•NCP - NetWare Core Protocol provides for client/server interactions
such as file and print sharing. It works at the application, presentation, and
session levels.
•SAP - Service Advertising Protocol packets are used by file and print
servers to periodically advertise the address of the server and the services
available. It works at the application, presentation, and session levels.

104

IPX/SP
X
•SPX - Sequenced Packet Exchange operates at the transport layer
providing connection oriented communication on top of IPX.
•IPX - Internetwork Packet Exchange supports the transport and
network layers of the OSI network model. Provides for network
addressing and routing. It provides fast, unreliable, communication
with network nodes using a connection less datagram service.

105

Other Network Support

 ODI - Open Data-link Interface
operates at the data link layer allowing
IPX to work with any network interface
card
 RIP - Routing Information Protocol is
the default routing protocol for
IPX/SPX networks which operates at
the network layer. A distance-vector
algorithm is used to calculate the best
route for a packet
 MHS - Message Handling Service by
Novell is used for mail on Netware
networks

Network Level

Protocols

Application
Presentation

NCP

SAP

Session
Transport
Network
Data Link

IPX

SPX

NDIS/NIC
drivers

106

NetBIOS
NetBIOS is an acronym for Network Basic Input/Output System. It
provides services related to the session layer of the OSI model allowing
applications on separate computers to communicate over a local area
network. As strictly an API, NetBIOS is not a networking protocol.
Older operating systems ran NetBIOS over IEEE 802.2 and IPX/SPX using
the NetBIOS Frames (NBF) and NetBIOS (NBX) protocols, respectively.
In modern networks, NetBIOS normally runs over TCP/IP via the NetBIOS
over TCP/IP (NBT) protocol. This results in each computer in the network
having both an IP address and a NetBIOS name corresponding to a
(possibly different) host name.

107

NetBEUI (NetBIOS Extended User Interface
NetBEUI (NetBIOS Extended User Interface) is a new, extended version
of NetBIOS, the program that lets computers communicate within a local
area network. NetBEUI formalizes the frame format (or arrangement of
information in a data transmission) that was not specified as part of
NetBIOS. NetBEUI was developed by IBM for its LAN Manager
product and has been adopted by Microsoft for its Windows NT, LAN
Manager, and Windows for Workgroups products. Hewlett-Packard and
DEC use it in comparable products.
NetBEUI is the best performance choice for communication within a
single LAN. Because, like NetBIOS, it does not support the routing of
messages to other networks, its interface must be adapted to other
protocols such as Internetwork Packet Exchange or TCP/IP. A
recommended method is to install both NetBEUI and TCP/IP in each
computer and set the server up to use NetBEUI for communication
within the LAN and TCP/IP for communication beyond the LAN.
108

Difference between NetBIOS & NetBEUI
NetBIOS (Network Basic Input/Output System) isn't a network protocol.
It's an API (applications programming interface) for File and Printer
Sharing. NetBIOS names identify computers on the network. NetBIOS
broadcasts locate computers and shared disks and folders on the network
and allow them to appear in My Network Places and Network
Neighborhood.
NetBEUI (NetBIOS Extended User Interface) is a network protocol, like
TCP/IP and IPX/SPX. All three protocols support file and printer sharing
using the NetBIOS API.
Nothing in Windows networking requires the NetBEUI protocol. All
network functions are available using the TCP/IP and/or NW Link
IPX/SPX protocols.
NetBEUI is available as an un-supported protocol in Windows XP.
109

Apple Talk

AppleTalk is a proprietary suite of networking protocols developed
by Apple Inc. for their Mac computers. AppleTalk included a number of
features that allowed local area networks to be connected with no prior
setup or the need for a centralized router or server of any sort. Simply
connecting together AppleTalk equipped systems would automatically
assign addresses, update the distributed namespace, and configure any
required inter-networking routing. It was a true plug-n-play system.
AppleTalk was released for the original Macintosh in 1985, and was the
primary protocol used by Apple machinery through the 1980s and 90s.
Versions were also released for the IBM PC and compatibles, and the Apple
IIGS. AppleTalk support was also available in most networked printers
(especially laser printers), some file servers and a number of routers.
Through this period, AppleTalk was, by far, the most popular networking
system in the world.
110

Apple Talk..Continued
The rise of TCP/IP during the 1990s led to a re-implementation of most of
these types of support on that protocol, and AppleTalk became unsupported
as of the release of Mac OS X v10.6 in 2009. Many of AppleTalk's more
advanced auto-configuration features have since been introduced
in Bonjour.

111

Associated TCP/IP Protocols & Services
HTTP

This protocol, the core of the World Wide Web, facilitates
retrieval and transfer of hypertext (mixed media) documents.
Stands for the HyperText Transfer protocol

Telnet

A remote terminal emulation protocol that enables clients to log
on to remote hosts on the network.

SNMP

Used to remotely manage network devices. Stands for the Simple
Network Management Protocol.

DNS

Provides meaningful names like achilles.mycorp.com for
computers to replace numerical addresses like 123.45.67.89.
Stands for the Domain Name System.

SLIP/
PPP

SLIP (Serial Line Internet Protocol) and PPP (Point to Point
Protocol) encapsulate the IP packets so that they can be sent over
a dial up phone connection to an access provider’s modem.

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SKILLS FOR INDIA

IP Addressing

What is an IP address?







IP (Internet Protocol) address
Device used by routers, to select best path from source to
destination, across networks and internetworks
Network layer address, consisting of NETWORK portion,
and HOST portion
Logical address, assigned in software by network
administrator
Part of a hierarchical ‘numbering scheme’ - unique, for
reliable routing
May be assigned to a host pc, or router port

116

Types of IP address
 Static address
 Dynamic address

117

Static IP address

 Manually input by network administrator
 Manageable for small networks
 Requires careful checks to avoid duplication

118

Dynamic IP address

Examples - BOOTP, DHCP
 Assigned by server when host boots
 Derived automatically from a range of addresses
 Duration of ‘lease’ negotiated, then address released back to server

119

Class A IP address
 1st octet = network address, octets 2-4 = host address
 1st bits of 1st octet set to 0
 up to (2^24 - 2) host addresses (16.8M)

121

Class A IP address

124. 224. 224.100

01111100

11100000

11100000

01100100

122

Class B IP address
 1st 2 octets = network address, octets 3-4 = host address
 1st 2 bits of 1st octet set to 10
 up to (2^16 - 2) host addresses (65534)

123

Class B IP address

129. 224. 224. 100

10000001

11100000

11100000

01100100

124

Class C IP address

 1st 3 octets = network address, octet 4 = host address
 1st 3 bits of 1st octet set to 110
 up to (2^8 - 2)

host addresses (254)

125

Class C IP address

193. 224. 224. 100

11000001

11100000

11100000

01100100

126

IP addresses and routing

 Routing tables
 Identifying source and destination
 IP packet routing

127

IP addresses and routing -Routing

Tables
 Created by router, held in memory, constantly updated
 Based on cross-referencing
 IP packet source address, and port on which received

128

IP addresses and routing Identifying source
and destination

 As part of a layer 3 packet, IP header contains source and destination
address
 Each address is 32 bits long, and unique to device or port
 Router reads destination IP address, checks against routing tables

129

IP addresses and routing - IP packet routing

 If destination address not on the same segment as receive port,
router sends packet to correct port for routing to destination
 If destination on same segment as receive port, packet not
forwarded

130

Networks and subnets
 Why subnet
 Subnet mask
 Restrictions on ‘borrowed’ bits

131

When an organization is granted a block of addresses, it can create
subnets to meet its needs. The prefix length increases to define the
subnet prefix length.

Why subnet
Reduce broadcast domain, improve network efficiency

Why subnet
Reduce broadcast domain, improve network efficiency

132

Subnet masks

 Extend NETWORK portion, borrow from HOST portion
 Allow external networks to route packets direct to subnet

133

Network Address Translation
Network Address Translation or NAT
Kinds of Network Address Translation
Operation of Network Address Translation
Security and Administration

135

IP Routing
When we want to connect two or more networks using different n/w
addresses then we have to use IP Routing technique. The router will
be used to perform routing between the networks. A router will
perform following functions for routing.
 Path determination
 Packet forwarding
 Path determination
The process of obtaining path in routing table is called path
determination. There are three different methods to which router can
learn path.
 Automatic detection of directly connected n/w.
 Static & Default routing
 Dynamic routing
136

IP Routing
 Packet forwarding
It is a process that is by default enable in router. The router will
perform packet forwarding only if route is available in the routing
table.

137

Routing Process
 The pc has a packet in which destination address is not same as the
local n/w address.
 The pc will send an ARP request for default gateway. The router will
reply to the ARP address and inform its Mac address to pc.
 The pc will encapsulate data, in which source IP is pc itself,
destination IP is server, source Mac is pc’s LAN interface and
destination Mac is router’s LAN interface.

138

Routing Process

R1

10.0.0.1
S. MAC
PC1
D. IP
S. IP

D. MAC
R1
172.16.0.5
10.0.0.6

172.16.0.5
139

The router will receive the frame, store it into the buffer. When obtain
packet from the frame then forward data according to the destination
IP of packet. The router will obtain a route from routing table
according to which next hop IP and interface is selected
 According to the next hop, the packet will encapsulated with new
frame and data is send to the output queue of the interface.

140

Static Routing
In this routing, we have to use IP route commands through which we
can specify routes for different networks. The administrator will analyze
whole internetwork topology and then specify the route for each n/w
that is not directly connected to the router.
Steps to perform static routing
Create a list of all n/w present in internetwork.
Remove the n/w address from list, which is directly connected to n/w.
Specify each route for each routing n/w by using IP route command.
Router(config)#ip route <destination n/w> <mask> <next hop ip>
Next hop IP it is the IP address of neighbor router that is directly
connected our router.
141

Advantages of static routing
(1) Fast and efficient.
(2) More control over selected path.
(3) Less overhead for router.
(4) Bandwidth of interfaces is not consumed in routing updates.
Disadvantages of static routing
(1) More overheads on administrator.
(2) Load balancing is not easily possible.
(3) In case of topology change routing table has to be change
manually.

142

Alternate command to specify static route

Static route can also specify in following syntax: Old
Router(config)#ip route 172.16.0.0 255.255.0.0 172.25.0.2
Or
Router(config)#ip route 172.16.0.0 255.255.0.0 serial 0

143

Backup route or loading static route
If more than one path are available from our router to destination then
we can specify one route as primary and other route as backup route.
Administrator Distance is used to specify one route as primary and
other route as backup. Router will select lower AD route to forward
the traffic. By default static route has AD value of 1. With backup
path, we will specify higher AD so that this route will be used if
primary route is unavailable.
Protocols
AD
Directly Connected
0
Static
1
BGP
20
EIGRP
90
IGRP
100
OSPF
110
RIP
120
144

Syntax: To set backup path Router(config)#ip route <dest. n/w>
<mask> <next hop> <AD>
Default Routing
Default routing means a route for any n/w. these routes are
specify with the help of following syntax: Router(config)#ip route 0.0.0.0 0.0.0.0 <next hop>
Or
<exit interface>
To display routing table
Router#sh ip route
145

To display routing table
Router#sh ip route
To display static routes only
Router#sh ip route static
S 192.168.10.0/28 [1/0] via 172.16.0.5
To display connected n/ws only
Router#sh ip route connected
To check all the interface of a router
Router#sh interface brief

146

Dynamic Routing
In dynamic routing, we will enable a routing protocol on router. This protocol
will send its routing information to the neighbor router. The neighbors will
analyze the information and write new routes to the routing table.
The routers will pass routing information receive from one router to
other router also. If there are more than one path available then routes are
compared and best path is selected. Some examples of dynamic protocol are: RIP, IGRP, EIGRP, OSPF
Types of Dynamic Routing Protocols
According to the working there are two types of Dynamic Routing Protocols.
(1) Distance Vector
(2) Link State

147

Dynamic Routing
According to the type of area in which protocol is used there are again two
types of protocol: (1) Interior Routing Protocol
(2) Exterior Routing Protocol
Interior Routing

Exterior Routing

RIP

BGP

IGRP

EXEIGRP

EIGRP
OSPF
148

Distance Vector Routing
The Routing, which is based on two parameters, that is distance and direction
is called Distance Vector Routing. The example of Distance Vector Routing is
RIP & IGRP.
Operation: (1) Each Router will send its directly connected information to the neighbor
router. This information is send periodically to the neighbors.
(2) The neighbor will receive routing updates and process the route
according to following conditions:  If update of a new n/w is received then this information is stored in
routing table.
 If update of a route is received which is already present in routing
table then route will be refresh that is route times is reset to zero.
149

 If update is received for a route with lower metric then the route, which is
already present in our routing table. The router will discard old route and
write the new route in the routing table.
 If update is received with higher metric then the route that is already
present in routing table, in this case the new update will be discard.
 A timer is associated with each route. The router will forward routing
information on all interfaces and entire routing table is send to the
neighbor. There are three types of timers associated with a route.
 Route update timer
It is the time after which the router will send periodic update to the
neighbor.
150

 Route invalid timer
It is the time after which the route is declared invalid, if there are no
updates for the route. Invalid route are not forwarded to neighbor routers
but it is still used to forward the traffic.
 Route flush timer
It is the time after which route is removed from the routing table, if there
are no updates about the router.

151

Metric of Dynamic Routing
 Metric are the measuring unit to calculate the distance of destination n/w. A
protocol may use a one or more than one at a time to calculate the distance.
Different types of metric are:  Hop Count
 Band Width
 Load
 Reliability
 Delay
 MTU

152

Hop Count
It is the no. of Hops (Routers) a packet has to travel for a destination n/w.
Bandwidth
Bandwidth is the speed of link. The path with higher bandwidth is preferred to
send the data.
Load
Load is the amount of traffic present in the interface. Paths with lower load
and high throughput are used to send data.
Reliability
Reliability is up time of interface over a period of time.
Delay
Delay is the time period b/w a packet is sent and received by the destination
153

MTU Maximum Transmission Unit
It is the maximum size of packet that can be sent in a frame mostly MTU is set
to 1500.
Problems of Distance Vector
There are two main problems of distance vector routing
•Bandwidth Consumption
•Routing Loops
Bandwidth Consumption
The problem of accessive bandwidth consumption is solved out with the help
of autonomous system. It exchanges b/w different routers. We can also
perform route summarization to reduce the traffic.
154

Routing Loops
It may occur b/w adjacent routers due to wrong routing information. Distance
Vector routing is also called routing by Rumor. Due to this the packet may
enter in the loop condition until their TTL is expired.
Method to solve routing loops
There are five different methods to solve or reduce the problem of routing
loop.
Maximum Hop Count
Flash Updates/Triggered Updates
Split Horizon
Poison Reverse
Hold Down
155

Maximum Hop Count
This method limits the maximum no. of hops a packet can travel. This method
does not solve loop problem. But it reduce the loop size in the n/w. Due to this
method the end to end size of a n/w is also limited.
Flash Updates/Triggered Updates
In this method a partial update is send to the all neighbors as soon as there is
topology change. The router, which receives flash updates, will also send the
flash updates to the neighbor routers.
Split Horizon
Split Horizon states a route that update receive from an interface can not be
send back to same interface.
156

Poison Reverse
This method is the combination of split Horizon and Flash updates. It
implements the rule that information received from the interface can not be
sent back to the interface and in case of topology change flash updates will be
send to the neighbor.
Hold Down
If a route changes frequently then the route is declared in Hold Down state and
no updates are received until the Hold Down timer expires.

157

Routing Information Protocol
Features of RIP:  Distance Vector
 Open standard
 Broadcast Updates
(255.255.255.255)
 Metric
Hop Count
Timers
Update 30 sec
Invalid 180 sec
Hold 180 sec

158

 Loop Control
 Split Horizon
 Triggered Updates
 Maximum Hop Count
 Hold Down
 Maximum Hop Count 15
 Administrative Distance 120
 Equal Path Cost Load Balancing
 Maximum Load path 6

Default 4
 Does not support VLSM
 Does not support Autonomous system
159

Configuring RIP
Router#conf ter
Router(config)#router rip
Router(config-router)#network <own net address>
Router(config-router)#network <own net address>
--------------------------Router(config-router)#exit
Router(config-router)#network 10.0.0.0
175.2.0.0 via 172.16.0.6

160

Configuring RIP

172.16.0.6

10.0.0.1

17

.5
.16.0
172

5. 2

R1

1
.1.

200.100.100.12

161

Display RIP Routers
Router#sh ip route rip
R 192.168.75.0/24 [120/5] via 172.30.0.2 00:00:25 serial 1/0
RIP Dest. n/w mask AD Metric Next Hop Timer own Interface

RIP advanced configuration
Passive Interfaces
An interface, which is not able to send routing updates but able to
receive routing update only is called Passive Interface. We can declare
an interface as passive with following commands: Router#conf ter
Router(config-router)#Passive-interface <type> <no>
Router(config-router)#exit
162

Neighbor RIP
 In RIP, by default routing updates are send to the address 255.255.255.255.
In some scenarios, it may be required to send routing updates as a unicast
from router to another. In this case, we have to configure neighbor RIP.
 For example: - in a Frame Relay n/w the broadcast update is discarded by
the switches, so if we want to send RIP updates across the switches then
we have to unicast updates using Neighbor RIP.

163

Unicast 10.0.0.2
255.255.255.255
10.0.0.1

Frame
Relay
Cloud

10.0.0.2

R1

R1
Router(config-router)#neighbor 10.0.0.2
neighbor

R2

R2
Router(config router)#
10.0.0.1

164

To change Administrative Distance
Router(config-router)#distance <value>
Router(config-router)#exit 95 or 100
To configure Load Balance
RIP is able to perform equal path cost Load Balancing. If multiple paths
are available with equal Hop Count for the destination then RIP will
balance load equally on all paths.
Load Balancing is enabled by default 4 paths. We can change the no. of
paths. It can use simultaneously by following command: Router(config)#router rip
Router(config-router)#maximum-path <1-6>
165

To display RIP parameters
Router#sh ip protocol
Or
Router#sh ip protocol RIP
This command display following parameters: (i) RIP Timers
(ii) RIP Version
(iii) Route filtering
(iv) Route redistribution
(v) Interfaces on which update send
(vi) And receive
(vii) Advertise n/w
(viii) Passive interface
(ix) Neighbor RIP
(x) Routing information sources
(xi) Administrative Distance

166

RIP version 2
RIP version 2 supports following new features: Support VLSM (send mask in updates)
Multicast updates using address 224.0.0.9
Support authentication

Commands to enable RIP version 2
We have to change RIP version 1 to RIP version 2. Rest all communication
will remain same in RIP version 2.
Router(config)#Router RIP
Router(config-router)#version 2

167

To debug RIP routing
Router#debug ip rip
To disable debug routing
Router#no debug ip rip
Or
Router#no debug all
Or
Router#undebug all

168

Interior Gateway Routing Protocol
Features:  Cisco proprietary
 Distance vector
 Timers
Update 90 sec
Invalid 270 sec
Hold time 280 sec
Flush 630 sec
 Loop control
All methods

169

Metric (24 bit composite)

Bandwidth (default)

Delay (default)

Load

Reliability

MTU

170







Broadcast updates to address 255.255.255.255
Unequal path cost load balancing
Automatic route summarization
Support AS
Does not support VLSM

171

Configuring IGRP
Router(config)#router igrp <as no>(1 – 65535)
Router(config-router)#network <net address>
Router(config-router)#network <net address>
Configuring Bandwidth on Interface for IGRP
By default the router will detect maximum speed of interface and use this
value as the bandwidth metric for IGRP. But it may be possible that the
interfaces and working at its maximum speed then we have to configure
bandwidth on interface, so that IGRP is able to calculate correct method

172

Router(config)#interface <type> <no>
Router(config-if)#bandwidth <value in kbps>
Router(config-if)#exit
Router(config)#interface serial 0
Router(config-if)#bandwidth 256
Configuring Unequal path cost load balancing
To configure load balancing, we have to set two parameters
(1) Maximum path (by default 4)
(2) Variance (default 1)
Maximum Path: - it is maximum no. of paths that can be used for load
balancing simultaneously.

173

Variance: - it is the multiplier value to the least metric for a destination n/w up
to which the load can be balanced.
Router(config)#Router igrp <as no>
Router(config-router)#variance <value>

174

Configuring IGRP
Configuring following options in IGRP as same as in case of RIP:  Neighbor
 Passive interface
 Timer
 Distance (AD)
 Maximum path

175

Network Address Translation
 RFC-1631
 A short term solution to the problem of the depletion of IP addresses
 Long term solution is IP v6 (or whatever is finally agreed on)
 CIDR (Classless Inter Domain Routing ) is a possible short term
solution
 NAT is another
 NAT is a way to conserve IP addresses
 Hide a number of hosts behind a single IP address
 Use:
• 10.0.0.0-10.255.255.255,
• 172.16.0.0-172.32.255.255 or
• 192.168.0.0-192.168.255.255 for local networks
176

Translation Modes
 Dynamic translation (IP masquerading)
 Large number of internal users share a single external address
 Static translation
 A block external addresses are translated to a same size block of
internal addresses
 Load balancing translation
 A single incoming IP address is distributed across a number of
internal servers
 Network redundancy translation
 Multiple internet connections are attached to a NAT firewall that
it chooses and uses based on bandwidth, congestion and
availability
177

Dynamic Translation (IP Masquerading )

 Also called Network Address and Port Translation (NAPT)
 Individual hosts inside the Firewall are identified based on of each
connection flowing through the firewall
 Since a connection doesn’t exist until an internal host requests a
connection through the firewall to an external host, and most
Firewalls only open ports only for the addressed host only that
host can route back into the internal network
 IP Source routing could route back in; but, most Firewalls block
incoming source routed packets
 NAT only prevents external hosts from making connections to internal
hosts.
 Some protocols won’t work; protocols that rely on separate
connections back into the local network
 Theoretical max of 216 connections, actual is much less
178

Static Translation
 Map a range of external address to the same size block of internal
addresses
 Firewall just does a simple translation of each address
 Port forwarding - map a specific port to come through the Firewall
rather than all ports; useful to expose a specific service on the internal
network to the public network

179

Load Balancing

 A firewall that will dynamically map a request to a pool of identical
clone machines
 often done for really busy web sites
 each clone must have a way to notify the Firewall of its current load
so the Fire wall can choose a target machine
 or the firewall just uses a dispatching algorithm like round robin
 Only works for stateless protocols (like HTTP)

180

Network Redundancy

 Can be used to provide automatic fail-over of servers or load balancing
 Firewall is connected to multiple ISP with a masquerade for each ISP
and chooses which ISP to use based on client load
 Kind of like reverse load balancing
 A dead ISP will be treated as a fully loaded one and the client will
be routed through another ISP

181

Problems with NAT

Can’t be used with:
 Protocols that require a separate back-channel
 Protocols that encrypt TCP headers
 Embed TCP address info
 Specifically use original IP for some security reason

182

Working of NAT & PAT

10.0.0.5

10.0.0.6

10.0.0.1

NAT

200.100.100.12

Internet

Switch

10.0.0.5
10.0.0.7

200.100.100.12
1080

10.0.0.8

10.0.0.6
200.100.100.12
1085
183

10.0.0.7
200.100.100.12

1100

Port Translation

1024

10.0.0.8
200.100.100.12
1024

184

Static NAT
This NAT is also used for servers. It provides port-based access to the servers
with the help of NAT.

Static NAT
200.1.1.5 = 192.168.10.6
Router

Internet
.1.5
200.1
Live

Local 192.168.10.6
185

Port Base Static NAT
This NAT is used for servers in which one Live IP is directly mapped to one
Local IP. This NAT will forward on the traffic for the Live IP to the Local
PC in the n/w.
200.1.1.5:80 -> 192.168.10.6
Router200.1.1.5:53 -> 192.168.10.7

Internet

Router

Web
192.168.10.6

DNS
192.168.10.7

186

Dynamic NAT using Pool
Dynamic NAT is used for clients, which want to access Internet. The
request from multiple client IPs are translated with the Live IP obtained
from the Pool. It is also called Pool Based Dynamic NAT.
Pool => 200.1.1.8 – 200.1.1.12/28
Internet
Local address => 172.16.X.X Except => 172.16.0.5
172.16.0.6
172.16.0.7
Pool allotted => 200.1.1.0 – 15/28
Server
Static => 200.1.1.3 = 172.16.0.7
Port Based Static NAT
200.1.1.4:53 = 172.16.0.6
200.1.1.4:80 = 172.16.0.5
187

Dynamic NAT using Pool
Client
Dynamic NAT
Pool => 200.1.1.8 – 200.1.1.12/28
Local address => 172.16.0.X
Except
172.16.0.5
172.16.0.6
172.16.0.7

188

Configuring NAT
Router#conf ter
Router(config)#int serial 0
Router(config-if)#ip nat outside
Router(config-if)#int eth 0
Router(config-if)#ip nat inside
Router(config)#ip nat inside source static 172.16.0.7 200.1.1.3
Router(config)#ip nat inside source static tcp 172.16.0.5 80 200.1.1.4
80
Router(config)#ip nat inside source static udp 172.16.0.6 53 200.1.1.4
53
Router(config)#access-list 30 deny 172.16.0.5
Router(config)#access-list 30 permit any
Router(config)#ip nat pool abc 200.1.1.8 200.1.1.12 netmask
189
255.255.255.240

Command for Basic NAT
Router(config)#ip nat inside source list 30 interface serial 0
<exiting interface name>
To display NAT translation
Router#sh ip nat translations
(after ping any address, it shows ping details)
To clear IP NAT Translation
Router#clear ip nat Translation *
190


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

191


192

SKILLS FOR INDIA

Remote Access Mode

Remote Access Service
Remote Access Services (RAS) refers to any combination of hardware and
software to enable the remote access tools or information that typically
reside on a network of IT devices. A RAS server is a specialized computer
which aggregates multiple communication channels together. Because these
channels are bidirectional, two models emerge: Multiple entities connecting
to a single resource, and a single entity connecting to multiple resources.
Both of these models are widely used. Both physical and virtual resources
can be provided through a RAS server: centralized computing can provide
multiple users access to a remote virtual operating system. Access Providers
often use RAS servers to terminate physical connections to their customers,
for example customers who get Internet through some form of modem.
Originally coined by Microsoft when referring to their built-in NT
remote access tools, RAS was a service provided by Windows
NT which allows most of the services which would be available on
a network to be accessed over a modem link.
194

The service includes support for dialup and logon, presents the same
network interface as the normal network drivers (albeit slightly slower). It is
not necessary to run Windows NT on the client - there are client versions for
other Windows operating systems.
A feature built into Windows NT enables users to log into an NTbased LAN using a modem, X.25 connection or WAN link. RAS works
with several major network protocols, including TCP/IP, IPX, and NBF.
To use RAS from a remote node, you need a RAS client program, which is
built into most versions of Windows, or any PPP client software. For
example, most remote control programs work with RAS.
Starting in the mid-1990s, several manufacturers such as U.S.
Robotics produced "modem terminal servers". Instead of having RS232ports, these would directly incorporate an analog modem. These devices
were commonly used by Internet service providers to allow consumer dialup. Modern versions interface to an ISDN PRI instead of having analog
modem ports.
195

Complete these steps to configure RAS on a Cisco ICM Logger.
Select Start > Settings > Control Panel
Double-click the Network Applet
Select Services
Double-click the Remote Access Service

196

Figure 1: Remote Access Setup

197

Click Configure. Figure 2: Configure Port Usage

198

Media Access Methods
An access method is a set of rules governing how the network nodes
share the transmission medium. The rules for sharing among
computers are similar to the rules for sharing among humans in that
they both boil down to a pair of fundamental philosophies:
 first come, first served and
 take turns.
These philosophies are the principles defining the three most
important types of media access methods:

199

Media Access Methods
Contention.
-(CSMA/CD Carrier Sense Multiple Access with Collision
Detection,
 -CSMA/CA Carrier Sense Multiple Access with Collision
Avoidance)
 Token passing.
 Demand Priority.

200

Contention
CSMA/CD Carrier Sense Multiple Access with Collision Detection
IEEE 802.3 Ethernet LANs use the Carrier Sense Multiple Access
with Collision detection(CSMA/CD) protocol to detect and handle
collisions on the network. However, WLANs can’t use CSMA/CD
because they can’t transmit and listen at the same time.
CSMA/CA Carrier Sense Multiple Access with Collision Avoidance
The IEEE 802.11b standard specifies the carrier sense multiple access
with collision avoidance (CSMA/CA) protocol for WLANs.
CSMA/CA tries to avoid collisions by using explicit packet
acknowledgment.
With CSMA/CA, an acknowledgment packet is sent by the receiving
station to confirm it has received a data packet. If the transmitting
station does not receive the acknowledgment, it assumes that a
collision has occurred and transmits the data packet again.
201

Token passing
IEEE 802.5 standard deals with Token Ring networks
Token passing is implemented on a token-ring network.
IEEE 802.5 Token Ring networks use a token-passing media access method. A
token is a special packet that gives permission to a device to transmit data on
to the network. When a device receives a token and transmits a frame, the
frame is forwarded around the ring by all attached devices.
When the frame reaches its destination, it is copied and processed by the
receiving device and placed back on the ring. Before placing the frame back on
the ring, the receiving device sets frame-status bits to indicate that the frame
was received. The frame circles the ring until it returns to the original
transmitting device.

202

Demand Priority

Demand priority is an access method used with the new 100Mbps
100VG-AnyLAN standard. Although demand priority is officially
considered a contention-based access method, demand priority is
considerably different from the basic CSMA/CD Ethernet. In demand
priority, network nodes are connected to hubs, and those hubs are
connected to other hubs. Contention, therefore, occurs at the hub.
(100VG-AnyLAN cables can actually send and receive data at the
same time.) Demand priority provides a mechanism for prioritizing
data types. If contention occurs, data with a higher priority takes
precedence

203

Collision & Broadcast Domains

MAC Address
Contains 48-bit destination address field.
Who is this frame for?
00-C0-F0-56-BD-97
“Hey Joe”

204

MAC Address

How will all other NICs handle
the frame?
Drop it (in the “bit bucket”)

205

Special MAC Address

Who is this frame for?
FF-FF-FF-FF-FF-FF
“Hey everybody”

206

Broadcast MAC Address

FF-FF-FF-FF-FF-FF
48 bits, all 1s
All NICs copy the
frame & send it up
the stack

207

Broadcast Frames
Necessary for network function
Used for
finding services: “Hey, is there a server out there?”
Advertising services: “Hey, I’m a printer you can use.”
Some Layer 3 (Network Layer) protocols use broadcasts
frequently:
Appletalk
IPX (older Novell protocol)
Networks that use these protocols must be limited in size, or
they will become saturated with broadcast frames.
TCP/IP (a Layer 3 protocol) uses broadcasts sparingly.
Therefore, networks that use TCP/IP can be made quite large
without broadcast problems. (They “scale” well.)
208

Collision Domain
Network region in which
collisions are propagated.
Repeaters and hubs propagate
collisions.
Bridges, switches and routers do
not.

Reducing Collisions
 Collision frequency can be kept low by breaking the network into
segments bounded by:
 bridges
 switches
 routers

Broadcast Domain
Network region in which
broadcast frames are propagated.
Repeaters, hubs, bridges, &
switches propagate broadcasts.
Routers either do or don’t,
depending on their configuration.

Reducing Broadcasts
Broadcasts are necessary for network function.
Some devices and protocols produce lots of broadcasts; avoid them.
Broadcast frequency can be kept manageable by limiting the LAN
size.
LANs can then be cross-connected by routers to make a larger
internetwork.

Shared Ethernet
A single segment that is shared among all connected NICs.
A single collision domain.
A logical “bus” (may be a physical star).
The segment includes repeaters and hubs.
Sometimes called a “single flat Ethernet”.

Switched Ethernet
Consists of a several segments, each of which is shared by NICs
attached to it.
The network is segmented into several collision domains.
Bridges, switches, and routers create the segment and collision
domain boundaries.
Segments may contain hubs and repeaters.

Switched Ethernet
Switch - 1 port per hub

Hub

Hub

Micro segmented Switched Ethernet
Each user NIC is connected directly to a
switch port.
Provides one switched segment to each
connected NIC.
No sharing.
No collisions.

Micro segmented Switched Ethernet
Switch - 1 port per PC

Summary
Term
LAN Segment
(Collision domain)
Entire LAN
(Broadcast domain)
Internetwork
(Group of LANs
cross-connected
by Routers)

Includes
Cable
Repeaters
Hubs

Boundary
Bridges
Switches
(Routers)

Everything
except
Routers

Edge of LAN
Routers

LANs &
Routers

Edge of
Internetwork

Example

switch

router

switch

Identify the collision domains
& broadcast domains
switch

hub

hub

& broadcast domains
hub

hub

& broadcast domains
switch

hub

& broadcast domains:

router
switch

Router connects separate networks.
One broadcast domain per router interface.

Application
First, complete Lab 7A
Then, on a printed copy of the “Teaching Topology” (curriculum
p7.5.5)
Circle each collision domain - use a solid line.
Circle each broadcast domain - use a dashed line.

Reminder
Collisions
spread throughout a LAN segment
spread across hubs & repeaters
are stopped by switches & bridges
Broadcasts
spread throughout an entire LAN
spread across hubs, switches, bridges
are stopped only by routers

225

LAN Switching
Ethernet switches are used in LAN to create Ethernet n/ws. Switches
forward the traffic on the basis of MAC address. Switches maintain a
Mac Addresse table in which mac addresses and port no.s are used to
perform switching decision. Working of bridge and switch is similar to
each other.

226

Classification of switches
Switches are classified according to the following criteria: Types of switches based on working
(1) Store & Forward
This switch receives entire frame then perform error checking and
start forwarding data to the destination.
(2) Cut through
This switch starts forwarding frame as soon as first six bytes of the
frame are received.
(3) Fragment-free
This switch receives 64 bytes of the frame, perform error checking
and then start forwarding data.
(4) Adaptive cut-through
It changes its mode according the condition. If it see there are
errors in many frames then it changes to Store & Forward mode from
Cut through or Fragment-free.

227

Classification of switches
Types of switches based on management
(1) Manageable switches
(2) Non-Manageable switches
(3) Semi-Manageable switches
Types of switches based on OSI layer
(1) Layer 2 switches (only switching)
(2) Layer 3 switches (switching & routing)
Types of switches based on command mode (only in Cisco)
(1) IOS based
(2) CLI based
Type of switches based on hierarchical model
(1) Core layer switches
(2) Distribution layer switches
(3) Access layer switches
228

Basic Switch Administration
IOS based switches are similar to the routers. We can perform following
function on switches in a similar manner as performed on router.
(1) Access switch using console
(2) Commands to enter & exit from different mode
(3) Commands to configure passwords
(4) Manage configuration
(5) Backup IOS and configuration
(6) Configuring and resolving hostnames
(7) Managing telnet
(8) Configuring CDP
(9) Configuring time clock
(10) Configuring Banners
(11) Command line shortcuts and editing shortcuts
(12) Managing history
(13) Configure logging
(14) Boot system commands
229

Basic Switch Administration
Following function and options are not similar in router and switch.
(1) Default hostname is ‘Switch’
(2) Auxiliary port is not present
(3) VTY ports are mostly 0 to 15
(4) By default interfaces are enabled
(5) IP address cannot be assign to interfaces
(6) Routing configuration mode is not present
(7) Interface no. starts from 1
(8) Web access is by default enabled
(9) Configuration registry is not present in similar manner
(10) Flash memory may contain multiple files and startup-configuration
is also saved in flash

230

Configuring IP and Gateway on switch
We can configure IP address on switch for web access or telnet IP
address is required for the administration of the switch. If we have to
access switch from remote n/w then we will configure default gateway
in addition to IP address.
IP address is assigned to the logical interface of switch with following
command:Switch(config)#interface vlan 1
Switch(config)#IP address <ip> <mask>
Switch(config)#no sh
Switch(config)#exit

231

Old Switches
Switch(config)#ip address <ip> <mask>
Switch(config)#exit
Configuring Gateway
Switch(config)#ip default-gateway <ip>
Switch(config)#exit

232

Breaking Switch Password
(1) Power off switch press mode button present in front of switch then
power on the switch.
(2) Keep mode button press until ‘Switch:’ prompt appears on console.
(3) In switch monitor mode, type following commands: flash_init
load_helper
rename flash:config.text flash:<anyname>
dir flash:
boot
(4) After booting switch will prompt to enter in initial configuration
dialog. Enter ‘no’ here and type.
Switch>enable
Rename flash:<anyname> Flash:config.text
Configure memory
Change password and save config. Then copy run start_config.
233


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

234


235

SKILLS FOR INDIA

Security Protocol

A security protocol (cryptographic protocol or encryption protocol) is
an abstract or concrete protocol that performs a security-related function and
applies cryptographic methods.
A protocol describes how the algorithms should be used. A sufficiently
detailed protocol includes details about data structures and representations,
at which point it can be used to implement multiple, interoperable versions
of a program.
Cryptographic protocols are widely used for secure application-level data
transport. A cryptographic protocol usually incorporates at least some of
these aspects:
Key agreement or establishment
Entity authentication
Symmetric encryption and message authentication material construction
Secured application-level data transport
Non-repudiation methods
237

Internet Key Exchange
Internet Key Exchange (IKE or IKEv2) is the protocol used to set up
a security association (SA) in the IPSec protocol suite. IKE builds upon
the Oakley protocol and ISAKMP. IKE uses X.509 certificates for
authentication which are either pre-shared or distributed
using DNS (preferably with DNSSEC), and a Diffie–Hellman key
exchange to set up a shared session secret from which cryptographic
keys are derived. In addition, a security policy for every peer which will
connect must be manually maintained

238

IPsec
Internet Protocol Security (IPsec) is a protocol suite for securing Internet
Protocol (IP) communications by authenticating andencrypting each IP
packet of a communication session. IPsec also includes protocols for
establishing mutual authentication between agents at the beginning of the
session and negotiation of cryptographic keys to be used during the session.
IPsec is an end-to-end security scheme operating in the Internet Layer of
the Internet Protocol Suite. It can be used in protecting data flows between a
pair of hosts (host-to-host), between a pair of security gateways (networkto-network), or between a security gateway and a host (network-to-host).[1]
Some other Internet security systems in widespread use, such as Secure
Sockets Layer (SSL), Transport Layer Security (TLS) andSecure
Shell (SSH), operate in the upper layers of the TCP/IP model. In the past,
the use of TLS/SSL had to be designed into an application to protect the
application protocols. In contrast, since day one, applications did not need to
be specifically designed to use IPsec.
239

Hence, IPsec protects any application traffic across an IP network. This
holds true now for SSL as well with the rise of SSL based VPN revolution
with implementations like OpenVPN.
IPsec originally was developed at the Naval Research Laboratory as part of
a DARPA-sponsored research project. ESP was derived directly from the
SP3D protocol, rather than being derived from the ISO Network-Layer
Security Protocol (NLSP). The SP3D protocol specification was published
by NIST, but designed by the Secure Data Network System project of
the National Security Agency (NSA), IPsec AH is derived in part from
previous IETF standards work for authentication of the Simple Network
Management Protocol (SNMP).
IPsec is officially specified by the Internet Engineering Task Force (IETF)
in a series of Request for Comments documents addressing various
components and extensions. It specifies the spelling of the protocol name to
be IPsec
240

Kerberos (protocol)
Kerberos is a computer network authentication protocol which works on
the basis of "tickets" to allow nodes communicating over a non-secure
network to prove their identity to one another in a secure manner. Its
designers aimed primarily at a client–server model, and it provides mutual
authentication—both the user and the server verify each other's identity.
Kerberos protocol messages are protected against eavesdropping and replay
attacks. Kerberos builds on symmetric key cryptography and requires
a trusted third party, and optionally may use public-key cryptography by
utilizing asymmetric key cryptography during certain phases of
authentication. Kerberos uses port 88 by default.
"Kerberos" also refers to a suite of free software published
by Massachusetts Institute of Technology (MIT) that implements the
Kerberos protocol.
241

Point-to-point protocol
In networking, the Point-to-Point Protocol (PPP) is a data
link protocol commonly used in establishing a direct connection between
two networking nodes. It can provide connection authentication,
transmission encryption (using ECP, RFC 1968), and compression.
PPP is used over many types of physical networks including serial
cable, phone line, trunk line, cellular telephone, specialized radio links, and
fiber optic links such as SONET. PPP is also used over Internet
access connections (now marketed as "broadband"). Internet service
providers (ISPs) have used PPP for customer dial-up access to the Internet,
since IP packets cannot be transmitted over a modem line on their own,
without some data link protocol. Two encapsulated forms of PPP, Point-toPoint Protocol over Ethernet (PPPoE) and Point-to-Point Protocol over
ATM (PPPoA), are used most commonly by Internet Service Providers
(ISPs) to establish a Digital Subscriber Line (DSL) Internet service
connection with customers.
242

PPP is commonly used as a data link layer protocol for connection
over synchronous and asynchronous circuits, where it has largely
superseded the older Serial Line Internet Protocol (SLIP) and telephone
company mandated standards (such as Link Access Protocol,
Balanced (LAPB) in the X.25 protocol suite). PPP was designed to work
with numerous network layer protocols, including Internet
Protocol (IP), TRILL, Novell's Internetwork Packet
Exchange (IPX), NBF and AppleTalk.

243

Transport Layer Security

Transport Layer Security (TLS) and its predecessor, Secure Sockets
Layer (SSL), are cryptographic protocols that provide
communication security over the Internet. TLS and SSL encrypt the
segments of network connections at the Application Layer for the Transport
Layer, using asymmetric cryptography for key exchange, symmetric
encryption for privacy, and message authentication codes for message
integrity.
Several versions of the protocols are in widespread use in applications such
as web browsing, electronic mail, Internet faxing, instant
messaging and voice-over-IP (VoIP).
TLS is an IETF standards track protocol, last updated in RFC 5246, and is
based on the earlier SSL specifications developed by
Netscape Communications.
244

Wireless Technology
Wireless telecommunications is the transfer of information between two or
more points that are not physically connected. Distances can be short, such
as a few meters for television remote control, or as far as thousands or even
millions of kilometers for deep-space radio communications. It encompasses
various types of fixed, mobile, and portable two-way radios, cellular
telephones, personal digital assistants (PDAs), and wireless networking.
Other examples of wireless technology include GPS units, Garage door
openers or garage doors, wireless computer mice, keyboards and Headset
(audio), headphones, radio receivers,satellite television, broadcast
television and cordless telephones.

245

Infrared
Infrared (IR) light is electromagnetic radiation with
longer wavelengths than those of visible light, extending from the
nominal red edge of the visible spectrum at 0.74 micrometers (µm) to
300 µm. This range of wavelengths corresponds to a frequency range of
approximately 1 to 400 THz, and includes most of the thermal
radiation emitted by objects near room temperature. Infrared light is emitted
or absorbed by molecules when they change their rotationalvibrational movements.
Much of the energy from the Sun arrives on Earth in the form of infrared
radiation. Sunlight at zenith provides an irradiance of just over
1 kilowatt per square meter at sea level. Of this energy, 527 watts is infrared
radiation, 445 watts is visible light, and 32 watts is ultraviolet radiation. The
balance between absorbed and emitted infrared radiation has a critical effect
on the Earth's climate.
246

Infrared light is used in industrial, scientific, and medical applications.
Night-vision devices using infrared illumination allow people or animals to
be observed without the observer being detected. In astronomy, imaging at
infrared wavelengths allows observation of objects obscured by interstellar
dust. Infrared imaging cameras are used to detect heat loss in insulated
systems, observe changing blood flow in the skin, and overheating of
electrical apparatus.

247

Light Comparison[3]
Name

Wavelength

Frequency (Hz)

Photon Energy (eV)

Gamma ray

less than 0.01 nm

more than 10 EHZ

100 keV - 300+ GeV

X-Ray

0.01 nm to 10 nm

30 EHz - 30 PHZ

120 eV to 120 keV

Ultraviolet

10 nm - 390 nm

30 PHZ - 790 THz

3 eV to 124 eV

Visible

390 - 750 nm

790 THz - 405 THz

1.7 eV - 3.3 eV

Infrared

750 nm - 1 mm

405 THz - 300 GHz

1.24 meV - 1.7 eV

Microwave

1 mm - 1 meter

300 GHz - 300 MHz

1.24 µeV - 1.24 meV

Radio

1 mm - 100,000 km

300 GHz - 3 Hz

12.4 feV - 1.24 meV

248

Bluetooth








What is the Bluetooth?
Radio modules operate in 2.45GHz. RF channels:2420+k MHz
Devices within 10m of each other can share up to 1Mbps
Projected cost for a Bluetooth chip is ~$5.
Its low power consumption
Can operate on both circuit and packet switching modes
Providing both synchronous and asynchronous data services
Bluetooth

IEEE 802.11A

UWB

frequency

2.4Ghz

5GHz

3.1~10.6GHz

MAX data rate

1Mbps

54Mbps

100Mbps~1Gbps

Range

5~10m

35~50m

10~30m

The number of channel

79

12

…..
249

Bluetooth versions
 Bluetooth 1.0 and 1.0B
 Versions 1.0 and 1.0B had many problems
• Manufacturers had difficulty making their products interoperable
 Bluetooth 1.1
 Many errors found in the 1.0B specifications were fixed
 Added support for non-encrypted channels
 Received Signal Strength Indicator (RSSI)
 Bluetooth 1.2
 Faster Connection and Discovery
 Use the Adaptive frequency-hopping spread spectrum (AFH)
• Improves resistance to radio frequency interference
 Higher transmission speeds in practice, up to 721 kbps
250

Bluetooth 2.0
This version, specified November 2004
The main enhancement is the introduction of an enhanced data
rate (EDR) of 3.0 Mbps.
Lower power consumption through a reduced duty cycle.
Simplification of multi-link scenarios due to more available
bandwidth.

Bluetooth 2.1
A draft version of the Bluetooth Core Specification Version 2.1 +
EDR is now available

251

Ultra Wide Band(UWB)

 What is the UWB?
 Transmitting information spread over a large bandwidth (>500 MHz)
 Provide an efficient use of scarce radio bandwidth
• High data rate in WPAN connectivity and longer-range
 A February 14, 2002
• Report and Order by the FCC authorizes the unlicensed use of
UWB
 November of 2005
• ITU-R have resulted in a Report and Recommendation on UWB
 Expected to act on national regulations for UWB very soon

252

Advantage of the UWB

Take advantage of inverse relationship between distance and
throughput
Huge bandwidth : very high throughput
Low power consumption
Convenience and flexibility
No interference

253

Ultra Wide Band(UWB)
Current wireless Comparison
Wireless
technology

Power mW

Rage meter

BW/channel

Rate bps

CDMA
1xEVDO

600

~2000

1.25 MHz

2.4M

802.16(WiMAX
)

250

~4000

25MHz

120M

802.11g(WiFi)

50

~100

25MHz

54M

Bluetooth

1

~10

1MHz

<1M

UWB

<30

10~30

500MHz

100M~1G








Key application
Wireless USB
Toys and game
Consumer electronics
Location tracking
Handset

254

Factors Affecting Wireless Signals
Because wireless signals travel through the atmosphere, they are
susceptible to different types of interference than standard wired networks.
Interference Types
The following are some factors that cause interference:
Physical objects: Trees, masonry, buildings, and other physical structures
are some of the most common sources of interference. The density of the
materials used in a building’s construction determines the number of walls
the RF signal can pass through and still maintain adequate coverage.
Concrete and steel walls are particularly difficult for a signal to pass
through. These structures will weaken or at times completely prevent
wireless signals.

255

Radio frequency interference: Wireless technologies such as 802.11b/g
use an RF range of 2.4GHz, and so do many other devices, such as cordless
phones, microwaves, and so on. Devices that share the channel can cause
noise and weaken the signals.
Electrical interference: Electrical interference comes from devices such as
computers, refrigerators, fans, lighting fixtures, or any other motorized
devices. The impact that electrical interference has on the signal depends on
the proximity of the electrical device to the wireless access point. Advances
in wireless technologies and in electrical devices have reduced the impact
that these types of devices have on wireless transmissions.
Environmental factors: Weather conditions can have a huge impact on
wireless signal integrity. Lightning, for example, can cause electrical
interference, and fog can weaken signals as they pass through.
256

How to Install a Wireless Router to Share DSL Internet
It makes no difference to a router whether
your Internet arrives through DSL or cable;
it will work just the same. By installing a
wireless router, you can easily share your
Internet connection among multiple
computers and enjoy connectivity without
the constraints of cables or wires.

257

Step 1
Attach the incoming DSL cable to the "Input," "Cable" or "DSL" port on
your DSL modem.
Step 2
Plug one end of an Ethernet cable into the Ethernet port on your DSL
modem and plug the other end of the cable into the "Internet," "WLAN" or
"WAN" port on your wireless router.
Step 3
Plug one end of the Ethernet cable supplied with your wireless router into
one of the output ports on the router. Plug the other end of the cable into the
Ethernet port on your computer.
Step 4
Connect your DSL modem and router to a power source.

258

Step 5
Open a browser and type the router's IP address, which likely will be either
"http://192.168.0.1" or "http://192.168.1.1." Enter the username, which is
frequently "admin." Enter the password, which may be set to "admin",
"password" or blank as the default. Set up the router according to the
instructions provided with the router. The product documentation will also
provide the IP address and username/password. During setup, the most
important things you should do are change the SSID network name,
configure encryption and change the router password.
Step 6
Disconnect the Ethernet cable from your computer, if you prefer to connect
wirelessly.
Step 7
Click the wireless icon, located by the system clock on your Windows 7 PC.
Click the router name that corresponds to the SSID you entered during
setup. Click "Connect" and enter the password to connect to the router.
Repeat for each computer requiring access.
259

Configuring a Wireless Access Point
When you access the configuration page of your wireless access point on
the Internet, you have the following configuration options that are related to
the wireless access point functions of the device. Although these options are
specific to this particular device, most access points have similar
configuration options.
Enable/Disable: Enables or disables the device's wireless access point
functions.
SSID: The Service Set Identifier used to identify the network. Most access
points have well-known defaults. You can talk yourself into thinking that
your network is more secure by changing the SSID from the default to
something more obscure, but in reality, that only protects you from firstgrade hackers. By the time most hackers get into the second grade, they
learn that even the most obscure SSID is easy to get around.
260

Allow broadcast SSID to associate? Disables the access point's periodic
broadcast of the SSID. Normally, the access point regularly broadcasts its
SSID so that wireless devices that come within range can detect the network
and join in. For a more secure network, you can disable this function. Then,
a wireless client must already know the network's SSID in order to join the
network.
Channel: Lets you select one of 11 channels on which to broadcast. All the
access points and computers in the wireless network should use the same
channel. If you find that your network is frequently losing connections, try
switching to another channel. You may be experiencing interference from a
cordless phone or other wireless device operating on the same channel.
WEP — Mandatory or Disable: Lets you use a security protocol
called wired equivalent privacy.

261

Troubleshooting Wireless Network
Connections
Check the wires and wireless network adapter
Checking that all your wires are plugged in at the router and from the plug
is one of the first things you should do – provided of course that you have
access to them. Verify that the power cord is connected and that all the
lights of the router and cable/DSL modem are on. This may seem like a
ridiculous suggestion but you should never disregard the obvious. You’d be
surprised at how your configuration can be perfect, and after a while of
playing around with settings you realize that the network cable leading from
the router to the cable modem has come undone slightly.

262

Driver Compatibility
It is important to make sure that you have installed the correct device driver
for your wireless network adapter. This can cause all sorts of problems or
your adapter not to function at all. A friend of mine recently set up his own
wireless network at home but complained to me that his wireless network
connection was going “crazy”. Upon inspection I realized that he had
configured his router properly but installed the 5v instead of the 3v driver
on his laptop PCMCIA network card. Once the correct driver was installed,
everything began to run smoothly. It just goes to show how even the
smallest detail can make all the difference so make sure you have the correct
driver installed!

263

Low Signal Strength
There are a number of factors that can cause the signal of your access point
to deteriorate and the performance of your network to fall under par.
Practically any appliance that operates on the same frequency level (2.4
GHz) as 802.11b or 802.11g can cause interference with your wireless
network. Be sure to keep cordless phones, microwaves and other electrical
equipment at least 1m away from the access point. Try changing channels
on the access point and test it out on one of the clients. To change the radio
channel on the access point login to the configuration (usually a web based
interface) and go to the Wireless Settings (will vary depending on vendor)
section, select a different channel and save settings. On the client, go to
Device Manager, right click your wireless network adapter and go to
Properties.

264

In the advanced tab select the Channel Property and change the Value to
the same number as the one you chose on the Access Point. Disable and
then re-enable the wireless connection.

265

Access Point Location
You may also want to try changing the position of your access point antenna
to improve performance. Play around with its position and see if you notice
a difference. I find that if I point the antenna sideways or downwards I have
better reception on the floor below. The following images demonstrate what
I mean.
Antenna pointing upwards (default)
Antenna pointing sideways

266

Access Point Location
The location of your access point is vital. Try and place it in a central
location, as much as possible avoiding physical obstructions and reflective
surfaces. Remember that wireless signals bounce of windows and mirrors,
thus decreasing the range. Experiment with different locations until you find
one that is practical and promising. Most people, including myself, like
placing it near the ceiling since most obstructions are nearer to the floor.
It’s always a good idea to monitor the performance of your signal by using a
diagnostic utility. This will help you to identify how strong your signal is in
different locations and whether other electrical equipment is interfering.
Run the utility when the microwave or cordless phone is in use and see if
you notice a difference. Usually your access point will come with its own
monitoring utility.

267


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

268


269

SKILLS FOR INDIA

Proxy Server

Proxy Server
In computer networks, a proxy server is a server (a computer system or an
application) that acts as an intermediary for requests from clients seeking
resources from other servers. A client connects to the proxy server,
requesting some service, such as a file, connection, web page, or other
resource available from a different server. The proxy server evaluates the
request as a way to simplify and control their complexity. Today, most
proxies are web proxies, facilitating access to content on the World Wide
Web.

271

Utility of a Proxy server
To keep machines behind it anonymous, mainly for security
To speed up access to resources (using caching). Web proxies are
commonly used to cache web pages from a web server
To apply access policy to network services or content, e.g. to block
undesired sites
To access sites prohibited or filtered by your ISP or institution
To log / audit usage, i.e. to provide company employee Internet usage
reporting
To bypass security / parental controls
To circumvent Internet filtering to access content otherwise blocked by
government
To scan transmitted content for malware before delivery
To scan outbound content, e.g., for data loss prevention
To allow a web site to make web requests to externally hosted resources
(e.g. images, music files, etc.) when cross-domain restrictions prohibit the
272
web site from linking directly to the outside domains

Types of proxy

Forward proxies
Open proxies
Reverse proxies

273

Forward proxies
Forward proxies are proxies where the client server names the target server
to connect to. Forward proxies are able to retrieve from a wide range of
sources (in most cases anywhere on the Internet).
The terms "forward proxy" and "forwarding proxy" are a general description
of behavior (forwarding traffic) and thus ambiguous. Except for Reverse
proxy, the types of proxies described in this article are more specialized subtypes of the general forward proxy concept.

274

Open proxies
An open proxy is a forwarding proxy server that is accessible by any
Internet user. Gordon Lyon estimates there are "hundreds of thousands" of
open proxies on the Internet. An anonymous open proxy allows users to
conceal their IP address while browsing the Web or using other Internet
services. There are varying degrees of anonymity however, as well as a
number of methods of 'tricking' the client into revealing itself regardless of
the proxy being used.

275

Reverse proxies
A reverse proxy (or surrogate) is a proxy server that appears to clients to be
an ordinary server. Requests are forwarded to one or more origin servers
which handle the request. The response is returned as if it came directly from
the proxy server.
Reverse proxies are installed in the neighborhood of one or more web
servers. All traffic coming from the Internet and with a destination of one of
the neighborhood's web servers goes through the proxy server. The use of
"reverse" originates in its counterpart "forward proxy" since the reverse
proxy sits closer to the web server and serves only a restricted set of
websites.

276

Issues with Proxy Server
The diversion / interception of a TCP connection creates several issues.
Firstly the original destination IP and port must somehow be communicated
to the proxy. This is not always possible (e.g. where the gateway and proxy
reside on different hosts). There is a class of cross site attacks that depend
on certain behavior of intercepting proxies that do not check or have access
to information about the original (intercepted) destination. This problem can
be resolved by using an integrated packet-level and application level
appliance or software which is then able to communicate this information
between the packet handler and the proxy.
Intercepting also creates problems for HTTP authentication, especially
connection-oriented authentication such as NTLM, since the client browser
believes it is talking to a server rather than a proxy. This can cause problems
where an intercepting proxy requires authentication, then the user connects
to a site which also requires authentication.
277

Issues with Proxy Server
Finally intercepting connections can cause problems for HTTP caches, since
some requests and responses become un cacheable by a shared cache.
Therefore intercepting connections is generally discouraged. However due
to the simplicity of deploying such systems, they are in widespread use.

278


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

279


280

A virtual local area network, virtual LAN or VLAN, is a group of hosts
with a common set of requirements, which communicate as if they were
attached to the same broadcast domain, regardless of their physical location.
A VLAN has the same attributes as a physical local area network (LAN),
but it allows for end stations to be grouped together even if not on the
same network switch. VLAN membership can be configured through
software instead of physically relocating devices or connections.
To physically replicate the functions of a VLAN would require a separate,
parallel collection of network cables and equipment separate from the
primary network. However, unlike a physically separate network, VLANs
must share bandwidth; two separate one-gigabit VLANs that share a single
one-gigabit interconnection can suffer reduced throughput and congestion.
It virtualizes VLAN behaviors (configuring switch ports, tagging frames
when entering VLAN, lookup MAC table to switch/flood frames to trunk
links, and un tagging when exit from VLAN.)
282

Types Of VLANs
Today there is essentially one way of implementing VLANs - port-based
VLANs. A port-based VLAN is associated with a port called an access
VLAN.
However in the network there are a number of terms for VLANs. Some
terms define the type of network traffic they carry and others define a
specific function a VLAN performs. The following describes common
VLAN terminology:
Data VLAN
Default VLAN
Native VLAN
Management VLAN
Voice VLANs
283

Utility of VPN
VLANs are created to provide the segmentation services traditionally
provided by routers in LAN configurations. VLANs address issues such as
scalability, security, and network management. Routers in VLAN topologies
provide broadcast filtering, security, address summarization, and traffic flow
management. By definition, switches may not bridge IP traffic between
VLANs as it would violate the integrity of the VLAN broadcast domain.
This is also useful if someone wants to create multiple layer 3 networks on
the same layer 2 switch. For example, if a DHCP server is plugged into a
switch it will serve any host on that switch that is configured to get its IP
from a DHCP server. By using VLANs you can easily split the network up
so some hosts won't use that DHCP server and will obtain link-local
addresses, or obtain an address from a different DHCP server.

284

Advantages of VLAN
The main advantages of VLAN are listed below.
Broadcast Control: Broadcasts are required for the normal function of a
network. Many protocols and applications depend on broadcast
communication to function properly. A layer 2switched network is in a
single broadcast domain and the broadcasts can reach the network
segments which are so far where a particular broadcast has no scope and
consume available network bandwidth. A layer 3 device (typically a router)
is used to segment a broadcast domain.
If we segment a large LAN to smaller VLANs we can reduce
broadcast traffic as each broadcast will be sent on to the relevant VLAN
only

285

Security: VLANs provide enhanced network security. In a VLAN
network environment, with multiple broadcast domains, network
administrators have control over each port and user. A malicious user can no
longer just plug their workstation into any switch port and sniff the
network traffic using a packet sniffer. The network administrator controls
each port and whatever resources it is allowed to use.
VLANs help to restrict sensitive traffic originating from an enterprise
department within itself.
Cost: Segmenting a large VLAN to smaller VLANs is cheaper than
creating a routed network with routers because normally routers costlier
than switches
Physical Layer Transparency: VLANs are transparent on the physical
topology and medium over which the network is connected
286

VLAN provides Virtual Segmentation of Broadcast Domain in the network.
The devices, which are member of same Vlan, are able to communicate with
each other. The devices of different Vlan may communicate with each other
with routing. So that different Vlan devices will use different n/w addresses.
Vlan provides following advantages: (1) Logical Segmentation of network
(2) Enhance network security
Creating port based Vlan
In port based Vlan, first we have to create a Vlan on manageable switch
then we have to add ports to the Vlan.

287

Commands to create Vlan
Switch#config ter
Switch(config)#vlan <no>
[name <word>]
Switch(config)#exit

optional

Or
Switch#vlan database
Switch(vlan)#vlan <no>
[name <word>]
Switch(vlan)#exit

288

Commands to configure ports for a Vlan
By default, all ports are member of single vlan that is Vlan1. we can
change vlan membership according to our requirement.
Switch#conf ter
Switch(config)#interface <type> <no>
Switch(config-if)#switchport access vlan <no>
Switch(config-if)#exit
Commands to configure multiple ports in a vlan
Switch#conf ter
Switch(config)#interface range <type> <slot/port no (space)–(space)
port no>
Switch(config-if)#switchport access vlan <no>
289

Example: - Suppose we want to add interface fast Ethernet 0/10 to 0/18 in
vlan5
Switch#config ter
Switch(config)#interface range fastethernet 0/10 – 18
Switch(config-if)#switchport access vlan 5
Switchconfig-if#exit
In 1900 & Compatible switches
Switch#config ter
Switch(config-if)#vlan-membership static <vlan no>
To Disable web access in switch
Switch#config ter
Switch(config)#no ip http server
To display mac address table
Switch#sh mac-address-table
Vlan
Mac address
type
ports
20
00-08-a16-ab-6a-7b
dynamic fa0/7
290

Trunking
To Display Vlan and port membership
Switch#sh vlan
When there are multiple switches then we have to use trunk links to
connect one switch with other. If we are not using trunk links then we
have to connect one cable from each vlan to the corresponding vlan
of the other switch.
Switches will perform trunking with the help of frame tagging. The
trunk port will send data frames by adding a Vlan id information to
the frame, at the receiving end vlan id information is removing from
the end and according to the tag data is delivered to the
corresponding vlan. There are two protocols to perform frame
tagging.
(1) Inter switch link (cisco prop)
(2) IEEE 802.1 q
291

Configuring Trunking
In cisco switches all switch ports may be configured in three
modes
(1) Trunk desirable (default)
(2) Trunk on
(3) Trunk off
Switch#conf ter
Switch(config-if)#switchport mode <trunk|access|auto>
on
off
desirable

292

To configure Vlans allowed on Trunk
By default all Vlans are allowed on Trunk port. We can add/remove
a partucular Vlan from trunk port with following command
Switch#config ter
Switch(config-if)#switchport trunk allowed vlan all
Remove <vlan>
Add <vlan>
Except <vlan>
To display trunk interfaces
Switch#sh interface trunk
Switch#sh interface <type> <no> trunk

293

VLAN Trunking Protocol
On Cisco Devices, VTP (VLAN Trunking Protocol) maintains VLAN
configuration consistency across the entire network. VTP uses Layer 2 trunk
frames to manage the addition, deletion, and renaming of VLANs on a
network-wide basis from a centralized switch in the VTP server mode. VTP
is responsible for synchronizing VLAN information within a VTP domain
and reduces the need to configure the same VLAN information on each
switch.
VTP minimizes the possible configuration inconsistencies that arise when
changes are made. These inconsistencies can result in security violations,
because VLANs can cross connect when duplicate names are used. They
also could become internally disconnected when they are mapped from one
LAN type to another, for example, Ethernet to ATM LANE ELANs or FDDI
802.10 VLANs. VTP provides a mapping scheme that enables seamless
trunking within a network employing mixed-media technologies.
294

With the help of VTP, we can simplify the process of creating Vlan.
In multiple switches, we can configure one switch as VTP server and
all other switches will be configured as VTP client. We will create
Vlans on VTP server switch. The server will send periodic updates
to VTP client switches. The clients will create Vlans from the update
received from the VTP server.
VTP server
VTP server is a switch in which we can create, delete or modify
Vlans. The server will send periodic updates for VTP clients.
VTP client
On VTP client, we are not able to create, modify or delete Vlans.
The client will receive and forward vtp updates. The client will
create same Vlans as defined in vtp update.
295

Transparent is a switch, which will receive and forward VTP
update. It is able to create, delete and modify Vlans locally. A
transparent will not send its own VTP updates and will not learn
any information from received vtp update.
Commands
Switch#conf ter
Switch(config)#vtp domain <name>
Switch(config)#vtp password <word>
Switch(config)#vtp mode <server|client|transparent>
Switch(config)#exit
By default in cisco switches the VTP mode is set as VTP server
with no domain and no password.
To display VTP status
Switch#sh vtp status
296

Inter Vlan Communication
After creating Vlans, each Vlan has own broadcast domain. If we
want communication from one Vlan to another Vlan then we need to
perform routing. There are three methods for inter vlan
communication.
(1) Inter Vlan using multi-interface router
(2) Inter Vlan using router on a stick method
(3) Inter Vlan using layer 3 switch
1751, 2621 routers supports Vlan
(1) Inter Vlan using multi-interface router
In this case, we have to connect one interface of router in each Vlan.
This interface will act as gateway for the corresponding vlan. Each
Vlan has to use different n/w addresses. Data from one Vlan to
another Vlan will travel by router.

297

Inter Vlan Communication
(2) Inter Vlan using router on a stick method
In this method a special router is used for Inter Vlan. In this router, we
can create one interface for each Vlan. The physical interface of router
will be connected on trunk port switch. This router will route traffic
on the same interface by swapping vlan id information with the help
of frame tagging protocol.

298

Configuration on Router
Router#config ter
Router(config)#interface fastethernet 0/0
Router(config-if)#no ip address
Router(config-if)#no sh
Router(config)#interface fastethernet 0/0.1
Router(config-if)#encapsulation dot1q 1
Router(config-if)#ip address 10.0.0.1 255.0.0.0

299

Configuration on Router

300

Configuration on Core switch
(1) Configure switch as VTP server
(2) Create Vlans
(3) Configure interface connected to router as Trunk
(4) Configure interfaces connected to other switches as trunk (if
required)
Configuration on Distribution layer switches
(1) Configure switch as VTP client
(2) Configure required interface as Trunk (optional)
(3) Add ports to Vlan
Configuration on Pc
Configure IP and Gateway

301

VTP provides the following benefits:
VLAN configuration consistency across the network
Mapping scheme that allows a VLAN to be trunked over mixed media
Accurate tracking and monitoring of VLANs
Dynamic reporting of added VLANs across the network
Plug-and-play configuration when adding new VLANs

302

As beneficial as VTP can be, it does have disadvantages that are normally
related to the spanning tree protocol (STP) as a bridging loop propagating
throughout the network can occur. Cisco switches run an instance of STP for
each VLAN, and since VTP propagates VLANs across the campus LAN,
VTP effectively creates more opportunities for a bridging loop to occur.
Before creating VLANs on the switch that will propagate via VTP, a VTP
domain must first be set up. A VTP domain for a network is a set of all
contiguously trunked switches with the same VTP domain name. All
switches in the same management domain share their VLAN information
with each other, and a switch can participate in only one VTP management
domain. Switches in different domains do not share VTP information.
Using VTP, each Catalyst Family Switch advertises the following on its
trunk ports:
Management domain
Configuration revision number
Known VLANs and their specific parameters
303


S.No

Description

Author

Version

Date

1
2
3
4
5
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305

SKILLS FOR INDIA

Network Storage

A network storage system maintains copies of digital data across highspeed local area network (LAN) connections. It is designed to back up files,
databases and other data to a central location that can easily accessed via
standard network protocols and tools.
Importance of Network Storage
Storage is an essential aspect of any computer. Hard drives and USB keys,
for example, are designed to hold the data generated by individuals on their
PCs, but when these types of local storage fail, the data is lost. Additionally,
the process of sharing local data with other computers can be timeconsuming, and sometimes the amount of local storage available is
insufficient to store everything desired. Network storage addresses these
problems by providing a reliable, external data repository for all computers
on the LAN to share efficiently. Besides freeing up local storage space,
network storage systems also typically support automated backup programs
to prevent critical data loss.
307

Evolution in Storage Architecture

308

Network-attached storage
Network-accessed storage (NAS) is file-level computer data
storage connected to a computer network providing data access
to heterogeneous clients. NAS not only operates as a file server, but is
specialized for this task either by its hardware, software, or configuration of
those elements. NAS is often made as a computer appliance – a specialized
computer built from the ground up for storing and serving files – rather than
simply a general purpose computer being used for the role.
As of 2010 NAS devices are gaining popularity, as a convenient method of
sharing files among multiple computers. Potential benefits of networkattached storage, compared to file servers, include faster data access, easier
administration, and simple configuration.
NAS systems are networked appliances which contain one or more hard
drives, often arranged into logical, redundant storage containers
or RAID arrays. Network-attached storage removes the responsibility of file
serving from other servers on the network. They typically provide access to
files using network file sharing protocols such as NFS,SMB/CIFS, or AFP.
309

Network-Attached Storage(NAS)

310

NAS

 Scalability: good
 Availability: as long as the LAN and NAS device work,
generally good
 Performance: limited by speed of LAN, traffic conflicts,
inefficient protocol
 Management: OK
 Connection: homogeneous vs. heterogeneous

311

What is SAN about






Data is Asset
How to Store Data
How to Access Data
How to Manage Data Storage

312

Storage Area Network (SAN)

313

Storage Area Network (SAN)

 SAN is created by using
the Fibre Channel to link
peripheral devices such as
disk storage and tape
libraries

314

SAN vs. NAS






Dedicated Fibre Channel Network for Storage
More efficient protocol
==> higher availability
==> reduce traffic conflict
==> longer distance (up to 10 km)

315

Fibre Channel

 Provides high-performance, any-to-any interconnection
 Server to server
 Server to storage
 Storage to storage
 Combines the characteristics of networks (large address space,
scalability) and I/O channels (high speed, low latency, hardware error
detection) together

316

Benefits of SAN

 Scalability ==> Fibre Channel networks allow the number of attached
nodes to increase without loss of performance because as switches are
added, switching capacity grows. The limitations on the number of
attached devices typical of channel interconnection disappears
 High Performance ==> Fibre Channel fabrics provide a switched
100Mbytes/second full duplex interconnect
 Storage Management ==> SAN-attached storage allows the entire
investment in storage to be managed in a uniform way

317

Easy Migration to SAN

 Host Bus Adapters (HBAs) -- connect servers to the SAN
 Fibre Channel storage -- connects directly to the SAN
 SCSI-FC bridge -- allows SCSI (disk and tape) components to be
attached to the SAN
 SAN Network Components -- Fibre Channel switches

318


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
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319


320

SKILLS FOR INDIA

Network Operating System

Operating System






Program that manages the computer hardware
Provides a basis for application programs and acts as an
Intermediary between the user and the hardware
Offers a reasonable way to solve the problem of creating a usable
computing system

Types of Operating Systems: Windows Vista
Linux and Unix
Microsoft Windows
Mac OS X

322

User 1

Compiler

User 2

User 3

Assembler

Text editor

System and Application Programs

User n

Databases
System

Operating System
Computer Hardware
Figure: Abstract view of the components of a computer system

323

Network Operating System
 Provides an environment in which users, who are aware of multiplicity
of machines, can access remote resources either:
 Logging in to the remote machine* or
 Transferring data from the remote machine to their own
machines
 Mostly used with local area networks and wide area networks

*Remote machine: refers to a computer connected to the network which a
user is using

324

Features
 Provides basic operating system features; support for processors,
protocols, automatic hardware detection, support multi-processing of
applications
 Security features; authentication, authorization, access control
 Provides names and directory services
 Provides files, print, web services, back-up and replication services

325

 Supports Internetworking such as routing and WAN ports
 User management and support for login and logoff, remote access,
system management
 Clustering capabilities, fault tolerant and and high availability systems

Cluster: = group of linked computers working together closely, connected
to LAN

326

Remote Login with an example
 Important function of a NOS is to allow users to log in remotely
 Internet provides the telnet facility for this purpose
 Example: A user at westminster college wishes to compute
on “cs.Yale.Edu,“ a computer that is located at yale
University
 User must have a valid account on that machine
to log in remotely the user issues the command:
telnet cs.yale.edu

Command results in the formation of a socket connection between
the local machine at
Westminster College and the “cs.yale.edu“ computer
327

 Connection has been established
 Transparent, bidirectional link that all characters entered by the user
are sent to a process “cs.yale.edu“
 All the output from that process is sent back to the user

328

Remote File Transfer

 Provide a mechanism for remote file transfer from one machine to
another
 Each computer maintains its own local file system
 User: “cs.uvm.edu“ wants to access a file located on another computer
“cs.yale.edu“ file must be copied from the computer at Yale to the PC
at Uni of Vermont
 Internet provides the transfer with file transfer protocol (FTP) program

329

Example:

 User on “cs.uvm.edu“ -> copy Java program Server.java that resides
on “cs.yale.edu“
 Invoke FTP program ftp cs.yale.edu
 Login name and password
 Correct information has been received, user must connect to the file
Server.java and after copy the file by executing get Server.java

330

 File location is not transparent to the user
 No real file sharing
 Remember: User at the Uni of Vermont must have login permission on
“cs.yale.edu“
 FTP provides a way to allow a user to copy files remotely
 Remote copying is accomplished through “anonymous FTP“ method

331

Anonymous FTP Method
 File to be copied (Server.java) must be placed in a subdirectory (ftp)
with the protection set to allow the public to read the file
 User uses ftp command
 Login name – “anonymous“ and password
 Anonymous login is accomplished
 User is allowed to access only those files that are in the directory tree
of user “anonymous“

332

www.trainsignaltraining.com/.../ftp_iis7_10.png
333

 FTP mechanism is implemented (similar to telnet implementation)
 Daemon on remote site -> watches for connection requests to system‘s
FTP port
 Login authentication is accomplished ->user can execute commands
remotely
 Telnet daemon executes any command for user
 FTP daemon responds to a predefined set of file-related commands

334






Get: transfer a file from the remote machine to the local machine
Put: transfer from the local machine to the remote machine
Ls or dir: list files in the current directory on the remote machine
Cd: change the current directory on the remote machine

335

Network and Operating System Security







OS: system must protect itself
Runway process could constitute an accidental denial-of-service attack
Query to service could reveal passwords
Stack overflow could allow the launching of an unauthorized process
List of possible breaches is almost endless

336

 Travels over private leased lines, shared lines like the internet,
wireless connections, or dial-up lines
 Intercepting these data could be harmful as breaking into a computer
 Interruption of communications could constitute a remote denial-ofservice attack
 Diminishing user‘s use of and trust in
the system

337

Novell NetWare










Is a NOS
Used cooperative multitasking to run several services on a PC
File sharing instead of disk sharing
NDS (Novell Directory Services)
Server administration
Desktop Management
Software distribution
Integrated cache
Enhanced security

338

Novell NetWare Protocols
 Are widely used for PC LANs
 Windows XP Nwlink protocol connects the NetBIOs to NetWare
networks
 In combination with a redirector this protocol enables a Windows XP
client to connect to a NetWare server
 Some NOSs for DOS and Windows system include Novell NetWare:
Windows NT and 2000 OS/2 etc.

339

Linux
 Free OS based on Unix standards
 Provides a programming interface and user interface
 Core Linux OS kernel is original, but allows much existing free Unix
software to run
 Multiuser system, providing protection between processes and running
multiple processes according to a time-sharing (or multitasking)
scheduler
 Multiple networking protocols can be accessed simultaneously
through socket interface

341

SKILLS FOR INDIA

Installation of the Network Operating
Systems

Windows XP Installation

Assuming system is able to boot from a CD-ROM
Inserting Windows XP installation CD-ROM and poweron/restart your system

344

When you get the message to
"press any key to boot from CD...", press any key.

Once the boot from CD-ROM has started, it will display at the top of the
screen :

346

Setup will configure then your screen resolution.

The system will try to connect via the Internet to the Microsoft website, you can select to "Skip" that step.
You will be prompted to enter the first Usernames (which will be defined as Administrators)

and you will get the new XP Welcome screen :

366

Step By Step Windows Server 2003 Installation
Guide

368

Windows Server 2003 operating systems take the best of Windows 2000
Server technology and make it easier to deploy, manage, and use. The
result: a highly productive infrastructure that helps make your network a
strategic asset for your organization .
Windows Server 2003 SP2 provides enhanced security, increased
reliability, and a simplified administration to help enterprise customers
across all industries.

369

Microsoft Windows Server 2003 R2 Standard Edition Requirements
Computer and processor
PC with a 133-MHz processor required; 550-MHz or faster processor
recommended; support for up to four processors on one server
Memory
128 MB of RAM required; 256 MB or more recommended; 4 GB maximum
Hard disk
1.2 GB for network install; 2.9 GB for CD install
Drive
CD-ROM or DVD-ROM drive
Display
VGA or hardware that supports console redirection required; Super VGA
supporting 800 x 600 or higher-resolution monitor recommended
370











Check System Requirements
Check Hardware and Software Compatibility
Determine Disk Partitioning Options
Choose the Appropriate File System: FAT, FAT32, NTFS
Decide on a Workgroup or Domain Installation
Complete a Pre-Installation Checklist
After you made sure you can go on, start the installation process
Beginning the installation process
You can install Windows Server 2003 in several methods – all are valid
and good, it all depends upon your needs and your limitations
 In this tutorial we are installing directly from a CD by booting your
computer with the CD
 Start the computer from the CD
371


S.No

Description

Author

Version

Date

1
2
3
4
5
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8

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397

SKILLS FOR INDIA

Linux Installation

Installation Requirements

399

Linux installation requirements
 Minimum installation
 80386SX or better
 2 MB RAM
 Floppy disk drive
 40MB hard drive
 Video card
 Monitor

400

Linux installation requirements

 Realistic installation
 Text based
• 80386 or better
• 8 MB RAM
 GUI based
• 80486 or Pentium class
• 16 MB RAM

401

Linux recommended hardware
 Motherboards - ISA, EISA, PCI, VESA
 RAM – 2 MB will work, 16 is best
 Multi-user – 4 MB per user
 Hard disk – IDE, EIDE, ESDI, RLL, SCSI
 If using SCSI, only uses most common
 Video – Almost any
 Mouse – Any
 Tape – Any SCSI
 Removable media – Most SCSI
 Printer – Almost any parallel or serial port
 Modem – Most serial, if DOS can use it, Linux can too
 NIC – 3Com, Novell, HP, Intel
 Clones are NOT recommended!

402

RedHat Linux 6.2 Installation Notes
 Before installation
 Check hardware compatibility!!!
• www.redhat.com/support/hardware
 Make sure you have enough disk space
 Decide which installation method to use
 CD-ROM
 Hard Drive
 Ftp
 Http

403

 Decide how to start the installation
 Bootable CD-ROM
 Local media boot disk
 Included with Official RedHat Linux 6.2 set
 Network boot disk
 PCMCIA boot disk
• Used if CD-ROM drive is attached to PC
through PCMCIA card

404

A Note on Workstation Installations

 There are two types available, we will choose KDE for this
presentation
 GNOME
• www.gnome.org

 KDE
• www.kde.org

405

RedHat Installation





Insert RedHat CD into CD-ROM drive
After a short delay, a screen containing the boot: prompt should appear
Press ENTER to continue and install graphically
The next screen will ask you to determine which installation method
you would like to use

Note: All screenshots courtesy of redhat.com
406

 Choose the option for CD-ROM and select OK
 The installation program will probe your system and attempt to
identify your CD-ROM drive
 Using a common CD-ROM drive will prevent any problems
 The next screen will ask you to select a language – Choose English
and click Next

407

 Choose the keyboard that best fits your system – If no exact match,
choose the best GENERIC match and click Next

408

 Choose the mouse that best fits your system – If no exact match,
choose the best GENERIC match and click Next

409

 Read over the help text in the left and then click Next

410

 Choose to Install and select KDE Workstation and click Next

411

 For ease of installation, continue with Automatic Partitioning and click
Next
 Note: everything will be erased!

412

 Again, for ease of installation and use, leave defaults selected and
click Next

413

 Choose your Network device type, then enter your IP Address,
Netmask, Network, and Broadcast addresses and click Next
 Unsure? Ask your network administrator

414

 Choose your time zone by clicking on the map, ex. Pacific – Tijuana,
and click Next

415

 Set the ROOT PASSWORD - Write it down and keep it in a secure
place!
 You can add Users at this time too, then click Next

416

 Continue with the option detected for your system and click Next

417

 Choose the monitor that best fits your system - If none exist, choose
the best GENERIC monitor and click Next

418

 Continue with the video hardware detected for you unless you know it
is incorrect (change it) and click Next

You can test the Configuration if
you are not sure

Make sure USE GRAPHICAL
LOGIN is selected

419

 Almost done!!! Click Next
 If you would rather quit, this is your last chance! – You can
reboot and safely exit the installation now

Be sure
to read
the
Caution
Note!

420

 At this point, you can sit back and relax while RedHat is installed
 Depending on the speed of your system, the installation will take
from about 15 minutes to 1 hour

421

 Insert a blank, formatted disk into the floppy drive and click Next

422

 Congratulations!!!
 You can now click Exit to reboot your system and start to use
Linux

423


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

424


425

SKILLS FOR INDIA

Introduction to the DNS system

Purpose of Naming






Addresses are used to locate objects
Names are easier to remember than numbers
You would like to get to the address or other objects using a name
DNS provides a mapping from names to resources of several types

427

Names and addresses in general

 An address is how you get to an endpoint
 Typically, hierarchical (for scaling):
• 950 Charter Street, Redwood City CA, 94063
• 204.152.187.11, +1-650-381-6003
 A “name” is how an endpoint is referenced
 Typically, no structurally significant hierarchy
• “David”, “Tokyo”, “itu.int”

428

Naming History
 1970’s ARPANET
 Host.Txt maintained by the SRI-NIC
 Pulled from a single machine
 Problems
• Traffic and load
• Name collisions
• Consistency
 DNS related in 1983 by paul mock-apetris (rfcs 1034 and 1035),
modified, updated, and enhanced by a myriad of subsequent rfcs

429

DNS

 A lookup mechanism for translating objects into other objects
 A globally distributed, loosely coherent, scalable, reliable, dynamic
database
 Comprised of three components
• A “name space”
• Servers making that name space available
• Resolvers (clients) which query the servers about the name space

430

DNS Features: Global Distribution

 Data is maintained locally, but retrievable globally
 No single computer has all DNS data
 DNS lookups can be performed by any device
 Remote DNS data is locally catchable to improve performance

431

DNS Features: Loose Coherency

 The database is always internally consistent
 Each version of a subset of the database (a zone) has a serial number
• The serial number is incremented on each database change
 Changes to the master copy of the database are replicated according to
timing set by the zone administrator
 Cached data expires according to timeout set by zone administrator

432

DNS Features: Scalability
 No limit to the size of the database
 One server has over 20,000,000 names
• Not a particularly good idea
 No limit to the number of queries
 24,000 queries per second handled easily
 Queries distributed among masters, slaves, and caches

433

DNS Features: Reliability
 Data is replicated
 Data from master is copied to multiple slaves
 Clients can query
 Master server
 Any of the copies at slave servers
 Clients will typically query local caches
 DNS protocols can use either UDP or TCP
 If UDP, DNS protocol handles retransmission, sequencing, etc.

434

DNS Features: Dynamicity
 Database can be updated dynamically
 Add/delete/modify of any record
 Modification of the master database triggers replication
 Only master can be dynamically updated
• Creates a single point of failure

435


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

436


437

SKILLS FOR INDIA

Dynamic Host Configuration Protocol (DHCP)

438

Dynamic Assignment of IP addresses

 Dynamic assignment of IP addresses is desirable for several reasons:
 IP addresses are assigned on-demand
 Avoid manual IP configuration
 Support mobility of laptops

439

Solutions for dynamic assignment of IP
addresses
 Reverse Address Resolution Protocol (RARP)
 Works similar to ARP
 Broadcast a request for the IP address associated with a given MAC
address
 RARP server responds with an IP address
 Only assigns IP address (not the default router and subnet mask)

IP address
(32 bit)

ARP
RARP

Ethernet MAC
address
(48 bit)
440

BOOTP
 BOOT strap Protocol (BOOTP)
From 1985
Host can configure its IP parameters at boot time
3 services:
• IP address assignment
• Detection of the IP address for a serving machine
• The name of a file to be loaded and executed by the client machine
(boot file name)
Not only assign IP address, but also default router, network mask, etc.
Sent as UDP messages (UDP Port 67 (server) and 68 (host))
Use limited broadcast address (255.255.255.255):
These addresses are never forwarded
441

DHCP
 Dynamic Host Configuration Protocol (DHCP)
 From 1993
 An extension of BOOTP, very similar to DHCP
 Same port numbers as BOOTP
 Extensions:
• Supports temporary allocation (“leases”) of IP addresses
• DHCP client can acquire all IP configuration parameters needed to
operate
 DHCP is the preferred mechanism for dynamic assignment of IP
addresses
 DHCP can interoperate with BOOTP clients

442

BOOTP Interaction
(b)

(a)

(c)
Argon
128.143.137.144
00:a0:24:71:e4:44

DHCP Server

TFTP
“filename”

128.143.137.100

 BOOTP can be used for
downloading memory image for
diskless workstations
 Assignment of IP addresses to hosts
is static
443

DHCP Interaction (simplified)

Argon
00:a0:24:71:e4:44

DHCP Server

DHCP Request
00:a0:24:71:e4:44
Sent to 255.255.255.255

444

BOOTP/DHCP Message Format

(There are >100 different options)
445

DHCP Message Type

 Message type is sent as an
option.

Value

Message Type

1

DHCPDISCOVER

2

DHCPOFFER

3

DHCPREQUEST

4

DHCPDECLINE

5

DHCPACK

6

DHCPNAK

7

DHCPRELEASE

8

DHCPINFORM
446

Message Types
 DHCPDISCOVER: Broadcast by a client to find available DHCP servers
 DHCPOFFER: Response from a server to a DHCPDISCOVER and offering
IP address and other parameters
 DHCPREQUEST: Message from a client to servers that does one of the
following:
 Requests the parameters offered by one of the servers and declines all
other offers
 Verifies a previously allocated address after a system or network
change (a reboot for example)
 Requests the extension of a lease on a particular address

447

DHCPACK: Acknowledgement from server to client with parameters,
including IP address.
DHCPNACK: Negative acknowledgement from server to client,
indicating that the client's lease has expired or that a requested IP address is
incorrect.
DHCPDECLINE: Message from client to server indicating that the
offered address is already in use.
DHCPRELEASE: Message from client to server canceling remainder of
a lease and relinquishing network address.
DHCPINFORM: Message from a client that already has an IP address
(manually configured for example), requesting further configuration
parameters from the DHCP server.

448

DHCP Operation

 DCHP DISCOVER

 DCHP OFFER

449

DHCP Operation

DCHP DISCOVER
At this time, the DHCP
client can start to use the
IP address
Renewing a Lease
(sent when 50% of lease
has expired)
If DHCP server sends
DHCPNACK, then
address is released.
450

DHCP Operation

DCHP RELEASE
At this time, the DHCP client
has released the IP address

451

Client Server Interactions
 The client broadcasts a DHCPDISCOVER message on its local physical
subnet
 The DHCPDISCOVER message may include some options such as
network address suggestion or lease duration
 Each server may respond with a DHCPOFFER message that includes an
available network address (your IP address) and other configuration options
 The servers record the address as offered to the client to prevent the
same address being offered to other clients in the event of further
DHCPDISCOVER messages being received before the first client has
completed its configuration

452

 The client receives one or more DHCPOFFER messages from one or
more servers
 The client chooses one based on the configuration parameters
offered and broadcasts a DHCPREQUEST message that includes
the server identifier option to indicate which message it has selected
and the requested IP address option, taken from your IP address in
the selected offer
 In the event that no offers are received, if the client has knowledge
of a previous network address, the client may reuse that address if
its lease is still valid, until the lease expires

453

 The servers receive the DHCPREQUEST broadcast from the client
 Those servers not selected by the DHCPREQUEST message use
the message as notification that the client has declined that server's
offer
 The server selected in the DHCPREQUEST message commits the
binding for the client to persistent storage and responds with a
DHCPACK message containing the configuration parameters for
the requesting client

454

The combination of client hardware and assigned network address constitute
a unique identifier for the client's lease and are used by both the client and
server to identify a lease referred to in any DHCP messages.
The your IP address field in the DHCPACK messages is filled in with the
selected network address. The client receives the DHCPACK message with
configuration parameters. The client performs a final check on the
parameters, for example with ARP for allocated network address, and notes
the duration of the lease and the lease identification cookie specified in the
DHCPACK message. At this point, the client is configured.If the client
detects a problem with the parameters in the DHCPACK message (the
address is already in use on the network, for example), the client sends a
DHCPDECLINE message to the server and restarts the configuration
process.
455

The client should wait a minimum of ten seconds before restarting the
configuration process to avoid excessive network traffic in case of
looping.
On receipt of a DHCPDECLINE, the server must mark the offered address
as unavailable (and possibly inform the system administrator that there is a
configuration problem).
If the client receives a DHCPNAK message, the client restarts the
configuration process.
The client may choose to relinquish its lease on a network address by
sending a DHCPRELEASE message to the server.
The client identifies the lease to be released by including its network
address and its hardware address.

456

DHCP Pros

 It relieves the network administrator of a great deal of manual
configuration work
 The ability for a device to be moved from network to network and to
automatically obtain valid configuration parameters for the current network
can be of great benefit to mobile users
 Because IP addresses are only allocated when clients are actually active, it
is possible, by the use of reasonably short lease times and the fact that
mobile clients do not need to be allocated more than one address, to reduce
the total number of addresses in use in an organization

457

DHCP Cons
 Uses UDP, an unreliable and insecure protocol
 DNS cannot be used for DHCP configured hosts

458


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460

SKILLS FOR INDIA

Network Design and Implementation

Message transfer agent
Within Internet message handling services (MHS), a message transfer
agent or mail transfer agent (MTA) or mail relay is software that
transfers electronic mail messages from one computer to another using
a client–server application architecture. An MTA implements both the client
(sending) and server (receiving) portions of the Simple Mail Transfer
Protocol.
The terms mail server, mail exchanger, and MX host may also refer to
a computer performing the MTA function. The Domain Name
System (DNS) associates a mail server to a domain with mail
exchanger (MX) resource records containing the domain name of a host
providing MTA services.
A mail server is a computer that serves as an electronic post office for email.
Mail exchanged across networks is passed between mail servers that run
specially designed software. This software is built around agreed-upon,
standardized protocols for handling mail messages and the graphics they
might contain.
462

Operation
A message transfer agent receives mail from either another MTA, a mail
submission agent (MSA), or a mail user agent (MUA). The transmission
details are specified by the Simple Mail Transfer Protocol (SMTP). When a
recipient mailbox of a message is not hosted locally, the message is relayed,
that is, forwarded to another MTA. Every time an MTA receives an email
message, it adds aReceived trace header field to the top of the header of the
message,[4] thereby building a sequential record of MTAs handling the
message. The process of choosing a target MTA for the next hop is also
described in SMTP, but can usually be overridden by configuring the MTA
software with specific routes.

463

A MTA works in the background, while the user usually interacts directly
with a mail user agent. One may distinguish initial submission as first
passing through an MSA – port 587 is used for communication between an
MUA and an MSA while port 25 is used for communication between
MTAs, or from an MSA to an MTA, this distinction is first made in RFC
2476.
For recipients hosted locally, the final delivery of email to a recipient
mailbox is the task of a message delivery agent (MDA). For this purpose
the MTA transfers the message to the message handling service component
of the message delivery agent. Upon final delivery, the Return-Path field is
added to the envelope to record the return path.

464

Install a Windows Server 2003 Print Server

Click Start, point to Administrative Tools, and then
click Configure Your Server Wizard
Click Next
Click Next
Click Print server in the Server role box, and then click Next
On the "Printers and Printer Drivers" page, click the types of
Windows clients that your print server will support, and then click Next
Click Next
On the "Add Printer Wizard Welcome" page, click Next

465

Click Local printer attached to this computer, click to clear
the Automatically detect and install my Plug and Play printer check
box, and then click Next
Click the port for your printer, and then click Next
Click the printer make and model or provide the drivers from the printer
manufacturer media, and then click Next
NOTE: If you are prompted to keep or not keep your existing printer driver,
either keep the existing driver or replace the existing driver. If you replace
the driver, you must provide the manufacturer driver for this printer.
Click Next to continue.
•Accept the default name of the printer or provide a different name, and then
click Next.
•Click the Share as option, type the share name, and then click Next.

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SKILLS FOR INDIA

Network Security & Troubleshooting

Backup
In information technology, a backup or the process of backing up is
making copies of data which may be used to restore the original after a data
loss event. The verb form is back up in two words, whereas the noun
is backup.
Backups have two distinct purposes. The primary purpose is to recover data
after its loss, be it by data deletion or corruption. Data loss can be a common
experience of computer users. A 2008 survey found that 66% of
respondents had lost files on their home PC. The secondary purpose of
backups is to recover data from an earlier time, according to a userdefined data retention policy, typically configured within a backup
application for how long copies of data are required. Though backups
popularly represent a simple form of disaster recovery, and should be part of
a disaster recovery plan, by themselves, backups should not alone be
considered disaster recovery.
470

Since a backup system contains at least one copy of all data worth saving,
the data storage requirements are considerable. Organizing this storage
space and managing the backup process is a complicated undertaking. A
data repository model can be used to provide structure to the storage. In
the modern era of computing there are many different types of data storage
devices that are useful for making backups. There are also many different
ways in which these devices can be arranged to provide geographic
redundancy, data security, and portability.

471

Types of Backup
 There are five types of back up
Normal
Copy
Incremental
Differential
Daily Backup

472

 Selecting Backup Devices and Media
 Many tools are available for backing up data. Some are fast and
expensive. Others are slow but very reliable. The backup solution that's
right for your organization depends on many factors, including
 Capacity The amount of data that you need to back up on a routine
basis. Can the backup hardware support the required load given
your time and resource constraints?
 Reliability The reliability of the backup hardware and media. Can
you afford to sacrifice reliability to meet budget or time needs?
 Extensibility The extensibility of the backup solution. Will this
solution meet your needs as the organization grows?
 Speed The speed with which data can be backed up and recovered.
Can you afford to sacrifice speed to reduce costs?
 Cost The cost of the backup solution. Does it fit into your budget?
473

Recovering Data Using the Restore Wizard
 Make sure that the backup set you want to work with is loaded into the
library system, if possible.
 Start Backup. In the Welcome tab, click Restore Wizard, and then click
Next.

474

Select the check box next to any drive, folder, or file that you want to
restore. If the media set you want to work with isn't shown, click Import
File, and then type the path to the catalog for the backup.
To restore system state data, select the check box for System State as well as
other data you want to restore. If you're restoring to the original location, the
current system state will be replaced by the system state data you're
restoring. If you restore to an alternate location, only the registry, Sysvol,
and system boot files are restored. You can only restore system state data on
a local system.
Tip By default, Active Directory and other replicated data, such as Sysvol,
aren't restored on domain controllers. This information is instead replicated
to the domain controller after you restart it, which prevents accidental
overwriting of essential domain information. To learn how to restore Active
Directory, see the "Restoring Active Directory" section of this chapter.
475

Click Next. Click Advanced if you want to override default options, and
then follow steps 5–7. Otherwise, skip to step 8.
Select the restore location using one of the following options:
Original Location Restores data to the folder or files it was in when it was
backed up.
Alternate Location Restores data to a folder that you designate, preserving
the directory structure. After selecting this option, enter the folder path to
use or click Browse to select the folder path.
Single Folder Restores all files to a single folder without preserving the
directory structure. After selecting this option, enter the folder path to use or
click Browse to select the folder path.
Do Not Replace The Files On My Computer (Recommended) Select this
option if you don't want to copy over existing files.
Replace The File On Disk Only If the File On Disk Is Older Select this
option to replace older files on disk with newer files from the backup.
Always Replace The File On My Computer Select this option to replace
all the files on disk with files from the backup.
476

If they're available, you can choose to restore security and system files using
the following options:
Restore Security:Restores security settings for files and folders on
NTFS volumes.
Restore Removable Storage Database:Restores the Removable
Storage configuration if you archived SystemRoot%System32
Ntmsdata. Choosing this option will delete existing Removable Storage
information.
Restore Junction Points, Not The Folder And File Data They
Restores network drive mappings but doesn't restore the actual data to
the mapped network drive. Essentially, you're restoring the folder that
references the network drive.
Click Next, and then click Finish. If prompted, type the path and name of
the backup set to use. You can cancel the backup by clicking Cancel in the
Operation Status and Restore Progress dialog boxes.
When the restore is completed, click Close to complete the process or click
Report to view a backup log containing information about the restore
477
operation.


478

SKILLS FOR INDIA

Access Control List

An access control list (ACL), with respect to a computer file system, is a list
of permissions attached to an object. An ACL specifies which users or
system processes are granted access to objects, as well as what operations
are allowed on given objects. Each entry in a typical ACL specifies a
subject and an operation. For instance, if a file has an ACL that
contains (Alice, delete), this would give Alice permission to delete the file.
ACL are the basic security feature that is required in any network to control
the flow of traffic. Most of time our network may have servers and clients
for which traffic control is required.
We can also use ACL to classify the traffic. ACLs are used in features like
QOS (Quality of Service), Prioritize traffic and interesting traffic for ISDN.

480

Classification Access Control List
Types of ACL based on Protocol: (1) IP Access Control List
(2) IPX Access Control List
(3) Apple talk Access Control List
Types of ACL based on Feature: (1) Standard ACL
(2) Extended ACL
Types of ACL based on Access mode: (1) Numbered ACL
(2) Named ACL

481

Classification Access Control List
Types of ACL based on Order of rules: (1) Deny, permit
(2) Permit, deny
Types of ACL based on direction of implementation: (1) Inbound ACL
(2) Outbound ACL

482

Flow chart of Inbound ACL
A Packet is received

No

Is there any Accesslist applied on
interface in Inbound
direction?

The packet
is passed to
Routing
Engine

Yes
No

Is there any
macthine rule in ACL
from top-down
order?

The packet
is dropped.

Yes
The packet
is passed to
RE

Yes
Is it
permit
?

No

The packet
is dropped.

483

IP Standard ACL (Numbered)
In Standard ACL, we are only able to specify source address for the
filtering of packets. The syntax to create IP standard ACL are: Router#conf ter
Router(config)#access-list <no> <permit|deny> <source>
Router(config)#exit
<source>

Single pc

host 192.168.10.5
192.168.10.5
192.168.10.5 0.0.0.0

N/w

200.100.100.0 0.0.0.255

Subnet

200.100.100.32 0.0.0.15

All

any
484

Example: - 172.16.0.16 – 18 should not access Internet; rest of all other pc
should access Internet.
Internet
Router

172.16.0.1

172.16.x.x
Router#conf ter
Router(config)#access-list 30 permit any
Router(config)#exit
485

IP Standard ACL (Named)
In Numbered ACL editing feature is not available that is we are not
able to delete single rule from the ACL. In Named ACL editing
feature is available.
Router#config ter
Router(config)#ip access-list standard <name>
Router(config-std-nacl)#<deny|permit> <source>
Router(config-std-nacl)#exit
Router#conf ter
Router(config)#ip access-list standard abc
Router(config-std-nacl)#deny 172.16.0.16
Router(config-std-nacl)#permit any
Router(config-std-nacl)#exit
486

To control Telnet access using ACL
If we want to control telnet with the help of ACL then we can create
a standard ACL and apply this ACL on vty port. The ACL that we
will create for vty will be permit – deny order.
Example: - suppose we want to allow telnet to our router from
192.168.10.5 & 192.168.10.30 pc.
Router#conf ter
Router(config)#access-list 50 permit 192.168.10.5
Router(config)#access-list 50 permit 192.168.10.30
Router(config)#line vty 0 4
Router(config-line)#access-class 50 in
Router(config)#exit

487

IP Extended ACL (Numbered)
Extended ACL are advanced ACL. ACL,
which can control traffic flow on the basis
of five different parameters that are: (i) Source address
(ii) Destination address
(iii) Source port
(iv) Destination port
(v) Protocol (layer 3/layer 4)

488

The syntax to create Extended
ACL

Router#conf ter
Router(config)#access-list <no> <deny|permit> <protocol>
<source> [<s.port>]
<destination> [<d.port>]
router(config)#exit
<no>
->
100 to 199
<protocol> ->
layer ¾
IP
TCP
UDP
ICMP
IGRP

489

The syntax to create Extended
ACL
<Source port>
<Destination port>
<Source>
<Destination>

no (1 to 65535) or
telnet/www/ftp etc.
Single pc
192.168.10.4 0.0.0.0
host 192.168.10.4
N/w
200.100.100.0 0.0.0.255
Subnet
172.30.0.32 0.0.0.7
All
Any

490

To display ACL
Router#show access-lists or
Router#show access-list <no>
To display ACL applied on interface
Router#show ip interface
Router#show ip interface <type> <no>
Router#show ip interface Ethernet 0

491

Switch port ACL
You can only apply port ACLs to layer 2 interfaces on your switches
because they are only supported on physical layer 2 interfaces. You
can apply them as only inbound lists on your interfaces, and you can
use only named lists as well.
Extended IP access lists use both source and destination addresses as
well as optional protocol information and port number. There are
also MAC extended access lists that use source and destination MAC
addresses and optional protocol type information.
Switches scrutinize all inbound ACLs applied to a certain interface
and decide to allow traffic through depending on whether the traffic
is a good match to the ACL or not. ACLs can also be used to control
traffic on VLANs. You just need to apply a port ACL to a trunk port.

492

Switch#conf ter
Switch(config)#mac access-list extended abc
Switch(config-ext-mac)#deny any host 000d.29bd.4b85
Switch(config-ext-mac)#permit any any
Switch(config-ext-mac)#do show access-list
Switch(config-ext-mac)#int f0/6
Switch(config-if)#mac access-group abc

493

Lock and Key (Dynamic ACLs)
These ACLs depends on either remote or local Telnet authentication in
combination with extended ACLs. Before you can configure a dynamic
ACL, you need to apply an extended ACL on your router to stop the flow
of traffic through it.

Reflexive ACLs
These ACLs filter IP packets depending upon upper-layer session
information, and they often permit outbound traffic to pass but place
limitations on inbound traffic. You can not define reflexive ACLs with
numbered or standard IP ACLs, or any other protocol ACLs. They can be
used along with other standard or static extended ACLs, but they are only
defined with extended named IP ACLs.

494

Time-Based ACLs
In this you can specify a certain time of day and week and then
identity that particular period by giving it a name referenced by a
task. The reference function will fall under whatever time constraints
you have dictated. The time period is based upon the router’s clock,
but it is highly recommended that using it in conjunction with
Network Time Protocol (NTP) synchronization.
Router#conf ter
Router(config)#time-range no-http
Router(config-time-range)#periodic <Wednesday|weekdays|
weekend> 06:00 to 12:00
Router(config-time-range)#exit
Router(config)#time-range tcp-yes
Router(config-time-range)#periodic weekend 06:00 to 12:00
Router(config-time-range)#exit
495

Router(config)ip access-list extended time
Router(config-ext-nacl)#deny tcp any any eq www time-range
no-http
Router(config-ext-nacl)#permit tcp any any time-range tcpyes
Router(config-ext-nacl)#interface f0/0
Router(config-if)#ip access-group time in
Router(config-if)#do show time-range

496


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