DATA COMMUNICATION AND COMPUTER NETWORKS PRESENTATION

PRESENTED BY:

ADIL CHOUDHARY 11900BEE_5

TOPIC: BEST ETHERNET DESIGN AND IMPLEMENTATION TO MINIMIZE COLLISIONS

Dated: 05/12/2009

About Ethernet…

Ethernet is a Local Area Network (LAN) technology.

The original Ethernet enabled computers located

within a few hundred yards of one another to

exchange messages.

Ethernet in fact is the standard today

Reasons:

Simple

Cheap

Manufacturers keep making it faster

About Ethernet…

Ethernet architecture is based on the concept of

connecting multiple computers to a long cable

sometimes called the ether, using transceivers.

Source:

http://www.cs.unc.edu/Courses/jbs/lessons/Internet/ethe

rnet/

About Ethernet…

The three major elements of Ethernet networks are:

Ethernet packets are called frames. These are units of

data sent across the network.

The Ethernet access method, CSMA/CD. This method

controls packet transmission and information flow

across the Ethernet hardware.

Hardware cables, connectors, and circuitry. These

transfer data to and from systems across the network

CSMA/CD

Source:http://www.universalteacherpublications

.com/univ/free-asgn/mcs42/Image57.gif

Ethernet Frame Format…

Source

:http://www.mattjustice.com/ethernet/images/et

hernet_frame.gif

Concept of collisions…

The basic strategy goes like this:

A computer listens on the cable to see if another

computer is transmitting, which is indicated by a

voltage change on the cable. If busy, the computer

waits and listens.

When the cable is not busy, a computer attempts to

transmit.

Another computer may attempt to transmit at the

same time, which causes a collision.

Collision domain…

A collision domain is a physical network segment where data

packets can "collide" with one another for being sent on a

shared medium, in particular in the Ethernet networking

protocol.

Source

:http://www.thebryantadvantage.com/images/

Hub%202%20Data%20Collision.jpg

Traffic Domains…

Router

Switch

Hub Hub

Switch

Hub Hub

Broadcast Domain Collision Domain

Traffic Domains…

Try to eliminate collision domains

Get rid of hubs!

Designing…

Now we need such a design for Ethernet in which

we have a minimum number of collisions. For this

purpose we have to consider some very important

points.

We have to chose the best topology for the

networking

Segmentation of collision domains.

Will have to design the layer 1, 2 and 3 structure.

Segmentation of collision domain…

Collisions and collision domain size are two factors that negatively affect the performance of a network.

Segmentation is the process of splitting a single collision domain into smaller collision domains.

Creating smaller collision domains reduces the number of collisions on a LAN segment, and allows for greater utilization of bandwidth.

Layer 2 devices such as bridges and switches can be used to segment a LAN into smaller collision domains.

Segmentation of collision domain…

Micro segmentation of the network reduces the

size of collision domains and reduces collisions.

Micro segmentation is implemented through the

use of bridges and switches.

Evolution of Ethernet Topologies…

Bus

Everybody on the same coaxial cable

Source:http://en.wikipedia.org/wiki/File:Netwo

rkTopology-Bus.png

Evolution of Ethernet Topologies…

Star

One central device connects every other node

Source:http://upload.wikimedia.org/wikipedia

/commons/6/66/NetworkTopology-Star.png

Hub…

A frame sent by one node is always sent to every other node.

Hubs are also called “repeaters” because they just “repeat”

what they hear.

Hub

Switch…

Forwards each incoming frame to the port where the destination node is

Reduces the collision domain

Makes more efficient use of the wire

Nodes don’t waste time checking frames not destined to them

Switch

A

B

Switch vs. Router…

Routers do not forward Ethernet broadcasts. So:

Switches reduce the collision domain

Routers reduce the broadcast domain

This becomes really important when trying to design

hierarchical, scalable networks that can grow

sustainably

Design guidelines…

Always connect hierarchically

If there are multiple switches in a building, use an

aggregation switch

Locate the aggregation switch close to the building

entry point

Locate edge switches close to users (e.g. one per floor)

Minimize Path Between Elements

Build Incrementally

Start small

Switch

Hosts

Build Incrementally

As you have demand and money, grow like this:

Aggreg.

Hosts

Switch

Do not daisy-chain

Resist the temptation of doing this:

Connect buildings hierarchically

Router

References…

http://en.wikipedia.org/wiki/IEEE_802.3

http://www.cs.unc.edu/Courses/jbs/lessons/Internet/ethernet/

http://en.wikipedia.org/wiki/Collision_domain

http://www.softpanorama.org/Net/Network_interface_layer/ethernet.sht

ml

Thank You…!!!