Networking HMT-1

Computer Networks-1
Imranul Hasan
Greenwich University, UK

Objectives
At the end of this session, you will be able to:
• Define a Computer Network
• List the advantages of using computer networks
• Classify computer networks
• Differentiate between LAN ,MAN and WAN
• Explaining the functioning of the standard topology
• Explaining some other topologies used in computer networks

What is a Network?
o An interconnected system of things or people;
o A wide variety of systems of interconnected
components are called networks.

What is a Computer Network?
• Computer Network is two or more computers
connected so that they can communicate with each
other and share information, software, peripheral
devices, and/or processing power.
• Computer Network is a group of computers
connected by using various media is capable of
sharing, managing and providing resources
• In summary, all networks must have the following:
 Something to share (data/resource)
 A physical pathway (transmission medium)
 Rules of communication (protocols)

What is a Computer Network? (contd.)
Network Resources (which is to be shared):
• Printers
• Scanners
• Hard disks
• Floppy disks
• CD-ROMs
• Plotters
• Other devices
• Keeps information reliable and up to-date, etc.

Network Media (which is used as communication path):
• Twisted Pair Cable
• UTP Cable
• Coaxial Cable
• Fiber Optical Cable
• Hub, Switch, Router (as network management device too)
• Wireless Media

Network Protocol (Rules for Network):
Protocol is formal description of a set of rules and
conventions that govern how devices on a network exchange
information.
• TCP/IP
• UDP
• NWLink
• NetBEUI
• PPP
• IPX etc.

Classification of Networks?
Networks are classified using different point of view.
o Size: Geographic size of network;
o Security and Access control: Who can access and
who cannot
o Protocol: Which rules are using for communicating
in the network.
o Hardware: The physical link and hardware that
connects the network.

Classification of Network? (contd.)
There are three basic type of network on the
basis of the area covered:
• LAN (Local Area Network)
• MAN (Metropolitan Area Network)
• WAN (Wide Area Network)

 PAN/ LAN/ MAN/ WAN/ INTERNET

o High-speed, low-error data network
o Covering a relatively small geographic area (up to
1 km).
o LANs connect workstations, peripherals, terminals,
and other devices in a single building or other
geographically limited area.
o Uses cables as its connecting media
o Maximum distance between networks limited by:
 The strength of the signal
 The network system’s built-in time limit for sending and
receiving the messages via the connecting media
Local Area Network

o Network that spans a metropolitan area.
o Generally, a MAN spans a larger geographic area
than a LAN, but a smaller geographic area than a
WAN.
o Uses the LAN technology
o Carries information in the form of computer signals
Metropolitan Area Network

o Data communications network that serves users across a broad
geographic area
o Often uses transmission devices provided by common carriers.
o A Wide Area Network that uses phone lines, microwaves,
satellites, or a combination of communication channels to
connect several locations. It covers:
o Cities
o States
o Countries
o Establishes communication via:
o Phone lines
o Microwaves
o Satellites, or
o a combination of communication channels to connect
several locations.
Wide Area Network

o LAN designers can set up their own network that is
technically reliable
o Whereas WAN designers are forced to use existing
public telephone network that is technically unreliable
o LAN cables are more reliable since the error rates
are less than in WAN
o Error detection and correction are done at lower
levels in LANs as compared to WANs
Advantages of LAN over WAN

o A way for two elements on a network (server,
hosts, workstations etc.) to communicate in a
standard way.
o In an intermediate network facility, a set of rules
and procedures governing communication between
entities connected by the network.
o Three most common protocols are:
1. NWLink
2. NetBEUI
3. TCP/IP
Network Protocols

o NWLink Protocol:
o Used in Windows networks
o This protocol is Microsoft’s emulation of Novell’s IPX/SPX
protocol, was developed to enable interconnectivity
between Microsoft and NetWare networks.
o NWLink is routable, that means it can be transferred from
a local network to a remote one through a router.
o NWLink configures its own routing tables ,which makes it
nice for small networks,
o However, it is not practical for large WANs like the
Internet and cannot directly to the Internet.
Network Protocols (Contd)

o NetBEUI Protocol:
o NetBEUI, also known as the NetBIOS Extended User
Interface
o It is a non-routable network transport suit for use in small
networks consisting of a single LAN with 50 or fewer
computers.
o In the Microsoft networking world, NetBEUI was the
primary protocol for Windows 3.11 (Windows for
Workgroup).
o It is easy to work with, and may still be used where little
network configuration is required and where you do not
need to route to other network or communicate with
Internet.
o NetBEUI is easy to use because it is self-configuring.
There is nothing to do except install it.
o It cannot be used in a WAN environment.

TCP/IP Protocol:
o A protocol for communication between computers,
used as a standard for transmitting data over
networks and as the basis for standard Internet
protocols.
o TCP is one of the main protocols in TCP/IP networks.
Whereas the IP protocol deals only with packets, TCP
enables two hosts to establish a connection and
exchange streams of data. TCP guarantees delivery
of data and also guarantees that packets will be
delivered in the same order in which they were sent.

o The arrangement of nodes
o The physical and logical
relationship of nodes in a network
o Physical topology: Refers to the
configuration of cables, computers, and
other peripherals.
o Logical topology: The method used to
pass information between workstations.
Logical topology are called Protocol.
o Three basic physical Topologies
are:
o Bus
o Star
o Ring
What is a Topology?

o Bus Topology
o A network topology in which nodes are connected to a
single cable with terminators at each end.
o All devices are connected to a central cable, called the bus
or backbone. Bus networks are relatively inexpensive and
easy to install for small networks. Ethernet systems use a
bus topology.
Topology (Bus)

o Advantages of a Bus Topology
o Easy to connect a computer or peripheral to a linear bus.
o Requires less cable length than a star topology.
o Disadvantages of a Bus Topology
o Entire network shuts down if there is a break in the main cable.
o Terminators are required at both ends of the backbone cable.
o Difficult to identify the problem if the entire network shuts down.
o Not meant to be used as a stand-alone solution in a large
building.
Topology (Bus)

Topology (Star)
o A star topology is designed with each
node (file server, workstations, and
peripherals) connected directly to a
central network hub or concentrator
o Data on a star network passes through
the hub or concentrator before
continuing to its destination. The hub or
concentrator manages and controls all
functions of the network. It also acts as
a repeater for the data flow. This
configuration is common with twisted
pair cable; however, it can also be used
with coaxial cable or fiber optic cable.

o Advantages of a Star Topology
o Easy to install and wire.
o No disruptions to the network then connecting or
removing devices.
o Easy to detect faults and to remove parts.
o Disadvantages of a Star Topology
o Requires more cable length than a linear topology.
o If the hub or concentrator fails, nodes attached are
disabled.
o More expensive than linear bus topologies because of the
cost of the concentrators.
Topology (Star)

o Known as a ring network
o The ring topology is a type of
computer network configuration
where each network computer and
device are connect to each other
forming a large circle (or similar
shape). Each packet is sent
around the ring until it reaches its
final destination.
o Today the ring topology is seldom
used.
Topology (Ring)

Ring Topology (contd.)
 Offers the following advantages:
 Network efficiency can be as high as 100 per cent
under conditions of heavy load
 Equal access is given to all computers
 Suffers from the following disadvantages:
 Failure of one computer on the ring can affect the
entire network
 Troubleshooting is difficult
 Adding or removing computers disrupts the network

Other Topologies
 Star Bus
 Star Ring
 Physical Mesh

Star Bus Topology
 Is a combination of the bus and star
topologies
 Has several star topology networks linked
with linear trunks
 Does not adversely affect the network if
one computer fails

Star Ring Topology
 Is a combination of the ring and star
topologies.
 Has hubs that are connected in a star
pattern to the main hub

Physical Mesh Topology
 Has a link between each device on the network
 Gets unmanageable beyond a very small number of
devices
 Has each of its computers linked to most of the other
computers reducing the redundant links

Roles of Computer in a Network
Clients
 Which use network resources but do not share them
Peers
 Which use and share network resources
Servers
 Which provide network resources

Roles of Computers in a Network (contd.)
On the basis of the roles, networks are divided into
three categories:
 Peer-to-Peer networks
 Server-based networks
 Combination networks

Peer to Peer networks
 Does not have a central control over the network
 Computers are clients as well as servers
 Does not have any dedicated server
 Is organized into workgroups that have limited
security control

Peer to Peer Networks (contd)
Offers the following advantages:
 No extra investment on server hardware and
software
 Easy setup
 No network administrator required
 Users can controls sharing of resources
 Less cost

Peer-to-Peer Networks (contd.)
Have the following disadvantages:
 Weak and intrusive security
 Need to administer the computers
 Lack of centralized management
 Additional burden on the computers because of
resource sharing
 Non-handling of multiple network connections

Server-based Networks
Are organized into domains in a Windows NT
environment that provide:
 Security
 Administration
 Provide services to various clients
 Ensure security of files and directories

Windows NT Server is optimized for file, print, and application services. Windows NT
Workstation is optimized for desktop performance, either as a network client or as a peer.

Server-based Networks (contd.)
Offer the following advantages:
 Strong central security
 Centralized file storage that:
 Provides easy backup of critical data
 Allows users to work with the same set of data
 Reduced overall costs
 Easy management of multiple users
 Users are freed from managing resources

Server-based Networks (contd.)
Have the following disadvantages:
 Expensive dedicated server
 Expensive network operating system software
and
 Need for a dedicated network administrator

Servers
 Are dedicated to perform specific tasks
 May perform all the tasks
 or have separate servers for each task
Are classified into:
 File servers that allow users to share files
 Print servers that allow users to print on a common
network printer
 Application servers that allow clients to access
expensive software applications
 Message servers that provide message services

FILE SERVER
A file server stores files for users on other network machines.

server manages access to a shared printer, making it accessible to users at
other network machines.
PRINT SERVER

An application server runs all or part of an application on behalf of the client and then transmits the result to
the client for further processing.
APPLICATION SERVER

Networking HMT-1

More Related Content

What's hot (20)

Similar to Networking HMT-1 (20)

More from ImranulHasan6 (15)

Recently uploaded (20)

Networking HMT-1