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Multicast Signaling using BGP

Multicast Signaling using BGP. IETF 64 Nov 2005 Gargi Nalawade gargi@cisco.com Nidhi Bhaskar nidhi@cisco.com Pranav Mehta pmehta@cisco.com. PE-PE signaling for Multicast VPNs. Multicast VPN PE-PE signaling exists with PIM LAN procedures

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Multicast Signaling using BGP

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  1. Multicast Signaling using BGP IETF 64 Nov 2005 Gargi Nalawade gargi@cisco.com Nidhi Bhaskar nidhi@cisco.com Pranav Mehta pmehta@cisco.com

  2. PE-PE signaling for Multicast VPNs • Multicast VPN PE-PE signaling exists with PIM LAN procedures • Push for having the PE-PE signaling for non-LAN based approach • Latter requires procedures for PIM Join/Prune, binding (among other things) • Push for using BGP for the purpose • Aim to describe the required protocol changes and analyze the impact on BGP/PIM

  3. Enhancements required in BGP • Multicast PE-PE (Overlay) SAFI • RT/RD Import/Export • Filtering • PIM/BGP Interaction • Inter-AS No extensions for Unicast Reachability. Rely on existing VPNv4 Unicast for that.

  4. New SAFI – Multicast Overlay SAFI NLRI - {RD:G:Flags:S/RP:U-PE:D-PE} • Flags : RPT Bit, WC Bit • D-PE Optional, Label Optional. • Update from D-PE to U-PE : • RD:G:Flags:S/RP:U-PE:D-PE • Update from U-PE: • RD:G:Flags:S/RP:U-PE, Inner-Label • Tunnel Identifier carried as Attribute

  5. CE-2 CE-4 Receiver1 Source = 1.1.1.1 Transit for VPN SSM - BGP BGP Update: RD:232.1.1.1:SPT:1.1.1.1:PE-4:PE-2 BGP Update: RD:232.1.1.1:SPT:1.1.1.1:PE-4:PE-2 RR PE-1 PIM-V4 VRF JOIN:1.1.1.1, 232.1.1.1 e0 e1 BGP Update: RD:232.1.1.1:SPT:1.1.1.1:PE-4 Label=200, FEC=FEC200 PIM-V4 VRF JOIN:1.1.1.1, 232.1.1.1 PE-2 PE-4 PE-3 e0 CE-3 Receiver2

  6. Route-Targets/RD • RTs are carried as in Unicast VPNv4. • Cleaner to define new RTs for multicast. • RD, “traditionally” multicast uses U-PE’s RD.

  7. 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

  8. BGP - Filtering • Attach U-PE as Attribute for filtering J/P NLRI. • Or Assign an RT per upstream PE… • Use ORF/RT-Constrain to filter Tunnel Binding/RP Mappings. • Filtering further to keep binding state only along multicast tree is not specified.

  9. PIM/BGP Interaction • PIM Join or Prune is not part of NLRI. • S/RP,G Join is NLRI MP_REACH. • S/RP,G Prune is NLRI MP_UNREACH. • S,G,RPT Prune is NLRI MP_REACH. • S,G,RPT Join is NLRI MP_UNREACH • PIM Mode is not encoded in NLRI. • RP Mappings carried via separate BGP SAFI. • Can combine into same SAFI if necessary. • RD:Flags:G/mask:RP

  10. BGP Inter-AS • Multicast specific “aggregation”. No need to carry forward tracked downstream PEs from one AS to another. • “RPF lookup” to find Upstream ASBR. • Tunnel/Binding information updated at ASBR.

  11. 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

  12. BGP Futures/Open Issues • BGP will not restrict Binding state to multicast tree. • New functions in BGP like aggregating D-PE, U-PE based filtering, RPF lookup on ASBR and probably others. • Not enough bits to encode SAFI length for IPv6!! • RR Stores 1 multicast route as N*NLRI where N is #of D-PEs interested in stream. • Some PIM updates are full-state. Will need careful mapping of PIM states to BGP updates and state machine. • Need better understanding of the number of multicast streams and the rate at which they churn. • Extensions to support Bidir-PIM/BSR, PIM Asserts

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