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MVPN PE-PE Signaling

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MVPN PE-PE Signaling

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  1. MVPN PE-PE Signaling IETF 64 Nov 2005 Nidhi Bhaskar/Gargi Nalawade/Pranav Mehta

  2. PE-PE signaling for Multicast VPNs • Multicast VPN PE-PE signaling deployed using PIM LAN procedures • Push for replacing PIM with BGP • This is an analysis of the BGP enhancements and impact on BGP/PIM.

  3. Enhancements required in BGP draft-nalawade-l3vpn-mcast-signaling-bgp-00.txt • Multicast PE-PE (Overlay) SAFI NLRI - {RD:G:Flags:S/RP:U-PE:D-PE} • RT/RD Import/Export • Filtering • PIM/BGP Interaction • Inter-AS • New functions in BGP like aggregating D-PE, U-PE based filtering, RPF lookup on ASBR and probably others. No extensions for Unicast Reachability. Rely on existing VPNv4 Unicast for that.

  4. CE-2 CE-4 Receiver1 Source = 1.1.1.1 RR BGP State: RD:232.1.1.1:SPT:1.1.1.1:PE-4:PE-2 RD:232.1.1.1:SPT:1.1.1.1:PE-4:PE-3 RD:232.1.1.1:SPT:1.1.1.1:PE-4:Label200… Transit for VPN SSM - BGP PE-2 BGP State: RD:232.1.1.1:SPT:1.1.1.1:PE-4:PE-2 RD:232.1.1.1:SPT:1.1.1.1:PE-4:Label200… PE-4 BGP State: RD:232.1.1.1:SPT:1.1.1.1:PE-4:PE-2 RD:232.1.1.1:SPT:1.1.1.1:PE-4:PE-3 RD:232.1.1.1:SPT:1.1.1.1:PE-4:Label200… RR PE-1 PIM-V4 VRF JOIN:1.1.1.1,232.1.1.1 e0 e1 PIM-V4 VRF JOIN:1.1.1.1, 232.1.1.1 PE-2 PE-4 PE-3 PE-3 BGP State: RD:232.1.1.1:SPT:1.1.1.1:PE-4:PE-3 RD:232.1.1.1:SPT:1.1.1.1:PE-4:Label200… e0 CE-3 Receiver2

  5. PE-2 Unicast imports reachability for 1.1.1.1 into Red and Blue VRF. When host 1.1.1.1 joins towards 2.2.2.2 ->We don’t want join imported into both Red and Blue table. CE-Y CE-X Source=2.2.2.2 Host = 1.1.1.1 BGP- Issue w/ Re-using unicast RTs PE-2 Red VRF: RD2 Import RT: RT1 Export RT: RT2 Blue VRF: RD3 Import RT:RT1 Export RT:RT3 P PE-1 Red VRF: RD1 Import RT:RT2 Export RT:RT1 e0 e1 PE-2 PE-1 PE-3 e0 CE-Z Receiver2

  6. ABSR Exchange VPNv4 Routes - Option B Update Sent to PE1: PE1:G:SSM:S:ASBR1 Update Sent to ASBR1: ASBR1:G:SSM:S:Label100:FEC-Y Update sent to ASBR2: ASBR2:G:SSM:S:PE2 Update sent to PE2: ASBR2:G:SSM:S:Label20:FEC-X vpnv4 RD:S NH=PE1 vpnv4 RD:S NH=ASBR1 ASBR2 Update to ASBR1: ASBR1:G:SSM:S:ASBR2:Label10 vpnv4 RD:S NH=ASBR2 ASBR1 ASBR2 PE1 AS 2 PE2 AS 1 next-hop-self towards iBGP neighbors CE1 CE2 CE3 CE4 S

  7. BGP - Multicast Routing State • RR Stores 1 multicast route as N*NLRI where N is #of D-Pes interested in stream. And stores all mroutes in the AS. • If there are “N” messages/minute on “M” PEs, RR processes “N*M” messages/minute. • Multicast J/P or route change frequency is different from unicast. Potential load on RR processing a large number of multicast route changes. • Filtering semantics required to meet the MVPN requirements fundamentally different from filtering techniques available in BGP today

  8. BGP - Multicast Routing State (contd) • PIM today uses already converged routing state established by unicast routing • Putting PIM Join/Prune in BGP requires PIM Join/Prune to be routed as a BGP NLRI • This has latency implications on PIM • Potential load on RR has further implications for multicast.

  9. BGP <-> PIM Futures/Open Issues PIM State machine changes to interact with BGP. • No PIM hellos for option negotiation. Might be good to allow options to be carried in BGP. • No Join suppression or Prune override in PIM. Requires explicitly tracking downstream joiners in either PIM or BGP. • No support for Bidir DF Election. • No support for PIM Assert resolution.

  10. BGP <-> PIM Futures/Open Issues • PIM-SM shared tree pruning. Cannot preserve the full state nature of (*,G),(S,G,R) prunes in BGP. NLRI are not “associated” with each other => Re-flooding of the shared tree for pruned sources. • BSR mappings require “full state update” as well. • G/mask, RP1, RP2, RP3… For proper operation PIM needs all three RPs before it can make a decision based on the mapping. • Mappings carry holdtimes/priorities for RPs, where to put these, BGP attributes ?

  11. BGP Futures/Open Issues… • BGP will not restrict Binding state to multicast tree. • Not enough bits to encode SAFI length for IPv6!! • Need to define transition from LAN procedures to BGP.

  12. Comments / Questions ?

  13. Differences from other document • Differences from draft-raggarwa-l3vpn-2547bis-mcast-bgp-00.txt • Separate RTs for Multicast VPNs (required for correct functioning of extranets) • Tracking of Downstream PEs (required for SGR Joins/Prunes) • Does not require RT configuration on ASBRs • Aggregation done on ASBR • Differences in NLRI