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Published byBarbara Hensley Modified over 9 years ago
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IP/LDP Local Protection draft-atlas-ip-local-protect-00.txt Alia Atlas (aatlas@avici.com) Raveendra Torvi (rtorvi@avici.com) Gagan Choudhury (gchoudhury@att.com) Christian Martin (cmartin@verizon.com) Brent Imhoff (brent.imhoff@wcg.com) Don Fedyk (dwfedyk@nortelnetworks.com)
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IETF 59 Routing Area Meetingdraft-atlas-ip-local-protect-00.txt2 Pre-Compute an Alternate To be used in event of a single failure to protect IP and/or LDP traffic until SPF has converged. Idea of IGP Fast-Reroute discussed previously –IETF Routing Area Meeting Nov 2003 Cengiz Alaettinoglu & Alex Zinin –Expired draft ( draft-kini-traf-restore-nsp-00.txt ) R5 R2 R3 R6 R1 Time 2 Time 1 Time 3 Time 4 R4 10 2 1 11 22 Non-Primary neighbor N is loop-free with regard to a source S and a destination D if D !S (N,D) = D opt (N,D) < D opt (N,S) + D opt (S,D) Safe and Simple local decision but insufficient Loop-Free alternatives in real networks Multiple links to primary neighbor give alternate to primary neighbor (no node protection)
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IETF 59 Routing Area Meetingdraft-atlas-ip-local-protect-00.txt3 U-Turn Alternates to Expand Alternate Coverage R1 can provide a U-turn alternate if –R1 has a loop-free node-protecting alternate to the destination (R4) –R1 can break the loop –R1 is a U-Turn neighbor of R2 R5 R2 R6 R1 Time 2 1 3 4 R4 R3 10 2 1 11 22 R1 is a U-turn neighbor of R2 U-Turn alternatives give about 20% extra coverage to close to 100% source/destination pair coverage (topology dependent)
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IETF 59 Routing Area Meetingdraft-atlas-ip-local-protect-00.txt4 U-Turn Alternates Con’t R1 can break the loop, if its hardware can forward traffic received on the “wrong” interface to the alternate interface –The receiving interface is “wrong”, if it comes from a primary neighbor that the traffic should be sent to. This means R1 has to support IP/LDP Local Protection, and have the capability to be used as a U-turn alternate R5 R2 R6 R1 Time 2 1 4 R4 R3 10 2 1 11 22 R1 breaks the loop and sends traffic to alternate port Time 3 Each Router can use U-Turn alternates for best protection or selectively.
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IETF 59 Routing Area Meetingdraft-atlas-ip-local-protect-00.txt5 U-Turn Alternatives: IGP Extensions draft-martin-isis-local-protect-cap-00 draft-atlas-ospf-ip-local-protect-cap-00 A router must know if its neighbor can redirect U-turn traffic if that neighbor has a loop-free node-protecting alternate (based on topology and administrative control) A Link Capabilities sub-TLV provides the 2 bitflags.
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IETF 59 Routing Area Meetingdraft-atlas-ip-local-protect-00.txt6 Next Steps Is there interest in standardizing this? Accept as a Routing Area Working Group draft
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