draft-ietf-pce-comm-protocol-gen-reqs-07.txt   rfc4657.txt 
IETF Internet Draft PCE Working Group Jerry Ash (AT&T) Network Working Group J. Ash, Ed.
Proposed Status: Informational Editor Request for Comments: 4657 AT&T
Expires: December 2006 J.L. Le Roux (France Telecom) Category: Informational J.L. Le Roux, Ed.
Editor France Telecom
September 2006
Path Computation Element (PCE) Communication Protocol Path Computation Element (PCE) Communication Protocol
Generic Requirements Generic Requirements
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2006). Copyright (C) The Internet Society (2006).
Abstract Abstract
The PCE model is described in the "PCE Architecture" document and The PCE model is described in the "PCE Architecture" document and
facilitates path computation requests from Path Computation Clients facilitates path computation requests from Path Computation Clients
(PCCs) to Path Computation Elements (PCEs). This document specifies (PCCs) to Path Computation Elements (PCEs). This document specifies
generic requirements for a communication protocol between PCCs and generic requirements for a communication protocol between PCCs and
PCEs, and also between PCEs where cooperation between PCEs is PCEs, and also between PCEs where cooperation between PCEs is
desirable. Subsequent documents will specify application-specific desirable. Subsequent documents will specify application-specific
requirements for the PCE communication protocol. requirements for the PCE communication protocol.
Table of Contents Table of Contents
1. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction ....................................................2
2. Conventions used in this document . . . . . . . . . . . . . . . . 4 2. Conventions Used in This Document ...............................3
3. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Terminology .....................................................3
4. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Overview of PCE Communication Protocol (PCECP) ..................4
5. Overview of PCE Communication Protocol (PCECP) . . . . . . . . . 5 5. PCE Communication Protocol Generic Requirements .................5
6. PCE Communication Protocol Generic Requirements . . . . . . . . . 6 5.1. Basic Protocol Requirements ................................5
6.1 Basic Protocol Requirements . . . . . . . . . . . . . . . . . 6 5.1.1. Commonality of PCC-PCE and PCE-PCE Communication ....5
6.1.1 Commonality of PCC-PCE and PCE-PCE Communication . . . 6 5.1.2. Client-Server Communication .........................5
6.1.2 Client-Server Communication . . . . . . . . . . . . . . 6 5.1.3. Transport ...........................................5
6.1.3 Transport . . . . . . . . . . . . . . . . . . . . . . . 6 5.1.4. Path Computation Requests ...........................5
6.1.4 Path Computation Requests . . . . . . . . . . . . . . . 6 5.1.5. Path Computation Responses ..........................7
6.1.5 Path Computation Responses . . . . . . . . . . . . . . 8 5.1.6. Cancellation of Pending Requests ....................7
6.1.6 Cancellation of Pending Requests . . . . . . . . . . . 8 5.1.7. Multiple Requests and Responses .....................8
6.1.7 Multiple Requests and Responses . . . . . . . . . . . . 8 5.1.8. Reliable Message Exchange ...........................8
6.1.8 Reliable Message Exchange . . . . . . . . . . . . . . . 9 5.1.9. Secure Message Exchange .............................9
6.1.9 Secure Message Exchange . . . . . . . . . . . . . . . . 10 5.1.10. Request Prioritization ............................10
6.1.10 Request Prioritization . . . . . . . . . . . . . . . . 10 5.1.11. Unsolicited Notifications .........................10
6.1.11 Unsolicited Notifications . . . . . . . . . . . . . . 11 5.1.12. Asynchronous Communication ........................10
6.1.12 Asynchronous Communication . . . . . . . . . . . . . . 11 5.1.13. Communication Overhead Minimization ...............10
6.1.13 Communication Overhead Minimization . . . . . . . . . 11 5.1.14. Extensibility .....................................11
6.1.14 Extensibility . . . . . . . . . . . . . . . . . . . . 11 5.1.15. Scalability .......................................11
6.1.15 Scalability . . . . . . . . . . . . . . . . . . . . . 12 5.1.16. Constraints .......................................12
6.1.16 Constraints . . . . . . . . . . . . . . . . . . . . . 13 5.1.17. Objective Functions Supported .....................13
6.1.17 Objective Functions Supported . . . . . . . . . . . . 13 5.2. Deployment Support Requirements ...........................13
6.2 Deployment Support Requirements . . . . . . . . . . . . . . . 14 5.2.1. Support for Different Service Provider
6.2.1 Support for Different Service Provider Environments . . 14 Environments .......................................13
6.2.2 Policy Support . . . . . . . . . . . . . . . . . . . . 14 5.2.2. Policy Support .....................................14
6.3 Aliveness Detection & Recovery Requirements . . . . . . . . . 14 5.3. Aliveness Detection & Recovery Requirements ...............14
6.3.1 Aliveness Detection . . . . . . . . . . . . . . . . . . 14 5.3.1. Aliveness Detection ................................14
6.3.2 Protocol Recovery . . . . . . . . . . . . . . . . . . . 15 5.3.2. Protocol Recovery ..................................14
6.3.3 LSP Rerouting & Reoptimization . . . . . . . . . . . . 15 5.3.3. LSP Rerouting & Reoptimization .....................14
7. Security Considerations . . . . . . . . . . . . . . . . . . . . . 15 6. Security Considerations ........................................15
8. Manageability Considerations . . . . . . . . . . . . . . . . . . 16 7. Manageability Considerations ...................................16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . . 17 8. Contributors ...................................................17
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 17 9. Acknowledgements ...............................................18
11. Normative References . . . . . . . . . . . . . . . . . . . . . . 17 10. References ....................................................19
12. Informational References . . . . . . . . . . . . . . . . . . . . 17 10.1. Normative References .....................................19
13. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 10.2. Informative References ...................................19
Intellectual Property Statement . . . . . . . . . . . . . . . . . . 18
Disclaimer of Validity . . . . . . . . . . . . . . . . . . . . . . . 19
Copyright Statement . . . . . . . . . . . . . . . . . . . . . . . . 19
1. Contributors
This document is the result of the PCE Working Group PCE
Communication Protocol (PCECP) requirements design team joint effort.
In addition to the authors/editors listed in Section 13, the
following are the design team members who contributed to the
document:
Alia K. Atlas
Google Inc.
1600 Amphitheatre Parkway
Mountain View, CA 94043
Email: akatlas@alum.mit.edu
Arthi Ayyangar
Juniper Networks, Inc.
1194 N.Mathilda Ave
Sunnyvale, CA 94089 USA
Email: arthi@juniper.net
Nabil Bitar
Verizon
40 Sylvan Road
Waltham, MA 02145
Email: nabil.bitar@verizon.com
Igor Bryskin
Independent Consultant
Email: i_bryskin@yahoo.com
Dean Cheng
Cisco Systems Inc.
3700 Cisco Way
San Jose CA 95134 USA
Phone: 408 527 0677
Email: dcheng@cisco.com
Durga Gangisetti
MCI
Email: durga.gangisetti@mci.com
Kenji Kumaki
KDDI Corporation
Garden Air Tower
Iidabashi, Chiyoda-ku,
Tokyo 102-8460, JAPAN
Phone: 3-6678-3103
Email: ke-kumaki@kddi.com
Eiji Oki
NTT
Midori-cho 3-9-11
Musashino-shi, Tokyo 180-8585, JAPAN
Email: oki.eiji@lab.ntt.co.jp
Raymond Zhang
BT INFONET Services Corporation
2160 E. Grand Ave.
El Segundo, CA 90245 USA
Email: Raymond_zhang@bt.infonet.com
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
3. Introduction 1. Introduction
A Path Computation Element (PCE) [PCE-ARCH] supports requests for A Path Computation Element (PCE) [RFC4655] supports requests for path
path computation issued by a Path Computation Client (PCC), which may computation issued by a Path Computation Client (PCC), which may be
be 'composite' (co-located) or 'external' (remote) from a PCE. When 'composite' (co-located) or 'external' (remote) from a PCE. When the
the PCC is external from the PCE, a request/response communication PCC is external from the PCE, a request/response communication
protocol is required to carry the path computation request and return protocol is required to carry the path computation request and return
the response. In order for the PCC and PCE to communicate, the PCC the response. In order for the PCC and PCE to communicate, the PCC
must know the location of the PCE: PCE discovery is described in must know the location of the PCE; PCE discovery is described in
[PCE-DISC-REQ]. [PCE-DISC-REQ].
The PCE operates on a network graph in order to compute paths based The PCE operates on a network graph in order to compute paths based
on the path computation request(s) issued by the PCC(s). The path on the path computation request(s) issued by the PCC(s). The path
computation request will include the source and destination of the computation request will include the source and destination of the
paths to be computed, a set of constraints to be applied during the paths to be computed and a set of constraints to be applied during
computation, and may also include an objective function. The PCE the computation, and it may also include an objective function. The
response includes the computed paths or the reason for a failed PCE response includes the computed paths or the reason for a failed
computation. computation.
This document lists a set of generic requirements for the PCECP. This document lists a set of generic requirements for the PCE
Application-specific requirements are beyond the scope of this Communication Protocol (PCECP). Application-specific requirements
document, and will be addressed in separate documents. For example, are beyond the scope of this document, and will be addressed in
application-specific communication protocol requirements are given in separate documents. For example, application-specific communication
[PCECP-INTER-AREA] and [PCECP-INTER-LAYER] for inter-area and protocol requirements are given in [PCECP-INTER-AREA] and
inter-layer PCE applications, respectively. [PCECP-INTER-LAYER] for inter-area and inter-layer PCE applications,
respectively.
4. Terminology 2. Conventions Used in This Document
Domain: any collection of network elements within a common sphere of The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "MAY NOT", and
"OPTIONAL" in this document are to be interpreted as described in RFC
2119 [RFC2119].
3. Terminology
Domain: Any collection of network elements within a common sphere of
address management or path computational responsibility. Examples of address management or path computational responsibility. Examples of
domains include IGP areas, Autonomous Systems (ASs), multiple ASs domains include Interior Gateway Protocol (IGP) areas, Autonomous
within a service provider network, or multiple ASs across multiple Systems (ASs), multiple ASs within a service provider network, or
service provider networks. multiple ASs across multiple service provider networks.
GMPLS: Generalized Multi-Protocol Label Switching GMPLS: Generalized Multi-Protocol Label Switching
LSP: MPLS/GMPLS Label Switched Path LSP: MPLS/GMPLS Label Switched Path
LSR: Label Switch Router LSR: Label Switch Router
MPLS: Multi-Protocol Label Switching MPLS: Multi-Protocol Label Switching
PCC: Path Computation Client: any client application requesting a
PCC: Path Computation Client: Any client application requesting a
path computation to be performed by the PCE. path computation to be performed by the PCE.
PCE: Path Computation Element: an entity (component, application or PCE: Path Computation Element: An entity (component, application or
network node) that is capable of computing a network path or route network node) that is capable of computing a network path or route
based on a network graph and applying computational constraints (see based on a network graph and applying computational constraints (see
further description in [PCE-ARCH]). further description in [RFC4655]).
TED: Traffic Engineering Database, which contains the topology and TED: Traffic Engineering Database, which contains the topology and
resource information of the network or network segment used by a PCE. resource information of the network or network segment used by a PCE.
TE LSP: Traffic Engineering (G)MPLS Label Switched Path. TE LSP: Traffic Engineering (G)MPLS Label Switched Path.
See [PCE-ARCH] for further definitions of terms. See [RFC4655] for further definitions of terms.
5. Overview of PCE Communication Protocol (PCECP) 4. Overview of PCE Communication Protocol (PCECP)
In the PCE model, path computation requests are issued by a PCC In the PCE model, path computation requests are issued by a PCC to a
to a PCE that may be composite (co-located) or external (remote). If PCE that may be composite (co-located) or external (remote). If the
the PCC and PCE are not co-located, a request/response communication PCC and PCE are not co-located, a request/response communication
protocol is required to carry the request and return the response. protocol is required to carry the request and return the response.
If the PCC and PCE are co-located, a communication protocol is not If the PCC and PCE are co-located, a communication protocol is not
required, but implementations may choose to utilize a protocol for required, but implementations may choose to utilize a protocol for
exchanges between the components. exchanges between the components.
In order that a PCC and PCE can communicate, the PCC must know the In order for a PCC and PCE to communicate, the PCC must know the
location of the PCE. This can be configured or discovered. The PCE location of the PCE. This can be configured or discovered. The PCE
discovery mechanism is out of scope of this document, but discovery mechanism is out of scope of this document, but
requirements are documented in [PCE-DISC-REQ]. requirements are documented in [PCE-DISC-REQ].
The PCE operates on a network graph built from the TED in order to The PCE operates on a network graph built from the TED in order to
compute paths. The mechanism by which the TED is populated is out of compute paths. The mechanism by which the TED is populated is out of
scope for the PCECP. scope for the PCECP.
A path computation request issued by the PCC includes a specification A path computation request issued by the PCC includes a specification
of the path(s) needed. The information supplied includes, at a of the path(s) needed. The information supplied includes, at a
minimum, the source and destination for the paths, but may also minimum, the source and destination for the paths, but may also
include a set of further requirements (known as constraints) as include a set of further requirements (known as constraints) as
described in Section 6. described in Section 5.
The response from the PCE may be positive in which case it will The response from the PCE may be positive in which case it will
include the paths that have been computed. If the computation fails include the paths that have been computed. If the computation fails
or cannot be performed, a negative response is required with an or cannot be performed, a negative response is required with an
indication of the type of failure. indication of the type of failure.
A request/response protocol is also required for a PCE to communicate A request/response protocol is also required for a PCE to communicate
path computation requests to another PCE and for that PCE to return path computation requests to another PCE and for that PCE to return
the path computation response. As described in [PCE-ARCH], there is the path computation response. As described in [RFC4655], there is
no reason to assume that two different protocols are needed, and this no reason to assume that two different protocols are needed, and this
document assumes that a single protocol will satisfy all requirements document assumes that a single protocol will satisfy all requirements
for PCC-PCE and PCE-PCE communication. for PCC-PCE and PCE-PCE communication.
[PCE-ARCH] describes four models of PCE: composite, external, [RFC4655] describes four models of PCE: composite, external, multiple
multiple PCE path computation, and multiple PCE path computation with PCE path computation, and multiple PCE path computation with inter-
inter-PCE communication. In all cases except the composite PCE model, PCE communication. In all cases except the composite PCE model, a
a PCECP is required. The requirements defined in this document are PCECP is required. The requirements defined in this document are
applicable to all models described in the [PCE-ARCH]. applicable to all models described in [RFC4655].
6. PCE Communication Protocol Generic Requirements 5. PCE Communication Protocol Generic Requirements
6.1 Basic Protocol Requirements 5.1. Basic Protocol Requirements
6.1.1 Commonality of PCC-PCE and PCE-PCE Communication 5.1.1. Commonality of PCC-PCE and PCE-PCE Communication
A single protocol MUST be defined for PCC-PCE and PCE-PCE A single protocol MUST be defined for PCC-PCE and PCE-PCE
communication. A PCE requesting a path from another PCE can be communication. A PCE requesting a path from another PCE can be
considered as a PCC, and in the remainder of this document we refer considered a PCC, and in the remainder of this document we refer to
to all communications as PCC-PCE regardless of whether they are all communications as PCC-PCE regardless of whether they are PCC-PCE
PCC-PCE or PCE-PCE. or PCE-PCE.
6.1.2 Client-Server Communication 5.1.2. Client-Server Communication
PCC-PCE communication is by nature client-server based. The PCECP PCC-PCE communication is by nature client-server based. The PCECP
MUST allow a PCC to send a request message to a PCE to request path MUST allow a PCC to send a request message to a PCE to request path
computation, and for a PCE to reply with a response message to the computation, and for a PCE to reply with a response message to the
requesting PCC once the path has been computed. requesting PCC once the path has been computed.
In addition to this request-response mode, there are cases where In addition to this request-response mode, there are cases where
there is unsolicited communication from the PCE to the PCC (see there is unsolicited communication from the PCE to the PCC (see
Section 6.1.11). Section 5.1.11).
6.1.3 Transport 5.1.3. Transport
The PCECP SHOULD utilize an existing transport protocol that supports The PCECP SHOULD utilize an existing transport protocol that supports
congestion control. This transport protocol may also be used to congestion control. This transport protocol may also be used to
satisfy some requirements in other sections of this document, such as satisfy some requirements in other sections of this document, such as
reliability. The PCECP SHOULD be defined for one transport protocol reliability. The PCECP SHOULD be defined for one transport protocol
only in order to ensure interoperability. The transport protocol only in order to ensure interoperability. The transport protocol
MUST NOT limit the size of the message used by the PCECP. MUST NOT limit the size of the message used by the PCECP.
6.1.4 Path Computation Requests 5.1.4. Path Computation Requests
The path computation request message MUST include at least the source The path computation request message MUST include at least the source
and destination. Note that the path computation request is for an and destination. Note that the path computation request is for an
LSP or LSP segment, and the source and destination supplied are the LSP or LSP segment, and the source and destination supplied are the
start and end of the computation being requested (i.e. of the LSP start and end of the computation being requested (i.e., of the LSP
segment). segment).
The path computation request message MUST support the inclusion of a The path computation request message MUST support the inclusion of a
set of one or more path constraints, including but not limited to the set of one or more path constraints, including but not limited to the
requested bandwidth or resources (hops, affinities, etc.) to requested bandwidth or resources (hops, affinities, etc.) to
include/exclude. For example, a PCC may request the PCE to exclude include/exclude. For example, a PCC may request the PCE to exclude
points of failure in the computation of a new path if an LSP setup points of failure in the computation of a new path if an LSP setup
fails. The actual inclusion of constraints is a choice for the PCC fails. The actual inclusion of constraints is a choice for the PCC
issuing the request. A list of core constraints that must be issuing the request. A list of core constraints that must be
supported by the PCECP is supplied in Section 6.1.16. Specification supported by the PCECP is supplied in Section 5.1.16. Specification
of constraints MUST be future-proofed as described in Section 6.1.14. of constraints MUST be future-proofed as described in Section 5.1.14.
The requester MUST be allowed to select or prefer from an advertised The requester MUST be allowed to select from or prefer an advertised
list or minimal subset of standard objective functions and functional list or minimal subset of standard objective functions and functional
options. An objective function is used by the PCE to process options. An objective function is used by the PCE to process
constraints to a path computation request when it computes a path in constraints to a path computation request when it computes a path in
order to select the "best" candidate paths (e.g., minimum hop path), order to select the "best" candidate paths (e.g., minimum hop path),
and corresponds to the optimization criteria used for the computation and corresponds to the optimization criteria used for the computation
of one path, or the synchronized computation of a set of paths. In of one path, or the synchronized computation of a set of paths. In
the case of unsynchronized path computation, this can be, for the case of unsynchronized path computation, this can be, for
example, the path cost or the residual bandwidth on the most loaded example, the path cost or the residual bandwidth on the most loaded
path link. In the case of synchronized path computation, this can path link. In the case of synchronized path computation, this can
be, for example, the global bandwidth consumption or the residual be, for example, the global bandwidth consumption or the residual
bandwidth on the most loaded network link. bandwidth on the most loaded network link.
A list of core objective functions that MUST be supported by the A list of core objective functions that MUST be supported by the
PCECP is supplied in Section 6.1.17. Specification of objective PCECP is supplied in Section 5.1.17. Specification of objective
functions MUST be future-proofed as described in Section 6.1.14. functions MUST be future-proofed as described in Section 5.1.14.
The requester SHOULD also be able to select a vendor-specific or The requester SHOULD also be able to select a vendor-specific or
experimental objective function or functional option. Furthermore, experimental objective function or functional option. Furthermore,
the requester MUST be allowed to customize the function/options in the requester MUST be allowed to customize the function/options in
use. That is, individual objective functions will often have use. That is, individual objective functions will often have
parameters to be set in the request from PCC to PCE. Support for the parameters to be set in the request from PCC to PCE. Support for the
specification of objective functions and objective parameters is specification of objective functions and objective parameters is
required in the protocol extensibility specified in Section 6.1.14. required in the protocol extensibility specified in Section 5.1.14.
A request message MAY include TE parameters carried by the MPLS/GMPLS A request message MAY include TE parameters carried by the MPLS/GMPLS
LSP setup signaling protocol. Also, it MUST be possible for the PCE LSP setup signaling protocol. Also, it MUST be possible for the PCE
to apply additional objective functions. This might include policy to apply additional objective functions. This might include policy-
based routing path computation for load balancing instructed by the based routing path computation for load balancing instructed by the
management plane. management plane.
Shortest path selection may rely either on the TE metric or on the Shortest path selection may rely either on the TE metric or on the
IGP metric [METRIC]. Hence the PCECP request message MUST allow the IGP metric [METRIC]. Hence the PCECP request message MUST allow the
PCC to indicate the metric type (IGP or TE) to be used for shortest PCC to indicate the metric type (IGP or TE) to be used for shortest
path selection. Note that other metric types may be specified in the path selection. Note that other metric types may be specified in the
future. future.
There may be cases where a single path cannot fit a given bandwidth There may be cases where a single path cannot fit a given bandwidth
request, while a set of paths could be combined to fit the request. request, while a set of paths could be combined to fit the request.
Such path combination to serve a given request is called Such path combination to serve a given request is called load-
load-balancing. The request message MUST allow the PCC to indicate if balancing. The request message MUST allow the PCC to indicate if
load-balancing is allowed or not. It MUST also include the maximum load-balancing is allowed. It MUST also include the maximum number
number of paths in a load-balancing path group, and the minimum path of paths in a load-balancing path group, and the minimum path
bandwidth in a load-balancing path group. The request message MUST bandwidth in a load-balancing path group. The request message MUST
allow specification of the degree of disjointness of the members of allow specification of the degree of disjointness of the members of
the load-balancing group. the load-balancing group.
6.1.5 Path Computation Responses 5.1.5. Path Computation Responses
The path computation response message MUST allow the PCE to return The path computation response message MUST allow the PCE to return
various elements including, at least, the computed path(s). various elements including, at least, the computed path(s).
The protocol MUST be capable of returning any explicit path that The protocol MUST be capable of returning any explicit path that
would be acceptable for use for MPLS and GMPLS LSPs once converted to would be acceptable for use for MPLS and GMPLS LSPs once converted to
an Explicit Route Object for use in RSVP-TE signaling. In addition, an Explicit Route Object for use in RSVP-TE signaling. In addition,
anything that can be expressed in an Explicit Route Object MUST be anything that can be expressed in an Explicit Route Object MUST be
capable of being returned in the computed path. Note that the capable of being returned in the computed path. Note that the
resultant path(s) may be made up of a set of strict or loose hops, or resultant path(s) may be made up of a set of strict or loose hops, or
skipping to change at page 8, line 33 skipping to change at page 7, line 41
been computed. A positive PCECP computation response MUST support been computed. A positive PCECP computation response MUST support
the inclusion of a set of attributes of the computed path, such as the inclusion of a set of attributes of the computed path, such as
the path costs (e.g., cumulative link TE metrics and cumulative link the path costs (e.g., cumulative link TE metrics and cumulative link
IGP metrics) and the computed bandwidth. The latter is useful when a IGP metrics) and the computed bandwidth. The latter is useful when a
single path cannot serve the requested bandwidth and load balancing single path cannot serve the requested bandwidth and load balancing
is applied. is applied.
When a path satisfying the constraints cannot be found, or if the When a path satisfying the constraints cannot be found, or if the
computation fails or cannot be performed, a negative response MUST be computation fails or cannot be performed, a negative response MUST be
sent. This response MAY include further details of the reason(s) for sent. This response MAY include further details of the reason(s) for
the failure, and MAY include advice about which constraints might be the failure and MAY include advice about which constraints might be
relaxed to be more likely to achieve a positive result. relaxed to be more likely to achieve a positive result.
The PCECP response message MUST support the inclusion of the set of The PCECP response message MUST support the inclusion of the set of
computed paths of a load-balancing path group, as well as their computed paths of a load-balancing path group, as well as their
respective bandwidths. respective bandwidths.
6.1.6 Cancellation of Pending Requests 5.1.6. Cancellation of Pending Requests
A PCC MUST be able to cancel a pending request using an appropriate A PCC MUST be able to cancel a pending request using an appropriate
message. A PCC that has sent a request to a PCE and no longer needs message. A PCC that has sent a request to a PCE and no longer needs
a response, for instance because it no longer wants to set up the a response, for instance, because it no longer wants to set up the
associated service, MUST be able to notify the PCE that it can clear associated service, MUST be able to notify the PCE that it can clear
the request (i.e. stop the computation if already started, and clear the request (i.e., stop the computation if already started, and clear
the context). The PCE may also wish to cancel a pending request the context). The PCE may also wish to cancel a pending request
because of some congested state. because of some congested state.
6.1.7 Multiple Requests and Responses 5.1.7. Multiple Requests and Responses
It MUST be possible to send multiple path computation requests It MUST be possible to send multiple path computation requests within
within the same request message. Such requests may be correlated (for the same request message. Such requests may be correlated (e.g.,
example, requesting disjoint paths) or uncorrelated (requesting paths requesting disjoint paths) or uncorrelated (requesting paths for
for unrelated services). It MUST be possible to limit by unrelated services). It MUST be possible to limit by configuration
configuration of both PCCs and PCEs the number of requests that can of both PCCs and PCEs the number of requests that can be carried
be carried within a single message. within a single message.
Similarly, it MUST be possible to return multiple computed paths Similarly, it MUST be possible to return multiple computed paths
within the same response message, corresponding either to the same within the same response message, corresponding either to the same
request (e.g. multiple suited paths, paths of a load balancing path request (e.g., multiple suited paths, paths of a load-balancing path
group) or to distinct requests, correlated or not, of the same group) or to distinct requests, correlated or not, of the same
request message or distinct request messages. request message or distinct request messages.
It MUST be possible to provide "continuation correlation" where all It MUST be possible to provide "continuation correlation" where all
related requests or computed paths cannot fit within one message, and related requests or computed paths cannot fit within one message and
are carried in a sequence of correlated messages. are carried in a sequence of correlated messages.
The PCE MUST inform the PCC of its capabilities. Maximum acceptable The PCE MUST inform the PCC of its capabilities. Maximum acceptable
message sizes and the maximum number of requests per message message sizes and the maximum number of requests per message
supported by a PCE MAY form part of PCE capabilities advertisement supported by a PCE MAY form part of PCE capabilities advertisement
[PCE-DISC-REQ], or MAY be exchanged through information messages from [PCE-DISC-REQ] or MAY be exchanged through information messages from
the PCE as part of the protocol described here. the PCE as part of the protocol described here.
It MUST be possible for a PCC to specify, in the request message, the It MUST be possible for a PCC to specify, in the request message, the
maximum acceptable response message sizes and the maximum number of maximum acceptable response message sizes and the maximum number of
computed paths per response message it can support. computed paths per response message it can support.
It MUST be possible to limit the message size by configuration on It MUST be possible to limit the message size by configuration on
PCCs and PCEs. PCCs and PCEs.
6.1.8 Reliable Message Exchange 5.1.8. Reliable Message Exchange
The PCECP MUST support reliable transmission of PCECP packets. This The PCECP MUST support reliable transmission of PCECP packets. This
may form part of the protocol itself or may be achieved by the may form part of the protocol itself or may be achieved by the
selection of a suitable transport protocol (see Section 6.1.3). selection of a suitable transport protocol (see Section 5.1.3).
In particular, it MUST allow for the detection and recovery of lost In particular, it MUST allow for the detection and recovery of lost
messages to occur quickly and not impede the operation of the PCECP. messages to occur quickly and not impede the operation of the PCECP.
In some cases (e.g. after link failure), a large number of PCCs may In some cases (e.g., after link failure), a large number of PCCs may
simultaneously send requests to a PCE, leading to a potential simultaneously send requests to a PCE, leading to a potential
saturation of the PCEs. The PCECP MUST support indication of saturation of the PCEs. The PCECP MUST support indication of
congestion state and rate limitation state. This should enable, for congestion state and rate limitation state. This should enable, for
example, a PCE to limit the rate of incoming request messages if the example, a PCE to limit the rate of incoming request messages if the
request rate is too high. request rate is too high.
The PCECP or its transport protocol MUST provide: The PCECP or its transport protocol MUST provide the following:
- Detection and report of lost or corrupted messages - Detection and report of lost or corrupted messages
- Automatic attempts to retransmit lost messages without reference to - Automatic attempts to retransmit lost messages without reference to
the application the application
- Handling of out-of-order messages - Handling of out-of-order messages
- Handling of duplicate messages - Handling of duplicate messages
- Flow control and back-pressure to enable throttling of requests and - Flow control and back-pressure to enable throttling of requests and
responses responses
- Rapid PCECP communication failure detection - Rapid PCECP communication failure detection
- Distinction between partner failure and communication channel - Distinction between partner failure and communication channel
failure after the PCECP communication is recovered failure after the PCECP communication is recovered
If it is necessary to add functions to PCECP to overcome shortcomings If it is necessary to add functions to PCECP to overcome shortcomings
in the chosen transport mechanisms, these functions SHOULD be based in the chosen transport mechanisms, these functions SHOULD be based
on and re-use where possible techniques developed in other protocols on and re-use where possible techniques developed in other protocols
to overcome the same shortcomings. Functionality MUST NOT be added to overcome the same shortcomings. Functionality MUST NOT be added
to the PCECP where the chosen transport protocol already provides it. to the PCECP where the chosen transport protocol already provides it.
6.1.9 Secure Message Exchange 5.1.9. Secure Message Exchange
The PCC-PCE communication protocol MUST include provisions to ensure The PCC-PCE communication protocol MUST include provisions to ensure
the security of the exchanges between the entities. In particular, the security of the exchanges between the entities. In particular,
it MUST support mechanisms to prevent spoofing (e.g., it MUST support mechanisms to prevent spoofing (e.g.,
authentication), snooping (e.g., preservation of confidentiality of authentication), snooping (e.g., preservation of confidentiality of
information through techniques such as encryption) and DOS attacks information through techniques such as encryption), and Denial of
(e.g., packet filtering, rate limiting, no promiscuous listening). Service (DoS) attacks (e.g., packet filtering, rate limiting, no
Once a PCC is identified and authenticated, it has the same promiscuous listening). Once a PCC is identified and authenticated,
privileges as all other PCCs. it has the same privileges as all other PCCs.
To ensure confidentiality, the PCECP SHOULD allow local policy to be To ensure confidentiality, the PCECP SHOULD allow local policy to be
configured on the PCE to not provide explicit path(s). If a PCC configured on the PCE to not provide explicit path(s). If a PCC
requests an explicit path when this is not allowed, the PCE MUST requests an explicit path when this is not allowed, the PCE MUST
return an error message to the requesting PCC and the pending path return an error message to the requesting PCC and the pending path
computation request MUST be discarded. computation request MUST be discarded.
Authorization requirements [RFC3127] include reject capability, Authorization requirements [RFC3127] include reject capability,
reauthorization on demand, support for access rules and filters, and reauthorization on demand, support for access rules and filters, and
unsolicited disconnect. unsolicited disconnect.
Where the PCE-PCC communication takes place entirely within one IP addresses are used to identify PCCs and PCEs. Where the PCC-PCE
limited domain, the use of a private address space which is not communication takes place entirely within one limited domain, the use
available to customer systems MAY be used to help protect the of a private address space that is not available to customer systems
information exchange, but other mechanisms MUST also be available. MAY be used to help protect the information exchange, but other
mechanisms MUST also be available.
These functions may be provided by the transport protocol or directly These functions may be provided by the transport protocol or directly
by the PCECP. See Section 7 for further discussion of security by the PCECP. See Section 6 for further discussion of security
considerations. considerations.
6.1.10 Request Prioritization 5.1.10. Request Prioritization
The PCECP MUST allow a PCC to specify the priority of a computation The PCECP MUST allow a PCC to specify the priority of a computation
request. request.
Implementation of priority-based activity within a PCE is subject to Implementation of priority-based activity within a PCE is subject to
implementation and local policy. This application processing is out implementation and local policy. This application processing is out
of scope of the PCECP. of scope of the PCECP.
6.1.11 Unsolicited Notifications 5.1.11. Unsolicited Notifications
The normal operational mode is for the PCC to make path computation The normal operational mode is for the PCC to make path computation
requests to the PCE, and for the PCE to respond. requests to the PCE and for the PCE to respond.
The PCECP MUST support unsolicited notifications from PCE to PCC, or The PCECP MUST support unsolicited notifications from PCE to PCC, or
PCC to PCE. This requirement facilitates the unsolicited PCC to PCE. This requirement facilitates the unsolicited
communication of information and alerts between PCCs and PCEs. As communication of information and alerts between PCCs and PCEs. As
specified in Section 6.1.8, these notification messages must be specified in Section 5.1.8, these notification messages must be
supported by a reliable transmission protocol. The PCECP MAY also supported by a reliable transmission protocol. The PCECP MAY also
support response messages to the unsolicited notification messages. support response messages to the unsolicited notification messages.
6.1.12 Asynchronous Communication 5.1.12. Asynchronous Communication
The PCC-PCE protocol MUST allow for asynchronous communication. A The PCC-PCE protocol MUST allow for asynchronous communication. A
PCC MUST NOT have to wait for a response to one request before it can PCC MUST NOT have to wait for a response to one request before it can
make another request. make another request.
It MUST also be possible to have the order of responses differ from It MUST also be possible to have the order of responses differ from
the order of the corresponding requests. This may occur, for the order of the corresponding requests. This may occur, for
instance, when path request messages have different priorities (see instance, when path request messages have different priorities (see
Requirement 6.1.10). A consequent requirement is that path Requirement 5.1.10). A consequent requirement is that path
computation responses MUST include a direct correlation to the computation responses MUST include a direct correlation to the
associated request. associated request.
6.1.13 Communication Overhead Minimization 5.1.13. Communication Overhead Minimization
The request and response messages SHOULD be designed so that the The request and response messages SHOULD be designed so that the
communication overhead is minimized. In particular, the overhead per communication overhead is minimized. In particular, the overhead per
message SHOULD be minimized, and the number of bytes exchanged to message SHOULD be minimized, and the number of bytes exchanged to
arrive at a computation answer SHOULD be minimized. Other arrive at a computation answer SHOULD be minimized. Other
considerations in overhead minimization include the following: considerations in overhead minimization include the following:
- the number of background messages used by the protocol or its - the number of background messages used by the protocol or its
transport protocol to keep alive any session or association transport protocol to keep alive any session or association
between the PCE and PCC between the PCE and PCC
- the processing cost at the PCE (or PCC) associated with - the processing cost at the PCE (or PCC) associated with
request/response messages (as distinct from processing the request/response messages (as distinct from processing the
computation requests themselves). computation requests themselves)
6.1.14 Extensibility 5.1.14. Extensibility
The PCECP MUST provide a way for the introduction of new path The PCECP MUST provide a way for the introduction of new path
computation constraints, diversity types, objective functions, computation constraints, diversity types, objective functions,
optimization methods and parameters, etc., without requiring optimization methods and parameters, and so on, without requiring
major modifications in the protocol. major modifications in the protocol.
For example, the PCECP MUST be extensible to support various PCE For example, the PCECP MUST be extensible to support various PCE-
based applications, such as the following: based applications, such as the following:
- intra-area path computation - intra-area path computation
- inter-area path computation [PCECP-INTER-AREA] - inter-area path computation [PCECP-INTER-AREA]
- inter-AS intra provider and inter-AS inter-provider path - inter-AS intra provider and inter-AS inter-provider path
computation computation [PCECP-INTER-AS]
- inter-layer path computation [PCECP-INTER-LAYER] - inter-layer path computation [PCECP-INTER-LAYER]
The PCECP MUST support the requirements specified in the The PCECP MUST support the requirements specified in the
application-specific requirements documents. The PCECP MUST also application-specific requirements documents. The PCECP MUST also
allow extensions as more PCE applications will be introduced in the allow extensions as more PCE applications will be introduced in the
future. future.
The PCECP SHOULD also be extensible to support future applications The PCECP SHOULD also be extensible to support future applications
not currently in the scope of the PCE working group, such as, for not currently in the scope of the PCE working group, such as, for
instance, point-to-multipoint path computations, multi-hop pseudowire instance, point-to-multipoint path computations, multi-hop pseudowire
path computation, etc. path computation, etc.
Note that application specific requirements are out of the scope of Note that application specific requirements are out of the scope of
this document and will be addressed in separate requirements this document and will be addressed in separate requirements
documents. documents.
6.1.15 Scalability 5.1.15. Scalability
The PCECP MUST scale well, at least as good as linearly, with an The PCECP MUST scale well, at least as good as linearly, with an
increase of any of the following parameters. Minimum order of increase of any of the following parameters. Minimum order of
magnitude estimates of what the PCECP should support are given in magnitude estimates of what the PCECP should support are given in
parenthesis (note: these are requirements on the PCECP, not a PCE): parenthesis (note: these are requirements on the PCECP, not on the
PCE):
- number of PCCs (1000/domain) - number of PCCs (1000/domain)
- number of PCEs (100/domain) - number of PCEs (100/domain)
- number of PCCs communicating with a single PCE (1000) - number of PCCs communicating with a single PCE (1000)
- number of PCEs communicated to by a single PCC (100) - number of PCEs communicated to by a single PCC (100)
- number of domains (20) - number of domains (20)
- number of path request messages (average of 10/second/PCE) - number of path request messages (average of 10/second/PCE)
- handling bursts of requests (burst of 100/second/PCE within a 10- - handling bursts of requests (burst of 100/second/PCE within a 10-
second interval). second interval).
Note that path requests can be bundled in path request messages, for Note that path requests can be bundled in path request messages, for
example, 10 PCECP request messages/second may correspond to 100 path example, 10 PCECP request messages/second may correspond to 100 path
requests/second. requests/second.
Bursts of requests may arise, for example, after a network outage Bursts of requests may arise, for example, after a network outage
when multiple recomputations are requested. The PCECP MUST handle when multiple recomputations are requested. The PCECP MUST handle
the congestion in a graceful way so that it does not unduly impact the congestion in a graceful way so that it does not unduly impact
the rest of the network, and so that it does not gate the ability of the rest of the network, and so that it does not gate the ability of
the PCE to perform computation. the PCE to perform computation.
6.1.16 Constraints 5.1.16. Constraints
This section provides a list of generic constraints that MUST be This section provides a list of generic constraints that MUST be
supported by the PCECP. Other constraints may be added to service supported by the PCECP. Other constraints may be added to service
specific applications as identified by separate application-specific specific applications as identified by separate application-specific
requirements documents. Note that the provisions of Section 6.1.14 requirements documents. Note that the provisions of Section 5.1.14
mean that new constraints can be added to this list without impacting mean that new constraints can be added to this list without impacting
the protocol to a level that requires major protocol changes. the protocol to a level that requires major protocol changes.
The set of supported generic constraints MUST include at the least The set of supported generic constraints MUST include at least the
The following: following:
o MPLS-TE and GMPLS generic constraints: o MPLS-TE and GMPLS generic constraints:
- Bandwidth - Bandwidth
- Affinities inclusion/exclusion - Affinities inclusion/exclusion
- Link, Node, SRLG inclusion/exclusion - Link, Node, Shared Risk Link Group (SRLG) inclusion/exclusion
- Maximum end-to-end IGP metric - Maximum end-to-end IGP metric
- Maximum Hop Count - Maximum hop count
- Maximum end-to-end TE metric - Maximum end-to-end TE metric
- Degree of paths disjointness (Link, Node, SRLG) - Degree of paths disjointness (Link, Node, SRLG)
o MPLS-TE specific constraints o MPLS-TE specific constraints
- Class-type - Class-type
- Local protection - Local protection
- Node protection - Node protection
- Bandwidth protection - Bandwidth protection
o GMPLS specific constraints o GMPLS specific constraints
- Switching type, encoding type - Switching type, encoding type
- Link protection type - Link protection type
6.1.17 Objective Functions Supported 5.1.17. Objective Functions Supported
This section provides a list of generic objective functions that MUST This section provides a list of generic objective functions that MUST
be supported by the PCECP. Other objectives functions MAY be added be supported by the PCECP. Other objective functions MAY be added to
to service specific applications as identified by separate service specific applications as identified by separate application-
application-specific requirements documents. Note that the specific requirements documents. Note that the provisions of Section
provisions of Section 6.1.14 mean that new objective functions MAY be 5.1.14 mean that new objective functions MAY be added to this list
added to this list without impacting the protocol. without impacting the protocol.
The PCECP MUST support at least the following "unsynchronized" The PCECP MUST support at least the following "unsynchronized"
functions: functions:
- Minimum cost path with respect to a specified metric(shortest path) - Minimum cost path with respect to a specified metric
(shortest path)
- Least loaded path - Least loaded path
- Maximum available bandwidth path - Maximum available bandwidth path
Also the PCECP MUST support at least the following "synchronized" Also, the PCECP MUST support at least the following "synchronized"
objective functions: objective functions:
- Minimize aggregate bandwidth consumption on all links - Minimize aggregate bandwidth consumption on all links
- Maximize the residual bandwidth on the most loaded link - Maximize the residual bandwidth on the most loaded link
- Minimize the cumulative cost of a set of diverse paths. - Minimize the cumulative cost of a set of diverse paths
6.2 Deployment Support Requirements 5.2. Deployment Support Requirements
6.2.1 Support for Different Service Provider Environments 5.2.1. Support for Different Service Provider Environments
The PCECP must at least support the following environments: The PCECP must at least support the following environments:
- MPLS-TE and GMPLS networks - MPLS-TE and GMPLS networks
- packet and non-packet networks - Packet and non-packet networks
- centralized and distributed PCE path computation - Centralized and distributed PCE path computation
- single and multiple PCE path computation - Single and multiple PCE path computation
For example, PCECP is possibly applicable to packet networks (e.g., For example, PCECP is possibly applicable to packet networks (e.g.,
IP networks), non-packet networks (e.g., TDM transport), and perhaps IP networks), non-packet networks (e.g., time-division multiplexed
to multi-layer GMPLS control plane environments. Definitions of (TDM) transport), and perhaps to multi-layer GMPLS control plane
centralized, distributed, single, and multiple PCE path computation environments. Definitions of centralized, distributed, single, and
can be found in [PCE-ARCH]. multiple PCE path computation can be found in [RFC4655].
6.2.2 Policy Support 5.2.2. Policy Support
The PCECP MUST allow for the use of policies to accept/reject The PCECP MUST allow for the use of policies to accept/reject
requests. It MUST include the ability for a PCE to supply sufficient requests. It MUST include the ability for a PCE to supply sufficient
detail when it rejects a request for policy reasons to allow the PCC detail when it rejects a request for policy reasons to allow the PCC
to determine the reason for rejection or failure. For example, to determine the reason for rejection or failure. For example,
filtering could be required for a PCE that serves one domain (perhaps filtering could be required for a PCE that serves one domain (perhaps
an AS) such that all requests that come from another domain (AS) are an AS) such that all requests that come from another domain (AS) are
rejected. However, specific policy details are left to rejected. However, specific policy details are left to application-
application-specific PCECP requirements. Actual policies, specific PCECP requirements. Actual policies, configuration of
configuration of policies, and applicability of policies are out of policies, and applicability of policies are out of scope.
scope.
Note that work on supported policy models and the corresponding Note that work on supported policy models and the corresponding
requirements/implications is being undertaken as a separate work item requirements/implications is being undertaken as a separate work item
in the PCE working group. in the PCE working group.
PCECP messages MUST be able to carry transparent policy information. PCECP messages MUST be able to carry transparent policy information.
6.3 Aliveness Detection & Recovery Requirements 5.3. Aliveness Detection & Recovery Requirements
6.3.1 Aliveness Detection 5.3.1. Aliveness Detection
The PCECP MUST allow a PCC to The PCECP MUST allow a PCC/PCE to
- check the liveliness of the PCC-PCE communication - check the liveliness of the PCC-PCE communication,
- rapidly detect PCC-PCE communication failure (indifferently to - rapidly detect PCC-PCE communication failure (indifferently to
partner failure or connectivity failure), partner failure or connectivity failure), and
- distinguish PCC/PCE node failures from PCC-PCE connectivity - distinguish PCC/PCE node failures from PCC-PCE connectivity
failures, after the PCC-PCE communication is recovered. failures, after the PCC-PCE communication is recovered.
The aliveness detection mechanism MUST ensure reciprocal knowledge of The aliveness detection mechanism MUST ensure reciprocal knowledge of
PCE and PCC liveness. PCE and PCC liveness.
6.3.2 Protocol Recovery 5.3.2. Protocol Recovery
In the event of the failure of a sender or of the communication In the event of the failure of a sender or of the communication
channel, the PCECP, upon recovery, MUST support resynchronization of channel, the PCECP, upon recovery, MUST support resynchronization of
information (e.g. PCE congestion status) and requests between the information (e.g., PCE congestion status) and requests between the
sender and the receiver, and this SHOULD be arranged so as to sender and the receiver; this SHOULD be arranged so as to minimize
minimize repeat data transfer. repeat data transfer.
6.3.3 LSP Rerouting & Reoptimization 5.3.3. LSP Rerouting & Reoptimization
If an LSP fails owing to the failure of a link or node that it If an LSP fails owing to the failure of a link or node that it
traverses, a new computation request may be made to a PCE in order to traverses, a new computation request may be made to a PCE in order to
repair the LSP. Since the PCC cannot know that the PCE's TED has been repair the LSP. Since the PCC cannot know that the PCE's TED has
updated to reflect the failure network information, it is useful to been updated to reflect the failure network information, it is useful
include this information in the new path computation request. Also, to include this information in the new path computation request.
in order to re-use the resources used by the old LSP, it may be
Also, in order to re-use the resources used by the old LSP, it may be
advantageous to indicate the route of the old LSP as part of the new advantageous to indicate the route of the old LSP as part of the new
path computation request. path computation request.
Hence the path computation request message MUST allow an indication Hence the path computation request message MUST allow an indication
of whether the computation is for LSP restoration, and MUST support of whether the computation is for LSP restoration, and it MUST
the inclusion of the previously computed path as well as the identity support the inclusion of the previously computed path as well as the
of the failed element. Note that the old path might only be useful identity of the failed element. Note that the old path might only be
if the old LSP has not yet been torn down. The PCE MAY or MAY not useful if the old LSP has not yet been torn down. The PCE MAY choose
take into account failure indication carried in a given request when to take failure indication information carried in a given request
handling subsequent requests. This should be driven by local policy into account when handling subsequent requests. This should be
decision. driven by local policy decision.
IP addresses are used to identify PCCs and PCEs. However, as noted
in Section 6.1.9, a private address space MAY be used if the PCE-PCC
communication takes place entirely within one limited domain.
Note that a network failure may impact a large number of LSPs. In Note that a network failure may impact a large number of LSPs. In
this case, a potentially large number of PCCs will simultaneously this case, a potentially large number of PCCs will simultaneously
send requests to the PCE. The PCECP MUST properly handle such send requests to the PCE. The PCECP MUST properly handle such
overload situations, such as for instance through throttling of overload situations, such as, for instance, through throttling of
requests as set forth in section 6.1.8. requests as set forth in Section 5.1.8.
The path computation request message MUST support TE LSP path The path computation request message MUST support TE LSP path
reoptimization and the inclusion of a previously computed path. This reoptimization and the inclusion of a previously computed path. This
will help ensure optimal routing of a reoptimized path, since it will will help ensure optimal routing of a reoptimized path, since it will
allow the PCE to avoid double bandwidth accounting and help reduce allow the PCE to avoid double bandwidth accounting and help reduce
blocking issues. blocking issues.
7. Security Considerations 6. Security Considerations
Key management MUST be provided by the PCECP to provide for the Key management MUST be provided by the PCECP to provide for the
authenticity and integrity of PCECP messages. This will allow authenticity and integrity of PCECP messages. This will allow
protecting against PCE or PCC impersonation and also against message protecting against PCE or PCC impersonation and also against message
content falsification. content falsification.
The impact of the use of a PCECP MUST be considered in the light of The impact of the use of a PCECP MUST be considered in light of the
the impact that it has on the security of the existing routing and impact that it has on the security of the existing routing and
signaling protocols and techniques in use within the network. signaling protocols and techniques in use within the network.
Intra-domain security is impacted since there is a new interface, Intra-domain security is impacted since there is a new interface,
protocol and element in the network. Any host in the network could protocol, and element in the network. Any host in the network could
impersonate a PCC, and receive detailed information on network paths. impersonate a PCC and receive detailed information on network paths.
Any host could also impersonate a PCE, both gathering information Any host could also impersonate a PCE, both gathering information
about the network before passing the request on to a real PCE, and about the network before passing the request on to a real PCE and
spoofing responses. Some protection here depends on the security of spoofing responses. Some protection here depends on the security of
the PCE discovery process (see [PCE-DISC-REQ]). An increase in the PCE discovery process (see [PCE-DISC-REQ]). An increase in
inter-domain information flows may increase the vulnerability to inter-domain information flows may increase the vulnerability to
security attacks, and the facilitation of inter-domain paths may security attacks, and the facilitation of inter-domain paths may
increase the impact of these security attacks. increase the impact of these security attacks.
Of particular relevance are the implications for confidentiality Of particular relevance are the implications for confidentiality
inherent in a PCECP for multi-domain networks. It is not necessarily inherent in a PCECP for multi-domain networks. It is not necessarily
the case that a multi-domain PCE solution will compromise security, the case that a multi-domain PCE solution will compromise security,
but solutions MUST examine their impacts in this area. but solutions MUST examine their impacts in this area.
Applicability statements for particular combinations of signaling, Applicability statements for particular combinations of signaling,
routing and path computation techniques are expected to contain routing, and path computation techniques are expected to contain
detailed security sections. detailed security sections.
It should be observed that the use of an external PCE introduces It should be observed that the use of an external PCE introduces
additional security issues. Most notable amongst these are: additional security issues. Most notable among these are the
following:
- interception of PCE requests or responses - Interception of PCE requests or responses
- impersonation of PCE or PCC - Impersonation of PCE or PCC
- DoS attacks on PCEs or PCCs - DoS attacks on PCEs or PCCs
The PCECP MUST address these issues in detail using authentication, The PCECP MUST address these issues in detail using authentication,
encryption and DoS protection techniques. See also Section 6.1.9. encryption, and DoS protection techniques. See also Section 5.1.9.
There are security implications of allowing arbitrary objective There are security implications of allowing arbitrary objective
functions, as discussed in Section 6.1.17, and the PCECP MUST allow functions, as discussed in Section 5.1.17, and the PCECP MUST allow
mitigating the risk of, for example, a PCC using complex objectives mitigating the risk of, for example, a PCC using complex objectives
to intentionally drive a PCE into resource exhaustion. to intentionally drive a PCE into resource exhaustion.
8. Manageability Considerations 7. Manageability Considerations
Manageability of the PCECP MUST address the following considerations: Manageability of the PCECP MUST address the following considerations:
- the need for a MIB module for control and monitoring of PCECP - The need for a MIB module for control and monitoring of PCECP
- the need for built-in diagnostic tools to test the operation of the - The need for built-in diagnostic tools to test the operation of the
protocol (e.g., partner failure detection, OAM, etc.) protocol (e.g., partner failure detection, Operations
- configuration implications for the protocol Administration and Maintenance (OAM), etc.)
- Configuration implications for the protocol
PCECP operations MUST be modeled and controlled through appropriate PCECP operations MUST be modeled and controlled through appropriate
MIB modules. There are enough specific differences between PCCs and MIB modules. There are enough specific differences between PCCs and
PCEs to lead to the need of defining separate MIB modules. PCEs to lead to the need of defining separate MIB modules.
Statistics gathering will form an important part of the operation of Statistics gathering will form an important part of the operation of
the PCECP. The MIB modules MUST provide information that will allow the PCECP. The MIB modules MUST provide information that will allow
an operator to determine PCECP historical interactions and the an operator to determine PCECP historical interactions and the
success rate of requests. Similarly, it is important for an operator success rate of requests. Similarly, it is important for an operator
to be able to determine PCECP and PCE load and whether an individual to be able to determine PCECP and PCE load and whether an individual
PCC is responsible for a disproportionate amount of the load. It PCC is responsible for a disproportionate amount of the load. It
MUST be possible, through use of MIB modules, to record and inspect MUST be possible, through use of MIB modules, to record and inspect
statistics about the PCECP communications, including issues such as statistics about the PCECP communications, including issues such as
malformed messages, unauthorized messages and messages discarded malformed messages, unauthorized messages, and messages discarded
owing to congestion. owing to congestion.
The new MIB modules should also be used to provide notifications The new MIB modules should also be used to provide notifications
(traps) when thresholds are crossed or when important events occur. (traps) when thresholds are crossed or when important events occur.
For example, the MIB module may support indication of exceeding the For example, the MIB module may support indication of exceeding the
congestion state threshold or rate limitation state. congestion state threshold or rate limitation state.
PCECP techniques must enable a PCC to determine the liveness of a PCE PCECP techniques must enable a PCC to determine the liveness of a PCE
both before it sends a request and in the period between sending a both before it sends a request and in the period between sending a
request and receiving a response. request and receiving a response.
It is also important for a PCE to know about the liveness of PCCs to It is also important for a PCE to know about the liveness of PCCs to
gain a predictive view of the likely loading of a PCE in the future, gain a predictive view of the likely loading of a PCE in the future
and to allow a PCE to abandon processing of a received request. and to allow a PCE to abandon processing of a received request.
The PCECP MUST support indication of congestion state and rate The PCECP MUST support indication of congestion state and rate
limitation state, and MAY allow the operator to control such a limitation state, and MAY allow the operator to control such a
function. function.
9. IANA Considerations 8. Contributors
This document makes no requests for IANA action. This document is the result of the PCE Working Group PCECP
requirements design team joint effort. In addition to the
authors/editors listed in the "Authors' Addresses" section, the
following are the design team members who contributed to the
document:
10. Acknowledgements Alia K. Atlas
Google Inc.
1600 Amphitheatre Parkway
Mountain View, CA 94043 USA
EMail: akatlas@alum.mit.edu
Arthi Ayyangar
Nuova Systems,
2600 San Tomas Expressway
Santa Clara, CA 95051
EMail: arthi@nuovasystems.com
Nabil Bitar
Verizon
40 Sylvan Road
Waltham, MA 02145 USA
EMail: nabil.bitar@verizon.com
Igor Bryskin
Independent Consultant
EMail: i_bryskin@yahoo.com
Dean Cheng
Cisco Systems, Inc.
3700 Cisco Way
San Jose CA 95134 USA
Phone: 408 527 0677
EMail: dcheng@cisco.com
Durga Gangisetti
MCI
EMail: durga.gangisetti@mci.com
Kenji Kumaki
KDDI Corporation
Garden Air Tower
Iidabashi, Chiyoda-ku,
Tokyo 102-8460, JAPAN
Phone: 3-6678-3103
EMail: ke-kumaki@kddi.com
Eiji Oki
NTT
Midori-cho 3-9-11
Musashino-shi, Tokyo 180-8585, JAPAN
EMail: oki.eiji@lab.ntt.co.jp
Raymond Zhang
BT INFONET Services Corporation
2160 E. Grand Ave.
El Segundo, CA 90245 USA
EMail: Raymond_zhang@bt.infonet.com
9. Acknowledgements
The authors would like to extend their warmest thanks to (in The authors would like to extend their warmest thanks to (in
alphabetical order) Lou Berger, Ross Callon, Adrian Farrel, Thomas alphabetical order) Lou Berger, Ross Callon, Adrian Farrel, Thomas
Morin, Dimitri Papadimitriou, Robert Sparks, and JP Vasseur for their Morin, Dimitri Papadimitriou, Robert Sparks, and J.P. Vasseur for
review and suggestions. their review and suggestions.
11. Normative References 10. References
[PCE-ARCH] Farrel, A., Vasseur, JP, Ash, J., "Path Computation 10.1. Normative References
Element (PCE) Architecture", work in progress.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to
Requirement Levels", BCP 14, RFC 2119, March 1997. Indicate Requirement Levels", BCP 14, RFC 2119,
March 1997.
12. Informational References [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture",
RFC 4655, August 2006.
[METRIC] Le Faucheur, F., et. al., "Use of Interior Gateway Protocol 10.2. Informative References
(IGP) Metric as a second MPLS Traffic Engineering (TE) Metric", BCP
87, RFC 3785, May 2004.
[PCE-DISC-REQ] Le Roux, JL, et. al., "Requirements for Path [METRIC] Le Faucheur, F., Uppili, R., Vedrenne, A.,
Computation Element (PCE) Discovery," work in progress. Merckx, P., and T. Telkamp, "Use of Interior
Gateway Protocol (IGP) Metric as a second MPLS
Traffic Engineering (TE) Metric", BCP 87, RFC
3785, May 2004.
[PCECP-INTER-AREA] Le Roux, JL, et. al., "PCE Communication Protocol [PCE-DISC-REQ] Le Roux, J.L., et al., "Requirements for Path
(PCECP) specific requirements for Inter-Area (G)MPLS Traffic Computation Element (PCE) Discovery", Work in
Engineering," work in progress. Progress.
[PCECP-INTER-LAYER] Oki, E., et. al., "PCC-PCE Communication [PCECP-INTER-AREA] Le Roux, J.L., et al., "PCE Communication
Requirements for Inter-Layer Traffic Engineering," work in progress. Protocol (PCECP) specific requirements for
Inter-Area (G)MPLS Traffic Engineering", Work in
Progress.
[RFC3209] Awduche, D., et. al., "RSVP-TE: Extensions to RSVP for LSP [PCECP-INTER-LAYER] Oki, E., et al., "PCC-PCE Communication
Tunnels," RFC 3209, December 2001. Requirements for Inter-Layer Traffic
Engineering", Work in Progress.
[RFC3127] Mitton, D., et. al., "Authentication, Authorization, and [PCECP-INTER-AS] Bitar, N., Zhang, R., Kumaki, K., "Inter-AS
Accounting: Protocol Evaluation," RFC 3127, June 2001. Requirements for the Path Computation Element
Communication Protocol (PCECP)", Work in
Progress.
13. Authors' Addresses [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T.,
Srinivasan, V., and G. Swallow, "RSVP-TE:
Extensions to RSVP for LSP Tunnels", RFC 3209,
December 2001.
[RFC3127] Mitton, D., St.Johns, M., Barkley, S., Nelson,
D., Patil, B., Stevens, M., and B. Wolff,
"Authentication, Authorization, and Accounting:
Protocol Evaluation", RFC 3127, June 2001.
Authors' Addresses
Jerry Ash (Editor) Jerry Ash (Editor)
AT&T AT&T
Room MT D5-2A01 Room MT D5-2A01
200 Laurel Avenue 200 Laurel Avenue
Middletown, NJ 07748, USA Middletown, NJ 07748, USA
Phone: (732)-420-4578 Phone: (732)-420-4578
Email: gash@att.com EMail: gash@att.com
Jean-Louis Le Roux (Editor) Jean-Louis Le Roux (Editor)
France Telecom France Telecom
2, avenue Pierre-Marzin 2, avenue Pierre-Marzin
22307 Lannion Cedex, FRANCE 22307 Lannion Cedex, FRANCE
Email: jeanlouis.leroux@francetelecom.com
Intellectual Property Statement EMail: jeanlouis.leroux@orange-ft.com
Full Copyright Statement
Copyright (C) The Internet Society (2006).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
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The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
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skipping to change at page 19, line 11 skipping to change at page 21, line 45
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This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2006). This document is subject Funding for the RFC Editor function is provided by the IETF
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