Internet Engineering Task Force Q. Zhao
Internet-Draft Huawei Technology
Intended status: Standards Track Z. Ali
Expires: January 12, 2011 T. Saad
Cisco Systems
D. King
Old Dog Consulting
July 11, 2010
PCE-based Computation Procedure To Compute Shortest Constrained P2MP
Inter-domain Traffic Engineering Label Switched Paths
draft-zhao-pce-pcep-inter-domain-p2mp-procedures-05
Abstract
The ability to compute paths for constrained point-to-multipoint
(P2MP) Traffic Engineering Label Switched Paths(TE LSPs) across
multiple domains has been identified as a key requirement for the
deployment of P2MP services in MPLS and GMPLS networks. The Path
Computation Element (PCE) has been recognized as an appropriate
technology for the determination of inter-domain paths of P2MP TE
LSPs.
This document describes the procedures and extensions to the PCE
communication Protocol (PCEP) to handle requests and responses for
the computation of inter-domain paths for P2MP TE LSPs.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 12, 2011.
Copyright Notice
Zhao, et al. Expires January 12, 2011 [Page 1]
Internet-Draft PCEP P2MP Procedures July 2010
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 5
4. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 7
6. Object Functions . . . . . . . . . . . . . . . . . . . . . . . 8
7. P2MP Path Computation Procedures . . . . . . . . . . . . . . . 9
7.1. Core Tree Computation Procedures . . . . . . . . . . . . . 10
7.2. Sub Tree Computation Procedures . . . . . . . . . . . . . 10
7.3. PCEP Protocol Extensions . . . . . . . . . . . . . . . . . 10
7.3.1. The Extension of RP Object . . . . . . . . . . . . . . 10
7.3.2. The PCE Sequence Object . . . . . . . . . . . . . . . 11
8. Manageability Considerations . . . . . . . . . . . . . . . . . 13
9. Control of Function and Policy . . . . . . . . . . . . . . . . 13
10. Information and Data Models . . . . . . . . . . . . . . . . . 13
11. Liveness Detection and Monitoring . . . . . . . . . . . . . . 13
12. Verifying Correct Operation . . . . . . . . . . . . . . . . . 13
13. Requirements on Other Protocols and Functional Components . . 13
14. Impact on Network Operation . . . . . . . . . . . . . . . . . 14
15. Security Considerations . . . . . . . . . . . . . . . . . . . 14
16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
18. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
18.1. Normative References . . . . . . . . . . . . . . . . . . . 14
18.2. Informative References . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
Zhao, et al. Expires January 12, 2011 [Page 2]
Internet-Draft PCEP P2MP Procedures July 2010
1. Introduction
Multicast services are increasingly in demand for high-capacity
applications such as multicast Virtual Private Networks (VPNs), IP-
television (IPTV) which may be on-demand or streamed, and content-
rich media distribution (for example, software distribution,
financial streaming, or data-sharing). The ability to compute
constrained Traffic Engineering Label Switched Paths (TE LSPs) for
point-to-multipoint (P2MP) LSPs in Multiprotocol Label Switching
(MPLS) and Generalized MPLS (GMPLS) networks across multiple domains.
A domain can be defined as a collection of network elements within a
common sphere of address management or path computational
responsibility such as an IGP area or an Autonomous Systems.
The applicability of the Path Computation Element (PCE) [RFC4655] for
the computation of such paths is discussed in [RFC5671], and the
requirements placed on the PCE communications Protocol (PCEP) for
this are given in [PCE-P2MP-REQ].
This document describes how multiple PCE techniques can be combined
to address the requirements. These mechanisms include the use of the
per-domain path computation technique specified in [RFC5152],
extensions to the backward recursive path computation (BRPC)
technique specified in [RFC5441] for P2MP LSP path computation in an
inter-domain environment, and a new procedure for core-tree based
path computation defined in this document. These three mechanisms
are suitable for different environments (topologies, administrative
domains, policies, service requirements, etc.) and can also be
effectively combined.
2. Terminology
Terminology used in this document is consistent with the related
MPLS/GMPLS and PCE documents [RFC4461], [RFC4655], [RFC4875],
[RFC5376], [RFC5440], [RFC5441]. [RFC5671], and [PCE-P2MP-REQ].
ABR: Area Border Routers. Routers used to connect two IGP areas
(areas in OSPF or levels in IS-IS).
ASBR: Autonomous System Border Routers. Routers used to connect
together ASes of the same or different Service Providers via one or
more Inter-AS links.
Boundary Node (BN): a boundary node is either an ABR in the context
of inter-area Traffic Engineering or an ASBR in the context of
inter-AS Traffic Engineering.
Zhao, et al. Expires January 12, 2011 [Page 3]
Internet-Draft PCEP P2MP Procedures July 2010
Entry BN of domain(n): a BN connecting domain(n-1) to domain(n) along
a determined sequence of domains.
Exit BN of domain(n): a BN connecting domain(n) to domain(n+1) along
a determined sequence of domains.
Inter-AS TE LSP: A TE LSP that crosses an AS boundary.
Inter-area TE LSP: A TE LSP that crosses an IGP area boundary.
LSR: Label Switching Router.
LSP: Label Switched Path.
PCC: Path Computation Client. Any client application requesting a
path computation to be performed by the Path Computation Element.
PCE (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.
PCE(i) is a PCE with the scope of domain(i).
TED: Traffic Engineering Database.
VSPT: Virtual Shortest Path Tree.
P2MP LSP Path Tree: A set of LSRs and TE links that comprise the path
of a P2MP TE LSP from its ingress LSR to all of its egress LSRs.
Core Tree: The core tree is a P2MP tree where the root is the ingress
LSR, the transit node and branch node are the BNs of the transit
domains and the leaf nodes are the leaf BNs of the leaf domains.
Root Boundary Node: The egress LSR from the root domain on the path
of the P2MP LSP.
Root Domain: The domain that includes the ingress (root) LSR.
Transit/branch Domain: A domain that has an upstream and one or more
downstream neighbour domain.
Leaf Domain: A domain that doesn't has a downstream neighbor domain.
Leaf Boundary Nodes: The entry boundary node in the leaf domain.
Leaf Nodes: The LSR which is the P2MP LSP's final
Zhao, et al. Expires January 12, 2011 [Page 4]
Internet-Draft PCEP P2MP Procedures July 2010
Destination. The lead Nodes can be in Root Domain, Transit Domain
and Leaf Domain.
OF: Objective Function: A set of one or more optimization criterion
(criteria) used for the computation of a single path (e.g. path cost
minimization), or the synchronized computation of a set of paths
(e.g. aggregate bandwidth consumption minimization, etc.). See
[RFC4655] and [PCE-OF].
Path Domain Sequence: The known sequence of domains for a path
between root and leaf.
PCE Sequence: The known sequence of PCEs for calcaulting a path
between root and leaf.
PCE Topology Tree: A list of PCE Sequences which has all the PCE
Sequence for each path of the P2MP LSP path tree.
PCE(i): A PCE that performs path computations for domain(i).
VSPT: Virtual Shortest Path Tree [RFC5441].
3. Problem Statement
The Path Computation Element (PCE) defined in [RFC4655] is an entity
that is capable of computing a network path or route based on a
network graph, and applying computational constraints. A Path
Computation Client (PCC) may make requests to a PCE for paths to be
computed.
[RFC4875] describes how to set up P2MP TE LSPs for use in MPLS and
GMPLS networks. The PCE is identified as a suitable application for
the computation of paths for P2MP TE LSPs [RFC5671].
[RFC5441] specifies a procedure relying on the use of multiple PCEs
to compute (P2P) inter-domain constrained shortest paths across a
predetermined sequence of domains, using a backward recursive path
computation technique. The technique can be combined with the use of
path keys [RFC5520] to preserve confidentiality across domains, which
is sometimes required when domains are managed by different Service
Providers.
The PCE communication Protocol (PCEP) [RFC5440] is extended for
point-to-multipoint(P2MP) path computation requests and in [PCE-P2MP-
EXT]. However, that specification does not provide all the necessary
mechanisms to request the computation of inter-domain P2MP TE LSPs.
Zhao, et al. Expires January 12, 2011 [Page 5]
Internet-Draft PCEP P2MP Procedures July 2010
As discussed in [RFC4461], a P2MP tree is a graphical representation
of all TE links that are committed for a particular P2MP LSP. In
other words, a P2MP tree is a representation of the corresponding
P2MP tunnel on the TE network topology. A sub-tree is a part of the
P2MP tree describing how the root or an intermediate P2MP LSPs
minimizes packet duplication when P2P TE sub-LSPs traverse common
links. As described in [RFC5671] the computation of a P2MP tree
requires three major pieces of information. The first is the path
from the ingress LSR of a P2MP LSP to each of the egress LSRs, the
second is the traffic engineering related parameters, and the third
is the branch capability information.
Generally, an inter-domain P2MP tree (i.e., a P2MP tree with source
and at least one destination residing in different domains) is
particularly difficult to compute even for a distributed PCE
architecture. For instance, while the BRPC recursive path
computation may be well-suited for P2P paths, P2MP path computation
involves multiple branching path segments from the source to the
multiple destinations. As such, inter-domain P2MP path computation
may result in a plurality of per-domain path options that may be
difficult to coordinate efficiently and effectively between domains.
That is, when one or more domains have multiple ingress and/or egress
border nodes, there is currently no known technique for one domain to
determine which border routers another domain will utilize for the
inter-domain P2MP tree, and no way to limit the computation of the
P2MP tree to those utilized border nodes.
A trivial solution to the computation of inter-domain P2MP tree would
be to compute shortest inter-domain P2P paths from source to each
destination and then combine them to generate an inter-domain,
shortest-path-to-destination P2MP tree. This solution, however,
cannot be used to trade cost to destination for overall tree cost
(i.e., it cannot produce a Steiner tree) and in the context of inter-
domain P2MP LSPs it cannot be used to reduce the number of domain
border nodes that are transited.
Computing P2P LSPs individually is not an acceptable solution for
computing a P2MP tree. Even per domain path computation [RFC5152]
can be used to compute P2P multi-domain paths, but it does not
guarantee to find the optimal path which crosses multiple domains.
Furthermore, constructing a P2MP tree from individual source to leaf
P2P LSPs does not guarantee to produce a least-cost tree. This
approach may also be considered to have scaling issues during LSP
setup. That is, the LSP to each leaf is signaled separately, and
each border node must perform path computation for each leaf.
Apart from path computation difficulties faced due to the inter-
domain topology visibility issues, the computation of the minimum
Zhao, et al. Expires January 12, 2011 [Page 6]
Internet-Draft PCEP P2MP Procedures July 2010
P2MP Steiner tree, i.e. one which guarantees the least cost resulting
tree, is an NP-complete problem. Moreover, adding and/or removing a
single destination to/from the tree may result in an entirely
different tree. In this case, the frequent Steiner I tree
computation process may prove computationally intensive, and the
resulting frequent tunnel reconfiguration may even cause network
destabilization. There are several heuristic algorithms presented in
the literature that approximate the result within polynomial time
that are applicable within the context of a single-domain.
This document presents a solution, and procedures and extensions to
PCEP to support P2MP inter-domain path computation.
4. Assumptions
It is assumed that due to deployment and commercial limitations
(e.g., inter-AS peering agreements) the sequence of domains for a
path (the path domain tree) will be known in advance.
The examples and scenarios used in this document are also based on
the following assumptions:
o The PCE that serves each domain in the path domain tree is known,
and the set of PCEs and their relationships is propagated to each
PCE during the first exchange of path computation requests;
o Each PCE knows about any leaf LSRs in the domain it serves;
o The boundary nodes to use on the LSP are pre-determined and form
path of the path domain tree. In this version of the document we
do not consider multi-homed domains.
Additional assumptions are documented in [RFC5441] and will not be
repeated here.
5. Requirements
This section summarizes the requirements specific to computing inter-
domain P2MP paths. In these requirements we note that the actual
computation times by any PCE implementation are outside the scope of
this document, but we observe that reducing the complexity of the
required computations has a beneficial effect on the computation time
regardless of implementation. Additionally, reducing the number of
message exchanges and the amount of information exchanged will reduce
the overall computation time for the entire P2MP tree. We refer to
the "Complexity of the computation" as the impact on these aspects of
Zhao, et al. Expires January 12, 2011 [Page 7]
Internet-Draft PCEP P2MP Procedures July 2010
path computation time as various parameters of the topology and the
P2MP LSP are changed.
Its also important that the solution preserves confidentiality across
domains, which is required when domains are managed by different
Service Providers.
Other than the requirements specified in [RFC5376], a number of
requirements specific to P2MP are detailed below:
1. The computed P2MP LSP should be optimal when only considering the
paths among the BNs.
2. Grafting and pruning of multicast destinations in a domain should
have no impact on other domains and on the paths among BNs.
3. The complexity of the computation for each sub-tree within each
domain should be dependent only on the topology of the domain and
it should be independent of the domain sequence.
4. The number of PCEP request and reply messages should be
independent of the number of multicast destinations in each
domain.
5. Specifying the domain entry and exit nodes.
6. Specifying which nodes should be used as branch nodes.
7. Reoptimization of existing sub-trees.
8. Computation of P2MP paths that need to be diverse from existing
P2MP paths.
6. Object Functions
During the computation of a single or a set of P2MP TE LSPs a request
to meet specific optimization criteria, called an Objective Function
(OF), may be requested.
The computation of one or more P2MP TE-LSPs maybe subject to an OF in
order to select the "best" candidate paths. A variety of objective
functions have been identified as being important during the
computation of inter-domain P2MP LSPs. These are:
1. The sub-tree within each domain should be optimized, which can be
either the Minimum cost tree [PCE-P2MP-REQ] or Shortest path tree
[PCE-P2MP-REQ].
Zhao, et al. Expires January 12, 2011 [Page 8]
Internet-Draft PCEP P2MP Procedures July 2010
2. The P2MP LSP paths should be optimal while only considering the
entry and exit nodes of each domain as the transit, branch and
leaf nodes of the P2MP LSP path. (That is, the Core Tree should
be optimized.)
3. It should be possible to limit the number of entry points to a
domain.
4. It should be possible to force the branches for all leaves within
a domain to be in that domain.
7. P2MP Path Computation Procedures
The following sections describe the core tree based procedures to
satisfy the requirements specified in the previous section.
A core tree based solution provides an optimal inter-domain P2MP TE
LSP and meets the requirements and OFs outlined in previous sections.
A core tree is a path tree with nodes from each domain corresponding
to the PCE topology which satisfies the following conditions:
o The root of the core tree is the ingress LSR in the root domain;
o The leaf of the core tree is the entry node in the leaf domain;
o The transit and branch nodes of the core tree are from the entry
and exit nodes from the transit and branch domains.
Procedure Phase 1: Build the P2MP LSP Core Tree.
In this phase, the core tree, where the root is the ingress LSR, the
transit node and branch node are the BNs of the transit domains and
the leaf nodes are the leaf BNs of the leaf domains, is computed.
Procedure Phase 2: Grafting destinations to the P2MP LSP Core Tree.
Once the core tree is built, the grafting of all the leaf nodes from
each domain to the core tree can be achieved by a number of
algorithms. One algorithm for doing this phase is that the root PCE
will send the request with C bit set for the path computation to the
destination(s) directly to the PCE where the destination(s) belong(s)
along with the core tree computed from the phase 1.
Zhao, et al. Expires January 12, 2011 [Page 9]
Internet-Draft PCEP P2MP Procedures July 2010
7.1. Core Tree Computation Procedures
Computing the complete P2MP LSP path tree is done in two phases:
The algorithms to compute the optimal large core tree are outside
scope of this document. In the case that the number of domains and
the number of BNs are not big, the following extended BRPC based
procedure can be used to compute the core tree.
BRPC Based Core Tree Path Computation Procedure:
1. Using the BRPC procedures to compute the VSPT(i) for each leaf
BN(i), i=1 to n, where n is the total number of entry nodes for
all the leaf domains. In each VSPT(i), there are a number of
P(i) paths.
2. When the root PCE has computed all the VSPT(i), i=1 to n, take
one path from each VSPT and form a set of paths, we call it a
PathSet(j), j=1 to M, where M=P(1)xP(2)...xP(n);
3. For each PathSet(j), there are n S2L (Source to Leaf BN) paths
and form these n paths into a Core Tree(j);
4. There will be M number of Core Trees computed from step3. Apply
the OF to each of these M Core Trees and find the optimal Core
Tree.
7.2. Sub Tree Computation Procedures
The algorithms to compute the optimal large sub tree are outside
scope of this document. In the case that the number of destinations
and the number of BNs within a domain are not big, the incremental
procedure based on p2p path computation usign the OSPF can be used.
7.3. PCEP Protocol Extensions
7.3.1. The Extension of RP Object
The extended format of the RP object body to include the C bit is as
follows:
The C bit is added in the flag bits field of the RP object to signal
the receiver of the message that the request/reply is for inter-
domain P2MP Core Tree or not.
Zhao, et al. Expires January 12, 2011 [Page 10]
Internet-Draft PCEP P2MP Procedures July 2010
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |C|O|B|R| Pri |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request-ID-number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLV(s) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: RP Object Body Format
The following flag is added in this draft:
C bit ( P2MP Core Tree bit - 1 bit):
0: This indicates that this is normal PCReq/PCRrep for P2MP.
1: This indicates that this is PCReq or PCRep message for inter-
domain Core Tree P2MP. When the C bit is set, then the request
message should have the Core Tree passed along with the
destinations which and then graphed to the tree.
7.3.2. The PCE Sequence Object
The PCE Sequence Object is added to the existing PCE protocol. A
list of this objects will represent the PCE topology tree. A list of
Sequence Objects can be exchanged between PCEs during the PCE
capability exchange or on the first path computation request message
between PCEs. In this case, the request message format needs to be
changed to include the list of PCE Sequence Objects for the PCE
inter-domain P2MP calculation request.
Each PCE Sequence can be obtained from the domain sequence for a
specific path. All the PCE sequences for all the paths of P2MP
inter-domain form the PCE Topology Tree of the P2MP LSP.
The format of the new PCE Sequence Object for IPv4 (Object-Type 3) is
as follows:
Zhao, et al. Expires January 12, 2011 [Page 11]
Internet-Draft PCEP P2MP Procedures July 2010
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Object-Class | OT |Res|P|I| Object Length (bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 address for root PCE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 address for the downstream PCE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 address for the downstream PCE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| !! |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 address for the PCE corresponding to the leafDomain |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: The New PCE Sequence Object Body Format for IPv4
The format of the new PCE Sequence Object for IPv6 (Object-Type 3) is
as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Object-Class | OT |Res|P|I| Object Length (bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address for root PCE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address for the downstream PCE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address for the downstream PCE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| !! |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address for the PCE corresponding to the leafDomain |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: The New PCE Sequence Object Body Format for IPv6
Zhao, et al. Expires January 12, 2011 [Page 12]
Internet-Draft PCEP P2MP Procedures July 2010
8. Manageability Considerations
[PCE-P2MP-REQ] describes various manageability requirements in
support of P2MP path computation when applying PCEP. This section
describes how manageability requirements mentioned in [PCE-P2MP-REQ]
are supported in the context of PCEP extensions specified in this
document.
Note that [RFC5440] describes various manageability considerations in
PCEP, and most of manageability requirements mentioned in [PCE-P2MP
P2MP] are already covered there.
9. Control of Function and Policy
In addition to configuration parameters listed in [RFC5440], the
following parameters MAY be required.
o P2MP path computations enabled or disabled.
o Advertisement of P2MP path computation capability enabled or
disabled (discovery protocol, capability exchange).
10. Information and Data Models
As described in [PCE-P2MP-REQ], MIB objects MUST be supported for
PCEP extensions specified in this document.
11. Liveness Detection and Monitoring
There are no additional considerations beyond those expressed in
[RFC5440], since [PCE-P2MP-REQ] does not address any additional
requirements.
12. Verifying Correct Operation
There are no additional considerations beyond those expressed in
[RFC5440], since [PCE-P2MP-REQ] does not address any additional
requirements.
13. Requirements on Other Protocols and Functional Components
As described in [PCE-P2MP-REQ], the PCE MUST obtain information about
the P2MP signaling and branching capabilities of each LSR in the
Zhao, et al. Expires January 12, 2011 [Page 13]
Internet-Draft PCEP P2MP Procedures July 2010
network.
Protocol extensions specified in this document does not provide such
capability. Other mechanisms MUST be present.
14. Impact on Network Operation
It is expected that use of PCEP extensions specified in this document
will not have significant impact on network operations.
15. Security Considerations
As described in [PCE-P2MP-REQ], P2MP path computation requests are
more CPU-intensive and also use more link bandwidth. Therefore, it
may be more vulnerable to denial of service attacks. Therefore, it
is more important that implementations conform to security
requirements of [RFC5440], and the implementer utilize those security
features.
16. IANA Considerations
A new flag of the RP object (specified in [RFC5440]) is defined in
this document.
TBD.
17. Acknowledgements
The authors would like to thank Adrian Farrel and Dan Tappan for
their valuable comments on this draft.
18. References
18.1. Normative References
[1] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE)
Communication Protocol (PCEP)", RFC 5440, March 2009.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang, "OSPF
Protocol Extensions for Path Computation Element (PCE)
Zhao, et al. Expires January 12, 2011 [Page 14]
Internet-Draft PCEP P2MP Procedures July 2010
Discovery", RFC 5088, January 2008.
[4] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang, "IS-IS
Protocol Extensions for Path Computation Element (PCE)
Discovery", RFC 5089, January 2008.
[5] Yasukawa, S. and A. Farrel, "PCC-PCE Communication Requirements
for Point to Multipoint Multiprotocol Label Switching Traffic
Engineering (MPLS-TE)", draft-ietf-pce-p2mp-req-05 (work in
progress), January 2010.
[6] Yasukawa, S. and A. Farrel, "Applicability of the Path
Computation Element (PCE) to Point-to-Multipoint (P2MP)
Multiprotocol Label Switching (MPLS) and Generalized MPLS
(GMPLS) Traffic Engineering (TE)", draft-ietf-pce-p2mp-app-02
(work in progress), August 2009.
[7] Yasukawa, S., "Signaling Requirements for Point-to-Multipoint
Traffic-Engineered MPLS Label Switched Paths (LSPs)", RFC 4461,
April 2006.
[8] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS Requirements for
the Path Computation Element Communication Protocol (PCECP)",
RFC 5376, November 2008.
[9] Aggarwal, R., Papadimitriou, D., and S. Yasukawa, "Extensions
to Resource Reservation Protocol - Traffic Engineering
(RSVP-TE) for Point-to-Multipoint TE Label Switched Paths
(LSPs)", RFC 4875, May 2007.
[10] Roux, J., Vasseur, J., and Y. Lee, "Encoding of Objective
Functions in the Path Computation Element Communication
Protocol (PCEP)", draft-ietf-pce-of-06 (work in progress),
December 2008.
[11] Nishioka, I. and D. King, "The use of SVEC (Synchronization
VECtor) list for Synchronized dependent path computations",
draft-ietf-pce-pcep-svec-list-05 (work in progress), June 2010.
[12] Vasseur, JP., Zhang, R., Bitar, N., and JL. Le Roux, "A
Backward-Recursive PCE-Based Computation (BRPC) Procedure to
Compute Shortest Constrained Inter-Domain Traffic Engineering
Label Switched Paths", RFC 5441, April 2009.
18.2. Informative References
[13] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
Zhao, et al. Expires January 12, 2011 [Page 15]
Internet-Draft PCEP P2MP Procedures July 2010
Authors' Addresses
Quintin Zhao
Huawei Technology
125 Nagog Technology Park
Acton, MA 01719
US
Email: qzhao@huawei.com
Zafar Ali
Cisco Systems
Email: zali@cisco.com
Tarek Saad
Cisco Systems
US
Email: tsaad@cisco.com
Daniel King
Old Dog Consulting
UK
Email: daniel@olddog.co.uk
Contributors' Addresses
David Amzallag
British Telecommunications plc
UK
Email: david.Amzallag@bt.com
Fabien Verhaeghe
Thales Communication France
160 Bd Valmy 92700 Colombes
France
Email: fabien.verhaeghe@gmail.com
Kenji Kumaki
KDDI R&D Laboratories, Inc.
Japan
Email: ke-kumaki@kddi.com
Zhao, et al. Expires January 12, 2011 [Page 16]