BGP based Multi-homing in Virtual Private LAN Service Wim Henderickx Florin Balus

Problem Statement CE3 PE3 PE1 VPLS CE1 PE2 PE4 CE4 CE1 is multi-homed to PE1 and PE2; CE1 wants a resilient connectivity CE3 VPLS PE3 PE1 CE1 PE2 PE4 CE4 Simple dual connectivity leads to loops and duplicate packets. Proposal provides a complementary solution next to STP, MC-LAG, etc leveraging BGP

Goal Address both PE and access link failure Provides fast convergence times Only the traffic transiting the affected network elements should be impacted Decouple the Multi-Homing mechanism from the PW signaling Minimize the traffic load on the network; ideally just the local PEs should be involved in the selection process Re-use existing BGP procedures while minimizing the network migration to ease operation

Solution Let PE1 and PE2 know that they are connected to the same site using BGP-AD AFI/SAFI, procedures Add to BGP-AD NLRI an identifier for the Multi-homed Site Site ID to be the same between peer PEs PW infrastructure can be built using either LDP or BGP signaling Local Multi-homed PE(s) decide which PE is the designated forwarder for a given site/CE using BGP attributes LPREF e.g. VSI ID is the tie-breaker If none of the attached CE(s) is elected as designated forwarder for a given VSI, PW status can be used to minimize the BUM traffic in the network

Solution Designated PE forwards packets from and to CE Non-designated PEs (losing PEs) drop packets from CE as well as from other PEs The effect is as if CE was single-homed to just the designated PE

Proposal BGP AD MH NLRI to carry the VSI-ID identifying the base VSI and 2 byte Site ID

PE1 is elected as designated forwarder Operation Site1 LPREF=200 Site2 LPREF=200 CE3 PE3 VPLS CE1 PE1 CE2 PE2 PE4 CE4 Site1 LPREF=100 Site2 LPREF=100 PE1 is elected as designated forwarder

Operation: link failure Site1 LPREF=200 Site2 LPREF=200 CE3 PE3 VPLS CE1 PE1 CE2 PE2 PE4 CE4 Site1 LPREF=100 Site2 LPREF=100 PE1 withdraws the MH NLRI, send a MAC flush PE2 becomes designated forwarder for CE1

Operation: PE failure CE3 PE3 CE1 PE1 VPLS CE2 PE2 PE4 CE4 Site1 LPREF=200 Site2 LPREF=200 CE3 PE3 VPLS CE1 PE1 CE2 PE2 PE4 CE4 Site1 LPREF=100 Site2 LPREF=100 PE2 becomes designated forwarder for CE1/CE2 upon BGP neighbor failure detection or upon reception of MH-NLRI withdraw for CE1/CE2

Operation continued RR usage does not impact the operation since the VSI-ID is unique No impact in Inter-AS scenario’s since the designated forwarding decisions are local multi-homed PE(s) No impact on H-VPLS operation

Next steps Minimize BGP flooding through the usage of ORF Add startup procedures and procedures for re-configuration Do we use this framework for both LDP VPLS and BGP VPLS?

Questions?