1. NGN Automation:
Delivering Multicast Services
Quintin Zhao – Huawei Technologies
Daniel King – Old Dog Consulting www.huawei.com
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2. Agenda
 Drivers for NGN automation to deliver multicast
services
 Planning issues for deploying multicast services
across inter-domain networks
 Deployment components for delivery inter-domain
multicast services
 Summary and next steps
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3. Drivers for NGN automation for
delivering multicast services
 The customer expects:
 Rapid delivery of new services
 Greater bandwidth
 Higher QoS
 Protection
 More sophisticated SLAs
 The provider needs to:
 Drive up income from deployed resources
 Provide more complex services within existing networks
 Find a way to deliver QoS and meet SLAs
 Whilst reducing operational costs, and minimising network planning activities
 Maximize the use of P2MP technologies for efficient packet delivery
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4. General Planning Issues
 Throwing bandwidth at the problem?
 A guaranteed fat pipe is a good way to deliver quality
 High-speed delivery addresses delay problems
 Jitter can be handled in buffering
 But bandwidth may be expensive and impractical and doesn’t solve all issues
 Inevitably, even in a lightly used network, some links reach critical utilisation
 It can be hard to predict which links these will be in failure scenarios
 New customers can cause unforeseen congestion points
 Increasing capacity cannot be done on demand
 Better network planning and appropriate reoptimization of services
 Requires complex path computation capabilities
 Consider all current services and compute in parallel not serial
 Utilize P2MP transport and service technologies for delivering multicast services
 Today’s networks are comprised of many domains
 Domains share common address management or path computational responsibility. Information is
not generally shared outside of these domains.
 Establish domain interconnectivity and maintain policy
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5. Planning Inter-domain P2MP Services
 General network requirements
 Deterministic behavior and paths
 High bandwidth
 Fast service start-up (rapid graft and prune for channel switching)
 Minimise network transmission cost
 Minimise the aggregate cost of the tree
 Minimise data delivery delay, hop count, or path length
 Minimise per branch attributes
 Domain Path Selection
 Optimal domain paths
 Controlling network policy and confidentiality
 Maintain domain confidentiality when computing inter-domain end-to-end paths
 Provide domain disjoint and exclude and include functions
 Provide service resilience
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6. P2MP Signaling Solutions
 Extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for
Point-to-Multipoint TE Label Switched Paths (LSPs) - RFC4875
 Extensions to RSVP-TE for Point-to-Multipoint TE LSPs”
 Equally applicable to MPLS-TE and GMPLS
 Practical solution for all transport technologies (MPLS-TE, T-MPLS, Ethernet, TDM, Lambda, Fibre)
 Simple additions to Path and Resv message
 Session object identifies the whole P2MP tunnel (all leaf nodes)
 New object for individual leaf identifiers (destinations)
 Explicit routes (and recorded routes) represented as successive branch-to-leaf paths
 Can signal a tree using one or more Path messages
 Additional extensions exist for more advanced deployments
 IGP Routing Protocol Extensions for Discovery of Traffic Engineering Node Capabilities
RFC5073
 Which nodes support RSVP-TE P2MP signaling?
 Which nodes are branch-capable and bud-capable in the data plane?
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7. P2MP Deployments
 Orange UK: Deployment Experiences of MPLS P2MP LSPs for IPTV Distribution*
 Their core UK MPLS network was already based on RSVP LSPs with FRR. So RSVP based P2MP was a
natural choice.
 Two separate P2MP trees; i.e. two separate Forwarding Planes so each regional POP receives
multicast streams from both trees, active + active.
 Planned strict-ERO P2MP LSPs provide efficient use of bandwidth and LSP paths avoid using common
routers and links.
 For complex topologies that span multiple domains, additional technologies are required.
* Orange UK: Deployment Experiences of MPLS P2MP LSPs for IPTV Distribution
MPLS World Congress 2008
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8. PCE-enabled Planning
 Path Computation Element
 “An entity (component, application, or network node) that is capable of computing a network path
or route based on a network graph and applying computational constraints” (RFC4655)
 PCE is a path computation element (e.g., server) that specializes in complex path
computation on behalf of its path computation client (PCC)
 PCEs collect TE information
 They can “see” within the domain
 Path computation requires knowledge of the available network resources
 Nodes and links
 Constraints
 Connectivity
 Available bandwidth
 Link costs
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9. PCE Components
 Embedded path computation capabilities
 Part of the functional model
 Not very exciting for building networks!
 Path Computation Element (PCE)
 The remote component that provides path computation
 May be located in an LSR, NMS, or dedicated server
 Path Computation Client (PCC)
 The network element that requests computation services
 Typically an LSR
 Any network element including NMS
Server Server
LSR
NMS TED
TED TED
TED
PCE
PCE PCE
PCE
LSR LSR LSR LSR LSR LSR LSR
Signalling Signalling Signalling Signalling Signalling Signalling Signalling Signalling
Engine Engine Engine Engine Engine Engine Engine Engine
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10. Deploying Inter-domain P2MP Services
 Determine which domains should be used for the end-to-end path for each leaf
(domain sequences trees)
 Select the entry point and exit point from a domain
 Identify which nodes could be branch nodes
 Compute the minimum cost tree across all domains
 Compute a backup tree which has full or partial link/node/path diversity from the
primary tree
Border Nodes Border Nodes
TRANSIT TRANSIT Site
LEAF
INGRESS TRANSIT F
BRANCH BRANCH
Site
A TRANSIT LEAF
LEAF
BUD
TRANSIT
Site Site
LEAF
Site C E
Site
B D
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11. Deploying Inter-domain P2MP Services
 A Core-Tree solution provides an optimal inter-domain P2MP TE LSP and looks to
address the specific requirements and objective functions outlined in the previous
slides
 Assumes that the domain tree is already known by using hierarchical PCE (covered
in subsequent slides)
PCE1 PCE2
Border Nodes Border Nodes PCE4
PCC TRANSIT Site
TRANSIT LEAF
TRANSIT F
BRANCH BRANCH
Site INGRESS
A TRANSIT LEAF
LEAF
BUD
TRANSIT
Site Site
LEAF
Site C E
Site
B D
PCE3
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12. Comparison of CT versus
traditional techniques
 A Core-Tree based solution supports constrained inter-domain path computation
with the following advantages
 Allows a P2MP TE LSP to meet specific OF
 Allows the operator to maintain internal domain confidentiality
 Allows the operator to consider policy constraints
 The sub-tree within each domain is optimized subject to the OF
 The Computing each sub-tree is independent of the domain sequences
 The grafting and pruning of multicast destinations in a domain has no impact on
other domains and no impact on the core-tree
 Limits the number of entry and exit points to a domain
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13. 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
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14. Hierarchical PCE Topology
 Domain interconnectivity as seen by the Parent PCE
 The Parent PCE maintains a topology map of the Child domains and their interconnectivity
PCE 5
Domain 5
Domain 1 Domain 2 Domain 3
Domain 4
 Parent PCE cannot see the internal topology of Child domain
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15. Hierarchical PCE Procedures
1. Ingress LSR sends a
request to PCE1 for a path PCE 5
Domain 5
to egress
Domain 1 Domain 3
2. PCE 1 determines egress
is not in domain 1
PCE 1 PCE 3
3. PCE 1 sends computation BN 11 Domain 2
request to parent PCE (PCE 5)
PCE 2
4. Parent PCE determines likely
domain paths D
BN 12
5. Parent PCE sends
edge-to-edge computation
S
requests to PCE 2 responsible
for domain 2, and to PCE 4
responsible for domain 4
6. Parent PCE send source to
edge request to PCE 1
Domain 4
7. Parent PCE sends edge to
egress request to PCE3 BN 13 PCE 4
8. Parent PCE correlates
responses and applies policy
requirements
9. Parent PCE supplies ERO to PCE 1
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16. In Summary
 P2MP transport connections are required to deliver NGN customer services
 P2MP RSVP-TE Extensions are well defined and used for delivering multicast services
 PCE technology continues to mature
 A variety of PCE standards exist for helping to operate MPLS and GMPLS networks for intra-domain
and inter-domain environments
 Offloads path computation complexity for 10s, or 100s of planned LSP based services to enable
efficient use of network resources
 Able to consider a wide variety of network and commercial constraints
 It is possible, via H-PCE, to coordinate end-to-end paths across multi-domain
topologies.
 A variety of vendors and operators are coordinating to develop PCE-based point-
to-multipoint solutions
 The PCE intra-domain P2MP solution exists and is near completion and standardization
 As presented today, PCE inter-domain P2MP solutions exist, but requires further development and
discussion
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17. Questions & References
Questions?
 RFC5073: IGP Routing Protocol Extensions for Discovery of Traffic Engineering Node
Capabilities.
 RFC4875: Extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for
Point-to-Multipoint TE Label Switched Paths (LSPs).
 draft-ietf-pce-pcep-p2mp-extensions-09.txt: Extensions to the Path Computation Element
Communication Protocol (PCEP) for Point-to-Multipoint Traffic Engineering Label Switched
Paths .
 draft-king-pce-hierarchy-fwk-02: The Application of the Path Computation Element
Architecture to the Determination of a Sequence of Domains in MPLS & GMPLS.
 Orange UK: Deployment Experiences of MPLS P2MP LSPs for IPTV Distribution: MPLS World
Congress 2008.
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