1. Forward-Search P2P TE LSP Inter- Domain Path Computation draft-chen-pce-forward-search-p2p-path-computation Huaimo Chen (huaimochen@huawei.com)@huawei.com

2. Page 2 Contents  Issues in Existing P2P Inter-domain Path Computation  Comparing P2P Inter-domain Path Computation Methods  Forward Search P2P Inter-domain Path

3. Page 3 Issues in Existing P2P Inter-domain Path Computation  Domain sequence from source to destination must be given in advance  May not guarantee that the path found is best  Could be not efficient when topology of domains is complex

4. Page 4 Comparing P2P Inter-domain Path Computation Methods Existing Solution for P2P inter- domain path ：  Domain sequence from src to dest must be given in advance  May not guarantee the path found is best  Could be not efficient when topology of domains is complex New solution  No domain sequence is needed  Guarantee the path found is best  Simple and efficient

5. Page 5 Forward Search P2P Inter-domain Path Start from the source node and the source domain. Consider optimal path segment from source node to every exit boundary node of the source domain as a special link; Consider the optimal path segment from an entry boundary node to every exit boundary node of a domain as a special link; and the optimal path segment is computed as needed. The whole topology consisting of many domains can be considered as a special topology, which contains those special links, the normal links in the destination domain and the inter-domain links. Compute an optimal path in this special topology from the source node to the destination node using CSPF. Domain 120 J I F C G K L M N O Q T U X A B R H V B1 E D S W A1 Y Z P Domain 150 Domain 180 PCE2 PCE1 PCC PCE3 Boundary Node Src Node Dest Node 2 4 3 1 C1 Best path: A-C-F-J-L-O-U-X- A1-C1 Src to Boundary path computed as a link In Boundary to Out Boundary path computed as a link

6. Forward Search P2P Inter-domain Path (Animated) Domain 120 J I F C G K L M N O Q T U X A B R H V B1 E D S W A1 Y Z P Domain 150 Domain 180 PCE 113 115 PCC 111 PCE 117 Boundary Node Src Node Dest Node 2 4 3 1 C1 Best path: A-C-F-J-L-O- U-X-A1-C1 Src to Boundary path computed as a link In Boundary to Out Boundary path computed as a link A3 B3 C3 B4 A4 C4 B2 A2 C2 8 10 2 3 4 6 11 5 6 3 15 7 7 7 6 8 8 16 9 8 8

7. Next Step Welcome comments Request to make it into a working group document

8. Request Message Extension ::= [ ] ::= [ ] ::= [ ] [ [ ]] [ ]

9. Existing Solution for P2P inter-domain path computation: RFC5441(BRPC) (from page 6 of RFC5441) The PCE-based BRPC procedure applies to the computation of an optimal constrained inter-domain TE LSP. The sequence of domains to be traversed is either administratively predetermined or discovered by some means that is outside of the scope of this document. In the case of an arbitrary set of meshed domains, the BRPC procedure can be used to compute the optimal path across each domain set in order to get the optimal constrained path between the source and the destination of the TE LSP. The BRPC procedure can also be used across a subset of all domain sequences, and the best path among these sequences can then be selected.