MPLS Working Group D. Cohn R. Ram Internet Draft Orckit-Corrigent Intended status: Standards Track M. Yuxia July 5, 2011 ZTE Corp. Expires: February 5, 2012 M. Daikoku KDDI MPLS-TP Linear Protection Applicability to MS-PW draft-cohn-mpls-tp-pw-protection-01.txt 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), 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 This Internet-Draft will expire on February 5, 2012. Copyright Notice Copyright (c) 2011 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 (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 Cohn Expires February 5, 2012 [Page 1] Internet-Draft MPLS-TP LP Applicability to MS-PW Jul 2011 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. Abstract One of the requirements of the MPLS transport profile [RFC5654] is to provide linear protection for transport paths, which include both LSPs and PWs. The functional architecture described in [SurvivFwk] is applicable to both LSP and PWs, however [LinearProt] does not explicitly describe mechanisms for PW protection in MPLS-TP. This document extends the applicability of the linear protection mechanism described in [LinearProt] to MPLS-TP segmented PWs as defined in [RFC6073]. Table of Contents 1. Introduction ................................................ 2 1.1. Background on MS-PW..................................... 3 1.2. MS-PW protection requirements........................... 3 2. Conventions used in this document............................ 4 3. PSC applicability to PW...................................... 5 4. Security Considerations...................................... 5 5. IANA Considerations ......................................... 5 6. References .................................................. 5 6.1. Normative References.................................... 5 6.2. Informative References.................................. 5 7. Acknowledgments ............................................. 6 1. Introduction When specifying the requirements for an MPLS Transport Profile, [RFC5654] states that "In an MPLS-TP environment, a transport path corresponds to an LSP or a PW". It follows that recovery requirements in section 2.5 of [RFC5654] apply to PWs as well as to LSPs. The MPLS-TP survivability framework described in [SurvivFwk] states that "The general description of the functional architecture is applicable to both LSPs and pseudowires (PWs), however, PW recovery is only introduced in Section 7, and the relevant details are beyond the scope of this document and are for further study". Finally, the MPLS-TP OAM framework described in [OamFwk] provides tools for PW monitoring that are suitable for PW protection triggering. Cohn Expires February 5, 2012 [Page 2] Internet-Draft MPLS-TP LP Applicability to MS-PW Jul 2011 [LinearProt] describes a protection state coordination (PSC) protocol that can be used to provide linear protection for LSPs. This document extends the applicability of the PSC control logic and protocol to support MPLS-TP segmented PW (aka MS-PW) protection against S-PE failure. 1.1. Background on MS-PW This section reviews operator motivations for MS-PW usage in an MPLS-TP framework. Some of these are mentioned in [RFC5254] and [RFC6073]. o PSN Internetworking: The PW route may go across nodes that are interconnected using different PSN protocols. In this case, it is not possible to establish a single LSP between the terminating PEs, and therefore a single-segment PW (SS-PW) cannot be used. o Domain separation: The PW route may cross different administrative domains, either intra- or inter-operator. In this scenario, it may not be possible to establish a single transport path (LSP or PW) between nodes in different operators, so SS-PW cannot be used. o Reduce network delay variations: Some end users (e.g. financial customers) are very sensitive to the network delay provided by the operator service. Operators therefore want to minimize both the absolute network delay provided, and the variations in network delay upon different events, specifically node or link failures. SS-PW recovery from a link failure requires end-to-end switching to another SS-PW which will typically have a different network route and thus provide a significantly different network delay. MS-PW, on the other hand, allows link failure recovery by local switching on the failed segment, which typically achieves much lower network delay variation. MS-PW end-to-end switching, involving higher network delay variation, is performed only upon node (S-PE) failure. 1.2. MS-PW protection requirements PW protection is required to support PW recovery upon node failure of an S-PE in an MS-PW application. MS-PW and S-PE are defined in [RFC6073]. LSP recovery is not possible in this scenario and therefore a separate mechanism is required to provide MS-PW recovery. Figure 1 illustrates such a scenario, where two MS-PWs are established between T-PE A and T-PE Z, over S-PEs 1-2 and 3-4 Cohn Expires February 5, 2012 [Page 3] Internet-Draft MPLS-TP LP Applicability to MS-PW Jul 2011 respectively. Each PW segment is established over an LSP (e.g. PW- s12 over LSP12). <--------------MS-PW A12Z-------------> +----+ +-----+ +-----+ +----+ | |LSPA1 |SPE1 |LSP12 |SPE2 |LSP2Z | | | |------| X |------| X |------| | | |PW-sA1| |PW-s12| |PW-s2Z| | |TPEA| +-----+ +-----+ |TPEZ| | | | | | | +-----+ +-----+ | | | |PW-sA3|SPE3 |PW-s34|SPE4 |PW-s4Z| | | |------| X |------| X |------| | | |LSPA3 | |LSP34 | |LSP4Z | | +----+ +-----+ +-----+ +----+ <--------------MS-PW A34Z-------------> Figure 1: MS-PW protection Without loss of generality, it is assumed that MS-PW A12Z is active in the normal state. In the event of a failure in S-PE 1, LSPs A1 and 12 cannot recover by using LSP protection mechanisms, but the MS-PW can recover by switching to MS-PW A34Z. This mechanism requires coordination between the two MS-PW endpoints to decide which of the two MS-PWs will be active, i.e. transmitting data traffic. 2. 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 [ .1]. In this document, these words will appear with that interpretation only when in ALL CAPS. Lower case uses of these words are not to be interpreted as carrying RFC-2119 significance. Cohn Expires February 5, 2012 [Page 4] Internet-Draft MPLS-TP LP Applicability to MS-PW Jul 2011 3. PSC applicability to PW PSC control logic and protocol for MS-PW protection SHALL be as defined in sections 3 and 4 of [LinearProt]. All references therein to OAM indications SHALL be applied as referring to MS-PW OAM, i.e. provided by the MS-PW MEG (PMEG, as defined in section 4.3. of [OamFwk] ). All references therein to LER SHALL be applied as referring to T-PE. All reference therein to the server layer SHALL be applied as referring to the LSPs over which the MS-PW is carried. Protocol format SHALL be the same defined in section 4.2 of 0 .[LinearProt]. PW G-ACh is described in [RFC4385]. 4. Security Considerations No security considerations other than those mentioned in [LinearProt] apply. 5. IANA Considerations No new IANA considerations 6. References 6.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 6.2. Informative References [SurvivFwk] Sprecher, N., Farrel, A., and H. Shah, "Multi-protocol Label Switching Transport Profile Survivability Framework", draft-ietf-mpls-tp-survive-fwk-06, Jun 2010 [LinearProt] S. Bryant, E. Osborne, N. Sprecher, A. Fulignoli, Y. Weingarten, "MPLS-TP Linear Protection", draft-ietf- mpls-tp-linear-protection-06, Mar 2011 [OamFwk] I. Busi, D. Allan, "Operations, Administration and Maintenance Framework for MPLS-based Transport Networks", draft-ietf-mpls-tp-oam-framework-11, Feb 2011 Cohn Expires February 5, 2012 [Page 5] Internet-Draft MPLS-TP LP Applicability to MS-PW Jul 2011 [RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, February 2006. [RFC5254] Bitar, N., Ed., Bocci, M., Ed., and L. Martini, Ed., "Requirements for Multi-Segment Pseudowire Emulation Edge-to-Edge (PWE3)", RFC 5254, October 2008. [RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and S. Ueno, "Requirements of an MPLS Transport Profile", RFC 5654, Sep 2009 [RFC6073] Martini, L., Metz, C., Nadeau, T., Bocci, M., and M. Aissaoui, "Segmented Pseudowire", RFC 6073, Jan 2011. 7. Acknowledgments This document was prepared using 2-Word-v2.0.template.dot. Cohn Expires February 5, 2012 [Page 6] Internet-Draft MPLS-TP LP Applicability to MS-PW Jul 2011 Authors' Addresses Daniel Cohn Orckit-Corrigent Yigal Alon 126, Tel Aviv Israel Email: danielc@orckit.com Rafi Ram Orckit-Corrigent Yigal Alon 126, Tel Aviv Israel Email: rafir@orckit.com Ma Yuxia ZTE Corp. China Email: ma.yuxia@zte.com.cn Masahiro Daikoku KDDI Japan Email: ms-daikoku@kddi.com Cohn Expires February 5, 2012 [Page 7]