PROTOCOL STACK AND

ADDRESSINGBY

DNAAGROUP 11

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TEAM MEMBERS

DHANUSHA 1MS07IS025NISHITA.M 1MS07IS061ARCHANA.H.V 1MS07IS012ANANYA.B.NAIK 1MS07IS007

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TABLE OF CONTENTS

INTRODUCTION OSI MODELPHYSICAL LAYER DATA LINK LAYERNETWORK LAYERTRANSPORT LAYER

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INTRODUCTION

PROTOCOLSPROTOCOL STACKOSI MODEL

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OSI MODELAPPLICATION

LAYERPRESENTATION

LAYERSESSIONS LAYERTRANSPORT LAYERNETWORK LAYERDATA LINK LAYERPHYSICAL LAYER

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PHYSICAL LAYER

It is the first and lowest layer of OSI model of computer networking. The physical layer consists of the basic hardware transmission technologies of a network

Physical layer obtains the data obtained by data link layer in the form of frames which it will convert into bits

Physical layer converts the data sent by data link layer into signals compatible with the transmission media

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Techniques

Data present in the physical layer can be analog or digital. It has to be converted either to digital signal or analog signal

For the conversion of digital to digital signals three techniques are used:

1.Line coding

2.Block coding

3.scrambling

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Techniques

For the conversion of digital data to analog signals the techniques used are

1.Amplitude shift keying

2.Frequency shift keying

3.Phase shift keying

4.Quadrature amplitude modulation

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Functions Of physical Layer

Physical characteristics of interfaces and mediumRepresentation of bitsLine configurationPhysical topologyTransmission modeAutonegotiation

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Protocols of Physical Layer

X.21EIA-232-EATM

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X.21X.21 interface protocol is concerned only with

the set-up and clearing operating between DTE and DCE associated with each call

It is a circuit switching protocol using synchronous ASCII with odd parity to connect or disconnect a subscriber to bulic switching network

Any data can be transferred through the network after call establishment is successful via x.21 protocol

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EIA-232-E

It is also called RS-232-C.it is found in both synchronous and asynchronous environment

Almost all modems conform to the EIA-232 standard and most PC have an EIA-232 port for connecting a modem or other devices

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ATMAsynchronous transfer mode is an electronic digital

data transmission technology.It is mainly used to transfer real-time video

conference and audio as well as image files, text and email

ATM is a packet oriented transfer method that uses asynchronous time division multiplying techniques.

It encodes the data into small sized cells and provides data link layer services that run over OSI layer.

It is mainly designed for high speed(155 MBits) communication

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DATA LINK LAYER

The data link layer is the second layer in the OSI seven-layer reference model. It responds to service requests from the network layer above it and issues service requests to the physical layer below it.

FUNCTIONS:

1)Framing

2)Addressing

3)Flow Control

4)Error Control

5)Media Access Control

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Framing Framing in this layer separates a message from one source to a

destination, or from other messages to other destinations, by adding a sender address and a destination address.

TYPES:

1)Fixed-Size Framing

2)Variable-Size Framing

Character-Oriented Protocols:

flag trailer flagheader Data from upper layer

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Error detection

Data can be corrupted during transmission.TYPES of errors:

1)Single-Bit Error

2)Burst ErrorTo detect or correct errors, we need to send extra

(redundant) bits with data.Error detection:

1) The receiver has a list if valid codewords.

2) The original codeword has changed to an invalid one.

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Data word

generator

codeword

Data word

Checker

Codeword

SENDER RECEIVER

Encoder Decoder

ExtractDiscard

Unreliable Transmission

00 000

01 011

10 101

11 110

Data words

Codewords

Code fro error detection

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Error correction More redundant bits are required

for error correction than for error detection.

Example:

let the code word transferred be 01001.

Humming distance: between two words is the number of differences between corresponding bits.

Minimum humming distance is chosen.

Data word Code word

00 00000

01 01011

10 10101

11 11110

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Protocols

Flow control refers to a set of procedures used to restrict the amount of data that the sender can send before waiting for acknowledgment.

Error control in the data link layer is based on automatic repeat request, which is the retransmission of data.

Protocols are implemented in software by using one of the common programming languages.

Protocols

Noiseless channels

Noisy channel

Stop and waitsimplest Stop

and wait ARQ

Go back-N ARQ

Selective repeat ARQ

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Simplest protocol

sender site algorithm

While (true)

{

wait for event();

if(event ( request to send))

{

get data();

make frame();

send frame();

}

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Receiver site algorithm While ( true )

{

wait for event();

if( event ( arrival notification))

{

receive frame();

extract data();

deliver data();

[send frame] // for stop and wait protocol

}

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STOP AND WAIT PROTOCOL

While(true)

Can send= true

{

wait for event();

if( event(request to send)and can send)

{

get data();

make frame();

send frame();

can send= false;

}

Wait for event();

If ( event( arrival notification)

{

receive frame();

can send= true;

}

}

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POINT TO POINT PROTOCOL

provides network address configuration. That is when a home user needs a temporary network address to connect to the internet.

Defines format of the frame. Provides multiple network layer . Does not provide flow control. No sophisticated addressing mechanism to handle frames. Simple mechanism for error control.

flag address

control protocol

Payload (variable) FCS flag

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Multiple access Data link layer consists of data link contol and multiple-access

resolution. Lower sub layer is responsible for resolving access to the shared

media. One of the methods is random access method. Here, no station is

superior to another station and none is assigned the control over another.

In controlled access method, the stations consult one another to find which station has the right to send.

Channelization is a multiple access method in which the available bandwidth of a link is shared in time, frequency, or through code, between different stations.

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NETWORK LAYER

This is the third layer from the bottom of protocol stack.

There is a piece of network layer in each and every host and in the routers.

It determines how packets are routed from one route to another.

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Network layer

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Important functions

Main role of network layer is to move packets from a sending host to receiving host.

Functions are categorized into three typesPath determination: Determined by routing

algorithms.Forwarding: Done by routers.Call set up: Routers establish connections with

each other.

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Network service modelDefines characteristics of end to end

transmission of data.

Virtual circuit model•Network determines the path between sender and receiver.•Packets flow along the path set up.•Routers are aware of the connection made.•Connection oriented service.

Virtual circuit model•Network determines the path between sender and receiver.•Packets flow along the path set up.•Routers are aware of the connection made.•Connection oriented service.

Datagram model•Networks sends packets with the address of destination.•Packets flow towards nearest router along the destination.•Routers are not aware of the connection made. They maintain a forwarding table.•Connectionless service.

Datagram model•Networks sends packets with the address of destination.•Packets flow towards nearest router along the destination.•Routers are not aware of the connection made. They maintain a forwarding table.•Connectionless service. 28protocol stack

Network layer protocols

Internet protocol:

Responsible for network layer addressing.

IP address: An address assigned to every interface.

They are of two types: IPV4 and IPV6

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IPV4 addressing

32 bit length(4 bytes)Represented in dotted decimal notationEg: 193.32.216.9

Equivalent decimal notation

11000001 00100000 11011000 00001001Two ways of assigning IP address:

Manual configuration

Dynamic host configuration protocol

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IPV4 data packet format

version Header length Type of service Data packet length

16-bit identifier Flags 13-bit fragmentation offset

Time-to-live Upper-layer protocol Header checksum

32-bit source IP address

32-bit destination IP address

Options(if any)

Data

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32bits

ICMP – Internet Control Message Protocol•Used by routers, hosts and gateways.

•Used for error reporting when IP router in not able to find the path to the host specified as the target.

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TRANSPORT LAYER

Network layer oversees source to destination delivery of individual packets, it does not recognize any relationship between those packets.

It treats each one independently, as though each piece belonged to a separate message, whether or not it does.

Transport layer on the other hand ensures that the whole message arrives intact and in order overseeing both error control and flow control at the source to destination level.

Process to Process delivery

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Service Point Addressing- Several programs run at the same time.- Data transfer needed only between two specific

processes.- Port numbers of the destination process is assigned in

the header which ensures that only the specific process responds to it.

Segmentation and Reassembling- The message is divided into transmittable segments. - Each segment contains a sequence number .- This enables the correct reassembling of the message at

the destination end and also in retransmission.35protocol stack

Connection Control

Two types: Connectionless : Treats each segment as a

independent packet and delivers it. Connection Oriented: sets up a connection with

the transport layer at the destination machine before delivering the packets.

Flow Control- Oversees the proper co-ordination of transfer

between the source and destination.

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Error Control- Sending Transport Layer make sure that the entire

message arrives at the receiving transport layer without error (damage, loss or duplication).

Terminologies:Reliable : Flow and error control present at the transport

layer resulting in slower and more complex service.Non-Reliable: Uses Own Flow and error control

mechanism or it needs fast service or nature of the service does not demand flow and error control (Real Time Application)

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User Datagram Protocol (UDP) It’s a connectionless, unreliable transport protocol. No services added to IP except process to process

communication using port numbers. Limited error checking.

UDP Operations

Connectionless Services: It is important to note that the process which uses UDP cannot send a stream of data to UDP and expect UDP to chop them into different related user datagrams. Instead each request must be small enough to fit into one user datagram.

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Flow and Error Control No Flow Control: Receiver may overflow with incoming

messages.

No Error Control: Sender does not know if the message is lost or duplicated.

Checksum is one error control mechanism and if the receiver detects an error through the checksum, the user datagram is silently discarded.

UDP Uses- Process that require simple request response communication

with little concern for flow and error control.

- Process with internal flow and error mechanism.

Ex: Trivial File Transfer Protocol (TFTP) can easily use UDP

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Transmission Control Protocol (TCP)

16/09/09

• It’s a connection oriented, reliable transport protocol.

• TCP Services:

Process to process communication using port numbers.

Stream Delivery Service:

Data is sent as a stream of bytes and obtained also as a stream of bytes.

An environment is created in which the two processes seem to be connected by an imaginary tube that carries their data across the internet.

Sending And Receiving Buffers:

Sending or receiving processes may not read or write data at the same speed, hence buffers are needed for storage.

Segments The IP layer as a service provider for TCP cannot send

data as a stream of bytes. Therefore TCP groups a number of bytes together into a packet called segment.

TCP adds a header to each segment (for control purposes) and delivers the segment to the IP layer for transmission.

Full Duplex Communication TCP offers full duplex service in which data can flow in

both directions as each time.

Reliable Service: TCP is reliable transfer protocol which uses an Acknowledgement mechanism to check the safe and sound arrival of data

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Comparison Between UDP and TCP

UDP TCP

Packet Header Size 8 bytes 20 – 60 bytes

Transport Layer Packet entity Datagram Segment

Port Numbering Yes Yes

Error Detection Optional Yes

Reliability: Error recovery by automatic repeat request (ARQ) No Yes

Virtual circuits: Sequence numbering and reordering No Yes

Flow control No Yes

Congestion avoidance: Variable congestion window, slow start, time outs

No Yes

Multiple streams No No

ECN support No Yes42protocol stack

THANK YOU

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