IEEE and Lower Level LAN Protocols

8/2/2019 IEEE and Lower Level LAN Protocols

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CHAPTERProtocols and IEEE

Standards


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Chapter Objectives

Discuss different media level protocolsincluding their functioning

The major protocols chosen fordiscussion are as follows:

CSMA/CD, token passing and polling

Discuss the IEEE standards that applyto LANs based on different protocols


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Chapter Modules

LAN Protocol: Carrier Sense MultipleAccess/Collision Detection

(CSMA/CD)

LAN Protocol: Token Passing

LAN Protocol: Polling

IEEE Standards


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END OF CHAPTER

INTRODUCTION


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MODULE

IEEE and Lower Layer LANProtocols


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IEEE Background

Institution of Electrical and ElectronicEngineering (IEEE)

A professional non-profit organization

Project group 802 under IEEE Entrusted with the task of setting standards

relating to physical and logical links of nodes in anetwork

Standard mostly applies to the Physical andData Link layers

Example IEEE 802.3 standard for the Ethernet bus network


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The ISO-OSI Model Recalled

Models the end-to-end communicationprocess

It is a seven-layer model Proposed by International Standard

Organization (ISO)

The model is known as Open Systems

Interconnect (OSI) IEEE sets the standards at the lower levels of

the ISO-OSI model


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ISO-OSI Seven Layer Model

Layer 7 ApplicationLayer 6 PresentationLayer 5 SessionLayer 4 TransportLayer 3 NetworkLayer 2 Data LinkLayer 1 Physical

Source: http://starter.sdsu.edu/remote/demo/osi-tcp.html

Focus of

IEEE 802
http://starter.sdsu.edu/remote/demo/osi-tcp.htmlhttp://starter.sdsu.edu/remote/demo/osi-tcp.htmlhttp://starter.sdsu.edu/remote/demo/osi-tcp.htmlhttp://starter.sdsu.edu/remote/demo/osi-tcp.html


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Comparison of ISO-OSI Modeland the DOD (TCP/IP) Model

ApplicationApplicationPresentation

SessionTransport

Host-to-Host

Network InternetData Link

Network AccessPhysical



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Layer Reference to Protocol

ApplicationApplication FTP, Telnet, SMTP, HTTP,

SNMP ..PresentationSessionTransport Host-to-Host TCP, UDPNetwork Internet IP, ICMPData Link Network

Access Ethernet, Token-Ring ...Physical



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Network ProtocolsSource: www.networkmagzine.com


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Another Look at Network ProtocolsSource: www.networkmagzine.com


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Network Protocols in the TCP/IPModel

Source: www.networkmagzine.com
http://www.networkmagzine.com/http://www.networkmagzine.com/


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IEEE 802 Focus

OSI Reference

Data Link layer

Physical layer

Areas of applications

Network cards and cables

WAN connectivity etc.

Different subgroups under 802 thatfocus on different activities of the LAN


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IEEE 802 Subgroups and theirResponsibilities

802.1

Internetworking

802.2

Logical Link Control (LLC)

802.3

CSMA/CD

802.4

Token Bus LANContinued


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IEEE 802 Subgroups and theirResponsibilities (Cont.)

802.5

Token Ring LAN

802.6

Metropolitan Area Network

802.7

Broadband Technical Advisory Group

802.8

Fiber-Optic Technical Advisory GroupContinued


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IEEE 802 Subgroups and theirResponsibilities (Cont.)

802.9

Integrated Voice/Data Networks

802.10

Network Security

802.11

Wireless Networks

802.12

Demand Priority Access LANs

Ex: 100BaseVG-An LAN


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Ethernet Protocol Standards

10 Mbps IEEE 802.3

100 Mbps IEEE 802.3u

1 Gbps IEEE 802.3ab

Uses all 4 pairs of the RJ-45 cable(www.techfest.com/networking/lan/ethernet1.htm )

10 Gbps

IEEE 820.3ae
http://www.techfest.com/networking/lan/ethernet1.htmhttp://www.techfest.com/networking/lan/ethernet1.htmhttp://www.techfest.com/networking/lan/ethernet1.htmhttp://www.techfest.com/networking/lan/ethernet1.htm


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Wireless LAN Protocols

802.11 1-2 Mbps, 2.4 GHz, FHSS and DSSS

IEEE 802.11a 54 Mbps, 5 GHz, Orthogonal Frequency DivisionMultiplexing

IEEE 802.11b 11 Mbps, 2.4 GHz, DSSS

IEEE 802.11g 20+ Mbps, 2.4 GHZ 108 Mbps, 2.4 GHz (Extreme G)


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Newer Wireless Protocol

IEEE 802.11n


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A Perspective of IEEE 802 Standardsin Network Communication

LogicalLink

Control(LLC)

MediaAccessControl(MAC)

802.2

802.3

802.4802.5802.12

802.1 appliesto both.


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END OF MODULE


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MODULE

LAN Lower Layer Protocol:

IEEE 802.3 Carrier Sense MultipleAccess/ Collision Detection

(CSMA/CD)


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An Overview of CSMA/CD

CSMA/CD has two components asmentioned

First is the Carrier Sense MultipleAccess (CSMA) component

Second is the Collision Detection (CD)

component


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CSMA Component ofCSMA/CD

CSMA (Carrier Sense Multiple Access)

Check the bus for traffic

If the bus is free, then transmit

If it is busy, wait for a random period oftime before attempting to transmit again


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CD Component of CSMA/CD

Two stations may check the data bussimultaneously

Both may find the line free and engage in the

transmission of data Both transmission will collide

CD component will detect this collision Inform the workstations of the collision

Each station will wait for a random period oftime before attempting to transmit again


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CSMA/CD Usage

Used extensively in bus LANs


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CSMA/CD Standards

Highly standardized protocol

Different protocol standards fordifferent speeds of communication

10 Mbps Ethernet standard

IEEE 802.3


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IEEE 802.3

10G bps Ethernet IEEE 802.3z

1G bps Ethernet IEEE 802.3ab

100M bps Ethernet

IEEE 802.3u 10M bps Ethernet

IEEE 802.3


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END OF MODULE


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MODULE


IEEE 802.4 Token Bus Protocol


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Token Bus

Server

Client Client Client

Token

A token is distributed to each client in turn.


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Token Bus Data Pickup

A token is sent from one node to theother

The client wanting to transmit grabs anempty token

Data is attached

Token leaves for the next node and itstravel on the bus until it reaches theaddress to which the data is destined

Cont.


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Token Bus Data Delivery

Token delivers the data to the addressee

Acknowledgement is returned to the sender

Token is passed to the next node The process continues

If there is an error in delivering the

information, a request for retransmissionattached to the token and it is sent to thesender

T k B S d d d


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Token Bus Standard andApplications

IEEE 802.4

It can be used in both broadband andbaseband transmission


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END OF MODULE


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MODULE


IEEE 802.5 Token Passing Protocol


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Token Passing Protocol inOperation

D

A

B

C

Circulating

Token

Server Workstation

Workstation

No collisions


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Comparison with CSMA/CD

Absence of collision

Offers a systematic method of

transmitting information In theory, it is superior to CSMA/CD

More sophisticated to implement

Protocols used in the newer and mostpopular networks are, however, basedon CSMA/CD


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The Token

Token

Data packet that could carry data

Circulates around the ring

Offers an opportunity for each workstationand server to transmit data


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The Transmitting Workstation

Waits for a free token in order to be able toattach the data to be transmitted to the token

On finding a free token, attach the following:

Senders address Receivers address

Data block to be transmitted

Error checking details

etc.


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At the Receiving End

Data is received and checked for errors

Outcomes at the receiving end

Data received without errors

Date received with errors


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Error-free Delivery of Data

An acknowledgment is attached to thetoken

Acknowledgment is passed to thesender

Token is set free for other nodes to

transmit information At this time, the next workstation on

the ring will receive an opportunity


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Correcting Errors in Delivery

A request for retransmission is attachedto the token

Token carries the message forretransmission to the sender

The data is thus retransmitted


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Token Regeneration

The token is regenerated at regularintervals to sustain the timing of

circulation of the token


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Usage of Token Passing

Used extensively in ring LANs Especially in the IBM token-ring LAN

A version of this protocol is also usedon certain types of bus LANs Token-bus networks

Used in large fiber-optics backbones Used for the construction of very large

networks


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Usage in Practice

Used in backbones

Uses in a number of IBM shops

Overall, the usage of Ethernet surpassesthe usage of Token-Ring networks thatare based on the Token-Passing

protocol


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Token Passing Standards

IEEE 802.5

For the token-ring LANs

IEEE 802.4 For the token-bus LANs

A FDDI protocol is used on large fiber-

optic ring backbones


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END OF MODULE


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MODULE

WAN Protocol: Token Passing onFDDI


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ANSI X3T9.5 Protocol

This wide are network protocol isstandardized by ANSI

Works similar to Token PassingProtocol

Used in FDDI and CDDI backbone

networks Usually implemented in dual-ringformat for fault tolerance

R li bili C R i


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Reliability: Counter RotatingRing

By-pass

the defective

segment ofthe cable


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END OF MODULE


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MODULE


Polling


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Polling in Operation

Server

WS A WS B W S C

WS : Work Station

Poll

Data Delivery

Acknowledgement orRequest for

retransmission


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Polling and Delivery of Data

Server polls each workstation

A workstation responds by sending adata packet

Data packet is delivered to the addressfound in the packet


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At the Receiving End

If there are no errors : Acknowledgment is returned to the sender

The server then continues with the pollingprocess

If there are errors: A request for retransmission is conveyed to

the sender The entire transmission process is then

repeated


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The Usage of the Polling Protocol

Mainly used in multi-user micro-computer

Based on the physical and logical startopologies

Example

A multi-user microcomputer running theUnix operating systems

Diffi lti i I l ti


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Difficulties in ImplementingPolling in LANs

It is difficult to implement the pollingprotocols in large networks withmultiple segments

Multiple servers in different segmentsmay have problems in polling all the

workstations


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Polling Implementations

True multi-user systems such as a Unixbased multi-user system


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END OF MODULE


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END OF MODULEEND OF CHAPTER

Documents

IEEE and Lower Level LAN Protocols