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Ethernet Bridging

Ethernet Bridging. Gestione del traffico su reti Metro Ethternet. Sommario. Riepilogo Carrier Ethernet Riepilogo Spanning Tree Protocol Problemi con STP in reti MAN Soluzioni proposte: SPB Calcolo dei path Forwarding Altra soluzione :TRILL. Sommario.

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Ethernet Bridging

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  1. Ethernet Bridging Gestione del traffico su reti Metro Ethternet

  2. Sommario • Riepilogo Carrier Ethernet • Riepilogo SpanningTreeProtocol • Problemi con STP in reti MAN • Soluzioni proposte: SPB • Calcolo dei path • Forwarding • Altra soluzione :TRILL

  3. Sommario • Riepilogo Carrier Ethernet • Riepilogo SpanningTreeProtocol • Problemi con STP in reti MAN • Soluzioni proposte: SPB • Calcolo dei path • Forwarding • Altra soluzione :TRILL

  4. Perché ethernet nelle MAN?! <10 € Broadcast on unknown = tecnologia plug-and-play

  5. Riassunto: Metro Ethernet I

  6. Riassunto: Metro Ethernet II IEEE 802.1 ah IEEE 802.1d

  7. Gestione • Continuity Check messages = "heart beat" messages. Detect connectivity failures in an MA. CCMs are multicast messages and they are confined to a domain • Link Trace messages = track the path (hop-by-hop) Directly to the Originating MEP, and regenerates the Trace route Message • Loop-back messages = determine the location of a fault Administratively initiated and stopped • ITU-T Y.1731 additionally supports the following: • Loss Measurement • One way Delay • Two way Delay

  8. Sommario • Riepilogo Carrier Ethernet • Riepilogo SpanningTreeProtocol • Problemi con STP in reti MAN • Soluzioni proposte: SPB • Calcolo dei path • Forwarding • Altra soluzione :TRILL

  9. SpanningTreeProtocol • È necessaria una topologia fisica ridondante (supporto fault), ma è necessario che quella attiva sia loop-free (broadcast on unknown) • Soluzione: disattivazione di alcuni link • Scelgo la root in maniera casuale (ID più basso) ed ogni bridge si calcola il percorso più breve per raggiungerla. IEEE 802.1 D

  10. Sommario • Riepilogo Carrier Ethernet • Riepilogo SpanningTreeProtocol • Problemi con STP in reti MAN • Soluzioni proposte: SPB • Calcolo dei path • Forwarding • Altra soluzione :TRILL

  11. Problemi con STP in reti MAN • In caso di fault devo ricostruire le forwardingtable, quindi molti broadcast • Non utilizzo percorso ottimo • Non utilizzo tutta la banda che ho messo in campo • Anche con RSTP (IEEE 802.1W) tempo di convergenza troppo alto • Non posso gestire in maniera semplice il traffico

  12. Perché ho bisogno di gestire il traffico? • Affidabilità • Controllo della banda per servizio • Rispetto Service Level Agreement (SLA)

  13. PBB-TE trafficengineering

  14. Sommario • Riepilogo Carrier Ethernet • Riepilogo SpanningTreeProtocol • Problemi con STP in reti MAN • Soluzioni proposte: SPB • Calcolo dei path • Forwarding • Altra soluzione :TRILL

  15. SPB shortestpathbridging • IEEE 802.1 ad (SPBM in ambito PBB) • Calcolo di più path all’interno della rete • Shortest path bridging MAC operation uses MAC addresses to identify the SPT • 24 bits of the 802.1ah header service instance (I-SID) provide highly scalable support for service virtualization

  16. SPT Region Payload Payload SPVID = 22 45 45 SA SA Base VID 22 DA DA SPVID = 45 Payload SPVID = 66 Payload SPVID = 44 22 CST SA IST DA SPVID = 71 22 Payload SA DA SPVID = 41 Payload 41 VID = 6 Payload SA Payload DA 22 41 SA 22 SA DA SA DA DA SPB concept

  17. IS-IS IS-IS IS-IS IS-IS IS-IS IS-IS IS-IS IS-IS IS-IS SPB operation Shortest path between any two points is both the same and symmetrical for unicast and multicast BEB Backbone Edge Bridge BEB Backbone Core Bridge BCB BCB BCB BEB BEB “A” PBBN BEB BEB

  18. IS-IS IS-IS IS-IS IS-IS IS-IS IS-IS IS-IS IS-IS IS-IS SPB path da/per A Shortest path between any two points is both the same and symmetrical for unicast and multicast BEB Backbone Edge Bridge BEB Backbone Core Bridge BCB BCB BCB BEB BEB “A” PBBN All pairs shortest path computation performed in parallel BEB BEB

  19. IS-IS IS-IS IS-IS IS-IS IS-IS IS-IS IS-IS IS-IS IS-IS SPBB Multicast Groups I-SID 5 I-SID 5 MMAC for 5 from A BEB Backbone Edge Bridge BEB Backbone Core Bridge BCB BCB BCB BEB BEB “A” PBBN I-SID 5 BEB BEB I-SIDs define efficient subsets

  20. Sommario • Riepilogo Carrier Ethernet • Riepilogo SpanningTreeProtocol • Problemi con STP in reti MAN • Soluzioni proposte: SPB • Calcolo dei path • Forwarding • Altra soluzione :TRILL

  21. Soluzione iniziale: MSTP

  22. Perché è stato scelto IS-IS? • Network loop prevention requires synchronizing state at island/core boundaries with bridges that only understand RSTP/MSTP BPDUs • Thatmeans: • using ISIS-SPB results in BPDUs • injecting BPDU information into ISIS-SPB • ISIS-SPB can make some decisions faster, e.g. determine CIST Port Roles and priority vectors • Stop existing mechanisms from overriding with temporarily incorrect information • Ports inside SPT Regions synchronize forwarding state with boundary ports • Need to specify how, without reinvention • Have to interoperate with existing bridges, and deploy in islands/network cores

  23. Perché è stato scelto IS-IS?

  24. IS-IS • IS-IS is the Intermediate System to Intermediate System intra-domainroutingprotocol • Usato per il calcolo dei path all’interno della rete • Disegnatooriginariamente per OSI routing • Facilmente estensibile

  25. Punti di contatto IS-IS e OSPF • Link state protocols • Hello packets per trovare e mantenere le adiacenze • Dijkstra / SPF algorithm • Visionegerarchicadellatopologiadellarete • Costo è metricadi default

  26. Differenze tra IS-IS e OSPF • ISIS Link State Packets contengono TLVs, mentre OSPF Link State Updates contengono Link State Advertisements (LSAs) Per questo IS-IS può essere usato su Ethernet: estendo le funzionalità aggiungendo TLVs per portare informazioni riguardanti le VLAN, la mappatura VID, gli indirizzi multicast, gli identificativi CIST, la service groupmembership…

  27. ISIS -SPB • Uses the standard ISIS procedures to construct and update the link state database in each SPT bridge • Disable B-MAC learning inside the backbone, only “border” learning • Sets up and maintains at least one SPT for each bridge, which connects to every other bridge in an SPT region • Support multiple pathwithsamecost

  28. ISIS -SPB SPTs have to meet two congruency criteria. • Forward and reverse paths must be the same between any two bridge pairs • Unicast and multicast paths also have to be congruent

  29. ISIS -SPB Can raise temporary loop • Loop mitigation: ingress filtering • Loop avoidance: discard until neighbor topology match

  30. Sommario • Riepilogo Carrier Ethernet • Riepilogo SpanningTreeProtocol • Problemi con STP in reti MAN • Soluzioni proposte: SPB • Calcolo dei path • Forwarding • Altra soluzione :TRILL

  31. SPB Computation – ClassicMethod • For every node in the network do: • Compute SPT: run Dijkstra for the node (the root of the spanning tree) • Prune paths: keep only the shortest paths that go through the node performingthe computation • I-SID computation: compute the intersection of the set of I-SIDs for which the root node transmits with the set of I-SIDs for which the paths’ endpointsreceive • Pluses: • Simple, elegant, and quite efficient when most paths are not pruned • Best possibleworst-case performance • Minuses: • Most of the paths computed by some nodes, most notably edge nodes, end up being pruned (because they are not offering transit) • For these nodes, the SPB computation can be very expensive relative to the amount of forwarding state produced

  32. SPB shortestpathbridging Multipathing Unicast

  33. SPB shortestpathbridging Multipathing Multicast

  34. TRILL Transparent Interconnection of Lots of Links Simile all’SPB, ma • Standardizzato da IETF • Ottimizzato per ambiente Data Center • Non compatibile con architettura reti PBB • Gestione dei loop temporanei con TTL

  35. TRILL Gestione e troubleshooting più complicati

  36. Sara Lago IPI Lab s.lago@cipi.unige.it

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