09-03-2025

COMPUTER NETWORK
(BCS-603 )

6-Semester- CSE-A

Vijay Subhash Katta 1

Vision and Mission of CSE

• Vision of Department
To be in the forefront of Computer Science and Engineering through academic excellence and
research to successfully contribute to the country’s nation-building initiatives, fostering ingenuity, values, and
quality.

• Mission of Department
1. Our mission is to strive for excellence in teaching, research, and entrepreneurship.
2. To nurture the students in both theory and practical in the field of Computer science and engineering.
3. Educate the students with well defined outcomes in order to foster their holistic growth.
4. To aid in the nation building by responding to industry and societal demands.
5. Instill ethics and morals to develop work dignity and to serve mankind.
6. To adopt a comprehensive strategy built on excellence, analytical ability, initiative, creativity, and
innovation with focus on interdisciplinary fields.

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Preamble
Computer Network
(BCS603)
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BCS-603 Computer Network

Source:- AKTU, Lucknow

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Bloom’s taxonomy cognitive domain levels.

Mohammed M, Omar N (2020) Question classification based on Bloom’s taxonomy cognitive domain using modified TF-IDF and word2vec. PLOS ONE 15(3): e0230442.
https://doi.org/10.1371/journal.pone.0230442
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0230442

Course Outcomes of CN
Course
Outcome Cos of Computer Network Bloom's knowledge Level
Explain basic concepts, OSI reference model, services and role of each layer of OSI
model and Remembering,
CO1 K1, K2
TCP/IP, networks devices and transmission media, Analog and digital data Understanding
transmission

CO2 Apply channel allocation, framing, error and flow control techniques. K3 Applying

Describe the functions of Network Layer i.e. Logical addressing, subnetting &
Understanding,
CO3 Routing K2, K3
Applying
Mechanism.
Explain the different Transport Layer function i.e. Port addressing, Connection
Understanding,
CO4 Management, K2, K3
Applying
Error control and Flow control mechanism.
Explain the functions offered by session and presentation layer and their Understanding,
CO5 K2, K3
Implementation. Applying
Explain the different protocols used at application layer i.e. HTTP, SNMP, SMTP,
CO6 FTP, TELNET and VPN. Understanding
K2

Source:- AKTU, Lucknow

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Unit wise Mapping of COs

Sr. No UNIT as per AKTU COs Bloom’s Knowledge Bloom’s Knowledge
Level (KL) Level (KL)

1 UNIT-1 CO-1 K1 ,K2 K1- Remembering,

K2- Understanding
2 UNIT-2 CO-2 K3 K3 –Applying
3 UNIT-3 CO-3 K2,K3 K2- Understanding,
K3 –Applying
4 UNIT-4 CO-4, CO-5 K2,K3 K2- Understanding,
K3 –Applying

5 UNIT-5 CO-6 K2 K2- Understanding

K1- Remembering, K2- Understanding, K3 –Applying, K4 –Analyzing, K5 – Evaluating, K 6 - Creating.

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Bloom’s Keywords
Knowledge Level
(KL)
K1- Define, identify, describe, label, list, name, state, match, recognize, select, examine, memorize, recall,
Remembering, reproduce, tabulate, tell, duplicate, enumerate, listen, observe, omit, read, recite, record, repeat

K2- Explain, describe, interpret, summarize, classify, compare, differentiate,

Understanding, discuss, distinguish, extend, predict, associate, contrast, convert, demonstrate, estimate, express, identify,
indicate, infer, relate, select, translate, discover, generalize, group, illustrate, judge, observe, order, report,
represent, research, review, rewrite, show, trace
K3 –Applying, Solve, apply, illustrate, modify, use, calculate, change, choose, demonstrate, discover,
experiment, relate, show, sketch, complete, construct, operate, practice, simulate, transfer, write
K4 –Analyzing, Analyze, compare, classify, contrast, distinguish, infer, connect
differentiate, survey, calculate, conclude, correlate, diagram, estimate, evaluate, experiment, focus, plan,
test
K5 – Evaluating Reframe, criticize, evaluate, compare, decide, discriminate, recommend, summarize, assess
choose, convince, defend, estimate, grade, measure, predict, select, test, argue, conclude, consider
,critique, debate, distinguish, editorialize, justify, rate, weight
K 6 - Creating. Design, compose, create, plan, formulate, invent, hypothesize, construct, develop, integrate, modify,
produce, anticipate, make, propose, simulate, solve, support, test, validate

Vijay Subhash Katta

https://www.miamioh.edu/cte/assessment/writing-student-learning-outcomes/blooms-action-verbs/index.html 8

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Engineering Program Outcomes (POs)

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By :- Forouzan

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By:-Andrew Tanenbaum

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:-Tools

• Packet tracer (freeware)

• NS2 (Linux Based)
• Qualnet (License)
• Wireshark

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CN- Books

• TEXTBOOKS:
1. Forouzan, "Data Communication and Networking", TMH
2. A.S. Tanenbaum, Computer Networks, Pearson Education
3. W. Stallings, Data and Computer Communication, Macmillan Press.

• REFRENCES:
1. Anuranjan Misra, “Computer Networks”, Acme Learning
2. G. Shanmugarathinam, ”Essential of TCP/ IP”, Firewall Media

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Past -> to -> Present

• Each of the past three centuries was dominated by a single new technology.

• The 18th century was the era of the great mechanical systems accompanying
the Industrial Revolution.

• The 19th century was the age of the steam engine.

• The 20th century, the key technology was information gathering, processing,
and distribution.

• The 21st Century, replacement of 20th century technologies for handling

information gathering, processing, and distribution.

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DATA COMMUNICATIONS

- The term telecommunication means communication at a distance.

- Data communications are the exchange of data between two devices via some
form of transmission medium such as a wire cable or radio frequencies.

Source:- Forouzen
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Topics of this section:

• Components
• Data Representation
• Data flow

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Figure 1.1 Five components of data communication

Source:- Forouzan
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Figure 1.2 Data flow (simplex, half-duplex, and full-

duplex)

Source:- Forouzen Vijay Subhash Katta 18

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Computer Network

• An Autonomous collection of interconnected, independent

computer Systems.

Source:- A. Tanenbaum Vijay Subhash Katta 19

NETWORKS
A network is a set of devices (often referred to as nodes) connected by
communication links.

A node can be a computer, printer, or any other device capable of

sending and/or receiving data generated by other nodes on the
network.

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Computer Network

• CN have many uses:

• Resource Sharing
• Data Sharing
• Business Applications
• Home Applications
• Mobile Users

• These uses raised:

• Security Concern » Students must discuss it.
• Social Issues» Students must discuss it.
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Categories of Networks

Networks can be described by category.

Valid network categories include
• Data
• Voice
• Video
• Multimedia
• Internet
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• Intranet

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Applications of computer network

• Scientific and Technical Computing

Client Server Model, Distributed Processing

Parallel Processing, Communication Media

• Commercial

Advertisement, Telemarketing, Teleconferencing

Worldwide Financial Services

• Network for the People (this is the most widely used application nowadays)

Telemedicine, Distance Education, Access to Remote Information, Person-to-Person Communication, Interactive Entertainment

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Applications of computer network

Financial services:
-Today's financial services are totally depended on computer networks.
- Application includes credit history searches, foreign exchange and
investment services, and electronic fund transfer, which allow user to
transfer money without going into a bank (an automated teller machine is
an example of electronic fund transfer, automatic pay-check is another).

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Applications of computer network

• Electronic data interchange (EDI): EDI allows business information,

including documents such as purchase orders and invoices, to be
transferred without using paper.

• Electronic mail: probably it's the most widely used computer network
application.

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Applications of computer network

• Manufacturing: Computer networks are used in many aspects of

manufacturing including manufacturing process itself.
• Two of them that use network to provide essential services are
computer-aided design (CAD) and computer-assisted manufacturing
(CAM), both of which allow multiple users to work on a project
simultaneously.

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Applications of computer network

• Voice over IP: Computer networks are also used to provide voice
communication. This kind of voice communication is pretty cheap as
compared to the normal telephonic conversation.
• Video on demand: Future services provided by the cable television
networks may include video on request where a person can request for a
particular movie or any clip at anytime he wish to see.
• Teleconferencing: Teleconferencing allows conference to occur
without the participants being in the same place.

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Network Technologies

Classification Based on

1. Transmission Technology

2. Scale

3. Machine architecture hierarchy

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1) Classification Based on Transmission Technology

Computer networks can be broadly categorized into two types based

on transmission technologies:

• Broadcast networks

• Point-to-point networks

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2) Classification based on Scale

• Local Area Network (LAN)

• Metropolitan Area Networks (MAN)
• Wide Area Network (WAN)
• The Internet

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3) Classification based upon Machine

Hierarchy Architecture
• Client –Server Architecture

• Peer to Peer communication

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Broadcast Networks

• Broadcast network have a single communication channel that is shared by

all the machines on the network

Example of a broadcast network

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Katta on shared bus 32

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Broadcast Networks

Example of a broadcast network based

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Point-to-Point Networks

• The end devices that wish to

communicate are called stations.
The switching devices are called
nodes.

Source:- Tanenbaum

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General rule in Computer Network

❖Smaller, geographically localized networks tend to use
broadcasting,

whereas

❖Larger networks normally use are point-to-point

communication.

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Short Questions

• Q-1. Which Technologies of this age had led to the emergence of

computer network?

Ans: The technologies are Computer technology and Communication

technology with the support of VLSI Technology.

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Short Questions

• Q-2. What are the two broad classifications under which Networks can be
divided?
Ans: All computer networks fit in one of the two dimensions namely,
a). Transmission Technology, this focuses on the basic underlying physical
network, for e.g. whether the nodes share a communication media or each
pair of node has a separate dedicated link.
b). Scale, it focuses on the scale of network how large is your network.

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Short Questions

• 3) Mention important benefits of computer network.

• Ans: Important benefits of computer networks are:
i) Resource sharing
ii) Powerful communication medium
iii) Higher reliability
iv) Higher flexibility
v) Lower cost
vi) Incremental expansion
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Short Questions

3) What are the advantages of multipoint connection over point-to-

point connection?

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Objective Questions

• A --------- connection provides a dedicated link between two devices.

1) point-to-point
2)multipoint
3)Primary
4) secondary

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Objective Questions

• In -------- connection ,more than two devices share a common link

1) point-to-point
2)multipoint
3)Primary
4) secondary

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Objective Questions

• In------- transmission, the channel capacity is shared by both

communicating devices at all time
1) Simplex
2)half-duplex
3)full- duplex
4) full -simplex

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Objective Questions

• In a ----- link,the only traffic is between the two connected devices.

1) Secondary
2)primary
3)dedicated
4)none of above

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2) Classification based on Scale

• Local Area Network (LAN)

• Metropolitan Area Networks (MAN)
• Wide Area Network (WAN)
• The Internet

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Classification based on Scale

Local Area Network (LAN)

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Local Area Network (LAN)

• LAN is usually privately owned and links the devices in a single office,
building or campus of up to few kilometers in size.

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Application of LAN

• Used to share resources (hardware, software) and to exchange

information.

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Local Area Network (LAN)

• LANs are distinguished from other kinds of networks by three

attributes
• their size
• Transmission technology
• Topology.

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Local Area Network- size

• LANs are restricted in size, which means that their worst-case transmission time
is bounded and known in advance.
• Hence this is more reliable as compared to MAN and WAN.
• Knowing this bound makes it possible to use certain kinds of design that would
not otherwise be possible.
• It also simplifies network management.

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Local Area Network (LAN)- Transmission

technology
• LAN typically used transmission technology consisting of single cable
to which all machines are connected.

• Traditional LANs run at speeds of 10 to 100 Mbps (but now much

higher speeds can be achieved).

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Local Area Network (LAN) -Topology

The most common LAN topologies are

❖ Bus
❖ ring
❖ star
❖ Mesh
❖ A hybrid

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Local Area Network (LAN) -Topology

Source:- Forouzan

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A Bus topology

Source:- Forouzan

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A Star topology

Source:- Forouzan
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A Ring topology

Source:- Forouzan
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A fully connected mesh topology

Source:- Forouzan
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A hybrid topology

Source:- Forouzan
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Classification based on Scale

Metropolitan Area Networks (MAN)

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Metropolitan Area Networks (MAN)

• MAN is designed to extend over the entire city.

• It may be a single network as a cable TV network or it may be means of
connecting a number of LANs into a larger network so that resources may
be shared.
•IEEE- 802.6 -DQDB (Distributed Queue Dual Bus), used for high-speed
MANs.
•Replaced by Metro Ethernet and MPLS (Multiprotocol Label Switching).

NOTE: FDDI (Fiber Distributed Data Interface)

FDDI is a high-speed networking standard primarily designed for Metropolitan Area Networks (MANs) and
high-performance LANs. It was developed by ANSI (X3T9.5) in the late 1980s and later recognized by the IEEE
802.8 standard.
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Wide Area Network (WAN)

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Wide Area Network (WAN)

• WAN provides long-distance transmission of data, voice, image and

information over large geographical areas that may comprise a
country, continent or even the whole world.

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Source:- Forouzan
Wide Area Network
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Wide Area Network (WAN)

Source:- Forouzan
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Internet

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The Internet

• Internet is a collection of networks or network of networks.

It allows various applications such as
1. e-mail,
2. file transfer
3. remote log-in,
4. World Wide Web
5. Multimedia, etc run across the internet.

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The Internet

Source:- Forouzan

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3) Classification based upon Machine

Hierarchy Architecture

• Client –Server Architecture

• Peer to Peer communication

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Short Questions

• Q-1. Mention different categories of computer networks (on the basis

of scale) and distinguish one from the other.
• Ans: Local Area Network (LAN): It is privately owned communication
systems that cover a small area, say a building or a complex of
buildings. Length is about 10 meters to few kilometers and operates
at a high speed like 10 MBPS to 1000 MBPS. It has very low error rate
(1:1011).
• Metropolitan Area Network (MAN): It is public or privately owned
communication system that typically covers a complete city. Speed is
about 10 MBPS and follows DQDB (Distributed Queue Double Bus)
standard. Its reliability is moderate.
• Wide Area Network (WAN): It covers a large geographical area and
usually owned by a state. Data transfer rate is low (few KBPS to 10
MBPS) and error rate is much higher.

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Short Questions

Q- 2.What are the two types of Transmission technologies, basis on which computer networks
can be categorized?
• Ans: Broadly there are two types of transmission technology:
• 1. Broadcast networks: a single communication channel that is shared by all the machines on
the network
• 2. Point-to-point networks: This network consists of many connections between individual
pairs of machines. To go from the source to destination a message (or packet) may have to
visit one or more intermediate machines

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Short Questions

• Q-3. What is Internet?

• Ans: Internet is a collection of networks or network of networks. Various
networks such as LAN and WAN connected through suitable hardware and
software to work in a seamless manner. It allows various applications such
as e-mail; file transfer, remote log-in, World Wide Web, Multimedia, etc
run across the internet.

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Short Questions

1) Discuss DQDB standard in context to MAN.

2) An alternative to LAN is simply a big timesharing system with
terminals
for all users. Give two advantages of client server system using a LAN.

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Short Questions

• Fill in the blanks

1. A computer network interconnects a number of _____________ computers.
2. Computer network emerges due to the development between two fields, namely _____________
and _____________.
3. Three main categories of networks are _____________, _____________ and _____________.
4. _____________ are privately owned while _____________ are usually owned by government
5. LAN operates at a _____________ speed with _____________error rate than WANs.
6. Internet is _____________ of networks.
7. Initially, computer network was developed for ________________.

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Objective Questions.

• Which Topology requires central controller or hub.

1) Mesh
2) star
3) bus
4) Ring

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Objective Questions

• In a network with 25 computers, which topology would requires most

expensive cabling.
1) Mesh
2) star
3) bus
4) Ring

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Objective Questions

• MAcKenzie Publication, with head quarter in London and branch

ofiices through-out Asia, Europe is probably connected by
1)LAN
2)MAN
3)WAN
4)None of above

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Objective Questions

• In a mesh topology ,the relation between one device and another

device is____________
1) Primary –to-peer
2) Peer-to-primary
3) Peer-to-peer
4) Primary –to-secondary

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CASE STUDY..

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ANS of case study

• A heterogeneous network made of four WANs and two LANs

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SHARDA GROUP OF INSTITUTIONS

Digital Course Content
Check list by Topic
Dept/ Year /
Semester Computer Science & Engineering/3/6 Content Creator Vijay Katta
Subject
Subject Code BCS 603 Coordinator

Subject Description Reviewer

Content Format Digital (Slides in PPT / Storyboard / Scanned Copy)

Lecture - Lecture-3
Unit 1 Topic Layering concept Sub-Topic

Fill Up the Following Check List (Should be filled by the Content Creator) Yes No

Did you included the diagrams/references to diagrams related to this topic? (Including flow of Diagram) Yes

Did you explained the Problem Solving Approach for the Problems related to this topic ?

Did you include Applications related to this topic in the Industry

Did you include Current Research and Development initiatives related to this topic?

Did you include Reading Assignment from the Reference Text Books? Yes

Did you Include Objective/ Interactive Questions/Answers related to this topic? Yes

Did you include short and descriptive questions related to this topic? Yes

Did you include References to the answers for the short and descriptive questions? Yes

Did you include references of the published content in the

VijayWeb/other resources (if you have referred it)
Subhash Katta Yes 82
Dept of Computer Science & Engineering – Hindustan College of Science & Technology

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Basic concept of layering

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Basic concept of layering

Specific Functional Objectives

On Completion of this lesson, the students will be able to:

• State the requirement for layered approach

• Explain the basic concept of layering in the network model
• Define entities protocols in networking context
• Describe ISO’s OSI Reference Model
• Explain information flow in OSI references Model.
• Explain functions of the seven layers of OSI Model
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Basic concept of layering

• Network architectures define the standards and techniques for designing and
building communication systems for computers and other devices.

• To reduce the design complexity, most of the networks are organized as a series
of layers or levels, each one build upon one below it.

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Basic concept of layering

• The basic idea of a layered architecture is to divide the design into

small pieces.

• Each layer adds to the services provided by the lower layers in such a
manner that the highest layer is provided a full set of services to
manage communications and run the applications.

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The benefits of the layered models

• The benefits of the layered models are modularity and clear

interfaces, i.e. open architecture and comparability between the
different providers' components.

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Tasks involved in sending a letter

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The basic elements of a layered model

• Services :-
a set of actions that a layer offers to another (higher) layer.
• protocols :-
set of rules that a layer uses to exchange information with a peer entity. These rules
concern both the contents and the order of the messages used

• Interfaces :-
defines which primitives operations and services the lower layer offers to the upper
layer adjacent to it.

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N-Layer Approch.

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Layer to Layer Communication

• Layer n on ‘A’talks to Layer n on ‘B’.

–No data transferred directly between layers at the same level.

–Data and control flow from one layer to the layer below it until it reaches
Physical Layer.
–All transmission only at the Physical Layer.
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Important Terms..

• A set of layers and protocols is known as network architecture.

• A list of protocols used by a certain system, atleast one protocol per

layer, is called protocol stack.

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Services and service access points

Service Users, Providers, and SAPs interact at the Network and

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Data Link Layers

Services and service access points

1) One OSI layer communicates with another layer to make use of the
services provided by the second layer.

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Services and service access points

Three basic elements are involved in layer services:

1) the service user,
2) the service provider, and
3) the service access point (SAP)

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Services and service access points

• the service user is the OSI layer that requests services from an
adjacent OSI layer.
• The service provider is the OSI layer that provides services to service
users.

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Short Question
A)Why Layered architecture?
1. To make the design process easy by breaking unmanageable tasks into several smaller and
manageable tasks (by divide-and-conquer approach).
2. Modularity and clear interfaces, so as to provide comparability between the different
providers' components.
3. Ensure independence of layers, so that implementation of each layer can be changed or
modified without affecting other layers. Each layer can be analyzed and tested
independently of all other layers.

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Short Questions

B) Why it is necessary to have layering in a network?

• Ans: A computer network is a very complex system. It becomes very difficult to implement as
a single entity. The layered approach divides a very complex task into small pieces each of
which is independent of others and it allow a structured approach in implementing a
network. The basic idea of a layered architecture is to divide the design into small pieces.
Each layer adds to the services provided by the lower layers in such a manner that the
highest layer is provided a full set of services to manage communications and run the
applications.

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Short Questions

C) What are the key benefits of layered network?

Ans: Main benefits of layered network are given below:

• Complex systems can be broken down into understandable subsystems.

• Any facility implemented in one layer can be made visible to all other layers.
• Services offered at a particular level may share the services of lower level.
• Each layer may be analyzed and tested independently.
• Layers can be simplified, extended or deleted at any time.
• Increase the interoperability and compatibility of various components build by different vendors.

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Short Questions

C) How two adjacent layers communicate in a layered network? (or What

do you mean by Service Access Point?)
• Ans: In layered network, each layer has various entities and entities of layer
i provide service to the entities of layer i+1. The services can be accessed
through service access point (SAP), which has some address through which
the layer i+1 will access the services provided by layer i.

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ISO-OSI Models

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Open Systems Interconnection (OSI) model

• The International Standards Organization (ISO), Established in 1947, is a

multinational body dedicated to worldwide agreement on international
standards.

• An ISO standard that covers all aspects of network communications is the

“Open Systems Interconnection (OSI) model”.

• It was first introduced in the late 1970s.

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Open Systems Interconnection (OSI) model

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The interaction between layers

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OSI Layer principles

1. A layer should be created where a different abstraction is needed.
2. Each layer should perform a well-defined function.
3. The function of each layer should be chosen with an eye toward defining
internationally standardized
protocols.
4. The layer boundaries should be chosen to minimize the information flow across
the interfaces.
5. The number of layers should be large enough that distinct functions need not be
thrown together in the same layer out of necessity and small enough that the
architecture does not become unwieldy.

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(OSI) model:- Application Layer:

The application layer enables the user, whether human or software, to access the
network.

• It provides user interfaces and support for services such as

• electronic mail,
• remote file access and transfer (Network virtual terminal.)
• Directory services
• shared database management, and
• other types of distributed information services.

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(OSI) Layer:- Presentation Layer:

• The presentation layer is concerned with the syntax and semantics of the information exchanged
between two systems.

• Determines the format used to exchange data among networked computers.

• The presentation layer is responsible for

• translation,
• compression, and
• encryption.

Vijay Subhash Katta 107

(OSI) model:- Session Layer:

• Session establishment
• Session Management
• Session termination
• Dialog control.
• Synchronization.
• Token management

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(OSI) model:-Transport Layer

• The transport layer is responsible for process-to-process delivery of

the entire message.
• Service-point addressing.
• Segmentation and reassembly.
• Connection control
• Flow control.
• Error control.
• Congestion Control with cordination to network layer

Vijay Subhash Katta 109

(OSI) model:- Network Layer:

• The network layer is responsible for

• Logical addressing.
• Routing.
• the source-to-destination delivery of a packet.

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(OSI) model:- Data-Link Layer:

• It makes the physical layer appear error-free to the upper layer

• It create a frame.
• Physical addressing
• Access control to Channel.
• provides error-free delivery.
• provides flow control.
• Error correction
• Error detection.
• Responsible to HOP- to- HOP delivery of frame
Vijay Subhash Katta 111

(OSI) model:- Physical Layer:

• The physical layer coordinates the functions required to carry a bit stream over a physical
medium.
• It deals with the mechanical and electrical specifications of the interface and transmission
medium.
• It also defines the procedures and functions that physical devices and interfaces have to perform
for transmission to Occur.
• It defines the electrical signals, line states and encoding of the data and the connector types
used. An example is 10BaseT.
• Physical topology.
• Transmission mode. (Simplex/half D/Full D) for cable only.

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An exchange using the OSI model

Vijay Subhash Katta 113

Summary of layers

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Short Questions

• Q-1. What do you mean by OSI?

• Ans: The Open System Interconnection (OSI) reference model describes how information
from a software application in one computer moves through a network medium to a
software application in another computer. The OSI reference model is a conceptual model
composed of seven layers, each specifying particular network functions. The model was
developed by the International Standardization Organization (ISO) in 1984, and it is now
considered the primary architectural model for inter-computer communications.

Vijay Subhash Katta 115

Short question

2) Which of the OSI layers handles each of the following

-Breaking the transmitted bit
stream in to frames.
-Determining which route through
the subnet to use .

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Short question

3) What are the important design issues of the data link layer
4)What are the important design issues of the transport layer
5) What are the important design issues of the Network layer

Vijay Subhash Katta 117

TCP/IP PROTOCOL SUITE

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TCP/IP PROTOCOL SUITE

• The layers in the TCP/IP protocol suite do not exactly match those in the OSI model.
• The original TCP/IP protocol suite was defined as having four layers:
• host-to-network,
• internet,
• transport, and
• application. However,
• When TCP/IP is compared to OSI, we can say that the TCP/IP protocol suite is made of five layers:
• physical,
• data link,
• network,
• transport, and
• application.

Vijay Subhash Katta 119

TCP/IP PROTOCOL SUITE

Stream Control Transmission Protocol (SCTP)

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ARP (IP to MAC)

Vijay Subhash Katta 121

TCP/IP PROTOCOL SUITE

• Four levels of addresses are used in an internet employing the

TCP/IP protocols:
• physical,
• logical,
• port and
• Specific (if Any)

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TCP/IP PROTOCOL SUITE

Vijay Subhash Katta 123

Relationship of layers and addresses in TCP/IP

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Short Questions

• Q-. Briefly write functionalities of different OSI layers?

Vijay Subhash Katta 125

Short Questions

• Q. What do you mean by Protocol?

• Ans: In the context of data networking, a protocol is a formal set of
rules and conventions that governs how computers exchange
information over a network medium. A protocol implements the
functions of one or more of the OSI layers.

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Short question

1) Give the difference between OSI & TCP/IP model . Which model is
more popular & why ?
2) What the different types of transmission technology ? Explain
different types of networks on the basis of transmission technology.

Vijay Subhash Katta 127

Objective questions.

• The end to end delivery of entire message is a responsibility of _____

1)Transport Layer
2)Network layer
3)Data link layer
4)Application layer

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Objective questions.

• Decryption and encryption is a responsibility of ____ layer

1)transport
2) presentation
3) Session
4) Data link

Vijay Subhash Katta 129

Objective questions.

• Dialog control is a function of the ____ layer

1)transport
2) presentation
3) Session
4) Data link

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Objective questions.

• As a packets are moves from upper layer to lower layer headers are---
--
1) added
2)Subtracted
3)Rearranged
4)Modified

Vijay Subhash Katta 131

Objective questions.

• Mail services and directory services are available to user by--------

layer
1)Application
2) Transport
3)internet layer
4) Physical layer

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Vijay Subhash Katta 133

Transmission Media

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Transmission Media

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Transmission Media

It may be classified into two types

• Guided:

• Unguided:

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Classes of transmission media

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Transmission Media

• Guided: Transmission capacity depends critically on the medium, the

length, and whether the medium is point-to-point or multipoint (e.g.
LAN).
• Examples are co-axial cable, twisted pair, and optical fiber.

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Transmission Media

• Unguided:
Free space provides a means for transmitting electro-magnetic signals but do
not guide them.

• Example wireless transmission

Vijay Subhash Katta 139

Guided transmission media

• Twisted Pair

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Twisted Pair

• Twisted pairs can be used for transmitting either analog or digital

information.
• The bandwidth depends on the thickness of the wire and the distance
travelled, but several megabits/sec can be achieved for a few
kilometers in many cases.

Vijay Subhash Katta 141

UTP and STP cables

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Twisted Pair

• The two wires are typically ``twisted'' together in a helix to reduce

interference between the two conductors.
• Twisting decreases the cross-talk interference between adjacent pairs
in a cable.
• Typically, a number of pairs are bundled together into a cable by
wrapping them in a tough protective sheath.

Vijay Subhash Katta 143

Twisted Pair

• Different LAN standards may use the twisted pairs differently.

• For example, 100-Mbps Ethernet uses two pairs (out of the four
pairs) ,one pair for each direction.
• To reach higher speeds, 1-Gbps Ethernet uses all four pairs in both
directions simultaneously;

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Twisted Pair

• Use: The oldest and the most popular use of twisted pair are in
telephony.
• In LAN it is commonly used for point-to-point short distance
communication (say, 100m) within a building or a room.

Vijay Subhash Katta 145

UTP connector

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3 types of UTP

• Simplex

• Cross over

• Roll over

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Coaxial cable

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coaxial cable

• Two kinds of coaxial cable are widely used.

• 50-ohm cable, is commonly used when it is intended for digital transmission from the start.
• 75-ohm cable, is commonly used for analog transmission and cable television.

• This distinction is based on historical, rather than technical factors.

• Modern cables have a bandwidth of up to a few GHz.

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COX

• Coaxial cables are categorized by their radio government (RG)

ratings.
• Each RG number denotes a unique set of physical specifications,
including
• the wire gauge of the inner conductor,
• the thickness and
• the type of the inner insulator,
• the construction of the shield, and the size and type of the outer
casing.
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BNC connectors (Bayone-Neill-Concelman)

Vijay Subhash Katta 151

Fiber Optics

• In fiber optic technology, the medium consists of a hair-width strand

of silicon or glass, and the signal consists of pulses of light.

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Fiber Optics

• Three components are required:

1. Fiber medium: Current technology carries light pulses for tremendous distances (e.g., 100s
of kilometers) with virtually no signal loss.

2. Light source: Typically a Light Emitting Diode (LED) or laser diode. Running current through
the material generates a pulse of light.

3. A photo diode light detector, which converts light pulses into electrical signals.

Vijay Subhash Katta 153

Fiber Optics

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Propagation mode

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multimode fibers Vs single mode

• In multimode fibers, the core is typically 50 microns in diameter,

about the thickness of a human hair.
• In single-mode fibers, the core is 8 to 10 microns.
• The core is surrounded by a glass cladding with a lower index of
refraction than the core, to keep all the light in the core.

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Propagation mode

Schematics of three optical fiber types, (a) Single-mode step-index,

(b) Multi-mode step-index,Vijay
and (c)Katta
Subhash Multi-mode graded-index 157

multimode fiber

• Multimode is so named because multiple beams from a light source move

through the core in different paths.
• How these beams move within the cable depends on the structure of the core.
• In multimode step-index fiber, the density of the core remains constant from the
center to the edges. A beam of light moves through this constant density in a
straight line until it reaches the interface of the core and the cladding.

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Multimode fiber

• A graded-index fiber, therefore, is one with varying densities.

• Density is highest at the center of the core and decreases gradually to
its lowest at the edge.

Vijay Subhash Katta 159

A comparison of semiconductor diodes and LEDs as light

sources.

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Short questions:

• Q-1. On what parameters the quality of transmission depends in

case of guided transmission media?
• Ans: It is mainly decided by the frequency of transmission and the
characteristics of the transmission media.

Vijay Subhash Katta 161

Short questions:

• Q-2. Why wires are twisted in case of twisted pair of transmission

medium?
• Ans: It minimizes electromagnetic interferences between the pairs of
wires, which are bundled together, so that the cross talk is minimum.

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Short questions:

• Q-3. Give a popular example where co-axial cables are used for
broadband signaling.
• Ans: Use of co-axial cable for broadband signaling is cable TV (CATV)
application.

Vijay Subhash Katta 163

Short questions:

• Q-4. What devices are used as source and detector in case of single
mode of fiber?
• Ans: LASER is used as source and photodiode is used as detector in
case of single mode of fiber.

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Short questions:

• Q-5. In what way multi-mode and single-mode fibers differ?

• Ans: The core diameter of single-mode fiber is much smaller than that of multi-mode fiber.
For example,
• For multi-mode fiber:
Core diameter lies in the range of 50-200μm
Cladding diameter lies in the range of 125-400μm
Repeater spacing is 2Km.
• For single-mode fiber:
Core diameter lies in the range of 8-12μm
Cladding diameter 125μm
Repeater spacing is 20Km. Vijay Subhash Katta 165

Short questions:

• Q-6. Why does single-mode fibres are used for large distance communications rather than
multi-mode fibres?
• Ans: In a multi-mode fiber, the quality of signal-encoded light deteriorates more rapidly than
single-mode fiber, because of interference of many light rays. As a consequence, single-mode
fiber allows longer distances without repeater. For multi-mode fiber, the typical maximum
length of the cable without a repeater is 2km, whereas for single-mode fiber it is 20km.

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Short questions:

• Q-7. What is crosstalk? How is it minimized in case of twisted-pair of wire?

Ans:
• (a) Crosstalk refers to the picking up of electromagnetic signals from other adjacent wires by
electromagnetic induction.
• (b) When a pair of wires is twisted together, the electromagnetic signals generated by the
two wires cancel each other as these are of opposite polarity. This helps to reduce the
susceptibility of interference to the adjacent wires.

Vijay Subhash Katta 167

Short questions:

• 8) Draw a passive star connection in fiber optics network and Active

repeater n/w in fiber optics and explain it .
• 9) Draw single and dual broadband cable n/w and explain it

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Objective Questions..

• In fiber optics ,the signal source is----

1)light
2)Radio wave
3)Infrared
4) UV light

Vijay Subhash Katta 169

Objective Questions..

• Which of following primarily uses guided media.

1)Cellular telephone system
2)Local telephone system
3)Satellite communication
4)Radio broadcasting.

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UNGUIDED MEDIA: WIRELESS

Vijay Subhash Katta 171

UNGUIDED MEDIA: WIRELESS

Unguided media transport electromagnetic waves without using a

physical conductor. This type of communication is often referred to
as wireless communication.

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Electromagnetic spectrum for wireless communication

Vijay Subhash Katta 173

Bands

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The electromagnetic spectrum and its uses for

communication.

Vijay Subhash Katta 175

Wireless transmission waves

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Radio waves

• Radio waves are used for multicast communications, such as radio

and television, and paging systems.

Vijay Subhash Katta 177

Microwaves

• Microwaves are used for unicast communication such as cellular

telephones, satellite networks,
and wireless LANs.

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Infrared signals

Infrared signals can be used for short-range communication in a

closed area using line-of-sight propagation.

Vijay Subhash Katta 179

Short questions:

• Q-1. What are the factors responsible for attenuation in case of terrestrial microwave
communication?
• Ans: Attenuation due to distance is 10 log (4πd/λ)2.
Factors responsible for attenuation are given below:
1. Distance – Attenuation is more if distance
increases.

2.Wavelength – Attenuation is less if wavelength is longer. (i.e high frequency components are
attenuated more than the low frequency component)

3.Rainfall – Attenuation is less if there is no rain.

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Short questions:

• Q-9. Why two separate frequencies are used for uplink and downlink transmission in case
of satellite communication?
• Ans: Two separate frequencies are used so that one cannot interfere with the other and full
duplex communication is possible.
• And other reason is that the Power required to transmit a signal is proportional to the
frequency of the signal. And more power requirement more would be the weight of the
system. As there are constraints on the load that can be carried with the satellite, mainly
down linking frequency is lower than the up linking one.

Vijay Subhash Katta 181

Fill in the blanks

(a) The quality of transmission primarily depends on the characteristics and nature of ____________ media.
(guided/unguided)
(b) Antenna Size plays an important role for data communication in ___________ media.
(c) The twisting in the twisted- pair cables reduce the ____________, which is generated due to the electromagnetic
interference..
(d) Co-axial cable can be used at a much higher frequency range than the twisted- pair cable ______ (True/False)
(e) In single cable mode of broadband communication, using coaxial cables, the frequency translation is performed by
a device known as _________ .
(f) The principle to _________________ is responsible for the optical signal propagation in fibre optic cables.

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Objective Questions

• At lower end of electromagnetic spectrum we have------

1) radio wave
2)power and voice
3)UV light
4)infrared

Vijay Subhash Katta 183

Objective Questions

• Smoke signal are an example of communication through---

1)Guided media
2)An unguided media
3)Refractive medium
4)Gamma rays.

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Vijay Subhash Katta 185

Switching

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Switching

• In the switched network methodology, the network consists of a set

of interconnected nodes, among which information is transmitted
from source to destination via different routes, which is controlled by
the switching mechanism.

Vijay Subhash Katta 187

Switching

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Circuit switching Technique

• A circuit-switched network consists of a set of switches connected by

physical links.

• A connection between two stations is a dedicated path made of one or more

links.

• However, each connection uses only one dedicated channel on each link.

• Each link is normally divided into n channels by using FDM or TDM.

Vijay Subhash Katta 189

Circuit switching Technique

• A circuit-switched network is made of a set of switches connected

by physical links, in which each link is
divided into n channels

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Circuit switching

• In circuit switching, the resources need to be reserved during the

setup phase;

• the resources remain dedicated for the entire duration of data

transfer until the teardown phase.

Vijay Subhash Katta 191

Circuit switching Industrial Use

• Switching at the physical layer in the traditional telephone network

uses the circuit-switching approach.

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Delay in a circuit-switched network

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circuit-switching..

• It involved the following three distinct steps

-Circuit Establishment:
-Data transfer:
-Circuit disconnect:

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Circuit Establishment:

• To establish an end-to-end connection before any transfer of data.

• Some segments of the circuit may be a dedicated link, while some other
segments may be shared.

Vijay Subhash Katta 195

Data transfer:

• Transfer data is from the source to the destination.

• The data may be analog or digital, depending on the nature of the

network.

• The connection is generally full-duplex.

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Circuit disconnect:

• Terminate connection at the end of data transfer.

• Signals must be propagated to deallocate the dedicated resources.

Vijay Subhash Katta 197

Examples of Circuit Switching

• Public switched telephone network (PSTN)

• ISDN B-channel
• Circuit Switched Data (CSD) and High-Speed Circuit-Switched Data (HSCSD)
service in cellular systems such as GSM
• X.21 (Used in the German DATEX-L and Scandinavian DATEX circuit switched data
network)
• Optical mesh network

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Circuit Switching Implementation

• Circuit switching uses any of the three technologies:

• Space-division switches
• Time-division switches
• combination of both.

Vijay Subhash Katta 199

Space-division switches

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Cross Bar Switch -Example

• Example: Xilinx crossbar switch using FPGAs (Field Programmable

Gate Arrays).
• It is based on reconfigurable routing infrastructure.
• It is a high-speed high capacity nonblocking type switch with sizes
varying from 64X64 to 1024X1024 and data rate of 200 Mbps.

Vijay Subhash Katta 201

Cross Bar switching Limitation

• Limitations of crossbar switches are as follows:

• The number of cross points grows with the square of the number of attached stations.

• Costly for a large switch.

• The failure of a cross point prevents connection between the two devices whose lines
intersect at that cross point.

• The cross points are inefficiently utilized.

• Only a small fraction of cross points are engaged even if all of the attached devices are active.
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space division switch

A three-stage space division switch

Vijay Subhash Katta 203

Time Division Switching

• Time-division switching uses time-division multiplexing to achieve

switching,
• different ongoing connections can use same switching path but at
different interleaved time intervals..

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Time Division Switching

• There are two popular methods of time-division switching namely

• Time-Slot Interchange (TSI) and
• the TDM bus

Vijay Subhash Katta 205

Time-Slot Interchange (TSI)

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TDM bus

Vijay Subhash Katta 207

Fill In the Blanks:

• 1 ________ uses the entire capacity of the link.

• 2 In ________ switching, each packet of a message need not follow
the same path from sender to receiver.
• 3. In ________ switching all the datagrams of a message follows the
same channel of a path.

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Objective Questions

• The ------ is a device that connects n inputs to m outputs.

1) crosspoint
2)crossbar
3)modem
4)RAM

Vijay Subhash Katta 209

Packet Switching

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Packet Switching

• In a packet-switched network, there is no resource reservation;

• resources are allocated on demand.

Vijay Subhash Katta 211

Packet Switching

• DATAGRAM NETWORKS

• VIRTUAL –CIRCUIT NETWORKS

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DATAGRAM NETWORKS

• In data communications, we need to send messages from one end

system to another.
• If the message is going to pass through a packet-switched network,
it needs to be divided into packets of fixed or variable size.
• The size of the packet is determined by the network and the
governing protocol.

Vijay Subhash Katta 213

DATAGRAM NETWORKS

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DATAGRAM NETWORKS

• A switch in a datagram network uses a routing table that is based on

the destination address.
• The destination address in the header of a packet in a datagram
network remains the same during the entire journey of the packet.

Vijay Subhash Katta 215

DATAGRAM NETWORKS

Switching in the internet is done by using the datagram approach

to packet switching at the network layer.

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VIRTUAL-CIRCUIT NETWORKS

A virtual-circuit network is a cross between a circuit-switched network

and a datagram network. It has some characteristics of both.

Vijay Subhash Katta 217

Switch and tables in a virtual-circuit network

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Source-to-destination data transfer in a virtual-circuit network

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VIRTUAL-CIRCUIT NETWORKS

• In virtual-circuit switching, all packets belonging to the same source

and
destination travel the same path;
• but the packets may arrive at the destination with different delays
if resource allocation is on demand.

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Examples

• ATM
• GPRS
• TCP
• X.25
• Frame Relay

Vijay Subhash Katta 221

Comparison between Switching

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Comparison between Switching

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Comparison between Switching

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Fill In the Blanks:

• 1. A switched virtual circuit involves _____________.

• 2. A permanent virtual circuit involves ____________.
• 3. Two basic approaches are common to Packet Switching are
_____________ packet switching and _________ packet switching.
• 4. X.25 is a standard for _________ communications.

Vijay Subhash Katta 225

• Ans:
• 1. creation of link as and when needed
• 2. permanent link
• 3. virtual circuit … datagram
• 4. packet switched communication

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Short Que.

• Q-1. How the drawback of circuit switching is overcome in message switching?

• Ans:
• Message switching is based on store and forward technique.
• Instead of establishing a dedicated path, the message is sent to the nearest directly
connected node.
• Each node stores the message, checks for error and forwards it.
• It allows more devices to share the network bandwidth and one message can be sent to
several users.
• Destination host need not be on at the time of sending message.

Vijay Subhash Katta 227

Q-2. What is the drawback of message switching? How is it overcome in packet

switching?

• Ans.:
• In message switching, large storage space is required at each node to buffer the complete
message blocks.

• On the other hand, in packet switching, messages are divided into subset of equal length, which
are generated in the source node and reassembled to get back the initial complete message in
destination node.

• Moreover, to transmit a message of large size, link is kept busy for a long time leading to increase
in delay for other messages.

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Q-3. Distinguish between circuit switching and virtual-circuit packet

switching.

• In circuit switching,
• a dedicated path is established.
• Data transmission is fast and interactive.
• Nodes need not have storage facility.
• However, there is a call setup delay.
• In overload condition, it may block the call setup.
• It has fixed bandwidth from source to destination and no overhead after the call setup.
• In virtual-circuit packet switching,
• there is no dedicated path.
• It requires storage facility and involves packet transmission delay.
• It can use different speed of transmission and encoding techniques at different segments of the route.

Vijay Subhash Katta 229

Q-5. How packet size affects the transmission time in a packet switching
network?

• Ans:
• Initially, transmission time decreases as packet size is reduced.
• But, as packet size is reduced and the payload part of a packet
becomes comparable to the control part, transmission time increases.

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BACKBONE NETWORKS

Vijay Subhash Katta 231

BACKBONE NETWORKS

A backbone network allows several LANs to be connected. In

a backbone network, no station is directly connected to the
backbone; the stations are part of a LAN, and the backbone
connects the LANs.

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Short Terms.

• In a bus backbone, the topology of the backbone is a bus.

• In a star backbone, the topology of the backbone is a star; the backbone

is just one switch.

• point-to-point link acts as a LAN in a remote backbone connected by

remote bridges.

Vijay Subhash Katta 233

Figure 15.12 Bus backbone

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Star backbone

Vijay Subhash Katta 235

5-4-3 rule

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Integrated Services Digital Network (ISDN)

Vijay Subhash Katta 237

Integrated Services Digital Network

(ISDN)

• ISDN is a digital transport and signaling systems

• ISDN defines a vendor independent interface between the user (telephones, PBXs, computers)
and the network
• The operations inside the network are typically governed by the common channel signalling
system No. 7 (SS-7 Layer)
• ISDN was designed primarily for circuit-switched voice traffic and secondarily for all other
aspects of data communication

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Integrated Services Digital Network

• Interfaces and Functional Groupings

• The ISDN user interface can be divided into two
areas
– Functional Groupings
– Reference Points
• Functional groupings (TE, TA, NT2, etc.) are a set of capabilities needed in an ISDN user
access
interface
• Reference points (R, S, T, and U) are the interfaces dividing the functional groupings.
• Usually a reference point is a physical interface between two pieces of equipment
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ISDN Architecture

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Interfaces and Functional Groupings

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Typical ISDN Configuration

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ISDN Logical Channel Concept

• ISDN employs time division multiplexing on its physical

channels
• Time slots in ISDN are named either B or D, depending on
the type of logical channel the utilises them – D slot
carries signalling or user data, B slot carries only user data
traffic
• Example of ISDN logical channels
– D channel: 16 or 64 kb/s
– B channel: 64kb/s
– H channel: Aggregate of B channels
•H0: 384kb/s (6 B channels)
• H11: 1536 kb/s (24 B channels)
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• H12: 1920 kb/s (30 B channels)

ISDN Layers

• ISDN only supports layer 1 to 3 of the OSI model

• ISDN service provision is divided into
– Bearer service – layers 1 to 3
– Teleservice – all 7 layers
• Layer 1 supports either
– Basic Rate Interface (BRI) – 2B+D, (144 Kbps)
– Primary Rate Interface (PRI) – 23B+1D, (1.544 Mbps
- 30B+2D(2.048 Mbps)
• Layer 2 is standardized in Q.921
• Layer 3 is standardized in Q.931
– Establishes, maintains and releases ISDN
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ISDN Switching Architecture

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Objective Question

• The ---- channel can be used for control of B channel

1)BC
2)D
3)H
4)C

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Objective Question

• The---channel has a lowest data rate

1)B
2)C
3)D
4)H

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Supplementary topics
-SAP
-Connection oriented service and connection less service

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Service Access Point (SAP)

• A Service Access Point (SAP) is an identifying label for network

endpoints used in Open Systems Interconnection (OSI) networking.

• The SAP is a conceptual location at which one OSI layer can request
the services of another OSI layer.

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Relation between layers at an interface

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SAP

• The boundaries between adjacent layers in the same system are

called Interfaces.

• Service Primitives are used to pass the information, and the protocol entity to
which the information is delivered is called a Service Access Point (SAP).

• Examples of SAPs are :-

• the type field in the Medium Access Control (MAC) protocol,
• the address field in HDLC,
• the protocol field in the IP network header,
• and the port identifier in UDP and TCP.
•
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Connection oriented service and connection

less service

• Connection Oriented Services

• There is a sequence of operation to be followed by the users of connection
oriented service. These are :
• Connection is established
• Information is sent
• Connection is released
• In connection oriented service we have to establish a connection before starting
the communication.
• When connection is established we send the message or the information and
then we release the connection.
• Connection oriented service is more reliable than connectionless service.
• We can resend the message in connection oriented service if there is an error at
the receivers end. Example of connection
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Connection Less Services

• It is similar to the postal services, as it carries the full address where the message (letter) is to be
carried.

• Each message is routed independently from source to destination.

• The order of message sent can be different from the order received.

• In connectionless the data is transferred in one direction from source to destination without
checking that destination is still there or not or if it prepared to accept the message.
• Authentication is not needed in this.

• Example of Connectionless service is UDP (User Datagram Protocol) protocol.

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Difference between Connection oriented

service and Connectionless service

• In connection oriented service authentication is needed while

connectionless service does not need any authentication.
• Connection oriented protocol makes a connection and checks
whether message is received or not and sends again if an error occurs
connectionless service protocol does not guarantees a delivery.
• Connection oriented service is more reliable than connectionless
service.
• Connection oriented service interface is stream based and
connectionless is message based.
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Service Primitives

• A service is specified by a set of primitives. A primitive means operation.

• There are five types of service primitives :
• LISTEN : When a server is ready to accept an incoming connection it executes the LISTEN
primitive. It blocks waiting for an incoming connection.
• CONNECT : It connects the server by establishing a connection. Response is awaited.
• RECIEVE: Then the RECIEVE call blocks the server.
• SEND : Then the client executes SEND primitive to transmit its request followed by the
execution of RECIEVE to get the reply. Send the message.
• DISCONNECT : This primitive is used for terminating the connection. After this primitive
one can’t send any message. When the client sends DISCONNECT packet then the server
also sends the DISCONNECT packet to acknowledge the client. When the server package
is received by client then the process is terminated.
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Different types of services

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Network delay

• Network delay is an important design and performance characteristic

of a computer network .
• The delay of a network specifies how long it takes for a bit of data to
travel across the network from one node or endpoint to another.
• It is typically measured in multiples or fractions of seconds.

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Types of Delay

• Processing delay – time routers take to process the packet header

• Queuing delay – time the packet spends in routing queues
• Transmission delay – time it takes to push the packet's bits onto the
link
• Propagation delay – time for a signal to reach its destination

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