Multicast Routing e LAN Switching

Transcript

1 Routing e LAN Switching Applicazioni one to many Applicazioni many to many Applicazioni many to one RTSP Manage ment RSVP RTCP UDP RTP Reliable multicast protocol TCP DB Routing multicast IP switching Servizio di Membership monitora la cardinalita del gruppo a fronte di cambiamenti dinamici e di modello CRASH e failure transienti In Internet i conoscono la membership (senza far parte del gruppo necessariamente) in wide area e broadcast su sottorete La membership serve ai per costruire l infrastruttura di distribuzione multicast

2 v1 [in IPv6 le funzioni di sono incorporate in ICMP] Un non deve conoscere la membership. E sufficiente conoscere l esistenza di un membro di gruppo routing update LAN 2 LAN 1 query report report LAN 3 query (TTL=1, all host group) member member member Pruning query Member Member Member

3 v2 v2 introduce una procedura di elezione del querier per ogni LAN. In v1 veniva eletto dal protocollo di routing con politiche spesso diverse. Specific Query introdotto per consentire queries da parte di un ad un gruppo specifico e non all indirizzo all host sulla subnet ( ). Leave introdotto per ridurre la latenza di leave. Viene inoltrato al gruppo all s ( ) Quando un riceve un messaggio di Leave, utilizza il messaggio Specific Query per verificare se si trattava dell ultimo membro del gruppo., Version 1, RFC 1112;, Version 2, RFC 2236;, Version 3,draft ietf idmr igmp v3 03.txt, feb.1999 packet format I Pacchetti viaggiano incapsulati in pacchetti IP TYPE MAX RES TYME CHECKSUM GROUP ADDRESS Used to distinguish Membership Queries Set to IP mcast group addr otherwise Set time limit (in unit of 1/10 sec) to send a report To Membership Query. Set to 0 otherwise Membership Query General Query (group addr = 0) Specific Query (group addr = IP group addr being queried) Membership Report Leave

4 Querier Router Election Query Interval 125 s GeneralQuery <all sys, IP#> Router IF IP# < myip THEN Non querier Other Querier Present Timer On expiry RESUME As Querier 400 s Quick Membership awareness at start up Host Start upquery Count Start upquery Timer QueryResponse Timer ¼ QueryInterval Report <G, TTL 1> On expiry RV Robust Variable = Default value 2

5 Query Operation {Entry for all G and for all subnet} {Entry for all G with membership} Host QueryResponseTimer<QInterval ForAll G, QueryResponse Timer for G QueryInterval Timer for G Random [0, MaxRespTime] 100 TimeTick 10 s Report <G, TTL 1> RV*QueryInterval + QueryResponseTimer SpecificQuery < > Set/reset Reset Timer Suppress duplicate Clear FLAG Select MIN [residual time, MaxRespTime] Membership Timer for G Report <G, TTL 1> Set FLAG On expiry On expiry no more members In G for that subnet Join and Leave Operations {Entry for all G and for all subnet} {Entry for all G with membership} Host UnsolicitedReport <G, TTL 1> UnsolicitedReport <G, TTL 1> Unsolicited Report Interval G JOIN G Default Value 10 s Default Value 10 = 1 s LastMemberQuery Timer for G LeaveReport <G, allr> SpecificQuery <G,LastMemberQTimer> SpecificQuery <G,LastMemberQTimer> LEAVE G IF FLAG set (when space to record) Tuned to reduce Leave Latency On expiry no more members In G for that subnet THEN Remove entry for G

6 Host state diagram Leave group (stop timer send leave IF flag set) join group (send report, set flag, Start timer) NON MEMBER Leave group (send leave IF flag set) DELAYING MEMBER Query received (start timer) Report received (stop timer, clear flag) IDLE MEMBER Query received (reset timer IF MaxRespTimer < current timer) Timer expired (send report, set flag) Querier Router state diagram MshipTimer expired (notify routing ) Mship Report received (notify routing+, startmship timer) NO MEMBERS PRESENT FOR G Mship Timer expired (notify routing, Clear LastMemberQ timer) MEMBERS PRESENT Mship Report received (startmship timer) CHECKING MEMBERSHIP Report received (startmship timer) Leave received (start LastMemberQ timer, Send SpecificQuery) LastMemberQ timer expired (send SpecQ, set LastMemberQ timer)