Ieee 802 standard

IEEE Standard

1. IEEE 802.X Standards
•TheInstituteofElectricalandElectronicsEngineers
(IEEE)hasdevelopedaseriesofnetworkingstandards
toensurethatnetworkingtechnologiesdevelopedby
manufacturersarecompatible.
•Thesestandardsdescribethecabling,physical
topology,electricaltopologyandaccessschemesof
networkproducts.
•Thesestandardsdescribetheprotocolsusedinthe
lowertwolayersoftheOSImodel:
1.Physicallayer
2.Datalinklayer.
Theydon’tgoabovethoselayers.

2. •ThecommitteestructureoftheIEEEis
numberedlikethedecimalsystem.
•Thegeneralcommitteeworkingonthese
standardsis802.
•Varioussubcommittees,designedbydecimal
numbers,haveworkedondifferentversionof
thestandards.

3. IEEE 802.5
•TheIEEE802.5standardspecifiesthe
characteristicsforTokenRingnetworks.
•TokenRingwasintroducedbyIBMinthemid-
1980s.

4. What is token ring LAN?
•TokenringLANtechnologyisalocalareanetwork
protocolwhichresidesatthedatalinklayer(DLL)of
theOSImodel.
•StationsonatokenringLANarelogicallyorganizedina
ringtopologywithdatabeingtransmittedsequentially
fromoneringstationtothenextwithatokentravelling
aroundthering.
•Thisstandarddescribesatokenpassingprotocolwhich
meansthatamachinecanonlyusethenetworkwhen
ithascontrolofthe“token”
•Thisensuresthattherearenocollisionsbecauseonly
onemachinecanusethenetworkatanygiventime.

5. •Tokenringprotocolusesaspecialthree-byte
framecalledatokenthattravelsaroundthe
ring.
•Tokenringframestravelcompletelyaround
theloop.
•Stationsthathavedataframestotransmit
mustfirstacquirethetokenbeforetheycan
transmitdataframes.

6. •Whennostationistransmittingadataframe,a
tokenframecirclestheloop.
•Thistokenframeisrepeatedfromstationto
stationuntilarrivingatastationthatneedsto
transmitdata.
•Whenastationneedstotransmitdata,itfirsthas
tocapturethefreeTokenandreplacethedata
withitsownmessage.
•Oncethesendingstationreceivesitsdataframe,
itconvertstheframebackintoatoken.
•On4Mbit/sTokenRing,onlyonetokenmay
circulate;on16Mbit/sTokenRing,theremaybe
multipletokens.

7. Operation of Token Ring
•Atthestart,afreeTokeniscirculatingonthe
ring.
•Ifmachine1wantstosendsomedatato
machine4,soitfirsthastocapturethefree
Token.
•Itthenwritesitsdataandtherecipient's
addressontotheToken(representedbythe
yellowflashingscreen).

8. •Thepacketofdataisthensenttomachine2who
readstheaddress,realizesitisnotitsown,so
passesitontomachine3.
•Machine3doesthesameandpassestheToken
ontomachine4.
•Thistimeitisthecorrectaddressandsonumber
4readsthemessage(representedbytheyellow
flashingscreen).
•Machine4cannot,however,releaseafreeToken
ontothering,itmustfirstsendthemessageback
tonumber1withanacknowledgementtosay
thatithasreceivedthedata(representedbythe
purpleflashingscreen).

9. •Thereceiptisthensenttomachine5who
checkstheaddress,realizesthatitisnotits
ownandsoforwardsitontothenext
machineinthering,number6.
•Machine6doesthesameandforwardsthe
datatonumber1,whosenttheoriginal
message.
•Machine1recognizestheaddress,readsthe
acknowledgementfromnumber 4
(representedbythepurpleflashingscreen)
andthenreleasesthefreeTokenbackonto
theringreadyforthenextmachinetouse.

10. •That's the basics of Token Ring and it shows
how data is sent, received and acknowledged.

11. •Thefollowingisalistofthespecificcharacteristics
specifiedinthe802.5standard:
•Speed:The802.5TokenRingspecifiesnetworkspeeds
of4and16Mbps.
•Topology:TokenRingnetworksusealogicalring
topologyandmostoftenaphysicalstar.
•Media:TokenRingnetworksuseunshieldedtwisted
paircablingorshieldedtwistedpair.
•Accessmethod:802.5specifyanaccessmethod
knownastokenpassing..Thetokentravelsaroundthe
networklookingforcomputerswithdatatosend.The
computer'sdataispassedalongwiththetokenuntilit
getstothedestinationcomputeratwhichpoint,the
dataisremovedfromthetokenandtheemptytoken
placedbackonthering.

12. 802.3 IEEE Standard
•TheIEEE802.3standarddefinesthecharacteristicsfor
Ethernetnetworks.
•TheEthernetspecificationservedasthebasisforthe
IEEE802.3standard
•WhatisanEthernet?
•ALANarchitectureortelecommunicationsnetworking
protocolintroducedbyXeroxCorp.in1979.
•Itwasdevelopedasaninexpensivewayofsending
informationquicklybetweenofficesmachines
connectedtogetherinasingleroomorbuilding.
•Theoriginaldatarateof10megabitspersecondhas
beenincreasedto100megabitspersecondforanew
standardknownasfastEthernet.

13. •Ethernetusesabusorstartopologyand
supportsdatatransferratesof10Mbps.

14. The features for 802.3 are listed here:
•Speed:TheoriginalIEEE802.3standardspecified
anetworktransferrateof10Mbps.
•Therehavebeenmodificationstothestandard,
theresultbeingFastEthernet(802.3u),whichcan
transmitnetworkdataupto100Mbpsandhigher,
aswellasGigabitEthernet(802.3z),whichcan
transmitatspeedsupto1000Mbps.
•802.3aeisaveryfast803.3standard.Knownas
10-GigabitEthernet.

15. Topology:
•TheoriginalEthernetnetworksusedabusor
startopologybecausetheoriginal802.3
standardincludedspecificationsforboth
twistedpairandcoaxialcabling.

16. Media
•Themediareferstothephysicalcablingused
totransmitthesignalaroundthenetwork.
•Theoriginal802.3specificationsidentified
coaxialandtwistedpaircablingtobeused.
•Themoremodernstandardsspecifytwisted
pairandfiber-opticcable.
•802.3aecurrentlyonlysupportsfibermedia.

17. Access method
•The access method refers to the way that the
network media is accessed.
•EthernetnetworksuseasystemcalledCarrier
SenseMultipleAccesswithCollision
Detection(CSMA/CD).
•TheCSMA/CDmethodisinternationally
standardizedinIEEE802.3
•CSMA/CDworksbymonitoringthecomputers
thataresendingdataonthenetwork.

18. •Iftwocomputerstransmitdataatthesame
time,adatacollisionwilloccur.
•Topreventcollisions,thesystemssendingthe
datawillberequiredtowaitaperiodoftime
andthenretransmitthedatatoavoidthe
collision.

19. •CarrierSenseMultipleAccess/Collision
Detection,asetofrulesdetermininghow
networkdevicesrespondwhentwodevices
attempttouseadatachannelsimultaneously
(calledacollision).
•CSMA/CDisatypeofcontentionprotocoli.e.
howtohandlecompetitionofresources.
•Thetermcontentionisusedespeciallyin
networkstodescribethesituationwheretwo
ormorenodesattempttotransmitamessage
acrossthesamewireatthesametime.