Cp7101 design and management of computer networks-flow analysis

CP7101-Design and Management
of Computer Networks
Dr.G.Geetha
Professor /CSE
Jerusalem College of Engineering

Flow Analysis
learn how to identify and
characterize traffic flows

Flows
• Flows (also known as traffic flows or data flows) are
sets of network traffic (application, protocol, and
control information) that have common attributes,
such as source/destination address, type of
information, directionality, or other end-to-end
information.
Figure 4.1

Flow Characteristics
• Performance Requirements
• Capacity (e.g., Bandwidth)
• Delay (e.g., Latency)
• Reliability (e.g., Availability)
• Quality of Service Levels
• Importance/ Priority Levels
• Business/Enterprise/Provider
• Political
• Other
• Directionality
• Common Sets of Users, Applications, Devices
• Scheduling (e.g., Time-of-Day)
• Protocols Used
• Addresses/Ports
• Security/Privacy Requirements
FIGURE 4.2, FIGURE 4.3

Two types of flows
• Individual
An individual flow is the flow for a single session of
an application
• Composite
A composite flow is a combination of requirements
from multiple applications, or of individual flows,
that share a common link, path, or network

Individual flow
• An individual flow is the basic unit of traffic flows
• When an individual flow has guaranteed requirements,
those requirements are usually left with the individual
flow and are not consolidated with other requirements
or flows into a composite flow
• Individual flows are derived directly from the
requirements specification, or are estimated from our
best knowledge about the application, users, devices,
and their locations.
FIGURE 4.4
• Most flows in a network are composites Figure 4.5

Presentation of Flows
upstream- downstream
• Upstream indicates the direction toward the
source and downstream is the direction
toward the destination.
• Upstream is often toward the core of the
network, while downstream is often toward
the edge of the network, particularly in
service provider networks
FIGURE 4.6

Critical Flows
• Critical flows can be considered more
important than others, in that they are higher
in performance or have strict requirements
(e.g., Mission-critical, rate-critical, real time,
interactive, high-performance).
• Critical flows may serve more important users,
their applications, and devices

Identifying and Developing Flows
• Identified and developed from information in
the requirements specification:
• User, application, device, and network
requirements
• User and application behavior (usage patterns,
models)
• User, application, and device location
information
• Performance requirements.

Identifying and Developing Flows
• Flows are determined based on the requirements
and locations of the applications and devices that
generate (source) or terminate (sink) each traffic
flow.

Process for identifying and developing
flows
1. Identifying one or more applications and/or
devices that you believe will generate and/or
terminate traffic flows
2. Use their requirements from the requirements
specification and their locations from the
requirements map
3. Based on how and where each application and
device is used, you may be able to determine
which devices generate flows and which devices
terminate flows (flow sources and sinks)
FIGURE 4.7

Flows: Application Perspective
1. Focusing on a particular application, application
group, device, or function(e.g., videoconferencing
or storage)
2. Developing a “profile” of common or selected
applications that can be applied across a user
population
3. Choosing the top N (e.g., 3, 5, 10, etc.) applications
to be applied across the entire network

1.Focusing on a Particular Application
Example: Data Migration
From requirements specification, for a single session of each
application:
• Application 1: Staging data from user devices
Capacity 100Kb/s; Delay Unknown; Reliability 100%
• Application 1: Migrating data between servers
Capacity 500Kb/s; Delay Unknown; Reliability 100%
• Application 2: Migration to remote (tertiary) storage
Capacity 10Mb/s; Delay N/A; Reliability 100%
FIGURE 4.8- 4.12

2.Developing a Profile
• Profile or template can be developed for set of
common applications apply to a group of
users or to the entire set of users
• Each flow that fits the profile is identified with
that profile’s tag
• Saving time and effort

3.Choosing the Top N Applications
• a combination of the first two approaches
Example: Top 5 Applications
1. Web Browsing
2. Email
3. File Transfer
4. Word Processing
5. Database Transactions
FIGURE 4.14

Data Sources and Sinks
• A data source generates a traffic flow, and a
data sink terminates a traffic flow
• Help provide directionality to flows
• Data sources are represented as a circle
with a dot in the center, and a data sink is
represented as a circle with a cross (i.e., star
or asterisk) in the center.
FIGURE 4.15 - 4.18

Flow Models
• Method to help describe flows in the network
• Flow models are groups of flows that exhibit
specific, consistent behavior characteristic
• Flow model apply to a single application.
• Directionality, hierarchy, and diversity are the
primary characteristics of flow models
• Directionality describes the preference to
have more requirements in one direction than
another.

Flow models
1. Peer-to-peer
2. Client–server
3. Hierarchical client–server
4. Distributed computing

Peer-to-Peer
• Peer-to-peer, is one where the users and
applications are fairly consistent in their flow
behaviors throughout the network
• They act at the same level in the hierarchy
• This has two important implications:
• cannot distinguish between flows in this model.
Therefore, either all of the flows or none of the
flows is critical
• Since the flows are equivalent, they can be
described by a single specification(e.g., Profile)

Flow Prioritization
• The purpose for prioritizing flows is to
determine which flows get the most resources
or which flows get resources first.
• primary resource is funding.
FIGURE 4.33-4.35

The Flow Specification
• results of identifying, defining, and describing
flows are combined into a flow specification,
or flowspec .
• Flow specifications can take one of three
types:
1. One-part, or unitary;
2. Two-part;
3. Multi-part.

Flowspec
• A one-part flowspec
– Describes flows that have only best-effort
requirements.
• A two-part flowspec
– Describes flows that have predictable requirements
and may include flows that have best-effort
requirements.
• A multipart flowspec
– Describes flows that have guaranteed requirements
and may include flows that have predictable and/or
best-effort requirements

Flowspec Algorithm
• Flowspecs are used to combine performance
requirements of multiple applications for a
composite flow or multiple flows in a section of a
path
• The flowspec algorithm is a mechanism to
combine these performance requirements
(e.g.,capacity, delay, and RMA) for flows in such a
way as to describe the optimal composite
erformance for that flow or group of flows.

• The flowspec algorithm applies the following rules:
1.Best-effort flows consist only of capacity requirements,
so only capacities are used in best-effort Calculations.
2.For flows with predictable requirements, we will use all
available performance requirements (Capacity, delay,
and RMA) in the calculations. Performance
requirements will be combined for Each characteristic
to maximize the overall performance of each flow
3.For flows with guaranteed requirements, we will list
each requirement (as an individual flow), not
Combining them with other requirements.

Cp7101 design and management of computer networks-flow analysis

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