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Quintin Zhao , qzhao@huawei.com Zafar Ali , zali@cisco.com Tarek Saad , tsaad@cisco.com

PCE-based Computation Procedure for P2MP Inter-domain TE LSP draft-zhao-pce-pcep-inter-domain-p2mp-procedures-06. Quintin Zhao , qzhao@huawei.com Zafar Ali , zali@cisco.com Tarek Saad , tsaad@cisco.com Daniel King, daniel@olddog.co.uk Ramon Casellas , ramon.casellas@cttc.es

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Quintin Zhao , qzhao@huawei.com Zafar Ali , zali@cisco.com Tarek Saad , tsaad@cisco.com

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  1. PCE-based Computation Procedure for P2MP Inter-domain TE LSPdraft-zhao-pce-pcep-inter-domain-p2mp-procedures-06 Quintin Zhao, qzhao@huawei.com Zafar Ali, zali@cisco.com Tarek Saad, tsaad@cisco.com Daniel King, daniel@olddog.co.uk Ramon Casellas, ramon.casellas@cttc.es Siva Sivabalan, msiva@cisco.com IETF 79 - Beijing

  2. Updates in this version IETF 79 - Beijing • Two new authors have joined this work: Ramon Casellas from CTTC and Siva Sivabalan from Cisco. • Fixed some spotted typos and unified a couple of redundant paragraphs • Added a couple of figures for core tree and domain tree examples. • Updated some definitions. • Added paragraphs to address the scalability of the Core Path procedure along with the hint that it could be computed offline for a large network or it could be computed inline for a small network. • Added a section on parallelism (section 7.6): • In order to minimize latency in path computation in multi-domain networks, intra-domain path segments and intra-domain sub-trees SHOULD be computed in parallel when possible.

  3. Quick Review for the procedures introduced in this draft IETF 79 - Beijing

  4. Inter-Domain P2MP Path Computation ProceduresExample: How to build a P2MP Tree? Domain1 Domain4 Domain3 Domain2 Domain5 Domain6 4

  5. Inter-Domain P2MP Path Computation ProceduresPhase1:Build the Core Tree PCE4 PCE1 D1 PCE3 T A W E P M Q R X PCE2 Z PCE5 U PCE6 D2 5

  6. Inter-Domain P2MP Path Computation ProceduresPhase2: Compute the sub-tree for each individual domains PCE4 PCE1 D1 PCE3 T PCE2 PCE5 U PCE6 D2 6

  7. Inter-Domain P2MP Path Computation ProceduresPhase3: Grafting sub-tree into the core-tree PCE4 PCE1 D1 PCE3 T A W E P M Q R X PCE2 Z PCE5 U PCE6 D2 7

  8. Core-Tree Computation: VSPT for D1 PCE 4 computes D1 (1) PCE 4 supplies {D1(1)} PCE4 PCE 3 computes V-T-D1 (3) W-T-D1 (3) PCE 3 supplies {VTD1(3), WTD1(3)} PCE1 D1 PCE3 T V A PCE 2 computes E-F-G-V-T-D1 (5) E-P-Q-R-M-W-T-D1 (7) H-P-E-F-G-V-T-D1 (7) H-P-Q-R-M-W-T-D1 (7) PCE 2 supplies {EGVTD1(5), EMWTD1(7), HGVTD1(7), HMWTD1(7)} B G PCE2 W C F E P M Q R 2 T A E V S G J Sub-path (D1-1) 4 H A E S M Sub-path (D1-2) T W K D1 2 2 B S H E C G T V Sub-path (D1-3) S C H B M T W Sub-path (D1-4) PCE 1 computes VSPT(D1) 8

  9. Core-Tree Computation: VSPT for D2 PCE 6 computes U-D2 (1) PCE 6 supplies {UD2(1)} PCE 5 computes X-Z-U-D2 (3) Y-U-D2 (3) PCE 5 supplies {XUD2(3), YUD2(3)} PCE1 A B G PCE2 PCE 2 computes E-P-Q-R-M-X-U-D2 (8) E-P-H-J-K-Y-U-D2(7) H-P-Q-R-M-X-Z-U-D2 (8) H-J-K-Y-U-D2(5) PCE 2 supplies {EMXUD2(8), EHYUD2(7), HMXZUD2(8), HKYUD2(5)} C F E P M Q R X J 2 4 PCE5 U Sub-path (D2-1) A E X S M Z H 2 2 K A E S H K Sub-path (D2-2) U Y D2 Y 4 2 U B S Sub-path (D2-3) H M U C X 2 D2 S Sub-path (2-4) C H B K U Y PCE6 PCE 1 computes VSPT(D2) 9

  10. Core-Tree Computation: Merging VSPTs Merging two sub-path from each VSPTs into a Core Tree Take a sub-path(D1-i) from VSPT(D1) and a sub-path(D2-j) from VSPT(D2). Merge them into a Core Tree(D1-i-D2-j) Compute the cost for the Core Tree(D1-i-D2-j) Repeat (1) to (3) for all the i and j combinations to generate all the possible Core Trees Evaluate and identify the Core Tree with the minimum cost among all the Core Trees 10

  11. Core-Tree Computation: Merging VSPTs Take a sub-path(D1-1) from VSPT(D1): 2 T A E V Sub-path (D1-1) S G 4 A E Sub-path (D1-2) S M T W D1 2 2 Sub-path (D1-3) B S H E C G T V S C H B M Sub-path (D1-4) T W Core Tree (D1-1-D2-2) (cost: 14) VSPT(D1) D1 2 T A E V S G Take a sub-path(D2-2) from VSPT(D2) 2 2 H Y K U D2 2 4 U Sub-path (D2-1) A E X S M 2 2 A E S H K U Sub-path (D2-2) Y D2 4 2 B S H M Sub-path (D2-3) U C X 2 S C H B K Sub-path (D2-4) U Y VSPT(D2) 11

  12. Core-Tree Computation: Merging VSPTs Take a sub-path(D1-1) from VSPT(D1): 2 T A E V Sub-path (D1-1) S G 4 A E Sub-path (D1-2) S M T W D1 2 2 Sub-path (D1-3) B S H E C G T V S C H B M Sub-path (D1-4) T W Core Tree (D1-2-D2-2) (cost: 13) VSPT(D1) D1 4 T A E W S M Take a sub-path(D2-2) from VSPT(D2) x U D2 2 4 2 U Sub-path (D2-1) A E X S M 2 2 A E S H K U Sub-path (D2-2) Y D2 4 2 B S H M Sub-path (D2-3) U C X 2 S C H B K Sub-path (D2-4) U Y VSPT(D2) 12

  13. Inter-Domain P2MP Path Computation Final Core Tree PCE4 Final Core Tree (D1-2-D2-1) with a minimum cost: 13 PCE1 D1 D1 4 PCE3 T A E S W M T A U X PCE2 W 2 D2 E P M Q R X PCE5 Z U D2 PCE6 13

  14. Inter-Domain P2MP Path Computation ProceduresFinal P2MP Tree PCE4 PCE1 D1 PCE3 T A W E P M Q R X PCE2 Z PCE5 U PCE6 D2 14

  15. Core-Tree Based Inter-Domain P2MP Path Computation A Core-Tree is a path tree with Boundary Nodes (BNs) from each domain corresponding to the PCE topology which satisfies the following conditions: The root of the core tree is the ingress LSR in the root domain The leaf of the core tree is the entry node in the leaf domain The transit and branch node are from the transit and branch domains. A Sub-Tree is a path tree within a domain with all of its sub root node, transit node and leaf node within the same domain. The sub-tree within each domain is optimized subject to theOF. The Computing each sub-tree is independent of the domain sequences The grafting and pruning of multicast destinations in a domainhas no impact on other domains and no impact on the core-tree 15

  16. Core-Tree Based Inter-Domain P2MP Path Computation Core-Tree Based Proceduresare done in three phases: Procedure Phase 1: P2MP LSP Core Tree Building for the Boundary Nodes (BNs) Based on Backward Recursive Path Computation (BRPC) procedures, builds a Extended Shortest Path Tree (VSPT) which has the egress as the root and the ingress as the leaf; The source PCE builds all possible Core-Trees based on the VSPT computed from previous step; Find out the optimal Core-Tree based on the OF; Procedure Phase 2: In each leaf domain, using domain specific algorithm such as CSPF to compute the sub-tree which has the entry BN as the root and each individual destination as leave of the sub-tree. Procedure Phase 3: Grafting destinations or the sub-trees in each domain to the P2MP LSP Core Tree computed from phase1. 16

  17. Conclusions Core-Tree based solution has the following advantages; It computes the optimal inter-domain P2MP path which satisfies the OF for the path, and also the path is remerge free; Domain confidentiality is kept; Policy for each individual domain can be applied individually; Each domain can has its own algorithms for its sub-tree computation; The individual destination’s pruning and graphing is independent of the core-tree computing; The solution is scalable; 17

  18. Next Steps • We ask the working group to adopt this draft as working group document. IETF 79 - Beijing

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