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

2. Page - 2 Problems without Stateful PCE Receive PCReq Path computation complete (per-PCE) End-to-end path computation complete RSVP signalling complete OSPF flooding update Time T 1T 2T 3T 4 T 5 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.

3. Page - 3 Realization of stateful PCE Discovery of Stateful PCEs Computation result saved, and resources reserved Synchronization between multiple PCEs (Inter-AS or Inter-Area) Synchronization between network states and PCEs PCC discovers stateful PCE PCE reserves resources Notify PCE the end-to-end path computation result Notify PCE the LSP setup result

4. Page - 4 PCED Extension BitCapabilities 0Path computation with GMPLS link constraints 1Bidirectional path computation 2Diverse path computation 3Load-balanced path computation 4Synchronized path computation 5Support for multiple objective functions 6Support for additive path constraints (max hop count, etc.) 7Support for request prioritization 8Support for multiple requests per message 9Stateful PCE 10-31Reserved for future assignments by IANA New PCE Capability Flag of PCE-CAP-FLAG Extended PCED TLV(RFC 5088), defined a new capability flag With the stateful PCE capability flag, the PCC can select which PCE to be used.

5. Page - 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. ::= ::= [ ] ::= [ ][ ] := [ ] := ::= [ ] – Both type 3 and type 4 Notification can carry the in the PCNtf Message. Notification-type=4: path delete – Notification-value=1: path delete

6. Page - 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 to indicate which path should delete – A timer maybe needed according to local policy

7. Page - 7 BRPC compute Inter-area/AS path For each PCE Compute potential paths Reserve resources for each potential path in local TED HFDB

8. Page - 8 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 to indicate the end-to-end path Each PCE released resources except those belong to the carried in the PCNtf 1. PCNtf LSP is created 2. PCNtf LSP is created 4. PCNtf LSP is created 3. Release reserved resource: EF 5. Release reserved resource: IJ BRPC compute Inter-area/AS path(Cont)

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

10. Page - 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. Page - 11 Thank You Comments?