TEAS Working Group R. Gandhi, Ed. Internet-Draft Cisco Systems Intended Status: Standards Track H. Shah Expires: March 14, 2017 Ciena Jeremy Whittaker Verizon September 10, 2016 Fast Reroute Procedures For Associated Co-routed Bidirectional Label Switched Paths (LSPs) draft-gandhishah-teas-assoc-corouted-bidir-02 Abstract In packet transport networks, there are requirements where reverse unidirectional LSP of a bidirectional LSP needs to follow the same path as its forward unidirectional LSP. The bidirectional LSP needs to maintain co-routed-ness even after a failure event in the network. This document describes RSVP signaling to unambiguously bind two co- routed point-to-point LSPs into an associated co-routed bidirectional LSP. Fast-reroute procedures are defined to ensure that the traffic flows on the co-routed path after a failure event. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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 http://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." Copyright Notice Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved. Gandhi, et al. Expires March 14, 2017 [Page 1] Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 2.1. Key Word Definitions . . . . . . . . . . . . . . . . . . . 3 2.2. Reverse Co-routed Unidirectional LSPs . . . . . . . . . . 3 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Message and Object Definitions . . . . . . . . . . . . . . . . 6 4.1. Extended ASSOCIATION Object . . . . . . . . . . . . . . . 6 5. Signaling Procedure . . . . . . . . . . . . . . . . . . . . . 7 5.1. Co-routed Bidirectional LSP Association . . . . . . . . . 7 5.2. Fast-Reroute For Associated Co-routed Bidirectional LSP . 8 6. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 8 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 9.1. Normative References . . . . . . . . . . . . . . . . . . . 10 9.2. Informative References . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Gandhi, et al. Expires March 14, 2017 [Page 2] Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016 1. Introduction In packet transport networks, there are requirements where a reverse Multi-Protocol Label Switching (MPLS) Label Switched Path (LSP) of a bidirectional LSP needs to follow the same path as its forward LSP [RFC6373]. The bidirectional LSP needs to maintain co-routed-ness even after a failure event in the network. The Resource Reservation Protocol (RSVP) Extended ASSOCIATION Object is specified in [RFC6780] which can be used generically to associate (G)MPLS LSPs. [RFC7551] defines mechanisms for binding two point-to- point unidirectional LSPs [RFC3209] into an associated bidirectional LSP. There are two models described for provisioning the bidirectional LSP, single-sided and double-sided. Only the single- sided provisioned bidirectional LSPs are considered in this document for providing fast-reroute for the co-routed bidirectional LSPs. The MPLS Transport Profile (TP) [RFC6370] architecture facilitates the co-routed bidirectional LSP by using GMPLS extensions [RFC3473] to achieve congruent paths. However, the RSVP association signaling allows to enable co-routed bidirectional LSPs without having to deploy GMPLS extensions in the existing networks. The association signaling also allows to take advantage of the existing Traffic Engineering (TE) mechanisms in the network. [GMPLS-FRR] defines fast-reroute procedures for GMPLS signaled LSPs to ensure traffic flows on a co-routed path after a failure event on the LSP path. [GMPLS-FRR] defined fast-reroute mechanisms are equally applicable to the associated co-routed bidirectional LSPs. This document describes how Extended ASSOCIATION Object can be used to unambiguously bind two reverse co-routed unidirectional LSPs into an associated co-routed bidirectional LSP in the single-sided provisioning case. Fast-reroute procedures are defined to ensure the traffic flows on the co-routed path after a failure event. 2. Conventions Used in This Document 2.1. Key Word Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 2.2. Reverse Co-routed Unidirectional LSPs Two reverse unidirectional point-to-point (P2P) LSPs are setup in the Gandhi, et al. Expires March 14, 2017 [Page 3] Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016 opposite directions between a pair of source and destination nodes to form an associated bidirectional LSP. A reverse unidirectional LSP originates on the same node where the forward unidirectional LSP terminates, and it terminates on the same node where the forward unidirectional LSP originates. A reverse co-routed unidirectional LSP traverses along the same path of the forward direction unidirectional LSP in the opposite direction. 3. Overview As specified in [RFC7551], in the single-sided provisioning case, the RSVP Traffic Engineering (TE) tunnel is configured only on one endpoint node. An LSP for this tunnel is initiated by the originating endpoint with Extended ASSOCIATION Object containing Association Type set to "single-sided associated bidirectional LSP" and REVERSE_LSP Object inserted in the Path message. The remote endpoint then creates the corresponding reverse TE tunnel and signals the reverse LSP in response using the information from the REVERSE_LSP Object and other objects present in the received Path message. The reverse LSP thus created may or may not be congruent and follow the same path as its forward LSP. LSP1 --> LSP1 --> LSP1 --> +-----+ +-----+ +-----+ +-----+ | A +-----------+ B +-----------+ C |-----------+ D | +-----+ +-----+ +-----+ +-----+ <-- LSP2 <-- LSP2 <-- LSP2 Figure 1a: An Example of Associated Co-routed Bidirectional LSP As shown in Figure 1a, LSP1 is provisioned on the originating endpoint A. The creation of reverse LSP2 on the remote endpoint D is triggered by the LSP1. LSP2 follows the path in the reverse direction using the EXPLICIT_ROUTE Object (ERO) from the received REVERSE_LSP Object in the Path message of LSP1 [RFC7551]. For co-routed bidirectional LSP, the originating endpoint A can ensure that the reverse LSP follows the same path as the forward LSP (e.g. A-B-C-D) by populating the ERO in the REVERSE_LSP Object using the hops traversed by the forward LSP in the reverse order (e.g. D-C- B-A). For fast-reroute, the associated co-routed bidirectional LSP signaled using mechanisms defined in [RFC7551] requires solutions for the following issues: Gandhi, et al. Expires March 14, 2017 [Page 4] Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016 o Multiple forward and reverse LSPs of a bidirectional LSP may be present at mid-point nodes with identical Extended ASSOCIATION Objects. As examples, this can happen while RSVP states are timing out, during recovery phase in RSVP graceful restart, etc. This creates an ambiguity at mid-point nodes to identify the correct associated LSP pair that can lead to undesirable fast-reroute bypass assignment. As shown in Figure 1b, LSP1 and LSP2 are an associated co-routed LSP pair, similarly LSP3 and LSP4 are an associated co-routed LSP pair, both pairs belong to the same associated bidirectional LSP and carry identical Extended ASSOCIATION Objects. In this example, mid-point nodes B and C may mistakenly associate LSP1 with non co-routed reverse LSP4 instead of co-routed reverse LSP3 due to the matching Extended ASSOCIATION Objects. In order to ensure co-routed-ness, the mid-point nodes must unambiguously identify the correct matching co-routed associated forward and reverse LSP pair. To ensure this, the Extended ASSOCIATION Object needs to be unique per associated co-routed forward and reverse LSP pair. LSP3 --> LSP3 --> LSP1 --> LSP1 --> LSP1 --> +-----+ +-----+ +-----+ +-----+ | A +-----------+ B +-----------+ C |-----------+ D | +-----+ +-----+ +-----+ +-----+ <--LSP2 | <-- LSP2 | <-- LSP2 <--LSP4 | | <-- LSP4 | | | LSP3 --> | +-----+ +-----+ + E +-----------+ F | +-----+ +-----+ <-- LSP4 Figure 1b: Example of LSPs with matching Extended ASSOCIATION Objects o The ERO for the reverse LSP signaled by the originating endpoint may contain loose next-hop(s) in case of loosely routed LSPs (e.g. inter-domain LSPs). For co-routed bidirectional LSP, the mid-point and endpoint nodes need to ensure that the loose next-hop expansion for the reverse LSP is on the co-routed path as its forward LSP. To achieve this, the expanding node may require the recorded path of the forward LSP. o In order to ensure that the traffic flows on the co-routed path Gandhi, et al. Expires March 14, 2017 [Page 5] Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016 after a link or node failure on the LSP path, the mid-point Point of Local Repair (PLR) nodes need to identify the correct matching pair and know that it is co-routed. This way PLR nodes can assign bidirectional co-routed bypass tunnels for fast-reroute. Such bypass assignment requires co-ordination between the forward and reverse direction PLR nodes. 4. Message and Object Definitions 4.1. Extended ASSOCIATION Object The Extended ASSOCIATION Object is populated using the rules defined in [RFC7551] for the Association Type "single-sided associated bidirectional LSP". The Extended Association ID is set by the originating node to the value specified as following when the associated bidirectional LSP is co-routed. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 LSP Source Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | LSP-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : : : Variable Length Extended ID : : : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: IPv4 Extended Association ID Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | IPv6 LSP Source Address | + + | (16 bytes) | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Gandhi, et al. Expires March 14, 2017 [Page 6] Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016 | Reserved | LSP-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : : : Variable Length Extended ID : : : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: IPv6 Extended Association ID Format LSP Source Address IPv4/IPv6 source address of the originating LSP. LSP-ID 16-bits LSP-ID of the originating LSP. Variable Length Extended ID Variable length Extended ID inserted by the originating node of the Associated co-routed bidirectional LSP. 5. Signaling Procedure 5.1. Co-routed Bidirectional LSP Association In general, the processing rules for the Extended ASSOCIATION Object as specified in [RFC6780] and [RFC7551] are followed for co-routed bidirectional LSP association. The originating head-end node MUST add Extended ASSOCIATION Object with Association Type set to "single-sided associated bidirectional LSP" and the Extended Association ID set to the values specified in Section 4.1 of this document in the RSVP Path message. The Extended Association ID thus added allows to identify each associated LSP pair of the associated co-routed bidirectional LSP. The presence of Extended Association ID in this format indicates the nodes on the LSP path that the bidirectional LSP is co-routed. In addition, the originating head-end node MUST add EXPLICIT_ROUTE Object (ERO) in the REVERSE_LSP Object by using the hops traversed by the forward LSP in the reverse order to ensure that reverse LSP follows the same path as forward direction LSP in the opposite direction. When the ERO contains one or more loose next-hop(s), the originating endpoint MUST add RECORD_ROUTE Object (RRO) in the Path message of the forward LSP to record the hops traversed by the LSP. Gandhi, et al. Expires March 14, 2017 [Page 7] Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016 As defined in [RFC7551], the remote endpoint simply copies the contents of the received Extended ASSOCIATION Object including the Extended Association ID in the Path message of the reverse LSP's Extended ASSOCIATION Object. In addition, the remote endpoint builds the ERO of the reverse LSP using the ERO from the received REVERSE_LSP Object of the forward LSP. If ERO contains one or more loose next-hop(s), the remote endpoint SHOULD use the recorded hops from the RRO in the forward LSP to expand the loose next-hop(s), to ensure that the reverse LSP follows the same path as the forward LSP. As contents of the Extended ASSOCIATION Objects are unique for each associated LSP pair of the associated co-routed bidirectional LSP, a mid-point node can unambiguously identify the associated LSP pair by matching their Extended ASSOCIATION Objects. When a mid-point node needs to expand the loose next-hop in the ERO, it SHOULD use the recorded hops from the RRO in the forward LSP to ensure that the reverse LSP is co-routed and follows the same path as its forward LSP. 5.2. Fast-Reroute For Associated Co-routed Bidirectional LSP The procedures defined in [GMPLS-FRR] are used for associated co-routed bidirectional LSP to ensure that the traffic flows on a co-routed path after a link or node failure. As described in [GMPLS-FRR], BYPASS_ASSIGNMENT subobject in the RRO is signaled to co-ordinate bypass tunnel assignment between its forward and reverse direction PLR nodes. This subobject MUST be added by the forward direction PLR node in the Path message of the originating LSP. The forward direction PLR node always initiates the bypass tunnel assignment for the originating LSP. The reverse direction PLR (forward direction LSP Merge Point (MP)) node simply reflects the bypass tunnel assignment for the reverse direction LSP on the co-routed path. After a link or node failure, PLR nodes in both directions trigger fast-reroute independently using the procedures defined in [RFC4090]. As specified in [GMPLS-FRR], reverse direction PLR node triggers the fast-reroute in the reverse direction on the matching associated co- routed bypass tunnel to ensure that both traffic and RSVP signaling flow on the co-routed path after the failure. 6. Compatibility The Extended ASSOCIATION Object has been defined in [RFC6780], with class number in the form 11bbbbbb, which ensures compatibility with Gandhi, et al. Expires March 14, 2017 [Page 8] Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016 non-supporting nodes. Per [RFC2205], such nodes will ignore the object but forward it without modification. This document defines the procedures for fast-reroute for associated co-routed bidirectional LSPs. Operators wishing to use this function SHOULD ensure that it is supported on the nodes on the LSP path. The Extended Association ID defined in this document is backwards compatible with the functions defined in [RFC7551] and [RFC6780]. 7. Security Considerations This document uses signaling mechanisms defined in [RFC7551] and [GMPLS-FRR] and does not introduce any additional security considerations other than already covered in [RFC7551], [GMPLS-FRR] and the MPLS/GMPLS security framework [RFC5920]. Using the Extended Association ID in the intercepted signalling message, a node may be able to get additional information of the LSP such as co-routed type and the originating node. This is judged to be a very minor security risk as this information is already available by other means. 8. IANA Considerations This document does not make any request for IANA action. Gandhi, et al. Expires March 14, 2017 [Page 9] Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, September 1997. [RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090, May 2005. [RFC6780] Berger, L., Le Faucheur, F., and A. Narayanan, "RSVP Association Object Extensions", RFC 6780, October 2012. [RFC7551] Zhang, F., Ed., Jing, R., and Gandhi, R., Ed., "RSVP-TE Extensions for Associated Bidirectional LSPs", RFC 7551, May 2015. [GMPLS-FRR] Taillon, M., Saad, T., Ed., Gandhi, R., Ed., Ali, Z., "Extensions to Resource Reservation Protocol For Fast Reroute of Traffic Engineering GMPLS LSPs", draft-ietf- teas-gmpls-lsp-fastreroute, work in progress. 9.2. Informative References [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001. [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC 3473, January 2003. [RFC5920] Fang, L., "Security Framework for MPLS and GMPLS Networks", RFC 5920, July 2010. [RFC6370] Bocci, M., Swallow, G., and E. Gray, "MPLS Transport Profile (MPLS-TP) Identifiers", RFC 6370, September 2011. [RFC6373] Andersson, L., Berger, L., Fang, L., Bitar, N., and E. Gray, "MPLS Transport Profile (MPLS-TP) Control Plane Framework", RFC 6373, September 2011. Gandhi, et al. Expires March 14, 2017 [Page 10] Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016 Authors' Addresses Rakesh Gandhi (editor) Cisco Systems, Inc. EMail: rgandhi@cisco.com Himanshu Shah Ciena EMail: hshah@ciena.com Jeremy Whittaker Verizon EMail: jeremy.whittaker@verizon.com Gandhi, et al. Expires March 14, 2017 [Page 11]