Network Working Group J.L. Le Roux Internet Draft France Telecom Category: Standard Track Created: December 27, 2008 J.P. Vasseur Expires: June 27, 2009 Cisco System Inc. Y. Lee Huawei Encoding of Objective Functions in the Path Computation Element Communication Protocol (PCEP) draft-ietf-pce-of-06.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. Abstract The computation of one or a set 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, referred to as objective functions (e.g. minimum cost path, widest path, etc.). In the Path Computation Element (PCE) architecture, a Path Computation Client (PCC) may want a path to be computed for one or more TE LSPs according to a specific objective function. Thus, the PCC needs to instruct the PCE to use the correct objective function. Furthermore, it is possible that not all PCEs support the same set of objective functions, therefore it is useful for the PCC to be able to automatically discover the set of objective functions supported by each PCE. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 1] Internet Draft draft-ietf-pce-of-06.txt December 2008 This document defines extensions to the PCE communication Protocol (PCEP) to allow a PCE to indicate the set of objective functions it supports. Extensions are also defined so that a PCC can indicate in a path computation request the required objective function, and so that a PCE can report in a path computation reply the objective function that was used for path computation. This document defines objective function code types for six objective functions previously listed in the PCE requirments work, and provides the definition of four new metric types that apply to a set of synchronized requests. Table of Contents 1. Introduction................................................3 1.1. Terminology.................................................4 1.2. Message Formats.............................................5 2. Discovery of PCE Objective Functions........................5 2.1. OF-List TLV.................................................5 2.2. Elements of procedure.......................................6 3. Objective Function in PCEP Path Computation Request and Reply Messages............................................6 3.1. OF Object...................................................6 3.1.1. Elements of Procedure.......................................7 3.2. Carrying The OF Object In a PCEP Message....................8 3.3. New RP Object Flag.........................................10 3.3.1. Elements Of Procedure......................................10 4. Objective Functions Definition.............................11 5. New Metric Types...........................................12 6. IANA Considerations........................................13 6.1. PCE Objective Function Sub-registry........................13 6.2. PCEP Code Points...........................................14 6.2.1. OF Object..................................................14 6.2.2. OF-List TLV................................................14 6.2.3. PCEP Error values..........................................15 6.2.4. RP Object Flag.............................................15 6.2.5. Metric Types...............................................15 7. Security Considerations....................................16 8. Manageability Considerations...............................16 8.1. Control of Function and Policy.............................16 8.2. Information and Data Models................................16 8.3. Liveness Detection and Monitoring..........................16 8.4. Verify Correct Operations..................................17 8.5. Requirements On Other Protocols............................17 8.6. Impact On Network Operations...............................17 9. Acknowledgments............................................17 10. References.................................................17 10.1. Normative Feferences.......................................17 10.2. Informative References.....................................17 11. Authors' Addresses.........................................18 Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 2] Internet Draft draft-ietf-pce-of-06.txt December 2008 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 [RFC2119]. 1. Introduction The Path Computation Element-based network architecture [RFC4655] defines a Path Computation Element (PCE) as an entity capable of computing the paths of Traffic Engineered Label Switched Paths (TE LSPs) based on a network graph, and applying computational constraints. A PCE services 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. The computation of one or a set of TE LSPs is subject to a set of one or more optimization criteria, 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 paths. 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 to advertise a list of supported objective functions, as well as extensions to carry the objective function in PCEP request and reply Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 3] Internet Draft draft-ietf-pce-of-06.txt December 2008 messages. It 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 be discovered using the PCE communication Protocol. Objective functions are in 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 2. The OF-List TLV is carried in the PCEP OPEN object and allows a PCE to list, during PCEP session setup phase, the objective functions that it supports. A new PCEP object, the OF object, is defined in Section 3. 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. 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]. This document also provides the definition of four new metric types that apply to a set of synchronized requests. 1.1. Terminology LSR: Label Switching Router. OF: Objective Function: A set of one or more optimization criteria used for the computation of a single path (e.g. path cost minimization), or the synchronized computation of a set of paths (e.g., aggregate bandwidth consumption minimization, etc.). 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. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 4] Internet Draft draft-ietf-pce-of-06.txt December 2008 1.2. Message Formats Message formats in this document are expressed using Reduced BNF as used in [PCEP] and defined in [RBNF]. 2. 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. 2.1. 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 PCEP 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 | padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ OF Code (2 bytes): Objective Function code point identifier. IANA is requested to manage the PCE objective function code point registry (see Section 6). Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 5] Internet Draft draft-ietf-pce-of-06.txt December 2008 2.2. Elements of procedure A PCE MAY include an 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. If it appears more than once the PCEP session MUST be rejected with error type 1 and error value 1 (PCEP session establishment failure / Reception of an invalid Open message). 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. 3. 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. The flag is used in a PCReq message to indicate that the PCE MUST include an OF object in the PCRep message to indicate the objective function that was used during path computation. Also, new PCEP error types and values are defined. 3.1. 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). The OF Object-Type is to be assigned by IANA (recommended value=1). Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 6] Internet Draft draft-ietf-pce-of-06.txt December 2008 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. IANA is requested to manage the PCE objective function code point registry (see Section 6). Reserved (2 bytes): This field MUST be set to zero on transmission and MUST be ignored on receipt. Optional TLVs may be defined in the future so as to encode objective function parameters. 3.1.1. Elements of Procedure To request the use of a specific objective function by the PCE, a PCC includes an OF object in the PCReq message. [PCEP] specifies a bit flag, referred to as the P bit, carried in the common PCEP object header. The P bit is set by a PCC to mandate that a PCE must take the information carried in the object into account during the path computation. If the P bit is set in the OF object, the objective function is mandatory (required objective function) and the PCE MUST use the objective function during path computation. If the P bit is clear in the OF object, the objective function is optional (desired objective function) and the PCE SHOULD apply the function if it is supported, but MAY choose to apply a different objective function according to local capabilities and policies. 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 3 or 4 (Unknown / Not supported object) and error value 1 or 2 (unknown / unsupported object class / object type), and the related path computation request MUST be discarded. If the P bit is cleared it is free to ignore the object. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 7] Internet Draft draft-ietf-pce-of-06.txt December 2008 - If the objective function is unknown / unsupported and the P bit is set, the PCE MUST send a PCErr message with error type 3 or 4 (Unknown / Not supported Object) and error value 4 (Unrecognized / Unsupported parameter), 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. 3.2. Carrying The OF Object In a PCEP Message The OF object MAY be carried within a PCReq message. If an objective function is to be applied to a set of synchronized path computation requests, the OF object MUST be carried just after the corresponding SVEC object, and MUST NOT be repeated for each elementary request. Similarly if a metric is to be applied to a set of synchronized requests, the METRIC object MUST follow the SVEC object and MUST NOT be repeated for each elementary request. Note that metrics applied to a set of synchronized requests are defined in section 5. 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: ::= [] Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 8] Internet Draft draft-ietf-pce-of-06.txt December 2008 where: ::= [] [] [] ::= [] ::= [] [] [] [] [[]] [] [] and 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. If a metric is applicable to the set of paths, the METRIC object MUST directly follow the SVEC object and 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: ::= [] [] [] Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 9] Internet Draft draft-ietf-pce-of-06.txt December 2008 ::= [] ::= [] [] [] ::= [] ::= and where: ::= [] [] [] [] [] ::= [] Note: The OF object MAY be associated to a negative reply, i.e., a reply with a NO-PATH object. 3.3. 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 request, 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 (bit number 24) (suggested value, to be assigned by IANA). When set in a PCReq message, this indicates that the PCE MUST 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. 3.3.1. Elements Of Procedure If the PCC wants to know the objective function used by the PCE during path computation for a given request, it sets the OF flag in the RP object. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 10] Internet Draft draft-ietf-pce-of-06.txt December 2008 On receipt of a PCReq message with the OF flag in the RP object set, the PCE proceeds 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). Note that a legacy PCE might not recognize the OF flag in the RP object. According to the definition of the RP object Flag Field in Section 7.4.1 of [PCEP], the legacy PCE will ignore the unknown flag resulting in it sending a PCRep that does not contain an OF object. In this case, the PCC's beahvior is an implementation choice. The PCC might: - Discard the PCRep because it really wanted the OF object returned. - Accept the PCRep without the knowledge of the OF that was applied. Note also that these procedures can give rise to the situation where a PCC receives a PCRep that contains an OF object with an Objective Function identifier that the PCC does not recognize. In this situation the PCC behavior is dependent on implementaiton and configuration. The PCC could choose any of the following (or some other action): - Ignore the OF object and use the computed path. - Add the Objective Function to its view of the PCE's repetoire for inclusion in future computation requests. - Discard the PCRep (i.e., the computed path) and send a PCReq to another PCE. - Discard the PCRep (i.e., the computed path) and send another PCReq to the same PCE explicitly requiring the use of some other Objective Function (i.e., by setting the P bit in the OF object). 4. 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: - 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 denoted M(L), this can be the IGP metric the TE metric, or any other metric. - the cost of a path P is denoted C(P), where C(P) = sum {M(Lpi), (i=1...K)}. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 11] Internet Draft draft-ietf-pce-of-06.txt December 2008 - residual bandwidth on link L is denoted r(L) - maximum reservable bandwidth on link L is denoted 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. 5. New Metric Types Three metric types are defined in PCEP for the METRIC object: TE metric, IGP metric and hop count. These metric types apply to an individual request. Here we define four new metric types that apply to a set of synchronized requests: Type 4 (suggested value to be assigned by IANA) : Aggregate bandwidth consumption. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 12] Internet Draft draft-ietf-pce-of-06.txt December 2008 Type 5 (suggested value to be assigned by IANA) : Load of the most loaded link. Type 6 (suggested value to be assigned by IANA) : Cumulative IGP cost. Type 7 (suggested value to be assigned by IANA) : Cumulative TE cost. These metrics may be used to indicate a bound (B bit set in the METRIC object) or a computed metric (C bit set in the METRIC object). A METRIC object with one of these four types follows the SVEC object for which it applies. 6. IANA Considerations 6.1. PCE Objective Function Sub-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 [RFC5226]) for the assignment of objective function code point values are as follows: - Function code value 0 is reserved. - Function code values 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". Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 13] Internet Draft draft-ietf-pce-of-06.txt December 2008 Six objective functions are defined in Section 4 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 6.2. PCEP Code Points 6.2.1. OF Object IANA manages the PCEP Objects code point registry (see [PCEP]). This is maintained as the "PCEP Objects" sub-registry of the "Path Computation Element Protocol (PCEP) Numbers" registry. This document defines a new PCEP object, the OF object, to be carried in PCReq and PCRep messages. IANA is requested to make the following allocation (suggested value): Object Name Object Name Reference Class Type 21 OF 1 Objective Function (this document) 6.2.2. OF-List TLV IANA manages the PCEP TLV code point registry (see [PCEP]). This is maintained as the "PCEP TLV Type Indicators" sub-registry of the "Path Computation Element Protocol (PCEP) Numbers" registry. This document defines a new PCEP TLV, the OF-List TLV, to be carried in the OPEN object. IANA is requested to make the following allocation (suggested value): Type TLV name References ----- -------- ---------- 4 OF-List (This document) Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 14] Internet Draft draft-ietf-pce-of-06.txt December 2008 6.2.3. PCEP Error values IANA maintains a registry of Error-types and Error-values for use in PCEP messages. This is maintained as the "PCEP-ERROR Object Error Types and Values" sub-registry of the "Path Computation Element Protocol (PCEP) Numbers" registry. 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 (this doc) allowed (request rejected) Error-value=4: OF bit of the RP object (this doc) set (request rejected) 6.2.4. RP Object Flag A new flag of the RP object (specified in [PCEP]) is defined in this document. IANA maintains a registry of RP object flags in the "RP Object Flag Field" sub-registry of the "Path Computation Element Protocol (PCEP) Numbers" registry. IANA is requested to make the following allocation (suggested value): Bit Description Reference 24 Supply OF on response This document 6.2.5. Metric Types Four new metric types are defined in this document for the METRIC object (specified in [PCEP]). IANA maintains a registry of metric types in the "METRIC Object T Field" sub-registry of the "Path Computation Element Protocol (PCEP) Numbers" registry. IANA is requested to make the following allocation (suggested values): - Type 4 : Aggregate bandwidth consumption - Type 5 : Load of the most loaded link - Type 6 : Cumulative IGP cost - Type 7 : Cumulative TE cost Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 15] Internet Draft draft-ietf-pce-of-06.txt December 2008 7. Security Considerations PCEP security mechanisms are described in [PCEP] and are used to secure entire PCEP messages. Nothing in this document changes the message flows or introduces any new messages, so the security mechanisms set out in [PCEP] continue to be applicable. This document introduces a single new object that may optionally be carried on PCEP messages and will be automatically secured using the mechanims described in [PCEP]. If a PCEP message is vulnerable to attack, for example because the security mechanisms are not used, then the OF object could be used as part of an attack, however, it is likely that other objects will provide far more significant ways of attacking a PCE or PCC in this case. 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 4. 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] could be extended to include Objective Functions. 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]. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 16] Internet Draft draft-ietf-pce-of-06.txt December 2008 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, Fabien Verhaeghe, Robert Sparks, and Adrian Farrel 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. [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. 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. [RFC5088] Le Roux, Vasseur, et al. "OSPF protocol extensions for Path Computation Element (PCE) Discovery", RFC5088, January 2008. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 17] Internet Draft draft-ietf-pce-of-06.txt December 2008 [RFC5089] Le Roux, Vasseur, et al. "IS-IS protocol extensions for Path Computation Element (PCE) Discovery", RFC5089, January 2008. [RFC5226] Narten, T. and Alverstrand, H., "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 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. [PCEP-MIB] Koushik, K., and Stephan, E., "PCE communication protocol (PCEP) Management Information Base", draft-kkoushik-pce- pcep-mib, work in progress. [RBNF] A. Farrel, "Reduced Backus-Naur Form (RBNF) - A Syntax Used in Various Protocol Specifications", draft-farrel-rtg- common-bnf, work in progress. 11. Authors' 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 Full Copyright Statement Copyright (c) 2008 IETF Trust and the persons identified as the document authors. All rights reserved. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 18] Internet Draft draft-ietf-pce-of-06.txt December 2008 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. 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