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Network Working Group J.L. Le Roux Internet Draft France Telecom Category: Standard Track Expires:MarchMay 2008 J.P. Vasseur Cisco System Inc. Y. Lee HuaweiSeptemberNovember 2007 Encoding of Objective Functions in Path Computation Element(PCE)communicationand discovery protocols draft-ietf-pce-of-00.txtProtocol (PCEP) draft-ietf-pce-of-01.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, LeePCEEncoding of Objective FunctionsEncodingin PCEP [Page 1] Internet Draftdraft-ietf-pce-of-00.txt Septemberdraft-ietf-pce-of-01.txt December 2007 Abstract The computation of one or a series of Traffic Engineering Label Switched Paths (TELSP)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 PCEDiscovery (PCED) TLV carried within the IS-IS Router Capability TLV and the OSPF Router Information LSA so ascommunication Protocol (PCEP) in order to allow a PCC to discover the set of objective functions supported by aPCE. Extensions to thePCEcommunication Protocol (PCEP) are also specified allowingas 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 functionactually applied.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................................................4Introduction................................................3 3.PCEDiscoveryExtensions....................................5of PCE Objective Functions........................5 3.1.IS-IS PCED Extensions.......................................5 3.1.1. IS-ISOF-Listsub-TLV.......................................5 3.1.2. Elements of Procedure.......................................6TLV.................................................5 3.2.OSPF PCED Extensions........................................6 3.2.1. OSPF OF-List sub-TLV........................................6 3.2.2.Elements ofprocedure.......................................7procedure.......................................6 4. Objective Function in PCEPExtensions.............................................7Path Computation request and reply messages..............................................6 4.1. OFObject...................................................8Object...................................................6 4.1.1. Elements ofprocedure.......................................8Procedure.......................................7 4.2. Carrying the OF object in a PCEPmessage....................9message....................8 4.3. New RP objectflag.........................................11flag.........................................10 4.3.1. Elements ofprocedure......................................11procedure......................................10 5. Objective Functionsdefinition.............................11definition.............................10 6. IANAConsiderations........................................13Considerations........................................12 6.1. PCE Objective Functionregistry............................13registry............................12 6.2. PCEP codepoints...........................................14points...........................................13 6.2.1. OFObject..................................................14Object..................................................13 6.2.2.OF Object TLV Space........................................14 Le Roux, Vasseur, Lee PCE Objective Functions Encoding [Page 2] Internet Draft draft-ietf-pce-of-00.txt September 2007OF-List TLV................................................13 6.2.3. PCEP Errorvalues..........................................14values..........................................13 6.2.4. RP Objectflag.............................................15 6.3. IS-IS OF-List sub-TLV......................................15 6.4. OSPF OF-List sub-TLV.......................................15flag.............................................14 7. SecurityConsiderations....................................16Considerations....................................14 8. ManageabilityConsiderations...............................16Considerations...............................14 8.1. Control of Function andPolicy.............................16Policy.............................14 Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 2] Internet Draft draft-ietf-pce-of-01.txt December 2007 8.2. Information and DataModels................................16Models................................14 8.3. Liveness Detection andMonitoring..........................16Monitoring..........................15 8.4. Verify CorrectOperations..................................16Operations..................................15 8.5. Requirements on otherprotocols............................17protocols............................15 8.6. Impact on networkoperations...............................17operations...............................15 9.Acknowledgments............................................17Acknowledgments............................................15 10.References.................................................17References.................................................15 10.1. Normativereferences.......................................17references.......................................15 10.2. Informativereferences.....................................18references.....................................16 11. Author'sAddresses:........................................18Addresses:........................................16 12. Intellectual PropertyStatement............................18Statement............................17 1. Terminology Terminology used in this documentIGP: Interior Gateway Protocol: Either of the two routing protocols Open Shortest Path First (OSPF) or Intermediate System to Intermediate system (IS-IS).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.PCED: PCE Discovery: Generic term to refer to a PCE Discovery Mechanism. IS-IS PCED: IS-IS based PCE Discovery. Le Roux, Vasseur, Lee PCE Objective Functions Encoding [Page 3] Internet Draft draft-ietf-pce-of-00.txt September 2007 OSPF PCED: OSPF based PCE Discovery.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.The IS-IS based PCE Discovery and OSPF based PCE Discovery mechanisms defined respectively in [ISIS-PCED] and [OSPF-PCED], allow a PCC to automatically discover a setLe Roux, Vasseur, Lee Encoding ofPCEs as well as some information required for PCE selection, in compliance with requirements set forthObjective Functions in[RFC4674].PCEP [Page 3] Internet Draft draft-ietf-pce-of-01.txt December 2007 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 functionappliesrefers to a set of path computation requests the computation of which is synchronized (e.g. minimize the aggregate bandwidth consumption of alllinks,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.For that purpose this document specifies PCE Discovery (PCED) extensions in order to allow a PCE advertising a list of supported objective functions. Le Roux, Vasseur, Lee PCE Objective Functions Encoding [Page 4] Internet Draft draft-ietf-pce-of-00.txt September 2007 As spelled out in [RFC4657],Furthermore, [RFC4657] requires the ability for a PCCmust be ableto indicate in a path computation request a required/desired objective function, as well as optional function parameters. Forthat purposethese purposes, this document extends the PCE communication Protocol(PCEP), so(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 functionas well as function parameters.in PCEP request and reply messages. It thus complements the PCEPspecification. Extensions tobase specification [PCEP]. Note that IS-IS and OSPF based PCE Discovery([ISIS-PCED], [OSPF- PCED])mechanisms are defined insection 3.([ISIS-PCED], [OSPF-PCED]). 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 newsub-TLV,PCEP TLV, named the OF-Listsub-TLVTLV is defined in section 3. The OF-List TLV isdefined, to becarriedwithinin thePCED TLV. ItPCEP OPEN object and allows a PCE advertising to a PCEP peer, during PCEP session setup phase, the list of objective functionssupported by a PCE. Extensions to PCEP ([PCEP]) are defined in section 4.that it supports. A new PCEP object, the OF object, is defined in section 4. The OF object isdefined, to becarried 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 wasactually applied by the PCE. A common PCE Objective Function code point registry is definedused forbothpath computation. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEPand PCED protocols, to be managed by IANA.[Page 4] Internet Draft draft-ietf-pce-of-01.txt December 2007 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.3.Note that additional objective functions are defined for PCE Global Concurrent Optimization (GCO) application, in [PCE-GCO]. 3. DiscoveryExtensions 3.1. IS-IS PCED Extensions 3.1.1. IS-IS OF-List sub-TLV The IS-ISof PCE ObjectiveFunction List (OF-List) sub-TLV is a new sub-TLV carried within the IS-IS PCED sub-TLV defined in [ISIS-PCED]. It allows advertisingFunctions This section defines PCEP extensions (see [PCEP]) so as to support thelistadvertisement of the objective functions supported by a PCE.TheA new PCEP OF-Listsub-TLV(Objective Function list) TLV isan optional sub-TLV. It MAY be present within the PCED sub-TLV. It MUST NOT be present more than once. If present more than once, all instances except the first one MUST be ignored.defined. Theformat of the IS-ISPCEP OF-Listsub-TLV is the identical to the TLV format used by the Traffic Engineering Extensions to IS-IS [RFC3784]. That is, theTLV iscomposed of 1 octet for the type, 1 octet specifying the TLV length, and a value field. The Length field defines the length of the value portion in octets. The IS-IS OF-List sub-TLV has the following format: Le Roux, Vasseur, Lee PCE Objective Functions Encoding [Page 5] Internet Draft draft-ietf-pce-of-00.txt September 2007 TYPE: To be assigned by IANA (suggested value = 6) LENGTH: N * 2 (where N is the number of objective functions) VALUE: list of 2-bytes objective function code points, identifying the supported objective functions. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ OF Code (2 bytes): Objective Function Identifier The IANA is requested to manage the PCE objective function code point registry (see IANA section). 3.1.2. Elements of Procedure The OF-List sub-TLV is advertisedcarried within anIS-IS PCED sub-TLV defined in [ISIS-PCED]. As such, elements of procedures are inherited from those definedOPEN object, in[ISIS-PCED]. The OF-List sub-TLV is OPTIONAL. Aorder for a PCEMAY include an OF-List sub-TLV within the PCED sub-TLV so asto advertise to aset of one or more objective functions. When a PCED sub-TLV does not contain any OF-List sub-TLV this means that the supported objective functions of that PCE are unknown. 3.2. OSPF PCED Extensions 3.2.1. OSPF OF-List sub-TLV The OSPF Objective Function List (OF-List) sub-TLV is a new sub-TLV carried within the OSPF PCED TLV defined in [OSPF-PCED]. It allows advertisingPCEP peer theobjective functions supported by a PCE. It includes alist of2-bytesobjectivefunction identifiers. Thefunctions it supports, during PCEP session setup phase. 3.1. OF-Listsub-TLV is an optional TLV. It MAY be present within the PCED TLV. It MUST NOT be present more than once. If present more than once, all instances except the first one MUST be ignored. Le Roux, Vasseur, Lee PCE Objective Functions Encoding [Page 6] Internet Draft draft-ietf-pce-of-00.txt September 2007TLV Theformat of the OSPFPCEP OF-Listsub-TLVTLV isthe identicaloptional. 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 formatused byis compliant with theTraffic Engineering Extensions to OSPF [RFC3630].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-octetalignment;alignment and padding is not included in the Length field(so(e.g. atwothree octet value would have a length oftwo,three, but the total size of the TLV would be eight octets). The OSPF OF-Listsub-TLVTLV has the following format: TYPE: To be assigned by IANA (suggested value =6)4 ) LENGTH: N * 2 (where N is the number of objective functions) VALUE: list of 2-bytes objective function code points, identifying thesupportedobjectivefunctions.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-01.txt December 2007 OF Code (2 bytes): Objective FunctionIdentifier Thecode point identifier. IANA is requested to manage the PCE objective function code point registry (see IANA section).3.2.2.3.2. Elements of procedureThe OF-List sub-TLV is advertised within an OSPF PCED TLV defined in [OSPF-PCED]. As such, elements of procedures are inherited from those defined in [OSPF-PCED]. The OF-List sub-TLV is OPTIONAL.A PCE MAY includeanand OF-Listsub-TLV within the PCEDTLVso aswithin an OPEN object in an Open message sent to a PCEP peer, to advertise a set of one or more objective functions.When a PCEDThe OF-List TLVdoes not contain anyMUST NOT appear more than once in an OPEN object. The absence of the OF-Listsub-TLV this means thatTLV in an OPEN object must be interpreted as an absence of information on the list of supported objective functionsofby the PCE. As specified in [PCEP], a PCEP peer thatPCE are unknown.does not recognize the OF- List TLV will silently ignore it. 4. Objective Function in PCEPExtensionsPath Computation request and reply messages This section definesextensions toPCEP extensions ([PCEP]) so as to support the communication of objectivefunctions.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 objectivefunction andfunction. The PCEP OF Object may also be carried within a PCRep message in order for the PCE to indicate the objective function thathas actually been appliedwas used by the PCE. A newLe Roux, Vasseur, Lee PCE Objective Functions Encoding [Page 7] Internet Draft draft-ietf-pce-of-00.txt September 2007flag is defined in the RP object, so as to indicate in aPCRepPCReq message that theinclusion of the objective function actually applied by thePCEis requiredMUST provide in theresponse.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 thathas been actually appliedwas used by thePCE.PCE during path computation. The OF object format is compliant with the PCEP object format defined in [PCEP]. Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 6] Internet Draft draft-ietf-pce-of-01.txt December 2007 The OF Object-Class is to be assigned by IANA (recommendedvalue=18).value=21). 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.The IANA is requested to create a registry for this TLVs' name space.4.1.1. Elements ofprocedureProcedure Tospecify anrequest the use of a specific objective function to beappliedused bya PCE,the PCE a PCC MUST include an OF object in the PCReq message.A[PCEP] specifies a bit flag referred to as the P bitis definedinthea PCEP common headerof each PCEP objectthat 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),Le Roux, Vasseur, Lee PCE Objective Functions Encoding [Page 8] Internet Draft draft-ietf-pce-of-00.txt September 2007the 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 PCEhas toMUST 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)else ifand 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 Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 7] Internet Draft draft-ietf-pce-of-01.txt December 2007 "unknown/unsupported objective function" (defined in this 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,andand 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: <PCReq Message>::= <Common Header> [<SVEC-list>] <request-list> where: <svec-list>::=<SVEC> [<OF>] [<svec-list>] <request-list>::=<request>[<request-list>] <request>::= <RP> Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 8] Internet Draft draft-ietf-pce-of-01.txt December 2007 <END-POINTS> [<OF>] [<LSPA>] [<BANDWIDTH>] [<metric-list>] [<RRO>] [<IRO>] [<LOAD-BALANCING>] where: <metric-list>::=<METRIC>[<metric-list>] 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 functionthat applies toused for an individual path computationrequest(non synchronized case) MUST follow the RP object for which it applies. The format of thePCReq message is updated as follows: Le Roux, Vasseur, Lee PCE Objective Functions Encoding [Page 9] Internet Draft draft-ietf-pce-of-00.txt September 2007 <PCReq Message>::= <Common Header> [<SVEC-list>] <request-list> where: <svec-list>::=<SVEC> [<OF>] [<svec-list>] <request-list>::=<request>[<request-list>] <request>::= <RP> <END-POINTS> [<OF>] [<LSPA>] [<BANDWIDTH>] [<metric-list>] [<RRO>] [<IRO>] [<LOAD-BALANCING>] where: <metric-list>::=<METRIC>[<metric-list>] The OF object MAY be carried within a PCRep message to indicate the objective function that was actually applied by the PCE. The format of thePCRep message is updated as follows: <PCRep Message> ::= <Common Header> [<SVEC-list>] <response-list> where: <svec-list> ::=<SVEC> [<OF>] [<svec-list>] <response-list>::=<response>[<response-list>] <response>::=<RP> [<NO-PATH>] [<path-list>] <path-list>::=<path>[<path-list>] <path>::= <ERO> [<OF>] [<LSPA>] [<BANDWIDTH>] [<metric-list>] [<IRO>]where: <metric-list>::=<METRIC>[<metric-list>]Le Roux, Vasseur, LeePCEEncoding of Objective FunctionsEncodingin PCEP [Page10]9] Internet Draftdraft-ietf-pce-of-00.txt Septemberdraft-ietf-pce-of-01.txt December 2007 where: <metric-list>::=<METRIC>[<metric-list>] 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 (Pbitflag cleared in the OF object common header) but the PCE does not follow the recommendation, the PCC may desire to know the objective functionactually appliedthat was used by thePCE. ForPCE during path computation. To thatpurpose,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 functionactually appliedthat was used by thePCE.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 PCEmusthas 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 Functionapplied by the PCEthat was used during path computation is included. 4.3.1. Elements of procedure If the PCC wants to know the objective functionactually appliedused byathe 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 itactually applied.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: - a network comprises a set of N links {Li,(i=1…N)}(i=1...N)} Le Roux, Vasseur, Lee Encoding of Objective Functions in PCEP [Page 10] Internet Draft draft-ietf-pce-of-01.txt December 2007 - a path P is a list of K links{Lpi,(i=1…K)}{Lpi,(i=1...K)} -Metricmetric of link L is noted M(L), this can be the IGP metric the TE metric or any other metric. -Thethe cost of a path P is noted C(P), C(P) = sum {M(Lpi),(i=1…K)}.(i=1...K)}. -Residualresidual bandwidth on link L is notedR(L)r(L) -Speed ofmaximum reservable bandwidth on link L is notedB(L) Le Roux, Vasseur, Lee PCE Objective Functions Encoding [Page 11] Internet Draft draft-ietf-pce-of-00.txt September 2007R(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{(B(Lpi){(R(Lpi) -R(Lpi))r(Lpi)) /B(Lpi), i=1…KR(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…Kr(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{B(Li){R(Li) -R(Li), i=1…N}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 {B(Li)(R(Li) -R(Li))r(Li)) /B(Li), i=1…N})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}{P1...Pm} such that (Sum { C(Pi),i=1…m})i=1...m}) is minimized. Other objective functions may be defined in separate documents. Le Roux, Vasseur, LeePCEEncoding of Objective FunctionsEncodingin PCEP [Page12]11] Internet Draftdraft-ietf-pce-of-00.txt Septemberdraft-ietf-pce-of-01.txt December 2007 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 theISIS and OSPFPCEP OF-Listsub-TLVs. TheTLV. 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 thePCEPOF object and theISIS and OSPFOF-Listsub-TLVsTLV 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, LeePCEEncoding of Objective FunctionsEncodingin PCEP [Page13]12] Internet Draftdraft-ietf-pce-of-00.txt Septemberdraft-ietf-pce-of-01.txt December 2007 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 Type1821 OF 1 Objective (this document) Function 6.2.2.OF Object TLV Space The new PCEP OF object referenced above includes optional TLVs that encode objective function parameters. Each TLV includes a 16-bit type identifier. The IANA is requested to create a new registry, the "PCEP OF TLV" registry, and manage TLV type identifiers as follows: -OF-List TLVType value -IANA is requested to manage the PCEP TLVName - Defining RFC Type values incode point registry (see [PCEP]). This document defines a new PCEP TLV, therange 1-32767 are to be assigned as follows: - Values 1 through 1023 areOF-List TLV, to beassigned by IANA usingcarried in the"IETF Consensus" policy. - Values 1024 through 32767 areOPEN object. The IANA is requested tobe assigned by IANA, usingmake the"First Come First Served" policy.following allocation (suggested value): Typevalues in the range 32768-65535 are for "Private Use".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)Le Roux, Vasseur, Lee PCE Objective Functions Encoding [Page 14] Internet Draft draft-ietf-pce-of-00.txt September 2007Two 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-01.txt December 2007 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 Number0816 0x200 OF (this document)When set, this indicates that the PCC requests the inclusion, in the PCRep message, of the objective function actually used to compute the path. 6.3. IS-IS OF-List sub-TLV Once a registry for the IS-IS PCED sub-TLV defined in [ISIS-PCED] will have been assigned, IANA will assign a new sub-TLV code-point for the OF-List sub-TLV carried in the PCED sub-TLV. Here is the suggested value: Value TLV name References ----- -------- ---------- 6 OF-List (This document) 6.4. OSPF OF-List sub-TLV Once a registry for the OSPF PCED TLV defined in [OSPF-PCED] will have been assigned, IANA will assign a new sub-TLV code-point for the OF-List sub-TLV carried in the PCED TLV. Here is the suggested value: Value TLV name References ----- -------- ---------- 6 OF-List (This document) Le Roux, Vasseur, Lee PCE Objective Functions Encoding [Page 15] Internet Draft draft-ietf-pce-of-00.txt September 2007 7. Security Considerations Mechanisms discussed in [ISIS-PCED] and [OSPF-PCED] to secure the PCED TLV can be used to secure the PCED sub-TLV as well.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 inthe PCED protocol.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 thatan implementation may support the specification of the OF to be used in PCEP without supporting the discovery of the set of OF via the IGP. Also note thatit 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 ThePCED MIB Module defined in [PCED-MIB] MUST be extended to include Objective Functions. ThePCEP 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-01.txt December 2007 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], [ISIS-PCED] and [OSPF-PCED].[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], [ISIS-PCED] and [OSPF-PCED]. Le Roux, Vasseur, Lee PCE Objective Functions Encoding [Page 16] Internet Draft draft-ietf-pce-of-00.txt September 2007[PCEP]. 8.5. Requirements on other protocols Mechanisms defined in thisdraftdocument do not imply any requirements on other protocols in addition to those already listed in[PCEP], [ISIS- PCED] and [OSPF-PCED].[PCEP]. 8.6. Impact on network operations Mechanisms defined in this document do notimplyhave any impact on network operations in addition to those already listed in[PCEP], [ISIS-PCED] and [OSPF-PCED].[PCEP]. 9. Acknowledgments The authors would like to thank Jerry Ash for his 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-01.txt December 2007 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. [ISIS-PCED] Le Roux, Vasseur, et al. "IS-IS protocol extensions for Path Computation Element (PCE) Discovery", draft-ietf-pce-disco- proto-isis, work in progress. [OSPF-PCED] Le Roux, Vasseur, et al. "OSPF protocol extensions for Path Computation Element (PCE) Discovery", draft-ietf-pce-disco- proto-ospf, work in progress. [PCE-GCO] Y. Lee, J.L. Le Roux,Vasseur, Lee PCE Objective Functions Encoding [Page 17] Internet Draft draft-ietf-pce-of-00.txt September 2007 10.2. Informative references [RFC4657] Ash, J., Le Roux, J.L., " PCED. King, and E. Oki, "Path Computation Element Communication ProtocolGeneric Requirements", RFC4657, September 2006. [RFC4674] Le Roux, J.L., et al. "Requirements for PCE discovery", RFC4674, October 2006.(PCECP) Requirements and Protocol Extensions In Support of Global Concurrent Optimization", draft-ietf-pce-global-concurrent-optimization-01.txt, 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-01.txt December 2007 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 anyLe Roux, Vasseur, Lee PCE Objective Functions Encoding [Page 18] Internet Draft draft-ietf-pce-of-00.txt September 2007copyrights, 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 (2007). 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, LeePCEEncoding of Objective FunctionsEncodingin PCEP [Page19]17] ----