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Stateful PCE

Stateful PCE. draft-tang-pce-stateful-pce-01.txt. Kexin Tang Xuerong Wang Yuanlin Bao ZTE Corporation. Problems without Stateful PCE. T 5. T 1. T 2. T 3. T 4. In network failure, a large number of LSPs need to be restored within very short time:

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Stateful PCE

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  1. Stateful PCE draft-tang-pce-stateful-pce-01.txt Kexin Tang Xuerong Wang Yuanlin Bao ZTE Corporation

  2. Problems without Stateful PCE T 5 T 1 T 2 T 3 T 4 • In network failure, a large number of LSPs need to be restored within very short time: • During restoration, same resource maybe assigned to two or more different requests (from T2 to T5), retry is needed. • Within the time window (T4 to T5), PCE will not know the LSPs failed to be created or the released LSPs, if the bandwith change below the bandwith threshold of IGP (this time window may last for half an in the IGP aging case). The restoration LSP may not succeed. Time Receive PCReq Path computation complete (per-PCE) End-to-end path computation complete RSVP signalling complete OSPF flooding update

  3. Realization of stateful PCE PCC discovers stateful PCE PCE reserves resources Notify PCE the end-to-end path computation result Notify PCE the LSP setup result

  4. PCED Extension Extended PCED TLV(RFC 5088), defined a new capability flag New PCE Capability Flag of PCE-CAP-FLAG With the stateful PCE capability flag, the PCC can select which PCE to be used.

  5. PCEP Extensions • Notification-type=3: end-to-end path computation result • Notification-value=1: end-to-end path computation success. • Notification-value=2: end-to-end path computation failure. • <PCNtf Message>::=<Common Header><notify-list> • <notify-list>::=<notify> [<notify-list>] • <notify>::=[<request-id-list>]<notification-list> • <request-id-list>::=<RP>[<path-list>][<request-id-list>] • <path-list>:=<path>[<path-list>] • <path>:=<ERO><attribute-list> • <notification-list> ::=<NOTIFICATION>[<notification-list>] • Both type 3 and type 4 Notification can carry the <path>in the PCNtf Message. • Notification-type=4: path delete • Notification-value=1: path delete

  6. Centralized PCE • After path computation, stateful PCE will save the computed result and reserve resources immediately • If LSP signaling failed, PCC should notify PCE to release resources from its TED: • Notification-type=4, Notification-value=1 • PCNtf optinally carries <path> to indicate which path should delete • A timer maybe needed according to local policy

  7. BRPC compute Inter-area/AS path • For each PCE • Compute potential paths • Reserve resources for each potential path in local TED B D F H

  8. BRPC compute Inter-area/AS path(Cont) • After end-to-end path computation • PCE of the first domain Sends PCNtf to each PCE in the PCE chain • Notification-type=3 • PCNtf carries <path> to indicate the end-to-end path • Each PCE released resources except those belong to the <path> carried in the PCNtf 3. Release reserved resource: EF 5. Release reserved resource: IJ 4. PCNtf LSP is created 2. PCNtf LSP is created 1. PCNtf LSP is created

  9. H-PCE compute Inter-area/AS path • For each child PCE and parent PCE • saves the computed result • reserves resources • After end-to-end path computation • Parent PCE sends PCNtf to each child PCE • Notification-type=3 • PCNtf carries <path> to indicate the end-to-end path In multi-domain path computation, if LSP signaling failed, PCC should also notify PCE to release resources from its TED.

  10. Next Steps • Refine it according to the feedback from the meeting or mailing list. • Maybe more scenarios of stateful PCE need to be identified.

  11. Comments? Thank You！

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