Network Working Group Fatai Zhang
Internet-Draft Huawei
Intended status: Standards Track A. Farrel
Old Dog Consulting
G. Bernstein
Grotto Networking
Expires: June 2, 2012 December 2, 2011
Conveying Vendor-Specific Constraints in the Path
Computation Element Protocol
draft-ietf-pce-vendor-constraints-05.txt
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with
the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as "work in
progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on June 2, 2012.
Abstract
The Path Computation Element Protocol (PCEP) is used to convey path
computation requests and responses between Path Computation Clients
(PCCs) and Path Computation Elements (PCEs), and also between
Farrel & Zhang Expires June 2012 [Page 1]
draft-ietf-pce-vendor-constraints-05.txt December 2011
cooperating PCEs. In PCEP the path computation requests carry
details of the constraints and objective functions that the PCC
wishes the PCE to apply in its computation.
The mechanisms defined for indicating objective functions include
the capability to convey vendor-specific objective functions. This
document defines a facility to carry vendor-specific constraints in
PCEP.
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].
Table of Contents
1. Introduction ................................................ .2
2. Procedures .................................................. .4
3. Protocol Elements ........................................... .6
4. IANA Considerations ......................................... .7
5. Management Considerations .................................. .7
5.1. Control of Function and Policy ......................... .8
5.2. Information and Data Models............................. .8
5.3. Liveness Detection and Monitoring ...................... .8
5.4. Verifying Correct Operation.............................. 8
5.5. Requirements on Other Protocols and Functional Components 8
5.6. Impact on Network Operation.............................. 9
6. Security Considerations ...................................... 9
7. References ................................................... 9
7.1. Normative References .................................... 9
7.2. Informative References ................................. 10
8. Acknowledgements ............................................. 11
9. Authors' Addresses ........................................... 11
1. Introduction
A Path Computation Element (PCE) is an entity (component,
application or network node) that is capable of computing a network
path or route based on a network graph and applying computational
constraints. An architecture for the use of PCEs is defined in
[RFC4655].
Farrel & Zhang Expires June 2012 [Page 2]
draft-ietf-pce-vendor-constraints-05.txt December 2011
The Path Computation Element Protocol (PCEP) is defined in [RFC5440]
to exchange path computation requests and responses between Path
Computation Clients (PCCs) and PCEs. It is also used between
cooperating PCEs.
Path computations performed by a PCE depend on a set of constraints
indicated by the PCC. These constraints include the end points of
the path to compute (source and destination), and may include other
simple constraints such as bandwidth requirements and metric maxima
(for example, a maximum threshold for the hop count or the TE metric
of the computed path).
The PCE also needs to use some objective function to qualify the
path it selects as meeting the requirements of the PCC. The PCE may
have a default objective function, but the PCC can also indicate
which objective function it wants applied by placing an Objective
Function object in the path computation request message [RFC5541]. A
core set of objective functions to be supported in PCEP messages is
defined in the base PCEP requirements [RFC4657], and [RFC5541]
defines each of these functions as an abstract formula.
The registry of codepoints used to indicate objective functions is
managed by IANA and can be extended in future documents. PCE
implementations may choose to offer proprietary, vendor-specific
objective functions, and there is scope for this within the
codepoint registry created by [RFC5541]. That is, in the "PCE
Objective Function" code point registry managed by IANA, the rules
for the assignment of objective function code point values are as
follows (using terms defined in [RFC5226])
o Function code values 1 through 1023 are assigned by IANA using the
"IETF Review" policy.
o Function code values 1024 through 32767 are assigned by IANA,
using the "First Come First Served" policy.
o Function code values in the range 32768-65535 are for "Private
Use".
Proprietary objective functions may operate on non-standard
constraints or metrics. The PCEP Metric Object defined in [RFC5440]
has scope for the definition of new, standardized metrics, but no
facility for the definition of vendor-specific metrics. At the same
time, there is no mechanism in PCEP for carrying other, more complex,
vendor-specific constraints.
Farrel & Zhang Expires June 2012 [Page 3]
draft-ietf-pce-vendor-constraints-05.txt December 2011
This document defines a new PCEP object, the Vendor Constraints
object that can be used to carry arbitrary constraint information.
This document also defines a new PCEP TLV, the VENDOR-CONSTRAINT-TLV
that can be used to carry arbitrary constraint information within an
existing PCEP object.
2. Procedures
A PCC that wants to convey proprietary or vendor-specific
constraints or metrics to a PCE does so by including a Vendor
Constraints object in the PCReq message. The contents and format of
the object are described in Section 3, but it is important to note
that the object includes an Enterprise Number that is a unique
identifier of an organization responsible for the definition of the
content and meaning of the object.
A PCC that wants to convey endpoints-specific vendor specific
constraints to a PCE may do so by including a Vendor Constraints TLV
in the endpoint-restriction-list of the END-POINTS with object type
Generalized Endpoint.
This Vendor Constraints TLV MAY also present in PCEP Objects
supporting TLVs and using the registry for the PCEP TLVs, to
indicate a vendor-specific constraint that applies to the PCEP
object.
A PCE that receives a PCReq message containing a Vendor Constraints
object MUST act according to the P-bit in the object header. That is,
if the P-bit is set, the object MUST be treated as mandatory and the
request must either be processed using the contents of the object or
rejected as defined in [RFC5440]. If the P-bit is clear, the object
MAY be used by the PCE or MAY be ignored. The PCC sets the P-bit
according to how it wishes the request to be processed.
The PCE determines how to interpret the Vendor Constraints object or
TLV by examining the Enterprise Number it contains.
The Vendor Constraints object is optional in a PCReq message.
Multiple instances of the object MAY be used on a single PCReq
message and each MUST be treated according to its P-bit setting. The
object can be present in two places within the PCReq message to
enable it to apply to a single path computation request or to a set
of synchronized requests. This usage mirrors the usage of the
Objective Function object [RFC5541]. Thus, the PCReq message based
Farrel & Zhang Expires June 2012 [Page 4]
draft-ietf-pce-vendor-constraints-05.txt December 2011
on [RFC6006] is encoded as follows using the syntax described in
[RFC5511].
<PCReq Message> ::= <Common Header>
[<svec_list>]
<request-list>
where
<svec-list> ::= <SVEC>
[<OF>]
[<GC>]
[<XRO>]
[<metric-list>]
[<vendor-constraint-list>]
[<svec-list>]
<metric-list> ::= <METRIC>
[<metric-list>]
<vendor-constraint-list> ::= <VENDOR-CONSTRAINT>
[<vendor-constraint-list>]
<request-list>::= <request>
[<request-list>]
<request>::= <RP>
[<vendor-constraint-list>]
<end-point-rro-pair-list>
[<LSPA>]
[<BANDWIDTH>]
[<metric-list>]
[<OF>]
[<RRO>]
[<IRO>]
[<LOAD-BALANCING>]
where
<end-point-rro-pair-list> ::=
<END-POINTS>
[<RRO-List>]
[<BANDWIDTH>]
[<vendor-constraint-list>]
[<end-point-rro-pair-list>]
<RRO-List>::=<RRO>[<BANDWIDTH>][<RRO-List>]
<metric-list>::=<METRIC>[<metric-list>]
Farrel & Zhang Expires June 2012 [Page 5]
draft-ietf-pce-vendor-constraints-05.txt December 2011
The Vendor Constraints object is included in a PCRep message in
exactly the same way as any other object as defined in [RFC5440].
The Vendor Constraints TLV is optional in the END-POINTS with object
type Generalized Endpoint. The vendor restriction TLV MAY be
inserted at any place in the endpoint-restriction-list.
The VENDOR-CONSTRAINT-TLV MUST be taken into account. If the P flag
of the containing object is set, but the PCE does not understand the
TLV and its enterprise number, the entire PCEP message MUST be
rejected and the PCE MUST send a PCErr message with Error-
Type="Reception of an invalid object" and Error-Value="Unsupported
VENDOR-CONSTRAINT-TLV" along with the corresponding object.
When present in the END-POINTS with object type Generalized Endpoint
the endpoint-restriction-list is encoded as follow:
<endpoint-restriction> ::=
<LABEL-REQUEST><label-restriction-list>|
<VENDOR-CONSTRAINT-TLV>]|
3. Protocol Elements
The Vendor Constraints object and TLV conform to the format for PCEP
objects and TLVs defined in [RFC5440].
VENDOR-CONSTRAINT Object-Class is to be assigned by IANA
(recommended value=23).
VENDOR-CONSTRAINT Object-Type is to be assigned by IANA
(recommended value=1)
VENDOR-CONSTRAINT-TLV Type is to be assigned by IANA (recommended
value=16)
The format of the VENDOR-CONSTRAINT object, VENDOR-CONSTRAINT-TLV
body is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Enterprise Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Enterprise-Specific Information ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Farrel & Zhang Expires June 2012 [Page 6]
draft-ietf-pce-vendor-constraints-05.txt December 2011
Enterprise Number
A unique identifier of an organization encoded as a 32-bit integer.
Enterprise Numbers are assigned by IANA and managed through an IANA
registry [RFC2578].
Enterprise-Specific Information
The detailed enterprise-specific constraint information carried by
the object. The format and interpretation of this information is a
matter for the enterprise identified by the Enterprise Number. Such
formats and interpretation MAY be published by the enterprise
(possibly through an informational RFC or through commercial
documentation) so that PCCs or PCEs that are not part of the
organization can use the information.
4. IANA Considerations
IANA maintains a registry of PCEP parameters. This includes sub-
registry for PCEP Objects and PCEP TLV Type Indicators.
IANA is requested to make an allocation from the sub-registry PCEP
Objects as follows. The values here are suggested for use by IANA.
Object Name Reference Class
23 VENDOR-CONSTRAINT [This.I-D]
Object-Type
1: Vendor-Specific Constraints [This.I-D]
IANA is requested to do the following allocations in the "PCEP TLV
Type Indicators" as follow. The Values are suggested for use by IANA.
Value Meaning Reference
16 Vendor Constraint TLV [This.I-D]
IANA is requested to make an allocation from the sub registry "PCEP-
ERROR Object Error Types and Values" as follow. The Values are
suggested for use by IANA.
Error Name Reference
Type
10 Reception of an invalid object
Error-Value=8 Unsupported VENDOR-CONSTRAINT-TLV [This.I-D]
5. Management Considerations
This section follows the guidance of [MANAGE].
Farrel & Zhang Expires June 2012 [Page 7]
draft-ietf-pce-vendor-constraints-05.txt December 2011
5.1. Control of Function and Policy
A PCEP implementation SHUOLD allow configuring of various parameters
as described in [RFC5440]. A PCC implementation that uses vendor-
specific constraints MAY make the use of these constraints
configurable either across the whole PCC, per PCE that the PCC uses,
or per path computation request. A PCE that supports vendor-specific
constraints MAY make the support of these constraints configurable,
and MAY allow configuration of policies for the use of the
constraints.
5.2. Information and Data Models
A PCEP MIB module is defined in [PCE-MIB] that describes managed
objects for modeling of PCEP communications.
It is NOT RECOMMENDED that standard MIB modules are extended to
include detailed information about the content of the Vendor
Constaints object. However, the standard MIB module MAY be extended
to report the use of the Vendor Specific object and the Enterprise
Numbers that the objects contain.
5.3. Liveness Detection and Monitoring
This document makes no change to the basic operation of PCEP and so
there are no changes to the requirements for liveness detection and
monitoring set out in [RFC4657] and [RFC5440].
5.4. Verifying Correct Operation
This document makes no change to the basic operation of PCEP and so
there are no changes to the requirements or techniques for
monitoring the correct operation of the protocol out in [RFC4657]
and [RFC5440].
Note that "correct operation" in this context referes to the
operation of the protocol itself, and not to the operation of the
computation algorithms which are out of scope for all PCEP work.
Mechanisms for verifying the correct operation of computation
algorithms might involve comparing the results returned by more than
one PCE. Scope for this might be limited by the use of vendor
constraints unless multiple PCEs support the same set of constraints.
5.5. Requirements on Other Protocols and Functional Components
This document does not place any new requirements on other network
components or protocols. However, it may be beneficial to consider
Farrel & Zhang Expires June 2012 [Page 8]
draft-ietf-pce-vendor-constraints-05.txt December 2011
whether a PCE should advertise the enterprise numbers and vendor
constraints it supports. This advertisement could be within PCE
Discovery ([RFC5088], [RFC5089]) or through extensions to PCEP
[RFC5440].
Extensions for discovery and advertisement are outside the scope of
this document.
5.6. Impact on Network Operation
The availability of vendor constraints in PCEP messages may
facilitate more complex and detailed path computations that may
enhance the way in which the network is operated.
On the other hand, the presence of additional vendor-specific
information in PCEP messages may congest the operation of the
protocol especially if the PCE does not support the constraints
supplied by the PCC. Thus, a PCC SHOULD monitor the capabilities of
a PCE either by discovery mechanisms as described in Section 5.5, or
through the receipt of negative responses. A PCC SHOULD NOT include
vendor constraints in a PCReq message to a PCE that it believes does
not support the constraints and that will not forward the request to
some other PCE that does support the constraints.
6. Security Considerations
The protocol extensions defined in this document do not
substantially change the nature of PCEP. Therefore, the security
considerations set out in [RFC5440] apply unchanged.
Operators should note that an attack on PCEP may involve making PCEP
messages as large as possible in order to consume bandwidth and
processing power. The Vendor Constraints object may provide a
mechanism for this type of attack. It may be protected against by
using the authentication and integrity procedures described in
[RFC5440].
7. References
7.1. Normative References
[RFC2119] S. Bradner, "Key words for use in RFCs to indicate
requirements levels", RFC 2119, March 1997.
Farrel & Zhang Expires June 2012 [Page 9]
draft-ietf-pce-vendor-constraints-05.txt December 2011
[RFC5440] Vasseur, J.P., Le Roux, J.L., Ayyangar, A., Oki, E.,
Ikejiri, A., Atlas, A., Dolganow, A., "Path Computation
Element (PCE) communication Protocol (PCEP)", RFC 5440,
March 2009.
[RFC5511] Farrel, A., "Reduced Backus-Naur Form (RBNF): A Syntax to
Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, April 2007.
[RFC6006] Q. Zhao, et al., "Extensions to the Path Computation
Element Communication Protocol (PCEP) for Point-to-
Multipoint Traffic Engineering Label Switched Paths", RFC
6006, September 2009.
7.2. Informative References
[RFC2578] McCloghrie, K., Perkins, D., and J. Schoenwaelder,
"Structure of Management Information Version 2 (SMIv2)",
STD 58, RFC 2578, April 1999.
[RFC4655] Farrel, A., Vasseur, J.P., Ash, J., "Path Computation
Element (PCE) Architecture", RFC 4655, August 2006.
[RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE)
Communication Protocol Generic Requirements", RFC 4657,
September 2006.
[RFC5088] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"OSPF Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5088, January 2008.
[RFC5089] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"IS-IS Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5089, January 2008.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Objective
Function Encoding in Path Computation Element
Communication and Discovery protocols", RFC 5541, June
2009.
[MANAGE] Farrel, A., "Inclusion of Manageability Sections in PCE
Working Group Drafts", draft-ietf-pce-manageability-
requirements, work in progress.
Farrel & Zhang Expires June 2012 [Page 10]
draft-ietf-pce-vendor-constraints-05.txt December 2011
[PCE-MIB] Stephan, E. and K. Koushik, "PCE Communication Protocol
(PCEP) Management Information Base", draft-ietf-pce-pcep-
mib, work in progress.
8. Acknowledgements
Thanks to Meral Shirazipour, Ramon Casellas and Cyril Margaria for
review and comments.
9. Authors' Addresses
Adrian Farrel
Old Dog Consulting
EMail: adrian@olddog.co.uk
Fatai Zhang
Huawei Technologies
Email: zhangfatai@huawei.com
Greg Bernstein
Grotto Networking
EMail: gregb@grotto-networking.com
Intellectual Property
The IETF Trust takes no position regarding the validity or scope of
any Intellectual Property Rights or other rights that might be
claimed to pertain to the implementation or use of the technology
described in any IETF Document or the extent to which any license
under such rights might or might not be available; nor does it
represent that it has made any independent effort to identify any
such rights.
Copies of Intellectual Property disclosures made to the IETF
Secretariat and any assurances of licenses to be made available, or
the result of an attempt made to obtain a general license or
permission for the use of such proprietary rights by implementers or
users of this specification can be obtained from the IETF on-line
IPR repository at http://www.ietf.org/ipr
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
Farrel & Zhang Expires June 2012 [Page 11]
draft-ietf-pce-vendor-constraints-05.txt December 2011
rights that may cover technology that may be required to implement
any standard or specification contained in an IETF Document. Please
address the information to the IETF at ietf-ipr@ietf.org.
The definitive version of an IETF Document is that published by, or
under the auspices of, the IETF. Versions of IETF Documents that are
published by third parties, including those that are translated into
other languages, should not be considered to be definitive versions
of IETF Documents. The definitive version of these Legal Provisions
is that published by, or under the auspices of, the IETF. Versions
of these Legal Provisions that are published by third parties,
including those that are translated into other languages, should
not be considered to be definitive versions of these Legal
Provisions.
For the avoidance of doubt, each Contributor to the IETF Standards
Process licenses each Contribution that he or she makes as part of
the IETF Standards Process to the IETF Trust pursuant to the
provisions of RFC 5378. No language to the contrary, or terms,
conditions or rights that differ from or are inconsistent with the
rights and licenses granted under RFC 5378, shall have any effect
and shall be null and void, whether published or posted by such
Contributor, or included with or in such Contribution.
Disclaimer of Validity
All IETF Documents and the information contained therein are
provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION
HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET
SOCIETY, THE IETF TRUST 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 THEREIN
WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Full Copyright Statement
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
Farrel & Zhang Expires June 2012 [Page 12]
draft-ietf-pce-vendor-constraints-05.txt December 2011
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Farrel & Zhang Expires June 2012 [Page 13]
