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Slides rev-09 PIM Routing Gorry Fairhurst University of Aberdeen gorry@erg.abdn.ac.uk IP Multicast Workshop at Networkshop 2006 Slides (as flash, QT) at: http://www.erg.abdn.ac.uk/users/gorry/ipmulticast/docs/ Gorry@erg.abdn.ac.uk • Part 1: Multicast Forwarding • Part 2: ASM Register • Part 3: Receiver Join • Part 4:Variations • Part 5: Pruning (0) Forwarding Process Gorry@erg.abdn.ac.uk (1) Check Admin Scope (ACL) olist No (2) Check RPF (to source) in MRIB Yes (3) Check RPF (to RP) - if SM in MRIB No No (4) Check Output list (olist) (5) Adjust TTL / Check TTL thresh (6) Replicate using olist (OIL) (1) (2) (3) (0) Multicast Forwarding Gorry@erg.abdn.ac.uk Interface forwarding table olist Yes No No No 224.2.132.76 Port MRIB 10.0.0.1 (1) (1) (2) (3) Tree Information Base Multicast routing table Gorry@erg.abdn.ac.uk • Part 1: Multicast Forwarding • Part 2: ASM Register • Part 3: Receiver Join • Part 4:Variations • Part 5: Pruning Sending to the LAN DR Gorry@erg.abdn.ac.uk Reg PIM Designated Router (DR) 139.133.204.31: 224.2.132.76 Receive DR receives from local Sources Creates a TIB entry Send unicast PIM-Register to RP Source 139.133.204.31 PIM Designated Router (DR) may be IGMP Querier Telling the RP about a Source Gorry@erg.abdn.ac.uk RP 139.133.204.31: 224.2.132.76 Reg STOP X Source DR does not forward flows Send a PIM-Register to the RP RP updates TIB RP sends PIM-Register-STOP Source DR stops registering (for a while) X DR 139.133.204.31 Source DR waits for a PIM-Join Gorry@erg.abdn.ac.uk • Part 1: Multicast Forwarding • Part 2: ASM Register • Part 3: Receiver Join • Part 4:Variations • Part 5: Pruning OS Sends IGMP Report Gorry@erg.abdn.ac.uk Receive DR (IGMP Querier) 224.2.132.76 X X X IGMP Report X Receiver X Tree Information Base (TIB) OS enables Ethernet Interface OS send IGMP-Report for Group(s) Router creates TIB entry Router enables LAN interface Router forwards packets to Receiver IGMP Query Gorry@erg.abdn.ac.uk Receive DR (IGMP Querier) 224.2.132.76 IGMP Report IGMP Query CHECK Router send IGMP-Query to LAN Receiver (or another computer) responds Router updates TIB entry Receiver Router continues to forward packets to Receiver Receiving via the RP RP Receive DR X 139.133.204.31: 224.2.132.76 Receive DR sends (*,G) PIM-Join to RP RP updates TIB RP sends (S,G) PIM-Join to Source DR Source DR forwards flow via RP X Receiver Gorry@erg.abdn.ac.uk X X X DR 139.133.204.31 Source Packets forwarded via the RP (RPT) Receiving from Source Gorry@erg.abdn.ac.uk Receive DR discovers Source address Receive DR sends (S,G) PIM-Join to Source RP Receive DR Source DR forwards packets to Receiver Receive DR sends a (S,G,rpt) PIM-Prune to RP Join Receiver 139.133.204.31: 232.2.132.76 RP sends a (S,G) PIM-Prune to Source DR X X X DR 139.133.204.31 Source Packets forwarded on shortest path (SPT) Turnabout Router RP Receive DR X Receiver X Gorry@erg.abdn.ac.uk 139.133.204.31: 224.2.132.76 Receive DR sends (*,G) PIM-Join to RP RP sends (S,G) PIM-Join to Source DR Source DR forwards towards RP Turnabout router “prunes” RP & Proxy Joins DR 139.133.204.31 Traffic never flows up the RPT to then flow back down the same SPT! Finding a Remote Source RP Gorry@erg.abdn.ac.uk Join 139.133.204.31: 224.2.132.76 X Join RP Join 139.133.204.31: 224.2.132.76 X X X X DR X 139.133.204.31 Source DR Receiver X X Receive DR sends (*,G) PIM-Join to local RP Local RP sends (S,G) PIM-Join to Source Source DR forwards flow to Receiver Note: Packets not forwarded via the RP Local RP needed to know Source! Gorry@erg.abdn.ac.uk • Part 1: Multicast Forwarding • Part 2: ASM Register • Part 3: Receiver Join • Part 4:Variations • Part 5: Pruning PIM-SSM - when there are few sources Bi-Dir PIM - when there are many sources Sending SSM from the DR Gorry@erg.abdn.ac.uk Rules change for 232/8 (SSM!) Source DR role changes No register sent from DR 139.133.204.31: 224.2.132.76 No (*,G) PIM-Join for 232/8 Receive DR Join changes (S,G) Join directly to source (IGMPv3) RPs not to handle these groups Source 139.133.204.31 Sending BiDir from the DR Gorry@erg.abdn.ac.uk BiDir negociated in PIM Hello Rules change Source DR role changes 139.133.204.31: 224.2.132.76 No Register sent from DR Receive DR forwarding changes Send natively to RP Other routers can see the packets Source 139.133.204.31 BiDir Routing Gorry@erg.abdn.ac.uk Source B Source A RP R0 R1 R2 R3 No per-source state Good for many sources (c.f SSM) No problems with bursty sources (as in SSM) Network changes for BiDir Gorry@erg.abdn.ac.uk RP much simpler (No tunnels) No problems with bursty sources Can be any multicast router Problems Does not directly interoperate with SM All traffic can flow to the RP RP placement important Gorry@erg.abdn.ac.uk • Part 1: Multicast Forwarding • Part 2: ASM Register • Part 3: Receiver Join • Part 4:Variations • Part 5: Pruning Leaving the Group Gorry@erg.abdn.ac.uk Prune Receive DR (IGMP Querier) 224.2.132.76 CHECK X Send IGMP-Query to check for Receivers No response indicates no members IGMP Query Receive DR stops forwarding flow PIM-Prune sent upstream Receiver Router prunes unwanted multicast group Stopping a Source Gorry@erg.abdn.ac.uk Prune X Source DR 139.133.204.31:224.2.132.76 Source DR receives a PIM-Prune Source DR stops forwarding Source DR periodically registers Source Source continues to send to DR So Finally Gorry@erg.abdn.ac.uk Three key things IGMP tells a Receive Router which flows to Receive RP's tell Receive Routers about Sources (via packets) Join/Prune used to build trees Multicast isn't hard It is very different to unicast Need to work with new "tools" Question & Answers ? Gorry@erg.abdn.ac.uk Slides (as flash, QT) at: http://www.erg.abdn.ac.uk/users/gorry/ipmulticast/docs/