Selecting Domain Paths in InterDomain MPLSTE and GMPLS - PowerPoint PPT Presentation

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Selecting Domain Paths in InterDomain MPLSTE and GMPLS

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TE aggregation or abstraction hides information and leads to failed path setup ... Minimize aggregate bandwidth consumption. Limit the number of domains crossed ... – PowerPoint PPT presentation

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Title: Selecting Domain Paths in InterDomain MPLSTE and GMPLS


1
Selecting Domain Paths in Inter-Domain MPLS-TE
and GMPLS
  • Adrian Farrel, Old Dog Consulting
  • Daniel King, Old Dog Consulting
  • Tomonori Takeda, NTT

2
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
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
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
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 3
Domain 2
Domain 5
Domain 1
Domain 4
6
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
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
Hierarchical Domain Topology
Domain 5
PCE 5
Domain 1
Domain 2
Domain 3
PCE 1
PCE 2
PCE 3
BN 11
BN 21
BN 23
BN 31
BN 12
BN 22
BN 24
BN 32
S
D
Domain 4
PCE 4
BN 13
BN 33
BN 41
BN 42
9
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
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
Hierarchical PCE Procedures
  • Hierarchical PCE, initial information exchange

2. Child PCE listens to Child IGP and learns
inter-domain connectivity
1. Child PCE configured for its Parent PCE
Domain 5
PCE 5
Domain 1
3. Child PCE establishes contact with Parent PCE
PCE 1
BN 11
BN 12
4. Child PCE reports neighbor domain connectivity
BN 13
5. Child PCE reports inter-domain link status
change
12
Hierarchical PCE Procedures
  • 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

PCE 5
Domain 5
Domain 1
Domain 2
Domain 3
Domain 4
13
Hierarchical PCE Procedures
Domain 5
PCE 5
Domain 1
Domain 3
2. PCE 1 determines egress is not in domain 1
PCE 3
PCE 1
Domain 2
BN 11
PCE 2
4. Parent PCE determines likely domain paths
D
BN 12
S
Domain 4
BN 13
PCE 4
8. Parent PCE correlates responses and applies
policy requirements
9. Parent PCE supplies ERO to PCE 1
14
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
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
Questions?
  • Please feel free to send any questions to
  • Adrian Farrel adrian_at_olddog.co.uk
  • Daniel King daniel_at_olddog.co.uk
  • Tomonori Takeda takeda.tomonori_at_lab.ntt.co.jp
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