BGP-based Auto-Discovery for L2VPNs draft-hlmu-l2vpn-bgp-discovery-00.txt Sue Hares - Vasile Radoaca - Wei Luo - Praveen Muley - Paul Unbehagen - March 2, 2004, 59 th IETF

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

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

AFI/SAFI Encoding AFI to be assigned by IANA The SAFI value will be set to the following bit pattern: – LW 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

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)

Discovery Process BGP transmit – Next Hop, AGI, & AII LDP/L2TP receive – Target, AGI, SAII, TAII PE 1 PE 2 CE 1. New Forwarder created 2. BGP sends AD Update message Next Hop RT MP_Reach_NLRI: AFI = xxxx SAFI = W 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.

AS 2AS 1 Inter-AS Options 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 PE 1 PE 2 CE ASBR 1 Transparent mode PW 1

AS 2AS 1 Inter-AS Options 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. PE 1 PE 2 CE ASBR 1 ASBR 2 PW 1PW 2PW 3 Proxy mode

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?