Presentation on theme: "BGP based Multi-homing in Virtual Private LAN Service"— Presentation transcript:
1 BGP based Multi-homing in Virtual Private LAN Service Wim HenderickxFlorin Balus
2 Problem Statement CE3 PE3 PE1 VPLS CE1 PE2 PE4 CE4 CE1 is multi-homed to PE1 and PE2; CE1 wants a resilient connectivityCE3VPLSPE3PE1CE1PE2PE4CE4Simple dual connectivity leads to loops and duplicate packets. Proposal provides a complementary solution next to STP, MC-LAG, etc leveraging BGP
3 Goal Address both PE and access link failure Provides fast convergence timesOnly the traffic transiting the affected network elements should be impactedDecouple the Multi-Homing mechanism from the PW signalingMinimize the traffic load on the network; ideally just the local PEs should be involved in the selection processRe-use existing BGP procedures while minimizing the network migration to ease operation
4 SolutionLet PE1 and PE2 know that they are connected to the same site using BGP-AD AFI/SAFI, proceduresAdd to BGP-AD NLRI an identifier for the Multi-homed SiteSite ID to be the same between peer PEsPW infrastructure can be built using either LDP or BGP signalingLocal Multi-homed PE(s) decide which PE is the designated forwarder for a given site/CE using BGP attributesLPREF e.g.VSI ID is the tie-breakerIf 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
5 Solution Designated PE forwards packets from and to CE Non-designated PEs (losing PEs) drop packets from CE as well as from other PEsThe effect is as if CE was single-homed to just the designated PE
6 ProposalBGP AD MH NLRI to carry the VSI-ID identifying the base VSI and 2 byte Site ID
7 PE1 is elected as designated forwarder OperationSite1 LPREF=200Site2 LPREF=200CE3PE3VPLSCE1PE1CE2PE2PE4CE4Site1 LPREF=100Site2 LPREF=100PE1 is elected as designated forwarder
8 Operation: link failure Site1 LPREF=200Site2 LPREF=200CE3PE3VPLSCE1PE1CE2PE2PE4CE4Site1 LPREF=100Site2 LPREF=100PE1 withdraws the MH NLRI, send a MAC flush PE2 becomes designated forwarder for CE1
9 Operation: PE failure CE3 PE3 CE1 PE1 VPLS CE2 PE2 PE4 CE4 Site1 LPREF=200Site2 LPREF=200CE3PE3VPLSCE1PE1CE2PE2PE4CE4Site1 LPREF=100Site2 LPREF=100PE2 becomes designated forwarder for CE1/CE2 upon BGP neighbor failure detection or upon reception of MH-NLRI withdraw for CE1/CE2
10 Operation continuedRR usage does not impact the operation since the VSI-ID is uniqueNo impact in Inter-AS scenario’s since the designated forwarding decisions are local multi-homed PE(s)No impact on H-VPLS operation
11 Next steps Minimize BGP flooding through the usage of ORF Add startup procedures and procedures for re-configurationDo we use this framework for both LDP VPLS and BGP VPLS?
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