1. Page 1 iPOP2009, Tokyo, Japan Selecting Domain Paths in Inter-Domain MPLS-TE and GMPLS Adrian Farrel, Old Dog Consulting Daniel King, Old Dog Consulting Tomonori Takeda, NTT Old Dog Consulting

2. Page 2 iPOP2009, Tokyo, Japan Old Dog Consulting Agenda Existing multi-domain PCE techniques Domain meshes Navigating the domain mesh Hierarchical PCE –Objective Functions –Procedures & Extensions Advanced applications Work to be done

3. Page 3 iPOP2009, Tokyo, Japan Old Dog Consulting Existing Multi-Domain PCE Techniques PCE can be used to determine end-to-end paths in multi-domain GMPLS and MPLS-TE networks –per-domain path computation techniques Devolve the computation of a path segment to each domain entry point Suits simply-connected domains and where the preferred points of interconnection are known –Backwards Recursive Path Computation (BRPC) Allow the PCEs to collaborate to select an optimal end-to-end path that crosses multiple domains Suits environments where multiple connections exist between domains and there is no preference for the choice of points of interconnection The assumption is the sequence of domains is well known, these techniques do not suit complex domain environments –Large, meshy environments –Multi-homed and multiply interconnected domains How do we derive an optimal end-to-end domain path sequences? –Definition of optimal will depend on policy Optimal trees Small number of domains crossed Reduce the number of border routers used

4. Page 4 iPOP2009, Tokyo, Japan Old Dog Consulting Existing Multi-Domain PCE Techniques Per domain –With per domain the sequence of domains is known –Domain border nodes are also usually known –Computation technique builds path segments across individual domains –Domain choice is only possible with crankback –The mechanism does not guarantee an optimal path BRPC –Current definition (RFC 5441) domain sequence is already known –BRPC is good for selecting domain border nodes –Computation technique derives optimal end-to-end path –BRPC could be applied to domain selection Functions correctly (optimal solution) Significant scaling issues

5. Page 5 iPOP2009, Tokyo, Japan Old Dog Consulting Domain Meshes Optical networks constructed from multiple sub-domains, or multi-AS environments often have multiple interconnect points –In an ASON subnetwork the computation of an end-to-end path requires the selection of nodes and links within a parent domain where some nodes may in fact be subnetwork The traffic engineering properties of a domain cannot be seen from outside the domain –TE aggregation or abstraction hides information and leads to failed path setup –Flooding TE information breaks confidentiality and does not scale in the routing protocol and in the aggregation process Domain 2 Domain 5 Domain 3 Domain 4 Domain 1

6. Page 6 iPOP2009, Tokyo, Japan Old Dog Consulting Navigating the Domain Mesh A computation solution needs to be scalable and maintain confidentiality while providing the optimal path. It also needs consider a number of factors: –Domain and Path Diversity Domain diversity should facilitate the selection of paths that share ingress and egress domains, but do not share transit domains Domain path selection should provide the capability to include or exclude specific border nodes –Existing Traffic Engineering Constraints The solution should take advantage of typical traffic engineering constraints (hop count, bandwidth, lambda continuity, path cost, etc.) –Commercial Constraints The solution should provide the capability to include commercially relevant constraints such as policy, SLAs, security, peering preferences, and dollar costs

7. Page 7 iPOP2009, Tokyo, Japan Old Dog Consulting Hierarchical PCE The Parent PCE maintains a topology map –The nodes are the Child domains –The map contains the inter-domain links –The TE capabilities of the links are also known Parent PCE knows the identify and location of the child PCEs responsible for the Child domains –Statically configured or dynamically discovered Domain confidentiality –A Parent PCE is aware of the topology and connections between domains, but is not aware of the contents of the domains –Child domains are completely confidential One child cannot know the topology of another Child Child domains do not know the general domain mesh connectivity

8. Page 8 iPOP2009, Tokyo, Japan Old Dog Consulting Domain 1 PCE 1 S BN 11 BN 12 BN 13 Domain 5 Hierarchical Domain Topology PCE 5 Domain 2 PCE 2 Domain 4 PCE 4 Domain 3 PCE 3 D BN 21 BN 22 BN 23 BN 24 BN 31 BN 32 BN 41 BN 42 BN 33

9. Page 9 iPOP2009, Tokyo, Japan Old Dog Consulting Hierarchical PCE Each Child PCE is configured with the address of its parent PCE –Typical, there will only be one or two Parents of any Child The Parent PCE also needs to be aware of the Child PCEs for all Child domains The Parent PCE could be configured with this information The Parent PCE could learn about this information when they connect Domain interconnection discovery –The Child PCE reports the following information to the Parent PCE: Each Child PCE knows the identity of its neighbor domains The IGP in each domain advertises inter-domain TE link capabilities No further automated discovery is required –Multi-domain and multi-provider discovery is undesirable Confidentiality Security Scalability

10. Page 10 iPOP2009, Tokyo, Japan Old Dog Consulting Hierarchical PCE Objective Functions Metric objectives when computing a inter-domain paths may include: –Minimum cost path –Minimum load path –Maximum residual bandwidth path –Minimize aggregate bandwidth consumption –Limit the number of domains crossed Policy objectives –Commercial relationships –Dollar costs of paths –Security implications –Domain reliability Domain confidentiality –Intra-domain topologies and paths may be kept confidential From other Child PCEs From the Parent PCE

11. Page 11 iPOP2009, Tokyo, Japan Old Dog Consulting Hierarchical PCE Procedures Hierarchical PCE, initial information exchange Domain 1 PCE 1 BN 11 BN 12 BN 13 PCE 5 Domain 5 1. Child PCE configured for its Parent PCE 2. Child PCE listens to Child IGP and learns inter-domain connectivity 3. Child PCE establishes contact with Parent PCE 4. Child PCE reports neighbor domain connectivity 5. Child PCE reports inter- domain link status change

12. Page 12 iPOP2009, Tokyo, Japan Old Dog Consulting Domain interconnectivity as seen by the Parent PCE –The Parent PCE maintains a topology map of the Child domains and their interconnectivity Parent PCE cannot see the internal topology of Child domain Hierarchical PCE Procedures Domain 5 Domain 1 PCE 5 Domain 2 Domain 3 Domain 4

13. Page 13 iPOP2009, Tokyo, Japan Old Dog Consulting Domain 1 S Hierarchical PCE Procedures PCE 1 BN 11 BN 12 BN 13 PCE 5 Domain 5 Domain 2 PCE 2 Domain 4 PCE 4 Domain 3 PCE 3 D 1. Ingress LSR sends a request to PCE1 for a path to egress 2. PCE 1 determines egress is not in domain 1 3. PCE 1 sends computation request to parent PCE (PCE 5) 5. Parent PCE sends edge-to-edge computation requests to PCE 2 responsible for domain 2, and to PCE 4 responsible for domain 4 4. Parent PCE determines likely domain paths 8. Parent PCE correlates responses and applies policy requirements 9. Parent PCE supplies ERO to PCE 1 6. Parent PCE send source to edge request to PCE 1 7. Parent PCE sends edge to egress request to PCE3

14. Page 14 iPOP2009, Tokyo, Japan Old Dog Consulting Advanced Applications Confidentiality –Simple application of PCE path-key –Parent PCE does not need to know the confidential information from domains Point-to-multipoint –Applies to multi-domain networks –See later presentation for more information (Multicast over optical multi-domain networks) Multi-level hierarchy –Parent PCE may itself have a parent –Regional and administrative hierarchies Horizontal cooperation between Parents –Parent PCEs could cooperate using existing PCE cooperation techniques –Cooperation between peer geographic or administrative hierarchies

15. Page 15 iPOP2009, Tokyo, Japan Old Dog Consulting Work to be done How do I know which domain contains my destination? –Discovery is impractical unless addressing identifies the domain –It is usual for the source to know the destination location Publish framework draft as RFC –draft-king-pce-hierarchy-fwk Minor protocol extensions Applicability statements –Point-to-multipoint –Applicability to ASON routing (G.7715.2)

16. Page 16 iPOP2009, Tokyo, Japan Old Dog Consulting Questions? Please feel free to send any questions to: Adrian Farrel adrian@olddog.co.ukadrian@olddog.co.uk Daniel King daniel@olddog.co.ukdaniel@olddog.co.uk Tomonori Takeda takeda.tomonori@lab.ntt.co.jptakeda.tomonori@lab.ntt.co.jp