Network Working Group Itaru Nishioka
Internet Draft NEC Corp.
Intended Status: Informational Daniel King
Expires: December 6, 2010 Old Dog Consulting
June 6, 2010
The use of SVEC (Synchronization VECtor) list for Synchronized
dependent path computations
draft-ietf-pce-pcep-svec-list-05.txt
Abstract
A Path Computation Element (PCE) may be required to perform
dependent path computations. Dependent path computations are
requests that need to be synchronized in order to meet specific
objectives. An example of a dependent request would be a PCE
computing a set of services which are required to be diverse
(disjointed) from each other. When a PCE computes sets of dependent
path computation requests concurrently, it is required to use the
Synchronization VECtor (SVEC) list for association among the sets of
dependent path computation requests. The SVEC object is optional and
carried within the Path Computation Element Protocol (PCEP)
PCRequest (PCReq) message.
This document does not specify the PCEP SVEC object or procedure.
This informational document clarifies the use of the SVEC list for
synchronized path computations when computing dependent requests.
The document also describes a number of usage scenarios for SVEC
lists within single domain and multi-domain environments.
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Table of Contents
1. Introduction ..................................................3
1.1. SVEC Object ...............................................4
1.2. Application of SVEC Lists .................................4
2. Terminology ...................................................6
3. SVEC association scenarios ....................................6
3.1. Synchronized computation for diverse path requests ........6
3.2. Synchronized computation for point-to-multipoint path
requests ..................................................8
4. SVEC association ..............................................8
4.1. SVEC list .................................................8
4.2. Associated SVECs ..........................................8
4.3. Non-associated SVECs ......................................9
5. Processing of SVEC list .......................................10
5.1. Single PCE, single domain environments ....................10
5.2. Multi-PCE, single domain environments .....................11
5.3. Multi-PCE, multi-domain environments ......................11
6. End-to-end diverse path computation ...........................12
6.1. Disjoint VSPT .............................................12
6.2. Disjoint VSPT encoding ....................................13
6.3. Path computation procedure ................................14
7. Manageability considerations ..................................14
7.1. Control of Function and Policy ............................14
7.2. Information and Data Models, e.g. MIB modules .............15
7.3. Liveness Detection and Monitoring .........................15
7.4. Verifying Correct Operation ...............................15
7.5. Requirements on Other Protocols and Functional Components..15
7.6. Impact on Network Operation ...............................15
8. Security Considerations .......................................15
9. IANA Considerations ...........................................16
10. References ...................................................16
10.1. Normative References .....................................16
10.2. Informative References ...................................17
11. Acknowledgements .............................................17
12. Authors' Addresses ...........................................17
1. Introduction
[RFC5440] describes the specifications for PCEP (Path Computation
Element communication Protocol). PCEP specifies the communication
between a Path Computation Client (PCC) and a Path Computation
Element (PCE), or between two PCEs based on the PCE architecture
[RFC4655]. PCEP interactions include path computation requests and
path computation replies.
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The PCE may be required to compute independent and dependent path
requests. Path computation requests are said to be independent if
they are not related to each other, and therefore not required to be
synchronized. Equally a set of dependent path computation requests,
that are required to be synchronized, cannot be performed
independently of each other. The Synchronization VECtor (SVEC) with
a list of the path computation request identifiers carried within
the request message allows the PCC or PCE to specify a list of
multiple path computation requests that must be synchronized.
Section 1.1 (SVEC Object) describes the SVEC object. Section 1.2
(Application of SVEC Lists) describes the application of SVEC lists
in certain scenarios.
This informational document clarifies the handling of dependent and
synchronized path computation requests, using the SVEC list, based
on the PCE architecture [RFC4655] and PCEP [RFC5440]. The document
also describes a number of usage scenarios for SVEC lists within
single domain and multi-domain environments. This document is not
intended to specify the procedure when using SVEC lists for
dependent and synchronized path computation requests.
1.1. SVEC Object
When a PCC or PCE sends path computation requests to a PCE, a PCEP
Path Computation Request (PCReq) message may carry multiple requests
each of which has a unique path computation request identifier. The
SVEC with a list of the path computation request identifiers carried
within the request message allows the PCC or PCE to specify a list
of multiple path computation requests that must be synchronized, and
also allows the specification of any dependency relationships
between the paths. The path computation requests listed in the SVEC
must be handled in a relation to each other (i.e. synchronized).
[RFC5440] defines two synchronous path computation modes for
dependent or independent path computation requests specified by the
dependency flags (i.e. Node, Link or SRLG diverse flags) in the SVEC.
(See [RFC5440] for more details of dependent, independent and
synchronous path computation.)
o A set of independent and synchronized path computation requests,
o A set of dependent and synchronized path computation requests.
These computation modes are exclusive each other in a single SVEC.
If one of the dependency flags in a SVEC is set, it indicates a set
of synchronous path computation requests has a dependency and does
not allow any other path computation requests. In order to be
synchronized with other path computation requests with a dependency,
it is necessary to associate them.
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The aim of the SVEC object carried within a PCReq message is to
request the synchronization of M path computation requests. Each
path computation request is uniquely identified by the Request-ID-
number carried within the respective RP object. The SVEC object
also contains a set of flags that specify the synchronization type.
The SVEC Object is defined in Section 7.13 (SVEC Object) of
[RFC5440].
1.2. Application of SVEC Lists
It is important for the PCE, when performing path computations, to
synchronize any path computation requests with a dependency. For
example, consider two protected end-to-end services:
o It would be beneficial for each back-up path to be disjointed so
they do not share the same links and nodes as the working path.
o Two diverse path computation requests would be needed to compute
the working and disjointed protected paths.
If the diverse path requests are computed sequentially, fulfillment
of the initial diverse path computation without consideration of the
second diverse path computation and disjoint constraint may result in
the PCE providing sub-optimal path disjoint results for the protected
path, or may fail to meet the end-to-end disjoint requirement
altogether.
Additionally, SVEC can be applied to end-to-end diverse path
computations that traverse multiple domains. [RFC5441] describes two
approaches, synchronous (i.e. simultaneous) and 2-step approaches,
for the end-to-end diverse path computation across a chain of
domains. The path computation procedure is specified for the 2-step
approaches in [RFC5521], but no guidelines are provided for a
synchronous approach which is described in this document.
The following scenarios are specifically described within this
document:
o Single domain, single PCE, dependent and synchronized path
computation request.
o Single domain, multi-PCE, dependent and synchronized path
request.
o Multi-domain, dependent and synchronized path computation request,
including end-to-end diverse path computation.
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The association among multiple SVECs for multiple sets of
synchronized dependent path computation is also described in this
document, as well as disjoint Virtual Shortest Path Tree (VSPT)
encoding rule for end-to-end diverse path computation across domains.
Path computation algorithms for these path computation scenarios are
out of the scope of this document.
The clarifications and use cases in this document are applicable to
the Global Concurrent Optimization (GCO) path computation mechanism
specified in [RFC5557]. The GCO application provides the capability
to optimize a set of services within the network, in order to
maximize efficient use of network resources. A single or set of
objective functions (OFs) can be applied to a GCO. To compute a set
of such traffic-engineered paths for the GCO application, PCEP
supports the synchronous and dependent path computation requests
required in [RFC4657].
The SVEC association and the disjoint VSPT described in this
document do not require any extension to PCEP messages and object
formats, when computing a GCO for multiple or end-to-end diverse
paths. In addition, the use of multiple SVECs is not restricted to
only SRLG, Node and Link diversity currently defined in the SVEC
object [RFC5440], but is also available for other dependent path
computation requests.
The SVEC association and disjoint VSPT are available to both single
PCE path computation and multi-PCE path computation.
2. Terminology
This document uses PCE terminology defined in [RFC4655], [RFC4875],
and [RFC5440].
Associated SVECs: A group of multiple SVECs (Synchronization
VECtors), defined in this document, to indicate a set of
synchronized or concurrent path computations.
Disjoint VSPT: A set of VSPTs, defined in this document, to indicate
a set of virtual diverse path tree.
GCO (Global Concurrent Optimization): A concurrent path computation
application, defined in [RFC5557], where a set of TE paths is
computed concurrently in order to efficiently utilize network
resources.
Synchronized: A set of path computation requests is said to be
synchronized if the PCE associates the requests, and does not
compute each request independently of each other.
VSPT: Virtual Shortest Path Tree defined in [RFC5441].
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3. SVEC association scenarios
This section clarifies several path computation scenarios, in which
SVEC association can be applied. Also, any combination of scenarios
described in this section could be applicable.
3.1. Synchronized computation for diverse path requests
A PCE may compute two or more point-to-point diverse paths,
concurrently, in order to increase the probability of meeting
primary and secondary path diversity (or disjointness) objective and
network resource optimization objective.
Two scenarios can be considered for the SVEC association of point-
to-point diverse paths.
o Two or more end-to-end diverse paths
When concurrent path computation of two or more end-to-end diverse
paths is requested, SVEC association is needed among diverse path
requests. Note here that each diverse path request consists of
primary, secondary, and tertiary and beyond path requests, in which
all path requests are grouped with one SVEC association.
Consider two end-to-end services that are to be kept separate by
using diverse paths. The path computation requests would need to be
associated so that diversity could be assured. Consider further that
each of these services requires a backup path that can protect
against any failure in the primary path. These backup paths must be
computed using requests that are associated with the primary paths
giving rise to a set of four associated requests.
o End-to-end primary path and its segmented secondary paths
When concurrent path computation for segment recovery paths, as
shown in figure 1, is requested, SVEC association is needed between
a primary path and several segmented secondary paths.
<------------ primary ----------->
A------B------C---D------E------F
\ / \ /
P---Q---R X---Y---Z
<--secondary1--> <--secondary2-->
Figure 1: Segment Recovery Paths
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In this scenario, we assume that the primary path may be pre-
computed, which is used for specifying the segment for secondary
paths. Otherwise, the segment for secondary path requests are
specified in advance, by using Exclude Route Object (XRO) and/or
Include Route Object (IRO) constraints in the primary request.
3.2. Synchronized computation for point-to-multipoint path requests
For point-to-multipoint path requests, SVEC association can be
applied.
o Two or more point-to-multipoint paths
If a point-to-multipoint paths request is represented as a set of
point-to-point paths [ID.pce-p2mp-ext], two or more point-to-
multipoint path computation requests can be associated for
concurrent path computation, in order to optimize network resources.
o Point-to-multipoint paths and their secondary paths
When concurrent path computation of a point-to-multipoint path and
its point-to-point secondary paths [RFC4875], or a point-to-
multipoint path and its point-to-multipoint secondary paths is
requested, SVEC association is needed among these requests. In this
scenario, we use the same assumption as "end-to-end primary path and
its segmented secondary paths scenario" in section 3.1.
4. SVEC association
This section describes the associations among SVECs in a SVEC list.
4.1. SVEC list
PCEP provides the capability to carry one or more SVEC objects in a
PCReq message, and this set of SVEC objects within the PCReq message
is termed a SVEC list. Each SVEC object in the SVEC list contains a
distinct group of path computation requests. When requesting
association among such distinct groups, associated SVECs described
in this document are used.
4.2. Associated SVECs
"Associated SVECs" defines that there are relationships among
multiple SVECs in SVEC list. Note that there is no automatic
association in [RFC5440] between the members of one SVEC and the
members of another SVEC in the same SVEC list. The associated SVEC
is introduced to associate these SVECs, especially for correlating
among SVECs with dependency flags.
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Request identifiers in the SVEC objects are used to indicate the
association among SVEC objects. If the same request-IDs exist in
SVEC objects, this indicates these SVEC objects are associated. When
associating among SVEC objects, at least one request identifier must
be shared between associated SVECs. The SVEC objects can be
associated regardless of the dependency flags in each SVEC object,
but it is recommended to use a single SVEC if the dependency flags
are not set in all SVEC objects. Similarly, when associating among
SVEC objects with dependency flags, it is recommended to construct
them using a minimum set of associated SVECs, thus avoiding complex
relational associations.
Below is an example of associated SVECs. In this example, the first
SVEC is associated with the other SVECs, and all of path computation
requests contained in the associated SVECs (i.e. Request-ID#1,#2,#3,
#4,#X,#Y,#Z) must be synchronized.
<SVEC-list>
<SVEC> without dependency flags
Request-ID #1, Request-ID #3, Request-ID #X
<SVEC> with one or more dependency flags
Request-ID #1, Request-ID #2
<SVEC> with one or more dependency flags
Request-ID #3, Request-ID #4
<SVEC> without dependency flag
Request-ID #X, Request-ID #Y, Request-ID #Z
4.3. Non-associated SVECs
Non-associated SVECs mean that there are no relationships among
SVECs. If none of the SVEC objects in the SVEC list on a PCReq
message contains a common request-ID, there is no association
between the SVECs and so no association between the requests in one
SVEC and the requests in another SVEC.
Below is an example of non-associated SVECs that does not contain
any common request-IDs.
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<SVEC-list>
<SVEC> with one or more dependency flags
Request-ID #1, Request-ID #2
<SVEC> with one or more dependency flags
Request-ID #3, Request-ID #4
<SVEC> without dependency flags
Request-ID #X, Request-ID #Y, Request-ID #Z
5. Processing of SVEC list
5.1. Single PCE, single domain environments
In this environment, there is a single PCE within the domain.
When a PCE receives PCReq messages with more than one SVEC objects
in the SVEC list, PCEP has to first check the request-IDs in all
SVEC objects in order to identify any associations among them.
If there are no matching request-IDs in the different SVEC objects,
these SVEC objects are not associated, and then each set of path
computation requests in the non-associated SVEC objects has to be
computed separately.
If there are matching request-IDs in the different SVEC objects,
these SVEC objects are associated, and then all path computation
requests in the associated SVEC objects are treated in a synchronous
manner for GCO application.
If the PCE does not have capability to handle the associated SVEC
objects, it may send a PCErr message with Error-Type="Capability not
supported".
In the case that M path computation requests are sent across
multiple PCReq messages, the PCE may start a SyncTimer as
recommended in Section 7.13.3 (Handling of the SVEC Object)
[RFC5440]. In this case, the associated SVECs should also be handled
as described in [RFC5440]. I.E. after receiving the entire set of M
path computation requests associated by SVECs, the computation
should start at one. If the SyncTimer has expired or the following
PCReq messages have been malformed; the PCE should cancel the path
computation request and respond to the PCC with the relevant PCErr
message.
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5.2. Multi-PCE, single domain environments
There are multiple PCEs in a domain, to which PCCs can communicate
directly, and PCCs can choose an appropriate PCE for load balanced
path computation requests. In this environment it is possible
dependent path computation requests are sent to different PCEs.
If a PCC sends path computation requests to a PCE and then sends
another path computation requests, which are dependent on the first
requests and has been associated by using a SVEC list. There is no
method for the PCE to correlate the dependent requests sent to
different PCEs. No SVEC object correlation function between the PCEs
is specified in [RFC5440]. As indentified, no mechanism exists to
resolve this problem and the issue is open for future study.
Therefore, a PCC must not send dependent path computation requests
associated by SVECs to different PCEs.
5.3. Multi-PCE, multi-domain environments
In this environment, there are multiple domains in which PCEs are
located in each domain, and end-to-end dependent paths (i.e. diverse
path) is computed using multiple PCEs. Note that we assume a chain
of PCEs are pre-determined and the BRPC procedure [RFC5441] is in
use.
The SVECs can be applied to end-to-end diverse path computations
that traverse multiple domains. [RFC5441] describes two approaches,
synchronous (i.e. simultaneous) and 2-step approaches, for the end-
to-end diverse path computation across a chain of domains. In the 2-
step approaches described in [RFC5521], it is not necessary to use
the associated SVECs because any of dependency flags in a SVEC
object are not set. On one hand, the simultaneous approach may
require the associated SVEC because at least one of dependency flags
is required in a SVEC object. Thus, a use case of the simultaneous
approach is described in this environment.
When a chain of PCEs located in separate domains are used for
simultaneous path computations, additional path computation
processing is required. It is described in this document (Section 6).
If the PCReq message contains multiple associated SVEC objects and
these SVEC objects contain path computation requests that will be
sent to the next PCE along the path computation chain, the following
procedures are applied.
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When a chain of PCEs is a unique sequence for all of path
computation requests in a PCReq message, it is not necessary to re-
construct associations among SVEC objects. Thus, the PCReq message
is passed to the tail end PCE. When a PCReq message contains more
than one SVEC objects with the dependency flag set, the contained
SVECs may then be associated. PCEs receiving the associated SVECs
must maintain their association, and consider their relationship in
path computing after receiving a corresponding PCRep message.
When a chain of PCEs is different, it is required that intermediate
PCEs receiving such PCReq messages may re-construct associations
among SVEC objects, and then send PCReq messages to corresponding
PCEs located in neighboring domains. If the associated SVECs are re-
constructed at the intermediate PCE, the PCE must not start its path
computation until all PCRep messages have been received from all
neighbor PCEs. However, a complex PCE implementation is required for
SVEC reconstruction, and waiting mechanisms must be implemented.
Therefore, it is not recommended to associate path computation
requests with different PCE chains. This is open issue and is
currently being discussed in [ID.h-pce] which proposes a
hierarchical PCE architecture.
6. End-to-end diverse path computation
In this section, the synchronous approach is provided to compute
primary and secondary paths simultaneously.
6.1. Disjoint VSPT
The BRPC procedure constructs a VSPT to inform the enquiring PCE of
potential paths to the destination node.
In the end-to-end diverse path computation, diversity (or
disjointness) information among the potential paths must be
preserved in the VSPT to ensure end-to-end disjoint path. In order
to preserve diversity (or disjointness) information, disjoint VSPTs
are sent in the PCEP PCRep message. The PCReq containing a SVEC
object with the appropriate diverse flag set would signal that the
PCE should compute a disjoint VSPT.
A definition of the disjoint VSPT is a collection of VSPTs, in which
each VSPT contains a potential set of primary and secondary paths.
Figure 2 shows an example network. Here, transit nodes in domains
are not depicted, and PCE1 and PCE2 may be located in border nodes.
In this network, there are three VSPTs for the potential set of
diverse paths shown in Figure 3, when the primary path and secondary
path are requested from S1 to D1. These VSPTs consist of a disjoint
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VSPT, which is replied to PCE1. When receiving the disjoint VSPT,
PCE1 recognizes the disjoint request and disjoint VSPT information.
PCE1 will then continue to process the request and compute the
diverse path using the BRPC procedure [RFC5441]. The detail encoding
for the disjoint VSPT is described in Section 6.2.
Domain1 Domain2
+----------+ +----------+
| PCE1 | | PCE2 | S1: Source node
| BN1---BN4 | D1: Destination node
| S1 BN2---BN5 D1 | BN1-BN6: Border nodes
| BN3---BN6 |
+----------+ +----------+
Figure 2: Example network for diverse path computation
VSPT1: VSPT2: VSPT3:
D1 D1 D1
/ \ / \ / \
BN4 BN5 BN4 BN6 BN5 BN6
Figure 2: Disjoint VSPT from PCE2 to PCE1
6.2. Disjoint VSPT encoding
Encoding for disjoint VSPT follows the definition of PCEP message
encoding in [RFC5440].
PCEP PCRep message returns a disjoint VSPT as <path list> for each
RP object (Request Parameter object). The order of <path> in <path
list> among <responses> implies a set of primary EROs (Explicit
Route Objects) and secondary EROs.
A PCE sending PCRep with a disjoint VSPT can reply with a partial
disjoint VSPT based on its network operation policy, but the order
of <path> in <path list> must be aligned correctly.
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If confidentiality is required between domains, path key mechanism
defined in [RFC5520] is used for a disjoint VSPT.
Detailed disjoint VSPT encoding in Figure 2 is shown below, when a
primary path and a secondary path are requested from S1 to D1.
o Request ID #1 (Primary)
- ERO1 BN4(TE route ID)- ...-D1(TE-Router ID) [for VSPT1]
- ERO2 BN4(TE route ID)- ...-D1(TE-Router ID) [for VSPT2]
- ERO3 BN5(TE route ID)- ...-D1(TE-Router ID) [for VSPT3]
O Request ID #2 (Secondary)
- ERO4 BN5(TE route ID)- ...-D1(TE-Router ID) [for VSPT1]
- ERO5 BN6(TE route ID)- ...-D1(TE-Router ID) [for VSPT2]
- ERO6 BN6(TE route ID)- ...-D1(TE-Router ID) [for VSPT3]
6.3. Path computation procedure
For end-to-end diverse path computation, the same mode of operation
as BRPC procedure can be applied (i.e. Step 1 to Step n in Section
4.2 [RFC5441]). During this procedure, a question is how to
recognize disjoint VSPTs.
The recognition of disjoint VSPT is achieved by the PCE sending
PCReq to its neighbor PCE which maintains the path computation
request (PCReq) information. If PCReq has one or more SVEC object(s)
with the appropriate dependency flags, the received PCRep will
contain the disjoint VSPT. If not, the received VSPT is a normal
VSPT based on the shortest path computation.
Note that the PCE will apply a suitable algorithm for computing
requests with disjoint VSPT. The selection and application of the
appropriate algorithm is out of scope in this draft.
7. Manageability considerations
This section describes manageability considerations specified in
[ID.pce-mngabl-reqs].
7.1. Control of Function and Policy
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In addition to [RFC5440], PCEP implementations should allow the PCC
to be responsible for mapping the requested paths to computation
requests. The PCC should construct the SVECs to indentify and
associate SVEC relationships.
7.2. Information and Data Models, e.g. MIB modules
There are currently no additional parameters for MIB modules. There
is value in a MIB module that details the SVEC association. This
work is currently out of scope of this document.
7.3. Liveness Detection and Monitoring
The associated SVEC in this document allows PCEs to compute optimal
sets of diverse paths. This type of path computation may require
more time to obtain its results. Therefore, it is recommended for
PCEP to support PCE monitoring mechanism specified in [ID.pce-
monitor].
7.4. Verifying Correct Operation
[RFC5440] provides the sufficient descriptions for this document. So,
there are no additional considerations.
7.5. Requirements on Other Protocols and Functional Components
This document does not require any other protocol and functional
components.
7.6. Impact on Network Operation
[RFC5440] provides descriptions for the mechanisms discussed in this
document. There is value in considering that large associated SVECs
will require greater PCE resources, compared to non-associated SVECs.
Additionally, the sending of large associated SVECs within multiple
PCReq messages will require more network resources. Solving these
specific issues is out of scope of this document.
8. Security Considerations
This document describes the usage of SVEC list, and does not have
any extensions for PCEP protocol. The security of the procedures
described in this document depends on PCEP protocol [RFC5440].
However, a PCE that supports associated SVECs may be open to DoS
attack from a rogue PCC. A PCE may be made to queue large numbers of
requests waiting for other requests that will never arrive.
Additionally a PCE might be made to compute exceedingly complex
associated SVEC computations. These DoS attacks may be mitigated
with the use of practical SVEC list limits, as well as:
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o Using the same number of simultaneous service provisioning
would be recommended.
o Priority-based multi-queuing mechanism in which path
computation requests with a smaller SVEC list are prioritized
for path computation processing
o Specifying which PCCs may request large SVEC associations
through PCE access policy control.
9. IANA Considerations
This document has no specific extension for PCEP messages, objects
and its parameters and does not require any registry assignment.
10. References
10.1. Normative References
[RFC4655] A. Farrel, JP. Vasseur and J. Ash, "A Path Computation
Element (PCE)-Based Architecture," RFC 4655, September
2006.
[RFC4657] J. Ash and J.L. Le Roux, "Path Computation Element (PCE)
Communication Protocol Generic Requirements," RFC 4757,
September 2006.
[RFC4875] R. Aggarwal, D. Papadimitriou, and S. Yasukawa,
"Extensions to Resource Reservation Protocol - Traffic
Engineering (RSVP-TE) for Point-to-Multipoint TE Label
Switched Paths (LSPs)," RFC4875, May 2007.
[RFC5440] Ayyangar, A., Farrel, A., Oki, E., Atlas, A., Dolganow A.
Ikejiri, Y., Kumaki, K., Vasseur, J., and J. Roux, "Path
Computation Element (PCE) communication Protocol (PCEP),"
RFC5440, March. 2009.
[RFC5441] JP. Vasseur, R. Zhang, N. Bitar and JL. Le Roux, "A
Backward Recursive PCE-based Computation (BRPC) Procedure
to Compute Shortest Constrained Inter-domain Traffic
Engineering Label Switched Paths," RFC5441, April 2009.
[RFC5520] R. Bradford, JP. Vasseur, and A. Farrel, "Preserving
Topology Confidentiality in Inter-Domain Path Computations
Using a Path-Key-Based mechanism," RFC5520, April 2009.
[RFC5521] E. Oki, T. Takeda and A. Farrel, "Extensions to the Path
Computation Element Communication Protocol (PCEP) for
Route Exclusions," RFC5521, April 2009.
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[RFC5557] Y. Lee, JL. Le Roux, D. King and E. Oki, "Path Computation
Element Communication Protocol (PCECP) Requirements and
Protocol Extensions In Support of Global Concurrent
Optimization," RFC5557, July 2009.
10.2. Informative References
[ID.pce-p2mp-ext] Takeda, T., Chaitou M., Le Roux, J.L., Ali Z.,Zhao,
Q., King, D., "Extensions to the Path Computation Element
Communication Protocol (PCEP) for Point-to-Multipoint
Traffic Engineering Label Switched Paths," draft-ietf-pce-
pcep-p2mp-extensions, work in progress, February, 2010.
[ID.pce-mngabl-reqs] A. Farrel, "Inclusion of Manageability Sections
in PCE Working Group Drafts," draft-ietf-pce-
manageability-requirements, work in progress, July 2009.
[ID.h-pce] King, D., Farrel, A. "The Application of the Path
Computation Element Architecture to the Determination of a
Sequence of Domains in MPLS & GMPLS", draft-king-pce-
hierarchy-fwk, work in progress, December 2009.
11. Acknowledgements
The authors would like to thank Adrian Farrel, Julien Meuric and
Filippo Cugini for their valuable comments.
12. Authors' Addresses
Itaru Nishioka
NEC Corp.
1753 Shimonumabe,
Kawasaki, 211-8666,
Japan
Phone: +81 44 396 3287
Email: i-nishioka@cb.jp.nec.com
Daniel King
Old Dog Consulting
United Kingdom
Phone: +44 7790 775187
Email: daniel@olddog.co.uk
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