--- 1/draft-ietf-pce-association-diversity-08.txt 2019-08-16 04:13:50.018731661 -0700 +++ 2/draft-ietf-pce-association-diversity-09.txt 2019-08-16 04:13:50.066732880 -0700 @@ -1,24 +1,24 @@ PCE Working Group S. Litkowski Internet-Draft Orange Intended status: Standards Track S. Sivabalan -Expires: January 5, 2020 Cisco Systems, Inc. +Expires: February 17, 2020 Cisco Systems, Inc. C. Barth Juniper Networks M. Negi Huawei Technologies - July 4, 2019 + August 16, 2019 Path Computation Element Communication Protocol (PCEP) Extension for LSP Diversity Constraint Signaling - draft-ietf-pce-association-diversity-08 + draft-ietf-pce-association-diversity-09 Abstract This document introduces a simple mechanism to associate a group of Label Switched Paths (LSPs) via an extension to the Path Computation Element (PCE) communication Protocol (PCEP) with the purpose of computing diverse paths for those LSPs. The proposed extension allows a Path Computation Client (PCC) to advertise to a PCE that a particular LSP belongs to a disjoint-group, thus the PCE knows that the LSPs in the same group need to be disjoint from each other. @@ -31,21 +31,21 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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." - This Internet-Draft will expire on January 5, 2020. + This Internet-Draft will expire on February 17, 2020. Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -54,47 +54,48 @@ include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 4. Protocol Extension . . . . . . . . . . . . . . . . . . . . . 7 - 4.1. Association Group . . . . . . . . . . . . . . . . . . . . 7 - 4.2. Disjoint TLVs . . . . . . . . . . . . . . . . . . . . . . 8 - 4.3. Relationship to SVEC . . . . . . . . . . . . . . . . . . 10 - 4.4. Disjointness Objective functions . . . . . . . . . . . . 10 - 4.5. P Flag Considerations . . . . . . . . . . . . . . . . . . 12 - 4.6. Disjointness Computation Issues . . . . . . . . . . . . . 15 - 5. Security Considerations . . . . . . . . . . . . . . . . . . . 16 - 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 - 6.1. Association Type . . . . . . . . . . . . . . . . . . . . 16 - 6.2. PCEP TLVs . . . . . . . . . . . . . . . . . . . . . . . . 16 - 6.3. Objective Functions . . . . . . . . . . . . . . . . . . . 17 - 6.4. NO-PATH-VECTOR Bit Flags . . . . . . . . . . . . . . . . 18 - 6.5. PCEP-ERROR Codes . . . . . . . . . . . . . . . . . . . . 18 - 7. Manageability Considerations . . . . . . . . . . . . . . . . 18 - 7.1. Control of Function and Policy . . . . . . . . . . . . . 18 - 7.2. Information and Data Models . . . . . . . . . . . . . . . 19 - 7.3. Liveness Detection and Monitoring . . . . . . . . . . . . 19 - 7.4. Verify Correct Operations . . . . . . . . . . . . . . . . 19 - 7.5. Requirements On Other Protocols . . . . . . . . . . . . . 19 - 7.6. Impact On Network Operations . . . . . . . . . . . . . . 19 - 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 - 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 - 9.1. Normative References . . . . . . . . . . . . . . . . . . 20 - 9.2. Informative References . . . . . . . . . . . . . . . . . 20 - Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 22 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 + 4. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 4 + 5. Protocol Extension . . . . . . . . . . . . . . . . . . . . . 7 + 5.1. Association Group . . . . . . . . . . . . . . . . . . . . 7 + 5.2. Disjoint TLVs . . . . . . . . . . . . . . . . . . . . . . 8 + 5.3. Relationship to SVEC . . . . . . . . . . . . . . . . . . 10 + 5.4. Disjointness Objective functions . . . . . . . . . . . . 10 + 5.5. P Flag Considerations . . . . . . . . . . . . . . . . . . 12 + 5.6. Disjointness Computation Issues . . . . . . . . . . . . . 15 + 6. Security Considerations . . . . . . . . . . . . . . . . . . . 16 + 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 + 7.1. Association Type . . . . . . . . . . . . . . . . . . . . 16 + 7.2. PCEP TLVs . . . . . . . . . . . . . . . . . . . . . . . . 17 + 7.3. Objective Functions . . . . . . . . . . . . . . . . . . . 18 + 7.4. NO-PATH-VECTOR Bit Flags . . . . . . . . . . . . . . . . 18 + 7.5. PCEP-ERROR Codes . . . . . . . . . . . . . . . . . . . . 18 + 8. Manageability Considerations . . . . . . . . . . . . . . . . 19 + 8.1. Control of Function and Policy . . . . . . . . . . . . . 19 + 8.2. Information and Data Models . . . . . . . . . . . . . . . 19 + 8.3. Liveness Detection and Monitoring . . . . . . . . . . . . 19 + 8.4. Verify Correct Operations . . . . . . . . . . . . . . . . 19 + 8.5. Requirements On Other Protocols . . . . . . . . . . . . . 20 + 8.6. Impact On Network Operations . . . . . . . . . . . . . . 20 + 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 + 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 + 10.1. Normative References . . . . . . . . . . . . . . . . . . 20 + 10.2. Informative References . . . . . . . . . . . . . . . . . 21 + Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 23 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 1. Introduction [RFC5440] describes the Path Computation Element communication Protocol (PCEP) which enables the communication between a Path Computation Client (PCC) and a Path Control Element (PCE), or between two PCEs based on the PCE architecture [RFC4655]. PCEP Extensions for Stateful PCE Model [RFC8231] describes a set of extensions to PCEP to enable active control of MPLS-TE and GMPLS @@ -169,20 +170,21 @@ different links that do not share fate (but may use common transit nodes). o Node+SRLG disjointness: the paths of the associated LSPs should transit different links that do not have any common shared fate and should transit different nodes. The associated LSPs may originate from the same or from different head-end(s) and may terminate at the same or different tail-end(s). +4. Applicability _________________________________________ / \ / +------+ \ | | PCE | | | +------+ | | | | ***********************> | | +------+ 10 +------+ | CE1 ****| PE 1 | ----- R1 ---- R2 ------- | PE 2 |**** CE2 | +------+ | | +------+ | @@ -198,21 +200,21 @@ Figure 1 - Disjoint paths with different head-ends and tail-ends In the figure above, let us consider that the customer wants to have two disjoint paths between CE1/CE2 and CE3/CE4. From an IP/MPLS network point view, in this example, the CEs are connected to different PEs to maximize their disjointness. When LSPs originate from different head-ends, distributed computation of diverse paths can be difficult, whereas, computation via a centralized PCE ensures path disjointness, correctness and simplicity. - Section 4.3 describes the relationship between the disjoint + Section 5.3 describes the relationship between the disjoint association group and Synchronization VECtor (SVEC) object. The PCEP extension for stateful PCE [RFC8231] defined new PCEP messages - Path Computation Report (PCRpt), Path Computation Update (PCUpd) and Path Computation Initiate (PCInitiate) [RFC8281]. These messages use PLSP-ID in the LSP object for identification. Moreover to allow diversity between LSPs originating from different PCCs, the generic mechanism to create a grouping of LSPs is described in [I-D.ietf-pce-association-group] (that is equally applicable to the active and passive modes of a stateful PCE). @@ -266,23 +268,23 @@ session Using the disjoint-group within a PCEP messages may have two purpose: o Configuration: Used to communicate the configured disjoint requirement to a PCEP peer. o Status: Used to communicate the status of the computed disjointness. -4. Protocol Extension +5. Protocol Extension -4.1. Association Group +5.1. Association Group As per [I-D.ietf-pce-association-group], LSPs are associated with other LSPs with which they interact by adding them to a common association group. The Association parameters, as described in [I-D.ietf-pce-association-group] as the combination of the mandatory fields Association type, Association ID and Association Source in the ASSOCIATION object, that uniquely identify the association group belonging to this association. If the optional TLVs - Global Association Source or Extended Association ID - are included, then they are included in combination with mandatory fields to uniquely @@ -323,38 +325,38 @@ polices MAY define the computational behavior for the other LSPs in the group. For example, the PCE may provide no path, a shortest path, or a constrained path based on relaxing disjointness, etc. The disjoint status is informed to the PCC. Associating a particular LSP to multiple disjoint groups is authorized from a protocol perspective, however there is no assurance that the PCE will be able to compute properly the multi-disjointness constraint. -4.2. Disjoint TLVs +5.2. Disjoint TLVs The disjoint group MUST carry the following TLV: o DISJOINTNESS-CONFIGURATION-TLV: Used to communicate some disjointness configuration parameters. In addition, the disjoint group MAY carry the following TLV: o DISJOINTNESS-STATUS-TLV: Used to communicate the status of the computed disjointness. This is applicable for messages from PCE to PCC (PCUpd, PCInitiate or PCRep message). o VENDOR-INFORMATION-TLV: Used to communicate arbitrary vendor- specific behavioral information, described in [RFC7470]. o OF-List TLV: Used to communicate the disjointness objective - function. See Section 4.4. + function. See Section 5.4. The DISJOINTNESS-CONFIGURATION-TLV is shown in the following figure: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = TBD2 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags |T|P|S|N|L| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -389,44 +391,44 @@ 2 with P=1, but LSP 2 with P=1 does not depend of LSP 1 with P=0). Multiple LSPs in the same disjoint group may have the P flag set. In such a case, those LSPs may not be disjoint from each other but will be disjoint from others LSPs in the group that have the P flag unset. * T (Strict disjointness) bit: when set, if disjoint paths cannot be found, PCE SHOULD return no path for LSPs that could not be be disjoint. When unset, the PCE is allowed to relax disjointness by either applying a requested objective function - (cf. Section 4.4 below) or using any other behavior if no + (cf. Section 5.4 below) or using any other behavior if no objective function is requested (e.g. using a lower disjoint type (link instead of node) or fully relaxing disjointness - constraint). + constraint). Further see Section 5.6 for details. * Unassigned bits are considered reserved. They MUST be set to 0 on transmission and MUST be ignored on receipt. If a PCEP speaker receives a disjoint-group without DISJOINTNESS- CONFIGURATION-TLV, it SHOULD reply with a PCErr Error-type=6 (Mandatory Object missing) and Error-value=TBD8 (DISJOINTNESS- CONFIGURATION-TLV missing). The DISJOINTNESS-STATUS-TLV uses the same format as the DISJOINTNESS- CONFIGURATION-TLV with a different type TBD3 (in the TLV). The L, N, and S flags are set based if the computed path meet the disjointness criteria. The P flag is set to indicate that the computed path is the shortest and the T flag has no meaning in the DISJOINTNESS- STATUS-TLV and MUST NOT be set while sending and ignored on receipt. Any new flag defined for the DISJOINTNESS-CONFIGURATION-TLV is be automatically applicable to the DISJOINTNESS-STATUS-TLV. -4.3. Relationship to SVEC +5.3. Relationship to SVEC [RFC5440] defines a mechanism for the synchronization of a set of path computation requests by using the SVEC object, that specifies the list of synchronized requests that can either be dependent or independent. The SVEC object identify the relationship between the set of path computation requests, identified by 'Request-ID-number' in RP (Request Parameters) object. [RFC6007] further clarified the use of the SVEC list for synchronized path computations when computing dependent requests as well as described a number of usage scenarios for SVEC lists within single-domain and multi-domain @@ -440,21 +442,21 @@ request as well as the diversity association group. The PCE MUST try to find a path that meets both the constraints. It is possible that the diversity requirement in the association group is different from the one in the SVEC object. The PCE would consider both the objects as per the processing rules and aim to find a path that meets both of these constraints. In case no such path is possible (or the constraints are incompatible), the PCE MUST send a path computation reply (PCRep) with a NO-PATH object indicating path computation failure as per [RFC5440]. -4.4. Disjointness Objective functions +5.4. Disjointness Objective functions An objective function (OF) MAY be applied to the disjointness computation to drive the PCE computation behavior. In this case, the OF-List TLV (defined in ([RFC5541]) is used as an optional TLV in the Association Group Object. Whereas the PCEP OF-List TLV allows multiple OF-codes inside the TLV, a sender SHOULD include a single OF-code in the OF-List TLV when included in the Association Group, and the receiver MUST consider the first OF-code only and ignore others if included. @@ -517,23 +519,23 @@ diversity as possible. o SVEC object with node-diverse bit=1 and OF=MSN - ensure full node- diversity. In the last example above, it is interesting to note that "OF" becomes redundant as "SVEC object" ensures full node-diversity, however this specification does not prohibit redundant constraints while using "SVEC object" and "OF" together for diversity. -4.5. P Flag Considerations +5.5. P Flag Considerations - As mentioned in Section 4.2, the P flag (when set) indicates that the + As mentioned in Section 5.2, the P flag (when set) indicates that the computed path of the LSP SHOULD satisfies all constraints and objective functions first without considering the diversity constraint. This could be required in some primary/backup scenarios where the primary path should use the more optimal path available (taking into account the other constraints). When disjointness is computed, it is important for the algorithm to know that it should try to optimize the path of one or more LSPs in the disjoint group (for instance the primary path) while other paths are allowed to be costlier (compared to a similar path without the disjointness constraint). Without such a hint, the disjointness algorithm may set @@ -638,99 +640,108 @@ of the paths. If the implementation elects only one path, there is a chance that picking up one path may prevent disjointness. In our example, if path 2 is used for PE1->PE2, there is no room left for PE3->PE4 while if path 1 is used, PE3->PE4 can be placed on R3->R4 link. When P flag is set for an LSP and when ECMPs are available, an implementation should aim to select a path that allows disjointness. -4.6. Disjointness Computation Issues +5.6. Disjointness Computation Issues There may be some cases where the PCE is not able to provide a set of disjoint paths for one or more LSPs in the association. When the T flag is set (Strict disjointness requested), if disjointness cannot be ensured for one or more LSPs, the PCE MUST reply to a Path Computation Request (PCReq) with a Path Computation - Reply (PCRep) message containing a NO-PATH object. In case of - network event leading to an impossible strict disjointness, the PCE - MUST send a PCUpd message containing an empty ERO to the - corresponding PCCs. In addition to the empty ERO Object, the PCE MAY - add the NO-PATH-VECTOR TLV ([RFC5440]) in the LSP Object. + Reply (PCRep) message containing a NO-PATH object. In case of other + PCEP message, the PCE MUST return a PCErr message with Error-Type 26 + "Association Error" and Error-Value 7 "Cannot join the association + group". Also, in case of network event leading to an impossible + strict disjointness, the PCE MUST send a PCUpd message containing an + empty ERO to the corresponding PCCs. In addition to the empty ERO + Object, the PCE MAY add the NO-PATH-VECTOR TLV ([RFC5440]) in the LSP + Object. This document adds new bits in the NO-PATH-VECTOR TLV: bit "TBD7": when set, the PCE indicates that it could not find a disjoint path for this LSP. bit "TBD8": when set, the PCE indicates that it does not support the requested disjointness computation. - When the T flag is unset, the PCE is allowed to reduce the required - level of disjointness. The actual level of disjointness computed by - the PCE can be reported through the DISJOINTNESS-STATUS-TLV by - setting the appropriate flags in the TLV. While the DISJOINTNESS- - CONFIGURATION-TLV defines the expected level of disjointness required - by configuration, the DISJOINTNESS-STATUS-TLV defines the actual - level of disjointness computed. + When the T flag is unset, the PCE is allowed to relax disjointness by + either applying a requested objective function (Section 5.4) if + specified. Otherwise the PCE is allowed to reduce the required level + of disjointness (as it deems fit). The actual level of disjointness + computed by the PCE can be reported through the DISJOINTNESS-STATUS- + TLV by setting the appropriate flags in the TLV. While the + DISJOINTNESS-CONFIGURATION-TLV defines the expected level of + disjointness required by configuration, the DISJOINTNESS-STATUS-TLV + defines the actual level of disjointness computed. There are some cases where the PCE may need to completely relax the disjointness constraint in order to provide a path to all the LSPs that are part of the association. A mechanism that allows the PCE to fully relax a constraint is considered by the authors as more global to PCEP rather than linked to the disjointness use case. As a consequence, it is considered as out of scope of the document. All LSPs in a particular disjoint group MUST use the same combination of T, S, N, L flags in the DISJOINTNESS-CONFIGURATION-TLV. If a PCEP peer receives a PCEP messages for LSPs belonging to the same disjoint group but having an inconsistent combination of T, S, N, L flags, the PCEP peer SHOULD NOT try to add the LSPs in disjoint group and SHOULD reply with a PCErr with Error-type 26 (Association Error) and Error- Value 6 (Association information mismatch). -5. Security Considerations +6. Security Considerations - This document defines one new type for association, which does not - add any new security concerns beyond those discussed in [RFC5440], - [RFC8231] and [I-D.ietf-pce-association-group] in itself. + This document defines one new type for association, which on itself + does not add any new security concerns beyond those discussed in + [RFC5440], [RFC8231] and [I-D.ietf-pce-association-group]. But, + adding of a spurious LSP into the disjointness association group + could lead to re-computation and set-up of all LSPs in the group, + that could be used to overwhelm the PCE and the network. - As stated in [I-D.ietf-pce-association-group], much of the + Also, as stated in [I-D.ietf-pce-association-group], much of the information carried in the Disjointness Association object, as per this document is not extra sensitive. It often reflects information that can also be derived from the LSP Database, but association provides a much easier grouping of related LSPs and messages. The disjointness association could provide an adversary with the - opportunity to eavesdrop on the relationship between the LSPs. Thus - securing the PCEP session using Transport Layer Security (TLS) + opportunity to eavesdrop on the relationship between the LSPs. + + Thus securing the PCEP session using Transport Layer Security (TLS) [RFC8253], as per the recommendations and best current practices in [RFC7525], is RECOMMENDED. -6. IANA Considerations +7. IANA Considerations -6.1. Association Type +7.1. Association Type This document defines a new Association type, originally described in [I-D.ietf-pce-association-group]. IANA is requested to make the assignment of a new value for the sub-registry "ASSOCIATION Type Field" (request to be created in [I-D.ietf-pce-association-group]), as follows: +------------------+-----------------------------+-------------+ | Association type | Association Name | Reference | +------------------+-----------------------------+-------------+ | TBD1 | Disjoint-group Association | [This.I-D] | +------------------+-----------------------------+-------------+ -6.2. PCEP TLVs +7.2. PCEP TLVs This document defines the following new PCEP TLVs and the IANA is requested to make the assignment of new values for the existing "PCEP TLV Type Indicators" registry as follows: +----------+---------------------------------+-------------+ | TLV Type | TLV Name | Reference | +----------+---------------------------------+-------------+ | TBD2 | Disjointness Configuration TLV | [This.I-D] | | TBD3 | Disjointness Status TLV | [This.I-D] | @@ -754,55 +765,55 @@ +------------+-------------------------+-------------+ | 31 | L - Link Diverse | [This.I-D] | | 30 | N - Node Diverse | [This.I-D] | | 29 | S - SRLG Diverse | [This.I-D] | | 28 | P - Shortest Path | [This.I-D] | | 27 | T - Strict Disjointness | [This.I-D] | +------------+-------------------------+-------------+ Table 1: Disjointness Configuration TLV -6.3. Objective Functions +7.3. Objective Functions Three new Objective Functions have been defined in this document. IANA is requested to make the following allocations from the PCEP "Objective Function" sub-registry: +------------+----------------------------------------+-------------+ | Code Point | Name | Reference | +------------+----------------------------------------+-------------+ | TBD4 | Minimize the number of shared Links | [This.I-D] | | | (MSL) | | | TBD5 | Minimize the number of shared SRLGs | [This.I-D] | | | (MSS) | | | TBD6 | Minimize the number of shared Nodes | [This.I-D] | | | (MSN) | | +------------+----------------------------------------+-------------+ -6.4. NO-PATH-VECTOR Bit Flags +7.4. NO-PATH-VECTOR Bit Flags This documents defines new bits for the NO-PATH-VECTOR TLV in the "NO-PATH-VECTOR TLV Flag Field" sub-registry of the "Path Computation Element Protocol (PCEP) Numbers" registry. IANA is requested to make the following allocation: +------------+-----------------------------------------+------------+ | Bit Number | Name | Reference | +------------+-----------------------------------------+------------+ | TBD7 | Disjoint path not found | [This.I-D] | | TBD8 | Requested disjoint computation not | [This.I-D] | | | supported | | +------------+-----------------------------------------+------------+ Table 2: NO-PATH-VECTOR TLV -6.5. PCEP-ERROR Codes +7.5. PCEP-ERROR Codes This document defines new Error-Value within existing Error-Type related to path protection association. IANA is requested to allocate new error values within the "PCEP-ERROR Object Error Types and Values" sub-registry of the PCEP Numbers registry, as follows: +----------+-------------------------+------------------------------+ | Error- | Meaning | Reference | | Type | | | +----------+-------------------------+------------------------------+ @@ -811,72 +822,75 @@ | | Error-value=TBD8: | [This.I-D] | | | DISJOINTNESS- | | | | CONFIGURATION TLV | | | | missing | | | 10 | Reception of an invalid | [RFC5440] | | | object | | | | Error-value=TBD9: | [This.I-D] | | | Incompatible OF code | | +----------+-------------------------+------------------------------+ -7. Manageability Considerations +8. Manageability Considerations -7.1. Control of Function and Policy +8.1. Control of Function and Policy An operator SHOULD be allowed to configure the disjointness association groups and disjoint parameters at the PCEP peers and associate it with the LSPs. The Operator-configured Association Range MUST be allowed to be set by the operator. Operator SHOULD be allowed to set the local policies to define various disjoint computational behavior at the PCE. -7.2. Information and Data Models +8.2. Information and Data Models An implementation SHOULD allow the operator to view the disjoint associations configured or created dynamically. Further implementation SHOULD allow to view disjoint associations reported by each peer, and the current set of LSPs in this association. The PCEP YANG module [I-D.ietf-pce-pcep-yang] includes association groups information. -7.3. Liveness Detection and Monitoring +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 [RFC5440]. -7.4. Verify Correct Operations +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 [RFC5440]. -7.5. Requirements On Other Protocols +8.5. Requirements On Other Protocols Mechanisms defined in this document do not imply any new requirements on other protocols. -7.6. Impact On Network Operations +8.6. Impact On Network Operations Mechanisms defined in [RFC5440], Section 8.6 also apply to PCEP extensions defined in this document. Additionally, a PCEP implementation SHOULD allow a limit to be placed on the number of LSPs that can belong to a disjoint association group. -8. Acknowledgments +9. Acknowledgments A special thanks to authors of [I-D.ietf-pce-association-group], this document borrow some of the text from it. Authors would also like to thank Adrian Farrel and Julien Meuric for the valuable comments. -9. References -9.1. Normative References + Thanks to Emmanuel Baccelli for RTGDIR reviews. + +10. References + +10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, . @@ -897,26 +911,27 @@ May 2017, . [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path Computation Element Communication Protocol (PCEP) Extensions for Stateful PCE", RFC 8231, DOI 10.17487/RFC8231, September 2017, . [I-D.ietf-pce-association-group] Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H., - Dhody, D., and Y. Tanaka, "PCEP Extensions for - Establishing Relationships Between Sets of LSPs", draft- - ietf-pce-association-group-09 (work in progress), April - 2019. + Dhody, D., and Y. Tanaka, "Path Computation Element + Communication Protocol (PCEP) Extensions for Establishing + Relationships Between Sets of Label Switched Paths + (LSPs)", draft-ietf-pce-association-group-10 (work in + progress), August 2019. -9.2. Informative References +10.2. Informative References [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, DOI 10.17487/RFC4655, August 2006, . [RFC6007] Nishioka, I. and D. King, "Use of the Synchronization VECtor (SVEC) List for Synchronized Dependent Path Computations", RFC 6007, DOI 10.17487/RFC6007, September 2010, . @@ -941,21 +956,21 @@ [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path Computation Element Communication Protocol (PCEP) Extensions for PCE-Initiated LSP Setup in a Stateful PCE Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, . [I-D.ietf-pce-pcep-yang] Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A YANG Data Model for Path Computation Element Communications Protocol (PCEP)", draft-ietf-pce-pcep- - yang-11 (work in progress), March 2019. + yang-12 (work in progress), July 2019. Appendix A. Contributor Addresses Dhruv Dhody Huawei Technologies Divyashree Techno Park, Whitefield Bangalore, Karnataka 560066 India EMail: dhruv.ietf@gmail.com @@ -979,11 +994,11 @@ Juniper Networks EMail: cbarth@juniper.net Mahendra Singh Negi Huawei Technologies Divyashree Techno Park, Whitefield Bangalore, Karnataka 560066 India - EMail: mahendrasingh@huawei.com + EMail: mahend.ietf@gmail.com