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Topic : Basics of WAN & WAN ProtocolsSub-Topic : Describe Different Layers of TCP/IP

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Recap

In the previous classes, you have learnt about

• Packet transfer mechanism in Routers using IP address

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Objectives

On completion of this period, you will be able to know about

• Functions of different layers of TCP/IP

• Various protocols used in different layers

• Importance of TCP/IP architecture

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What is the network architecture that we have already studied ?

ISO – OSI Model

Recap

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How many layers it has and name them ?

Seven -

Application

• Presentation

• Session

• Transport

• Network

• Data link

• Physical

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OSI Model

Application

Presentation

Session

Transport

Network

Data link

Physical

Fig .1

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• OSI model has seven layers in it

• Two of the layers namely presentation and session

layers were rarely used

• OSI architecture is rigidly structured

• As the technologies developed there was a need for a

new architecture

• Presentation and session layers are eliminated

• TCP/IP architecture has evolved to overcome the

shortcomings of OSI model

Need for TCP/IP

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TCP/IP Model

Application

Transport

Internet

Host-to-network

Not present in the model

Fig .2

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Layer Level Comparisons

OSI TCP / IP

Application Application

Transport Transport

Network Internet

Data link

Physical Host-to-Network

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Differences in Architectural Models

• OSI Network architecture model does not permit

communication between different heterogeneous

networks

• It does not support the latest networks developed

Differences in Architectural Models (Contd…)

• TCP/IP network architecture allows us to communicate

between any heterogeneous networks

• It is flexible and ready to change its architectural

structure to support the newly introduced networks

• For Ex: The wireless communication networks also can

be interconnected to the existing wired networks

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Functions of the TCP/IP Layers

Host-to-Network Layer

• It is the lowest layer in this model

• It is equivalent to the Physical layer of OSI model

• The TCP/IP reference model does not really say much about what happens in this layer

• It points out that the host has to connect to the network using some protocol so it can send IP packets over it

• This protocol is not clearly defined and varies from host to host and network to network

• It is concerned with the physical characteristics of the medium, connectors, voltage levels etc

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Host-to-Network Layer (Contd…)

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Internet Layer

• Internet layer is the lynchpin that holds the whole

architecture together

• Its job is to permit hosts to inject packets into any

network and have them travel independently to the

destination

• The destination can be in a local network or different

network

Internet Layer

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•They may even arrive in a different order than they were

sent, in which case it is the job of higher layers to rearrange

them

•The internet layer defines an official packet format and

protocol called IP (Internet Protocol)

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Internet Layer ( contd…)

• Packet routing is clearly the major issue here, as is avoiding congestion

• This layer also performs congestion control i.e. it can divert the data traffic to other routes to ease the congestion

• TCP/IP internet layer is very similar in functionality to the OSI network layer

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Transport Layer

• The layer above the internet layer in the TCP/IP model

• It is designed to allow peer entities on the source and

destination hosts to carry on a conversation

• Two end-to-end protocols have been defined here

a) Transmission control protocol

b) User data gram protocol

Transport Layer (Contd…)

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•The first one, TCP (Transmission Control Protocol) is a

reliable connection-oriented protocol.

•TCP allows a byte stream originating on one machine to

be delivered without error on to any other machine in the

internet.

•It fragments the incoming byte stream into discrete

messages and passes each one onto the internet layer.

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Transport Layer (Contd…)

• At the destination, the receiving TCP process reassembles the

received messages into the output stream

• TCP also handles flow control

• It makes sure that a fast sender cannot swamp a slow receiver

with more messages than it can handle

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UDP Protocol

• The second protocol in this layer is UDP (User Datagram

Protocol)

• UDP an unreliable, connectionless protocol for

applications that do not want TCP’s sequencing or flow

control

Transport Layer (Contd…)

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•It is widely used for one-short, client-server type request-

reply queries

•It is used in applications in which prompt delivery is more

important than accurate delivery, such as transmitting

speech or video

UDP Protocol contd…

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Protocols and Networks in the TCP/IP Model Initially

TELNET FTP SMTP DNS

TCP UDP

IP

ARPANET SATNET PACKET RADIO

LAN

Layer (OSI names)

Application

Transport

Network

Physical + Data link

Protocols

Networks

Fig .3

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Application Layer

• TCP/IP model does not have session or presentation layers

• On top of the transport layer is the application layer

• It contains all the higher-level protocols

• The early ones included virtual terminal (TELNET), file transfer (FTP), and electronic mail (SMTP)

• TELNET, the virtual terminal protocol allows a user on one machine to log into a distant machine and work there

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Application Layer (Contd….)

• SMTP (Simple Mail Transfer Protocol) also called as Electronic mail

• It was originally just a kind of file transfer, later a

specialized protocol was developed for it

• Domain Name Service (DNS) for mapping host names

onto their network addresses

• The file transfer protocol provides a way to move data in

the form of files efficiently from one machine to another

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•DNS is used to translate the email ID into IP address.

Users can identify themselves through email ID

•Network News Transfer Protocol (NNTP) the protocol

used for moving news articles, which will be used by the

news paper companies

•Hyper Text Transfer Protocol (HTTP), the protocol used

for fetching pages on the World Wide Web

Application Layer (Contd….)

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Summary

In this class, you have learnt about

• Functions of various layers in TCP/IP

• The various protocols used in TCP/IP along with their

importance

• The TCP/IP architecture and its functions

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Quiz

1) This layer deals with the physical transmission medium

a) Host-to-Network

b) Internet layer

c) Transport layer

d) Application layer

2) TCP protocol is related to which layer

a) Host-to-Network

b) Internet layer

c) Transport layer

d) Application layer

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Quiz

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Quiz

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3) UDP protocol is related to which layer

a) Host-to-Network

b) Internet layer

c) Transport layer

d) Application layer

4) IP protocol is related to which layer

a) Host-to-Network

b) Internet layer

c) Transport layer

d) Application layer

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Quiz

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Quiz

5) WWW can be accessed using this protocol

a) IP

b) UDP

c) HTTP

d) NNTP

6) News publishing companies use this protocol

a) IP

b) UDP

c) HTTP

d) NNTP

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Quiz

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Quiz

7) E-mail is supported by this protocol

a) IP

b) SMTP

c) HTTP

d) NNTP

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8) Traffic congestion is the function of this layer

a) Host-to-Network

b) Internet layer

c) Transport layer

d) Application layer

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Quiz

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Frequently Asked Questions

Short Questions

1. Name the various layers of TCP/IP architecture ?

2. What are the functions performed by Host-to-Network layer?

3. What are the functions performed by Internet layer ?

4. What are the functions performed by Transport layer ?

5. What are the functions performed by Application layer ?

6. What are the various protocols supported by TCP/IP architecture ?

7. Briefly describe about TCP and UDP ?

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Frequently Asked Questions

Essay Questions

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1. Discuss in detail about TCP/IP architecture and explain

the functions performed by different layers ?

2. Discuss about all the types of protocols supported by

TCP/IP network architecture model ?