Data Communication And Computer Networks Presentation 6241p

DATA COMMUNICATION AND COMPUTER NETWORKS PRESENTATION PRESENTED BY:

ADIL CHOUDHARY 11900 BEE_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

Switch Hub

Broadcast Domain

Hub

Hub

Collision Domain

Traffic Domains… 

Try to eliminate collision domains  Get

rid of hubs!

Deg… 

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

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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://.wikimedia.org/wikipedia /commons/6/66/NetworkTopology-Star.png

Hub… 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.

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

B A

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 s (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.

Switch

Hosts

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

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

Thank You…!!!