Unicasts, Multicasts and BroadcastsPart 1: Frame-Based LAN Operation V1.0: eo!! BennettLANs as a Shared Medium LANs as a Shared MediumA "Private" Conversation A "Private" ConversationMulticast Addressing Multicast AddressingPerformance Issues Performance Issues"n t#is tutorial"$ll e%plain t#e operation o! address reco&nition on a con'entional LAN, and #ilit t#e implications o! t#is mode o! operation (#en (e mo'e to a connection-oriented A)M net(or*.)o mo'e directl+ to one o! t#ese sections, clic* on t#e rele'ant rectan&le (it# t#e mouse.Ot#er(ise, continue to t#e ne%t slide.Contents Contents"n t#is section "$ll descri,e t#e (a+ t#at s#ared LAN tec#nolo&ies operate (it# respect to !rame addressin& and reco&nition.LANs as a Shared Medium LANs as a Shared MediumA "Private" Conversation A "Private" ConversationMulticast Addressing Multicast AddressingPerformance Issues Performance IssuesContents Contents-ere is a t+pical s#ared LAN.Multiple attac#ed #osts, usuall+ P.s, s#are a common communication c#annel.-ost 1-ost 1-ost /-ost /-ost 0-ost 01#ared LAN .a,le1#ared LAN .a,le"! -ost 1 transmits in!ormation into t#e s#ared c#annel, t#en it 2passes ,+2 all o! t#e ot#er de'ices connected to t#e c#annel.-ost 1-ost 1-ost /-ost /-ost 0-ost 0-ost /-ost /-ost 0-ost 0"! -ost 1 transmits in!ormation into t#e s#ared c#annel, t#en it 2passes ,+2 all o! t#e ot#er de'ices connected to t#e c#annel.-ost 1-ost 1Note t#at t#e e%act p#+sical representation o! 2passin& ,+2 is installation-speci!ic.)#is older 3t#ernet installation is a ,us-,ased s+stem.4in&-,ased LANs and #u,-,ased LANs ma+ loo* di!!erent ,ut t#e+ operate under t#e same assumption t#at all de'ices in t#e s#ared c#annel (ill ,e a,le to see eac# ot#ers$ messa&es. -ost /-ost /-ost 0-ost 0-ost 1-ost 1-ost /-ost /-ost 0-ost 0-ost 1-ost 1)#ere are t(o reasons t#at t#is ,roadcast nature in a LAN is not uni'ersall+ desira,le.First, (e o!ten (is# to send messa&es ,et(een t(o speci!ic de'ices, suc# as -ost 1 and -ost 0 (it#out ot#er de'ices, suc# as -ost /, ,ein& a,le to see t#e in!ormation.1econd, in a ,us+ LAN, ot#er de'ices$ con'ersations s#ould not ,e allo(ed to in!luence t#e per!ormance o! stations t#at are not in'ol'ed in t#e con'ersation.2Pri'ate2 .on'ersation5Be!ore (e loo* at t#e per!ormance aspects, let$s see #o( (e can ac#ie'e t#e impression o! pri'ac+ in our s#ared LAN s+stems.LANs as a Shared Medium LANs as a Shared MediumA "Private" Conversation A "Private" ConversationMulticast Addressing Multicast AddressingPerformance Issues Performance IssuesContents Contents-ost 1-ost 1-ost /-ost /-ost 0-ost 0)o ac#ie'e pri'ac+ in our con'ersations, (e can &i'e eac# de'ice on t#e s#ared c#annel a uni6ue address, and transmit our in!ormation in units (#ic# contain t#e address o! t#e destination de'ice.7e can also include our o(n, sendin& address, so t#at t#e ot#er de'ice can repl+ directl+ to us.Note t#at t#ese addresses operate at t#e MA. La+er o! t#e O1" model, as discussed in t#e module 8Addressin& in LANs9.Address: -1 -/ -0-ost 1-ost 1-ost /-ost /-ost 0-ost 0)#e in!ormation units t#at contain t#ese addresses are called !rames.FrameFrame)#e in!ormation units t#at contain t#ese addresses are called !rames.)#e+ are desci,ed ,+ protocols t#at are part o! t#e O1" :ata Lin* La+er.FrameFrameO1" ;-La+er ModelO1" ;-La+er Model:ata Lin*P#+sicalNet(or*)ransport1essionPresentationApplication:ata Lin* :ata Lin* Data Link-ost 1-ost 1-ost /-ost /-ost 0-ost 0"n particular, !rames are part o! t#e Media Access .ontrol -0:A>-0-ost 1-ost 1-ost /-ost /-ost 0-ost 0O1" ;-La+er ModelO1" ;-La+er ModelP#+sicalNet(or*)ransport1essionPresentationApplicationData LinkMACLL.:ata Lin*:A 1A1A>-11A>-1Note t#at real MA. addresses are ?@-,its lon&, and "$m usin& t#is a,stract representation to *eep t#in&s simple