Network Working Group J.L. Le Roux Internet Draft France Telecom Category: Standard Track Expires: August 2008 J.P. Vasseur Cisco System Inc. Y. Lee Huawei March 2008 Encoding of Objective Functions in Path Computation Element communication Protocol (PCEP) draft-ietf-pce-of-02.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 1] Internet Draft draft-ietf-pce-of-02.txt March 2008 Abstract The computation of one or a series of Traffic Engineering Label Switched Paths (TE LSPs) in MultiProtocol Label Switching (MPLS) and Generalized MPLS (GMPLS) networks, is subject to a set of one or more specific optimization criteria(s), referred to as an objective function (e.g. minimum cost path, widest path, etc.). A Path Computation Element (PCE) may support one or multiple objective functions, and it is desired for a Path Computation Client (PCC) to automatically discover the set of objective functions supported by a PCE. Furthermore, it may be useful for a PCC to specify in a path computation request the required objective function to be used by the PCE to compute a TE LSP or a set of TE LSPs. Thus the aim of this document is to define extensions to the PCE communication Protocol (PCEP) in order to allow a PCC to discover the set of objective functions supported by a PCE as well as to allow a PCC to indicate in a path computation request the required objective function and a PCE to indicate in a path computation reply the objective function that was used for path computation. 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. Table of Contents 1. Terminology.................................................3 2. Introduction................................................3 3. Discovery of PCE Objective Functions........................5 3.1. OF-List TLV.................................................5 3.2. Elements of procedure.......................................6 4. Objective Function in PCEP Path Computation request and reply messages............................................6 4.1. OF Object...................................................6 4.1.1. Elements of Procedure.......................................7 4.2. Carrying the OF object in a PCEP message....................8 4.3. New RP object flag.........................................10 4.3.1. Elements of procedure......................................10 5. Objective Functions definition.............................10 6. IANA Considerations........................................12 6.1. PCE Objective Function registry............................12 6.2. PCEP code points...........................................13 6.2.1. OF Object..................................................13 6.2.2. OF-List TLV................................................13 6.2.3. PCEP Error values..........................................13 6.2.4. RP Object flag.............................................14 7. Security Considerations....................................14 8. Manageability Considerations...............................14 8.1. Control of Function and Policy.............................14 Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 2] Internet Draft draft-ietf-pce-of-02.txt March 2008 8.2. Information and Data Models................................14 8.3. Liveness Detection and Monitoring..........................15 8.4. Verify Correct Operations..................................15 8.5. Requirements on other protocols............................15 8.6. Impact on network operations...............................15 9. Acknowledgments............................................15 10. References.................................................15 10.1. Normative references.......................................15 10.2. Informative references.....................................16 11. Author's Addresses:........................................16 12. Intellectual Property Statement............................17 1. Terminology Terminology used in this document LSR: Label Switching Router. OF: Objective Function: A set of one or more optimization criteria(s) used for the computation of a single path (e.g. path cost minimization), or the synchronized computation of a set of paths (e.g. aggregate bandwidth consumption minimization, etc.). PCC: Path Computation Client: Any client application requesting a path computation to be performed by a Path Computation Element. PCE: Path Computation Element: An entity (component, application, or network node) that is capable of computing a network path or route based on a network graph, and applying computational constraints. PCEP: Path Computation Element communication Protocol. TE LSP: Traffic Engineered Label Switched Path. 2. Introduction The PCE-based network architecture [RFC4655] defines a Path Computation Element (PCE) as an entity capable of computing TE LSP paths based on a network graph, and applying computational constraints. A PCE serves path computation requests sent by Path Computation Clients (PCC). The PCE communication Protocol (PCEP), defined in [PCEP], allows for communication between a PCC and a PCE or between two PCEs, in compliance with requirements and guidelines set forth in [RFC4657]. Such interactions include path computation requests and path computation replies. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 3] Internet Draft draft-ietf-pce-of-02.txt March 2008 The computation of one or a set of TE LSPs is subject to a set of one or more optimization criteria(s), called an objective function. An objective function is used by the PCE, when it computes a path or a set of paths, in order to select the "best" candidate path(s). There is a variety of objective functions: an objective function could apply either to a set of non synchronized path computation requests, or to a set of synchronized path computation requests. In the former case, the objective function refers to an individual path computation request (e.g. computation of the shortest constrained path where the metric is the IGP metric, computation of the least loaded constrained path, etc.). Conversely in the latter case, the objective function refers to a set of path computation requests the computation of which is synchronized (e.g. minimize the aggregate bandwidth consumption of all LSPs, minimize the sum of the delays for two diverse paths, or the delta between those delays, etc.). Moreover, some objective functions relate to the optimization of a single metric and others to the optimization of a set of metrics (organized in a hierarchical manner, using a weighted function, etc.). As spelled out in [RFC4674], it may be useful for a PCC to discover the set of objective functions supported by a PCE. Furthermore, [RFC4657] requires the ability for a PCC to indicate in a path computation request a required/desired objective function, as well as optional function parameters. For these purposes, this document extends the PCE communication Protocol (PCEP). It defines PCEP extensions allowing a PCE advertising a list of supported objective functions, as well as extensions so as to carry the objective function in PCEP request and reply messages. It thus complements the PCEP base specification [PCEP]. Note that IS-IS and OSPF based PCE Discovery mechanisms are defined in ([RFC5089], [RFC5088]). These mechanisms are dedicated to the discovery of a few generic parameters while more detailed PCE parameters should rather be discovered using the PCE communication Protocol. Objective functions pertain to this second category; thus the Objective Function discovery procedure is handled by PCEP. A new PCEP TLV, named the OF-List TLV is defined in section 3. The OF-List TLV is carried in the PCEP OPEN object and allows a PCE advertising to a PCEP peer, during PCEP session setup phase, the list of objective functions that it supports. A new PCEP object, the OF object, is defined in section 4. The OF object is carried within a PCReq message to indicate the required/desired objective function to be applied by a PCE or in a PCRep message to indicate the objective function that was used for path computation. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 4] Internet Draft draft-ietf-pce-of-02.txt March 2008 Six mandatory objective functions that must be supported by PCEP are listed in [RFC4657]. This document provides a definition of these six mandatory objective functions. Additional objective functions may be defined in other documents. Note that additional objective functions are defined for PCE Global Concurrent Optimization (GCO) application, in [PCE-GCO]. 3. Discovery of PCE Objective Functions This section defines PCEP extensions (see [PCEP]) so as to support the advertisement of the objective functions supported by a PCE. A new PCEP OF-List (Objective Function list) TLV is defined. The PCEP OF-List TLV is carried within an OPEN object, in order for a PCE to advertise to a PCEP peer the list of objective functions it supports, during PCEP session setup phase. 3.1. OF-List TLV The PCEP OF-List TLV is optional. It MAY be carried within an OPEN object sent by a PCE in an Open message to a PCEP peer, so as to indicate the list of supported objective functions. The OF-List TLV format is compliant with the PCEP TLV format defined in [PCEP]. That is, the TLV is composed of 2 octets for the type, 2 octets specifying the TLV length, and a value field. The Length field defines the length of the value portion in octets. The TLV is padded to four-octet alignment and padding is not included in the Length field (e.g. a three octet value would have a length of three, but the total size of the TLV would be eight octets). The OSPF OF-List TLV has the following format: TYPE: To be assigned by IANA (suggested value = 4 ) LENGTH: N * 2 (where N is the number of objective functions) VALUE: list of 2-bytes objective function code points, identifying the objective functions supported by the sender of the Open message. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OF Code #1 | OF Code #2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OF Code #N | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 5] Internet Draft draft-ietf-pce-of-02.txt March 2008 OF Code (2 bytes): Objective Function code point identifier. IANA is requested to manage the PCE objective function code point registry (see IANA section). 3.2. Elements of procedure A PCE MAY include and OF-List TLV within an OPEN object in an Open message sent to a PCEP peer, to advertise a set of one or more objective functions. The OF-List TLV MUST NOT appear more than once in an OPEN object. The absence of the OF-List TLV in an OPEN object must be interpreted as an absence of information on the list of supported objective functions by the PCE. As specified in [PCEP], a PCEP peer that does not recognize the OF- List TLV will silently ignore it. 4. Objective Function in PCEP Path Computation request and reply messages This section defines PCEP extensions ([PCEP]) so as to support the communication of objective functions in PCEP path computation request and reply messages. A new PCEP OF (Objective Function) object is defined, to be carried within a PCReq message in order for the PCC to indicate the required/desired objective function. The PCEP OF Object may also be carried within a PCRep message in order for the PCE to indicate the objective function that was used by the PCE. A new flag is defined in the RP object, so as to indicate in a PCReq message that the PCE MUST provide in the PCRep message the objective function that was used during path computation. Also new PCEP error type and value are defined. 4.1. OF Object The PCEP OF (Objective Function) object is optional. It MAY be carried within a PCReq message so as to indicate the desired/required objective function to be applied by the PCE during path computation, or within a PCRep message so as to indicate the objective function that was used by the PCE during path computation. The OF object format is compliant with the PCEP object format defined in [PCEP]. The OF Object-Class is to be assigned by IANA (recommended value=21). Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 6] Internet Draft draft-ietf-pce-of-02.txt March 2008 The OF Object-Types is to be assigned by IANA (recommended value=1). The format of the OF object body is: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Objective Function Code(IANA) | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional TLV(s) // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Objective Function Code (2 bytes): The identifier of the Objective Function. The IANA is requested to manage the PCE objective function code point registry (see IANA section). Reserved (2 bytes): This field MUST be set to zero on transmission and MUST be ignored on receipt. Optional TLVs may be defined so as to encode objective function parameters. 4.1.1. Elements of Procedure To request the use of a specific objective function to be used by the PCE a PCC MUST include an OF object in the PCReq message. [PCEP] specifies a bit flag referred to as the P bit in a PCEP common header that can be set by a PCC to enforce a PCE to take into account the related information during the path computation. If the objective function is mandatory (required objective function), the P bit in the OF object MUST be set, else if it is optional (desired objective function) the P bit MUST be cleared. On receipt of a PCReq message with an OF object, a PCE MUST proceed as follows: - If the OF object is unknown/unsupported, the PCE MUST follow procedures defined in [PCEP], that is if the P bit is set, it sends a PCErr message with error type unknown/unsupported object (type 3 and 4) and the related path computation request MUST be discarded. If the P bit is cleared it is free to ignore the object. - If the objective function is unknown / unsupported and the P bit is set, the PCE MUST send a PCErr message with a new PCEP error type "objective function error" and error value "unknown/unsupported objective function" (defined in this Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 7] Internet Draft draft-ietf-pce-of-02.txt March 2008 document), and the related path computation request MUST be discarded. - If the objective function is unknown / unsupported and the P bit is cleared, the PCE SHOULD apply another (default) objective function. - If the objective function is supported but policy does not permit applying it, and the P bit is set, the PCE MUST send a PCErr message with the PCEP error type "policy-violation" (type 5) and a new error value "objective function not allowed" (defined in this document). - If the objective function is supported but policy does not allow applying it, and the P bit is cleared, the PCE SHOULD apply another (default) objective function. - If the objective function is supported and policy allows applying it, then if the P bit is set the PCE MUST apply the requested objective function, else if the P bit is cleared the PCE is free to apply any other objective function. The default objective function may be locally configured. 4.2. Carrying the OF object in a PCEP message The OF object MAY be carried within a PCReq message. An OF object specifying an objective function that applies to a set of synchronized path computation requests MUST be carried just after the corresponding SVEC object, and MUST NOT be repeated for each elementary request. An OF object specifying an objective function that applies to an individual path computation request (non synchronized case) MUST follow the RP object for which it applies. The format of the PCReq message is updated as follows: ::= [] where: ::= [] [] ::=[] ::= Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 8] Internet Draft draft-ietf-pce-of-02.txt March 2008 [] [] [] [] [] [] [] where: ::=[] The OF object MAY be carried within a PCRep message to indicate the objective function used by the PCE during path computation. When the PCE wants to indicate to the PCC the objective function that was used for the synchronized computation of a set of paths, the PCRep message MUST include the corresponding SVEC object directly followed by the OF object, which MUST NOT be repeated for each elementary request. An OF object specifying an objective function used for an individual path computation (non synchronized case) MUST follow the RP object for which it applies. The format of the PCRep message is updated as follows: ::= [] where: ::= [] [] ::=[] ::= [] [] ::=[] ::= [] [] [] [] [] where: Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 9] Internet Draft draft-ietf-pce-of-02.txt March 2008 ::=[] Note: The OF object MUST NOT be associated to a negative reply, i.e. a reply with a NO-PATH object. 4.3. New RP object flag In some cases, where no objective function is specified in the request, or an optional objective function is desired (P flag cleared in the OF object common header) but the PCE does not follow the recommendation, the PCC may desire to know the objective function that was used by the PCE during path computation. To that end, a new flag is defined in the RP object, named the OF flag, allowing a PCC to request for the inclusion in the path computation reply of the objective function that was used by the PCE during path computation. The following new bit flag of the RP object is defined: Objective Function (OF) flag (1 bit): 0x200 (bit number 16) (suggested value, to be assigned by IANA). When set in a PCReq message, this indicates that the PCE has to provide the applied objective function (should a path satisfying the constraints be found) in the PCRep message. When set in a PCRep message this indicates that the Objective Function that was used during path computation is included. 4.3.1. Elements of procedure If the PCC wants to know the objective function used by the PCE during path computation for a given request, it MUST set the OF flag in the RP object. On receipt of a PCReq message with the OF flag in the RP object set, the PCE has to proceed as follows: - If policy permits it MUST include in the PCRep message an OF object indicating the objective function it used during path computation. - If policy does not permit, it MUST send a PCErr message with the PCEP error code "policy-violation" (type 5) and a new error value "objective function indication not allowed" (defined in this document). 5. Objective Functions definition Six objective functions that must be supported by PCEP are listed in [RFC4657]. Objective function codes should be assigned by IANA and are suggested below. Objective functions are formulated using the following terminology: Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 10] Internet Draft draft-ietf-pce-of-02.txt March 2008 - a network comprises a set of N links {Li, (i=1...N)} - a path P is a list of K links {Lpi,(i=1...K)} - metric of link L is noted M(L), this can be the IGP metric the TE metric or any other metric. - the cost of a path P is noted C(P), C(P) = sum {M(Lpi), (i=1...K)}. - residual bandwidth on link L is noted r(L) - maximum reservable bandwidth on link L is noted R(L). There are three objective functions that apply to the computation of a single path: Objective Function Code: 1 (suggested value, to be assigned by IANA) Name: Minimum Cost Path (MCP) Description: Find a path P such that C(P) is minimized. Objective Function Code: 2 (suggested value, to be assigned by IANA) Name: Minimum Load Path (MLP) Description: Find a path P such that ( Max {(R(Lpi) - r(Lpi)) / R(Lpi), i=1...K } ) is minimized Objective Function Code: 3 (suggested value, to be assigned by IANA) Name: Maximum residual Bandwidth Path (MBP) Description: Find a path P such that ( Min { r(Lpi)), i=1...K } ) is maximized. There are three objective functions that apply to a set of path computation requests the computation of which is synchronized: Objective Function Code: 4 (suggested value, to be assigned by IANA) Name: Minimize aggregate Bandwidth Consumption (MBC) Description: Find a set of paths such that ( Sum {R(Li) - r(Li), i=1...N} ) is minimized. Objective Function Code: 5 (suggested value, to be assigned by IANA) Name: Minimize the Load of the most loaded Link (MLL) Description: Find a set of paths such that ( Max { (R(Li) - r(Li)) / R(Li), i=1...N}) is minimized. Objective Function Code: 6 (suggested value, to be assigned by IANA) Name: Minimize the Cumulative Cost of a set of paths (MCC) Description: Find a set of paths {P1...Pm} such that (Sum { C(Pi), i=1...m}) is minimized. Other objective functions may be defined in separate documents. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 11] Internet Draft draft-ietf-pce-of-02.txt March 2008 6. IANA Considerations 6.1. PCE Objective Function registry This document defines a 16-bit PCE Objective Function identifier to be carried within the PCEP OF object, as well as the PCEP OF-List TLV. IANA is requested to create and manage the 16-bit "PCE Objective Function" code point registry, starting from 1 and continuing through 32767, as follows: - Objective Function code point value - Objective Function name - Defining RFC The same registry is applicable to the OF object and the OF-List TLV defined in this document. The guidelines (using terms defined in [RFC2434]) for the assignment of objective function code point values are as follows: - Function code value 0 is reserved. - Function code value in the range 1-32767 are to be assigned as follows: - Function code values 1 through 1023 are to be assigned by IANA using the "IETF Consensus" policy. - Function code values 1024 through 32767 are to be assigned by IANA, using the "First Come First Served" policy. - Function code values in the range 32768-65535 are for "Private Use". Six objective functions are defined in section 5 of this document and should be assigned by IANA: Code Point Name Defining RFC 1 MCP this doc 2 MLP this doc 3 MBP this doc 4 MBC this doc 5 MLL this doc 6 MCC this doc Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 12] Internet Draft draft-ietf-pce-of-02.txt March 2008 6.2. PCEP code points 6.2.1. OF Object The IANA has been requested to manage the PCEP Objects code point registry (see [PCEP]). This document defines a new PCEP object, the OF object, to be carried in PCReq and PCRep messages. The IANA is requested to make the following allocation (suggested value): Object Name Object Name Reference Class Type 21 OF 1 Objective (this document) Function 6.2.2. OF-List TLV IANA is requested to manage the PCEP TLV code point registry (see [PCEP]). This document defines a new PCEP TLV, the OF-List TLV, to be carried in the OPEN object. The IANA is requested to make the following allocation (suggested value): Type TLV name References ----- -------- ---------- 4 OF-List (This document) 6.2.3. PCEP Error values A new PCEP Error-Type is defined in this document, with two error values (Error-Type and Error-value to be assigned by IANA): Error-type Meaning and error values Reference 14 Objective Function Error (this doc) Error-value=1: unknown objective function (request rejected) Error-value=2: unsupported objective function (request rejected) Two new error values are defined for the error type "policy violation" (type 5): Error-type Meaning and error values Reference 5 Policy violation Error-value=3: objective function not allowed (this doc) (request rejected) Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 13] Internet Draft draft-ietf-pce-of-02.txt March 2008 Error-value=4: OF bit of the RP object set (this doc) (request rejected) 6.2.4. RP Object flag A new flag of the RP object (specified in [PCEP]) is defined in this document. The IANA is requested to make the following allocation (suggested value): Bit Hex Name Reference Number 16 0x200 OF (this document) 7. Security Considerations Mechanisms discussed in [PCEP] to secure a PCEP session can be used to secure the PCEP OF object and OF list TLV as well. 8. Manageability Considerations 8.1. Control of Function and Policy It MUST be possible to configure the activation/deactivation of Objective Function Discovery in PCEP. In addition to the parameters already listed in section 8.1 of [PCEP], a PCEP implementation SHOULD allow configuring on a PCE a list of authorized objective functions. This may apply to any session the PCEP speaker participates in, to a specific session with a given PCEP peer or to a specific group of sessions with a specific group of PCEP peers. Note that it is not mandatory for an implementation to support all objective functions defined in section 5. It MUST be possible to configure a default objective function used for path computation when a path request is received that requests to use an optional objective function. 8.2. Information and Data Models The PCEP MIB Module defined in [PCEP-MIB] MUST be extended to include Objective Functions. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 14] Internet Draft draft-ietf-pce-of-02.txt March 2008 8.3. Liveness Detection and Monitoring Mechanisms defined in this document do not imply any new liveness detection and monitoring requirements in addition to those already listed in [PCEP]. 8.4. Verify Correct Operations Mechanisms defined in this document do not imply any new operation verification requirements in addition to those already listed in [PCEP]. 8.5. Requirements on other protocols Mechanisms defined in this document do not imply any requirements on other protocols in addition to those already listed in [PCEP]. 8.6. Impact on network operations Mechanisms defined in this document do not have any impact on network operations in addition to those already listed in [PCEP]. 9. Acknowledgments The authors would like to thank Jerry Ash and Fabien Verhaeghe for their useful comments. 10. References 10.1. Normative references [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2740] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", RFC 2740, December 1999. [RFC3630] Katz, D., Yeung, D., Kompella, K., "Traffic Engineering Extensions to OSPF Version 2", RFC 3630, September 2003. [RFC3784] Li, T., Smit, H., "IS-IS extensions for Traffic Engineering", RFC 3784, June 2004. [RFC4655] Farrel, A., Vasseur, J.P., Ash, J., "Path Computation Element (PCE)-based Architecture", RFC4655, august 2006. [PCEP] Vasseur, Le Roux, et al., "Path Computation Element (PCE) communication Protocol (PCEP)", draft-ietf-pce-pcep, work in progress. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 15] Internet Draft draft-ietf-pce-of-02.txt March 2008 10.2. Informative references [RFC4657] Ash, J., Le Roux, J.L., " PCE Communication Protocol Generic Requirements", RFC4657, September 2006. [RFC4674] Le Roux, J.L., et al. "Requirements for PCE discovery", RFC4674, October 2006. [RFC5089] Le Roux, Vasseur, et al. "IS-IS protocol extensions for Path Computation Element (PCE) Discovery", RFC5089, January 2008. [RFC5088] Le Roux, Vasseur, et al. "OSPF protocol extensions for Path Computation Element (PCE) Discovery", RFC5088, January 2008. [PCE-GCO] Y. Lee, J.L. Le Roux, D. King, and E. Oki, "Path Computation Element Communication Protocol (PCECP) Requirements and Protocol Extensions In Support of Global Concurrent Optimization", draft-ietf-pce-global-concurrent-optimization, work in progress 11. Author's Addresses: Jean-Louis Le Roux France Telecom 2, avenue Pierre-Marzin 22307 Lannion Cedex FRANCE Email: jeanlouis.leroux@orange-ftgroup.com Jean-Philippe Vasseur Cisco Systems, Inc. 1414 Massachusetts avenue Boxborough , MA - 01719 USA Email: jpv@cisco.com Young Lee Huawei Technologies, LTD. 1700 Alma Drive, Suite 100 Plano, TX 75075 USA Email: ylee@huawei.com Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 16] Internet Draft draft-ietf-pce-of-02.txt March 2008 12. Intellectual Property Statement The IETF 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 this 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. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR 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 rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity 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, 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 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The IETF Trust (2008). 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. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 17]