BGP-based Auto-Discovery for L2VPNs draft-hlmu-l2vpn-bgp-discovery-00.txt

1. BGP-based Auto-Discovery for L2VPNs draft-hlmu-l2vpn-bgp-discovery-00.txt Sue Hares - shares@nexthop.com Vasile Radoaca - vasile@nortelnetworks.com Wei Luo - luo@cisco.com Praveen Muley - pmuley@nortelnetworks.com Paul Unbehagen - paulu@nortelnetworks.com March 2, 2004, 59th IETF

2. Intent • Use BGP to provide an Auto-discovery method for LDP and L2TP signaled L2VPNs. • Intent is to work for VPWS & VPLS (distributed and Non-distributed) • Information needed by the Signaling protocol include: • Remote PE IP address • VPN ID • VPN endpoints • This provides: • Automatic PW establishment • Can also provide automatic establishment of targeted signaling sessions

3. Overview • Use RT to color routes and control topology. • Capability Negotiation • MP Extensions (capability 1) • And the list of AFI/SAFI pairs for L2VPNs. • i.e. AFI x / SAFI 1, AFI x / SAFI 2, AFI x / SAFI 3 • AGI & AII Encoded in the portion of the MP_Reach_NLRI for creation announcement

4. AFI/SAFI Encoding • AFI to be assigned by IANA • The SAFI value will be set to the following bit pattern: • 0000 00LW • where L is the presence of VPLS • W is the presence of VPWS • SAFI value is set 3 to signify that the NRLI encoding can be used for both

5. NLRI Encodings • The encoding of the NRLI in the MP-BGP attribute is based on the AFI/SAFI identifiers. • For L2VPNs, the SAFI values of 1-3 will have the following NLRI encoding: Length of NLRI in bits, NLRI field (variable length) Where the NLRI field is further defined as: • Length of AGI (in bits), AGI (variable) • Length of AII (in bits), AII (variable)

6. Discovery Process BGP transmit – Next Hop, AGI, & AII LDP/L2TPreceive – Target, AGI, SAII, TAII PE1 PE2 CE CE Next Hop RT MP_Reach_NLRI: AFI = xxxx SAFI = 0000 000W Length of NH Next Hop AGI Length (bits) AGI value (variable) AII Length (bits) AII Value (variable) 3. BGP filters on RT and LDP receives the discovery message. 4. AII from the update message becomes the TAII in the signaling protocol. 1. New Forwarder created 2. BGP sends AD Update message

7. Inter-AS Options Transparent mode • 2 modes available to provide inter-AS • Transparent • Proxy • Transparent mode allows the ASBRs to pass reachabilties of L2VPN information through to the next AS directly to the remote PE’s • This also requires the network reachabilities for the originating PE to be announced as well AS 1 AS 2 ASBR1 ASBR1 PE1 PE2 CE CE PW 1

8. Inter-AS Options Proxy mode • 2 modes available to provide inter-AS • Proxy • Transparent • Proxy mode requires ASBRs to create PW for inter-AS communications and be L2VPN aware • ASBR1 sends an Update to ASBR2 with next-hop address of ASBR-1, and SNPA1 filled with PE-1 BGP Identifier • When ASBR-2 receives the update from ASBR-1, it performs the same procedures as ASBR-1 and announces the update to all PEs in AS2 with: • next-hop address of ASBR-2, and • SNPA1 with PE1 BGP Identifier, and • SNPA2 with ASBR-1 BGP Identifier. AS 1 AS 2 ASBR1 ASBR2 PE1 PE2 CE CE PW 1 PW 2 PW 3

9. Conclusion • Provide a method of Auto-discovery for LDP based L2VPNs • Works for VPWS & VPLS (distributed and Non-distributed) • New AFI needed for L2VPNs • Do we need to support PW-id?