ethernet wireless lan moh

8/4/2019 Ethernet Wireless LAN MOH

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ALTTC/ DX Faculty 1


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ALTTC/ DX Faculty 2

Background of Ethernet (First LAN)

Digital, Intel & Xerox (DIX) consortiumcreated original Ethernet 1980(originally known as Alto AlohaNetwork)

The first network to provide CarrierSense Multiple Access / CollisionDetection (CSMA/CD)

Ethernet_II to followed in 1984 (ver-2)

IEEE termed this as 802 projectInitially IEEE 802 Project divided intothree groups


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ALTTC/ DX Faculty 3

High level interface (HILI) became 802.1committee

Responsible for High level interworkingprotocols and management

LLC group became 802.2 committee,for end to end link connectivity betweenhigher layer and media access dependent

layers

DL & MAC (DLMAC) group becameresponsible medium access protocols

DL MAC has been split into three sub

committees

Initial IEEE 802 Project


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ALTTC/ DX Faculty 4

802.3 for Ethernet

Came of with Ethernet physical layerspec.

MAC addressing is same as Ethernet_IIbut length field replaced type filed

Bus topology LAN at 10 Mbps withcollision detection (CSMA/CD)

10base 2/ thinnet 185 meters segmentwithout repeater over RG58 coaxial cable at 50ohms

10base 5/ thicknet 500 meters segmentwithout repeater over RG8/11 coaxial cable at50 ohms

10base T/UTP cat 3 UTP(Unshielded TwistedPair) to support 10 Mbps

DL MAC committees 802.3


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ALTTC/ DX Faculty 5

802.4 for Token Bus

Burroughs, concord data systems,Honeywell, western digital, generalmotors & Boeing took over 802.4

802.5 for Token Ring

IBM worked on 802.5

DL MAC committees 802.4/802.5


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ALTTC/ DX Faculty 6

Ethernet Technology


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ALTTC/ DX Faculty 7

Ethernet Standards (802.3)

Ethernet (10 Mbps)Ethernet_II - (DIX- Ethernet)IEEE 802.3 - Ethernet

Fast Ethernet (100 Mbps)

IEEE 802.12 - 100VG AnyLANIEEE 802.3u - Fast Ethernet

Gigabit Ethernet (1000 Mbps or 1Gbps)

IEEE 802.3z - Gigabit EthernetIEEE 802.ab - Gigabit Ethernet

10 Gigabit Ethernet (10 Gbps)IEEE 802.3ae - 10 Gigabit Ethernet


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ALTTC/ DX Faculty 8

Ethernet_II vs. OSI Model

Upper

Layers

Network

Ethernet_II

Other

Layers

NetworkData Link

Physical

OSI model

Media Access Control

(MAC)

DIX-Ethernet Layers


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ALTTC/ DX Faculty 9

Ethernet_II- Frame

8B 6B 6B 2B 46~1500B 4B

SOURCE

HARDWAREADDRESS

CRCLAYER 3 DATA

TYPE

DESTINATION

HARDWAREADDRESS

PREAMBLE

64~1518B

72~1526B

Eg. Of Type Fields:

0800- IP 0806- ARP 8035- RARP


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ALTTC/ DX Faculty 10

Ethernet_II Frame - Details

Preamble: 8 bytes of alternating 0s and 1s

to synchronise the receiverDestination Address (DA): 6 bytes (48bits) unique physical address of destinationmachine encoded in NIC

Source Address (SA): 6 bytes (48 bits)unique physical address of source machineencoded in NIC

Type : 2 bytes (16 bits) indicates the type ofLayer 3 protocol being used Eg. IP, ARP orRARP (uses RFC 1700 Ethernet Type Values)

Layer 3 Data: Between 46-1500 bytes

CRC : 4bytes (32 bits) for error detectioninformation


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MAC Address structure (for all Ethernet)

Destination address : (LS Bit first and MS bit Last in each byte -

Little-Endian style)I/G Individual / group address:

0 - Individual address.

1 - Group address.

U/L Universal /local address:

0 - Universally administered.

1- Locally administered.

Source address(LS Bit first and MS bit Last in each byte -

Little-Endian style)

I/G bit is always 0. U/L Universal/local address may be 0/1

U/L I/G

Organisationally Unique Identifier (OUI)

(3 bytes)

LSB MSB LSB MSB LSB MSB LSB MSB LSB MSB LSB MSB

Vendor Assingned No. (Serial No.)

(3 bytes)

Most Significant Byte Least Significant Byte


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CSMA/CD

Ethernet Uses Carrier Sense Multiple Access

with Collision Detection (CSMA/CD) as accessmethod

Any station wishing to transmit must listen forCarrier on the line

If no carrier is detected, the line is idle andtransmission can be initiated

Two or more stations transmits at the sametime, when there was no carrier, results incollision which is indicated by high voltage on

the lineAfter collision retry is done at staggered timeby different devices

CSMA/CD reduces the number of collision butdoes not eliminate them


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Ethernet CSMA/CD algorithm

If adapter detects another transmissionwhile transmitting, aborts and sendsjamsignal

After aborting, adapter enters

exponential backoffafter mth collision

first collision: choose K from {0,1} i.e.{0, 22-1};delay is K x 512 bit transmission times

after second collision: choose K from{0,1,2,3}ie. {0,1,..22-1}

after ten collisions, choose K from{0,1,2,3,4,,1023}I.e. {0,1,..210-1}


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IEEE Project 802

IEEE Project 802 sets standard toenable interworking between devices ofvarious vendors.

Logical Link Control (LLC) sub-layerhas been added to achieve the aboveobjective

Other

Layers

Network

IEEE Project 802

Other

Layers

Network

Data Link

Physical

OSI model

Logical Link Control

Media Access Control


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Initial IEEE Project 802

Other Layers

Network

IEEE Project 802

802.2 - Logical Link Control

802.4

Token Bus

802.5

Token Ring

ANSI

FDDI

802.3

CSMA/CD

IEEE 802.2 LLC deals with logical address,control information and data

MAC sub layer resolves contention for shared

media


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802.3 MAC Frame/802.2 LLC without SNAP

802.2 LLC LAYER

ENCAPSULATION DATA

43~1497B3B

7B 1B 6B 6B 2B 46~1500B 4B

SOURCE

HARDWARE

ADDRESS

CRC802.2 PDU

LENGTH

DESTINATION

HARDWARE

ADDRESS

SF

D

PREAMBLE

64~1518B

72~1526B

DSAP SSAP Control

1B 1B 12 B


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802.3 MAC Frame

Preamble

7 bytes of alternating 0s and 1s that alertthe receiving system and enable it tosynchronise its input timing

Start Frame Delimiter (SFD)

One byte (10101011) signals thebeginning of the frame

Destination Address (DA)6 bytes (48 bits) unique physical address

of destination machine encoded in NICSource Address (SA)

6 bytes (48 bits) unique physical addressof source machine encoded in NIC


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802.3 MAC Frame

Length (2 bytes)Indicate number of bytes in the frame

802.2 PDU

Upper layer information between 46-1500 bytes

CRC (4 bytes)

For error detection information


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802.2 LLC Header

DSAP:Destination service access point structureI/G - Individual/group address

0 - Individual DSAP.

1 - Group DSAP.

SSAP:Source service access point structure

C/R - Command/response:

0 - Command.

1 - Response.

Control: The structure of the control field is same as HDLC .

For IP Network value is (03)

DSAP SSAP ControlI/G C/R

802.2 LLC Header


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802.3 MAC Frame/802.2 LLC with SNAP

802.2 LLC / SNAPENCAPSULATION

DATA

38~1492B8B

7B 1B 6B 6B 2B 46~1500B 4B

SOURCE

HARDWARE

ADDRESS

CRC802.2 PDU

LE

NGTH

DESTINATIO

NHARDWARE

ADDRESS

SFD

PREAMBLE

64~1518B

72~1526B

DSAP SSAP Control

1B 1B 12 B

OUI Ether Type

SNAP

5B

2B3B

OUI- Organisationally Unique Identifier

SNAP- Sub Network Access Point


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Ethernet (Cabling Spec.)

Three main Cabling specificationsare available in Ethernet:

10 Base 5

Uses Thick co-axial Cable

10 Base 2

Uses Thin Coaxial Cable

10 Base TUses Unshielded Twisted pair cable


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10Base5; Thick Ethernet; Thicknet

The nickname derives from the size of thecable

Each station on Ethernet network has itsown Network Interface Card (NIC) which

provides the station with a unique 6 bytesphysical address

Each frame is transmitted to every stationon the link but will be read only by the

station to which it is addressedTransceiver performs the CSMA/CD forchecking voltages and collisions on the line


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10Base5; Thick Ethernet; Thicknet

5 Segments; 2500 M; 1000 Stations

R RSegment 1

Segment 1

500 M; 200 Stations

2.5 M 50 M

1-NIC(Network Interface Card)

1

2-RG-8 Thick Coaxial Cable

2

3-Cable Terminator

3

5-Attachment Unit Interface (AUI);Transceiver Cable (15 Wires)

5

6-Media Attachment unit (MAU);commonly known as Transceiver

6

4

4-Transceiver Vampire Tap


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10Base2; Thin Ethernet; Thinnet

Also known as cheapnet or cheapernet

Provides same data rate as 10Base5but with distance limitation of 185meters and lesser number of workstations

Transceiver circuitry has moved into theNIC

Transceiver tap has been replaced by aconnector that splices the station

directly into the cableBNC-T connector is with 3 ports; onefor NIC, one each for input and outputends of the cable


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10Base2; Thin Ethernet; Thinnet

185 M

2-RG-58 Thin Coaxial Cable

2

4

4-Cable Terminator

1-NIC(Network Interface Card)

1

3-BNC-T Connector

3


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10BaseT

A star topology LANAll individual transceiver functions andnetworking operations are placed in anintelligent hub with a port for each

stationHub fans out any transmitted frame toall its connected stations

Frame will be read by all, but will onlybe processed by the station to which itis addressed


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10BaseT

100 M

10Base-T Hub

100 M

1-10 Base-T Hub

1

2-RJ-45 Connector Male

2 5

5-RJ-45; Four Pairs UTP (Unshielded Twisted Pair) Cable

4-Network Interface Card

4

3-RJ-45 Connector Female

3


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Fast Ethernet Standards

Two standards are approved byIEEE in June 1995

802.12

802.3u


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Fast Ethernet Standards- 802.12/802.3u

802.12Uses even efficient signaling techniquesthan CSMA/CD known as DemandPriority Access Method (DPAM)

Also known as 100VG-AnyLANNot popular and eventually disappearedfrom the market

802.3u

Most popular spec. in 100Mbps over cat5 UTP or cat 5 plus

Also known as Fast Ethernet


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Fast Ethernet (Cabling Spec.)

Fast Ethernet (100Base-T) isavailable in three different types ofcable technologies:

100Base-T4Utilizes four pairs of telephone-grade twisted-pairwire and is used for networks that need a low qualitytwisted-pair on a 100-Mbps Ethernet

100Base-TXDeveloped by ANSI 100Base-TX is also known as

100Base-X, 100Base-TX uses two wire data gradetwisted-pair wire

100Base-FXDeveloped by ANSI, 100Base-FX utilizes 2 stands offiber cable


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100 Base-TXUses 2 pairs (1 pair towards hub andother pair from hub) of CAT-5 UTP orSTP

Encoding used is 4B/5B

Distance between hub & station be

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