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PACKET SWITCHING

CHARU GUPTACHINKI AGGARWAL

RAHUL JOSHI

JASPREET KAUR

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What is a computer network?

Two or more connected computers

Major components in simple network

Client computer

Server computer

Network interfaces (N I Cs)

Connection medium

Network operating system Hub or switch

Router

The Internet - a large network

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Fibers

Coaxial Cable

Links Interfaces Switches/routers

Ethernetcard

Wireless card

Large router

Telephoneswitch

Network Components

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Packet Switching

Packet switching refers to protocols in which

messages are broken up into small packets before

they are sent.

Each packet contains a header (with address)

Packet is transmitted individually across the net

May even follow different routes to the destination.

Packet forwarding based on the header Network nodes may store packets temporarily

Destination reconstructs the message correctly.

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History

First invented by Paul Baran in the early 1960s

When he was asked to perform an investigation intosurvivable communications networks for the US Air

Force, building on one of the first wide area computernetworks.

Term packet switching coined by Donald Davies.

Baran's papers then influenced Leonard Kleinrock.

He conducted early research in the related field ofdigital message switching, and helped build theARPANET, the world's first packet switching network.

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Connectionless protocols :

Ethernet

IP

UDP Connection oriented packet-switching protocols :

X.25

Frame relay

Asynchronous Transfer Mode (ATM)

Multiprotocol Label Switching (MPLS)

TCP.

Packet Switching Networks

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Types of Switching

Circuit Switched Networks

Packet Switching

Datagram

Virtual Circuit

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Circuit Switching

Circuit switching was designed in 1878 in order to

send telephone calls down a dedicated channel

There are three phases in circuit switching:

Establish

Transfer

Disconnect

During a call, no other network traffic can use thoseswitches.

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Circuit vs Packet switching

Circuit-switched networks require dedicated point-to-point

connections during calls whereas packet-switched networks

move data in separate, small blocks based on the

destination address in each packet. Circuit-switched networks were used for phone calls and

packet-switched networks handled data.

It is easier to double the capacity of a packet

switched network than a circuit network

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Circuit vs Packet switching

It is cheaper to expand a packet switching system.

Circuit-switched technologies takes four times as

long to double their performance/cost than packet

switched technologies.

In circuit switching, bandwidth is guaranteed

whereas in packet switching bandwidth is

dynamically allocated on as-needed basis

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Types of Packet Switching

Station breaks long message into packets

Packets sent one at a time to the network

Packets handled in two ways Datagram

Virtual circuit

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Datagram

Each packet treated independently

Packets can take any practical route

Packets may arrive out of order Packets may go missing

Up to receiver to re-order packets and recover

from missing packets

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Virtual Circuit

Preplanned route established before any packetssent

Call request and call accept packets establish

connection (handshake) Each packet contains a virtual circuit identifier

instead of destination address

No routing decisions required for each packet

Clear request to drop circuit

Not a dedicated path

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Virtual

Circuit Diagram

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Virtual Circuits v Datagram

Virtual circuits Network can provide sequencing and error control

Packets are forwarded more quickly

Route established for entire conversation

Less reliable Loss of a node looses all circuits through that node

Datagram No call setup phase

Better if few packets More flexible

Route established for each packet and can be used to avoidcongested parts of the network

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Packet Size

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Advantages Of Packet Switching

Line efficiency

Single node to node link can be shared by many

packets at same time

Packets queued and transmitted as fast as possible

Data rate conversion

Each station connects to the local node at its own speed

Nodes buffer data if required to equalize rates Packets are accepted even when network is busy

Delivery may slow down.

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Disadvantages Of Packet Switching

It takes time to put back the data package as it

changes each time, which can be a problem.

More processing power is required due to complex

routing protocols.

Less hard drive space needed but more actual

memory needed.

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Research and resources

http://www.livinginternet.com/i/iw_packet_inv.htm

www.daxnetworks.com/technology/techdost/td-

042005.pdf

www.wisegeek.com/what-is-packet-switching.htm