MVPN PE-PE Signaling

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 - RDGFlagsS/RPU-PED-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
Transit for VPN SSM - BGP
RR BGP State RD232.1.1.1SPT1.1.1.1PE-4PE-2 R
D232.1.1.1SPT1.1.1.1PE-4PE-3 RD232.1.1.1SPT
1.1.1.1PE-4Label200
PE-2 BGP State RD232.1.1.1SPT1.1.1.1PE-4PE-2
RD232.1.1.1SPT1.1.1.1PE-4Label200
PE-4 BGP State RD232.1.1.1SPT1.1.1.1PE-4PE-2
RD232.1.1.1SPT1.1.1.1PE-4PE-3 RD232.1.1.1S
PT1.1.1.1PE-4Label200
RR
PE-1
PIM-V4 VRF JOIN1.1.1.1, 232.1.1.1
e0
e1
PIM-V4 VRF JOIN1.1.1.1, 232.1.1.1
PE-2
PE-4
PE-3
PE-3 BGP State RD232.1.1.1SPT1.1.1.1PE-4PE-3
RD232.1.1.1SPT1.1.1.1PE-4Label200
e0
CE-3
Receiver2
5
BGP- Issue w/ Re-using unicast RTs
PE-2 Red VRF RD2 Import RT RT1 Export RT
RT2 Blue VRF RD3 Import RTRT1 Export RTRT3
P
PE-1 Red VRF RD1 Import RTRT2 Export RTRT1
e0
e1
PE-2
PE-1
PE-3
e0
CE-Z
Receiver2
6
ABSR Exchange VPNv4 Routes - Option B
Update Sent to PE1 PE1GSSMSASBR1 Update Sent
to ASBR1 ASBR1GSSMSLabel100FEC-Y
Update sent to ASBR2 ASBR2GSSMSPE2 Update
sent to PE2 ASBR2GSSMSLabel20FEC-X
vpnv4 RDS NHPE1
vpnv4 RDS NHASBR1
ASBR2 Update to ASBR1 ASBR1GSSMSASBR2Label1
0
vpnv4 RDS NHASBR2
ASBR1
ASBR2
PE1
AS 2
PE2
AS 1
next-hop-self towards iBGP neighbors
CE1
CE4
CE2
CE3
S
7
BGP - Multicast Routing State

• RR Stores 1 multicast route as NNLRI 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 NM 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 lt-gt 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 lt-gt 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 gt
  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-mcas
  t-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