ETHERNET

Network ArchitectureCovers issue like how data will flow between

the computers on the network.Involves with:

Logical designPhysical design

Introduction to Ethernet IEEE 802.3Ethernet is commonly used Local Area

Network(LAN) technology developed by Xerox in 1970’s.

Ethernet is a non-proprietary industry standard that is widely accepted by network hardware manufacturers.

Characteristics:Flexible technology Can run on variety of network mediaExcellent bandwidthReasonable cost of bandwidth

Ethernet Features

Ethernet FeaturesFeature Description

Traditional topology Linear bus

Other topologies Star bus

Type of architecture Baseband

Access method CSMA/CD

Specification IEEE802.3

Transfer speed 10 Mbps / 100 Mbps

Cable type Thicknet, Thinnet, UTP

Traditional Ethernet (10Mbps)Ethernet has been proven to be inexpensive,

reasonably fast & very popular LAN technology.

Among 10Mbps Ethernet technologies are:10Base210Base510BaseT

10Base2 Ethernet10Base2 = Thin coaxial cable / thinnet cable

can be used to connect 4 computers without any hub or switch with both end of the cable terminated by a BNC terminator.

It relies on CSMA/CD access method to regulate the traffic.

The ethernet media is passive = means it requires no power source of its own & will not fail unless its physically cut / improperly terminated.

Limitation: 185meters cable length only, with minimum 0.5 meters between each station allowing maximum 30 computers.

10Base2 Ethernet specificationCategory Notes

Max segment length 185 meters (607 feet)

Connection to NIC BNC T connector

Trunk segments & repeaters

5 segments can be joined using 4 repeaters

Computers per segment 30 computers per segment by specification

Segment that can have computers

3 of the 5 segments can be populated

Max total network length 925 meters (3035 feet)

Thinnet 5-4-3 rule5 segments, 4 repeaters and 3 populated

segments.

10Base5 EthernetAlso known as thicknet & has distance limit of

1640feet without repeaters.10base5 topology uses an external transceiver

to attach to the network interface card.NIC attaches to the external transceiver by an

AUI cable to the DIX connector on the card.Some external transceivers clamp to the

thicknet using vampire taps, others use BNC or N-series barrel connector.

10Base5 Ethernet

10Base5 cabling components

10BaseT Ethernet1990’s IEEE introduced Ethernet using twisted

pair (unshielded) cable known as 10BaseT.At the end of the cable there is RJ45 connector

which resembles RJ11(for telephone) connector but bigger in size.

The hub/switch of 10BaseT network serves as multi-port repeater & always located in wiring closet of building.

Most are configured in star topology but internally they use bus signaling system.

Max cable length is 100m, but repeaters can be used to extend the max cable length, with min length between computers is 2.5m allowing total 1024 computers to be connected using 10BaseT network.

10BaseT Ethernet

Specification of 10BaseTCategory Notes

Cable Category

Connectors RJ45 at cable ends

Transceiver Each computer needs one, some have it built in

Transceiver to hub distance

100m (328 feet)

Backbones for hub Coaxial or fiber optic cable to connect to larger LAN

Total no of computers per LAN without connecting components

1024 by specification

Ethernet cablesMost current popular cable is CAT5, but CAT

5e cable supports Gigabit Ethernet.There are distance limitations to ethernet

cables, after which transmissions will likely fail due to line noise, reduced signal strength etc.Name Segment length

(max)Cable

10Base5

500m/1640ft RG-8 / RG-11 coaxial

10Base2

200m/606ft RG-58 A/U or RG-58 C/U coaxial

10BaseT

100m/328ft CAT 3 or better unshielded twisted pair

Switched EthernetTraditional ethernet are also known as shared

Ethernet.It provides a fixed bandwidth which must be

shared by all devices on the network within collision domain.

More than 2 computers cannot send & receive data simultaneously due to the reason that they share a segment/hub/repeater.

Hub/repeater doesn’t have ability to divide collision domain.

Switched Ethernet a switch/router can separate a network

segment, making each segment working as independent of other segments.

It makes the collision domain smaller & overall network becomes efficient.

Switched Ethernet enables multiple nodes to simultaneously transmit & receive data over different logical network segments.

It is much faster as fewer workstations must compete for the same time on media.

Switched Ethernet

hub hubhub

Switch

Collision domain

Collision domain

Collision domain

Fast EthernetFast Ethernet is a improved version of

traditional Ethernet operating at the speed of 100Mbps.

Fast Ethernet are:100BaseX100VG-AnyLAN

100BaseX Ethernet 802.3Also called Fast Ethernet & runs on UTP category 5

cable & uses CSMA/CD is a star wired star topology.

Similar to 10BaseT where all cables are attached to hub.

A traditional LAN is half duplex but fast Ethernet is full duplex & can operate at 200Mbps theoretically.

100BaseX incorporates 3 media specifications:100BaseT4 (4 pair Cat3,4 or 5 UTP)100BaseTX (2 pair Cat 5 UTP or STP)100BaseFX (2 strand fiber optic cable)

100BaseX Ethernet 802.3Value Represents Actual meaning

100 Transmission speed

100Mbps

Base Signal type Baseband

T4 Cable type Indicates UTP cable using 4 telephone grade pairs.

TX Cable type Indicates UTP cable using 2 data grade pairs

FX Cable type Indicates fiber optic links using 2 strands of fiber optic cable.

100VG-AnyLAN Network 802.12

100VG (Voice Grade) AnyLAN combines the feature of both Ethernet & Token Ring architectures.

Originally developed by Hewlett-Packard.Both 100BaseVG-AnyLAN & Fast Ethernet are

about 5 to 10 times faster than traditional Ethernet & compatible with existing 10BaseT cabling systems.

It allows easy & inexpensive upgrades from existing 10BaseT installations.

Different names of 100VG-AnyLAN;100BaseVGVGAnyLAN

Gigabit Ethernet (1Gbps)Latest version of Ethernet which offers a

bandwidth of 1000Mbps but the performance is still being in compatible with existing Ethernets & uses the same CSMA/CD & MAC protocols.

It can be used to aggregate traffic between clients & server farms & for connecting Fast Ethernet switches.

Can also be used for high bandwidth applications such as medical imaging & CAD.

Ethernet Frame Format Data frame is also called a frame is an

organized structure into which the data is placed for transmission across network.

Data frames defines how data is organized (relative position, length of fields, placement of control information)

In Ethernet data is sent in streams one bit at a time, data frame breaks the stream up into discrete chunks so that it can be managed.

If there is an error in transmission, only the affected frames need to be resent.

Ethernet Frame Format

Preamble 8 bytes

Destination address6 bytes

Source address6 bytes

Type2 bytes

Data46 - 1500 bytes

CRC4 bytes

Original Ethernet FrameMax size = 1,582 bytes)