Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net 1 Multicast in BGP/MPLS VPNs draft-ietf-l3vpn-2547bis-mcast-00.txt and draft-raggarwa-l3vpn-2547bis-mcast-bgp- 00.txt Eric Rosen Rahul Aggarwal

2 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net MVPN Improvements  Scalability: Control plane: reduce overhead needed to maintain state Data plane: more aggregation Tunnels on per-VPN or coarser basis  Control Integration: reuse general L3VPN mechanisms?  More optimality in data plane Less aggregation, but less scalable.  Eliminate requirement for MI-PMSI-based control  More flexibility in choosing tunneling technologies  Inter-AS Architecture

3 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net Tensions  Scale vs. Optimality, duh! More accepted in unicast rtg than in mcast rtg  “Known to Work” vs. “Being Invented Now”  Control: integration vs. optimization  Data vs. Control Plane Which is bottleneck??  Multicast has unpredictable demands  Dogma

4 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net Non-Goals  Generic Improvements to Multicast Technology Welcome, but not our focus  Solutions for non-L3VPN environments

5 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net Data Plane MI-PMSI Elimination?  Data MI-PMSI makes it easier to handle: Dense Mode Flooding-based applications Transparent when MI-PMSI is in place Require special measures otherwise E.g.:, BSR

6 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net Multi-Homed Sources and Duplicate Traffic  PE3 wants via PE1, via PE2  PE4 wants via PE2, via PE1  Data from both streams travels both trees: duplicates  With MI-PMSI in control plane, PIM Asserts can be used to prevent this by forcing a “designated forwarder”  Need alternative PE1PE2 PE3PE4PE3PE4 S1, S2

7 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net Eliminating Duplicates  Option 1: PE discards streams on “wrong” tree Possible, with MPLS even easy Wastes core bandwidth (trade-off)  Option 2: All PEs must choose same ingress How? no unique “best route” to S Can waste core bandwidth, increase latency  Maybe: best of both Policy to force same ingress per AS only Not to force the same ingress across ASs (prefer intra-AS path) Mandatory mechanism to force dups to be discarded

8 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net Theme for BGP Work  BGP: L3VPN PE-PE signaling mechanism  Prima facie advantages of using for PE-PE multicast signaling: Uniform control plane Leverage of capabilities: constrained distribution, security, summarization, inter-AS, etc.  Scaling needs to be carefully examined  Dynamics

9 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net Theme for BGP Work, 2  Don’t get carried away No need to suppress work on other options Don’t throw away “known to work” schemes  Two different functions to handle: Not new to BGP: auto-discovery for MVPNs, label distribution for m-tunnels, m-streams, binding streams to tunnels New to BGP: carrying PE-PE multicast routing, interfacing to PIM

10 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net Basic BGP Interactions 1.R-state: Egress PE gets PIM J/P from CE, instantiates state: "(S,G)receivers" 2.Distribute R-state based on RTs for VPN. Design issue: mapping PIM J/Ps to updates and withdraws, not always obvious 3.S-state: many-to-one binding of R-state to P-tunnel 4.When ingress PE receives R-state, it sends PIM J/P to CE, may or may not need to create and distribute new S-state New S-state only needed for S-PMSI binding S-state distribution based on RTs for VPN

11 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net S-State Scaling, 1  How many S-states are needed? Minimum: one per VPN each VPN has a default tunnel (possibly shared with others), MPLS label not used for per-stream demux, Maximum: one per stream each stream individually bound to a tunnel, or MPLS label used for per-stream demux What is the rate of change of S-state?

12 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net S-State Scaling, 2  Distributing S-state (only for S-PMSI) Needs to be known by ingress & each egress Possible to restrict distribution: only to egresses for stream, or to all PEs in VPN. Trades off more information with latency and signaling overhead  S-states increased by multi-homing of sources, perhaps not significantly

13 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net R-State Scaling 1  This is the stuff that PIM usually handles pure PIM states rather than labels/bindings  Total # R-states: At egress PE, # streams At ingress PE, we have choices: One per stream per egress PE (“explicit tracking”) One per stream (receivers somewhere, don’t remember where)  Applies to any control protocol

14 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net R-State Scaling (Intra-AS) 2  Is explicit tracking needed? No in these cases: Default tunnels (any tunnel setup protocol) Selective tunnels set up via PIM or mLDP Yes in these cases: Selective tunnels set up via RSVP-TE “Aggregation via congruence” S-PMSIs  Should be used only when needed, as determined by head-end

15 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net R-State Scaling (Intra-AS) 3  Without explicit tracking: R-states can be regarded by BGP as “comparable” routes (NLRI design) Aggregate R-state at RR RR gets one per stream per PE, forwards one per stream

16 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net BGP MVPN Functionality Intra-AS  MVPN Auto-Discovery/Inclusive Binding Granularity of Binding one or more MVPNs to a P-tunnel (I-PMSI)  C-multicast routing information exchange among PEs Granularity of  Selective binding and switching from I-PMSI to S-PMSI One or more specific C-multicast streams, from one or more MVPNs, to a P-Tunnel

17 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net BGP MVPN Functionality Inter-AS  MVPN Auto-Discovery Aggregation of Auto-discovery information Granularity of  Inter-AS tunnels constructed by stitching intra-AS tunnels Independent P-Tunneling technology per provider  MVPN PE-PE Routing Exchange Aggregation of R-state Granularity of  Routing peerings between ASs only at ASBRs or RRs  Use RT Constrain to limit distribution of auto-discovery routes and C-multicast routes  Support of all three options for inter-AS unicast

18 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net BGP MVPN Inter-AS  MVPN that is present in N ASs would result in N inter-AS P- tunnels (one per AS, not one per PE) To improve scalability multiple intra-AS tunnel segments within an AS could be aggregated into a single intra-AS P- tunnel Uses auto-discovery routes  Inter-AS R-state is propagated by egress PE towards the source AS Propagates using the inter-AS auto-discovery routes i.e. route No flooding of R-state No R-state in the ASBR forwarding plane

19 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net BGP Extensions – MCAST VPN NLRI  Consists of RD Src PE Address C-S length, C-S C-G length, C-G MPLS labels  Used for Auto-Discovery Routes MVPN intra/inter-AS auto-discovery Intra-AS I-PMSI and S-PMSI binding Inter-AS tunnels “stitched” from intra-AS segments  Also used for C-multicast routes Intra/Inter-AS C-multicast routing information exchange

20 Copyright © 2004 Juniper Networks, Inc. Proprietary and Confidentialwww.juniper.net Switching to S-PMSI  Driven by PE connected to C-S  Binds (C-S, C-G) to a particular P-tree P-tree may be shared with other (C-S, C-G) Sharing is not constrained by MVPN membership  Uses auto-discovery routes  Uses the same procedures as auto-discovery, except that MCAST VPN NLRI carries C-S, C-G Both for intra-AS and inter-AS