Network Working Group Neil Hart Internet Draft Mustapha Aissaoui Expires: December 2006 Tiberiu Grigoriu Matthew Bocci Alcatel VCCV Extensions for Segmented Pseudo-Wire draft-hart-pwe3-segmented-pw-vccv-00.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. This document may only be posted in an Internet-Draft. 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 December 19, 2006. Abstract This document describes extensions to Single Hop Virtual Circuit Connectivity Verification (SH-VCCV) procedures for segmented pseudo Hart et al. Expires December 19, 2006 [Page 1] Internet-Draft Segmented Pseudo Wire VCCV June 2006 wires to test the end-to-end forwarding datapath and to provide a PW segment trace capability. This is accomplished by changing the adaptation function for the Single Hop VCCV parameter at the switching point between two distinct PW control planes. Table of Contents 1. Terminology.................................................2 2. Introduction................................................3 2.1. Single Hop VCCV adaptation for end to end verification...4 2.1.1. Inband VCCV using Control Word.....................4 2.2. Single Hop VCCV adaptation for partial tracing from T-PE.5 2.3. VCCV between S-PEs......................................5 3. Security Considerations......................................5 4. IANA Considerations.........................................5 5. Acknowledgments.............................................5 5.1. Normative References....................................6 5.2. Informative References..................................6 Author's Addresses.............................................6 Intellectual Property Statement.................................6 Disclaimer of Validity.........................................7 Copyright Statement............................................7 Acknowledgment.................................................7 1. Terminology - PW Terminating Provider Edge (T-PE). A PE where the customer- facing attachment circuits (ACs) are bound to a PW forwarder. A Terminating PE is present in the first and last segments of a MS-PW. This incorporates the functionality of a PE as defined in [RFC3985]. - Single-Segment Pseudo Wire (SS-PW). A PW setup directly between two T-PE devices. Each PW in one direction of a SS-PW traverses one PSN tunnel that connects the two T-PEs. - Multi-Segment Pseudo Wire (MS-PW). A static or dynamically configured set of two or more contiguous PW segments that behave and function as a single point-to-point PW. Each end of a MS-PW by definition MUST terminate on a T-PE. - PW Segment. A part of a single-segment or multi-segment PW, which is set up between two PE devices, T-PEs and/or S-PEs. Hart et al. Expires December 19, 2006 [Page 2] Internet-Draft Segmented Pseudo Wire VCCV June 2006 - PW Switching Provider Edge (S-PE). A PE capable of switching the control and data planes of the preceding and succeeding PW segments in a MS-PW. The S-PE terminates the PSN tunnels of the preceding and succeeding segments of the MS-PW. - PW switching point for a MS-PW. A PW Switching Point is never the S-PE and the T-PE for the same MS-PW. A PW switching point runs necessary protocols to setup and manage PW segments with other PW switching points and terminating PEs 2. Introduction Virtual Circuit Connectivity Verification (VCCV) allows network operators to test the forwarding datapath of pseudo wire (PW) services. As pseudo wires are extended to cover multiple segments, it will be important to maintain the facility to verify the forwarding datapath. Figure 1 illustrates a multi-segment pseudo wire providing connectivity from T-PE1 to T-PE2 through the switching point S-PE. By suitable implementation at the S-PEs, VCCV can be simply extended to provide both end to end and single segment connection verification. Native |<-----------Pseudo Wire----------->| Native Layer2 | | Layer2 Service | |<-PSN1-->| |<--PSN2->| | Service (AC) V V V V V V (AC) | +----+ +-----+ +----+ | +----+ | | |=========| |=========| | | +----+ | |----------|........PW1.........|...PW3........|----------| | | CE1| | | | | | | | | |CE2 | | |----------|........PW2.........|...PW4........|----------| | +----+ | |=========| |=========| | +----+ ^ +----+ +-----+ +----+ ^ | T-PE1 S-PE T-PE2 | | | |<------------------- Emulated Service -------->| Figure 1 MS-PW Service In Figure 1 T-PE1 uses the VCCV parameter included in the interface parameter field of the PW ID FEC TLV or the sub-TLV interface parameter of the Generalized PW ID FEC TLV to indicate to the far end T-PE2 what VCCV capabilities T-PE1 supports. This is the same VCCV parameter as would be used if T-PE1 and T-PE2 were connected directly by T-LDP. S-PE2, which is a PW switching point, as part of the adaptation function for interface parameters, processes locally the VCCV parameter then passes it to T-PE2. If there were multiple S-PEs on the path between T-PE1 and T-PE2, each would carry out the same Hart et al. Expires December 19, 2006 [Page 3] Internet-Draft Segmented Pseudo Wire VCCV June 2006 processing, passing along the VCCV parameter. The local processing of the VCCV parameter removes CC Types specified by the originating T- PE, except PWE3 Control Word that is passed unchanged. For example, if T-PE1 indicates as supported CC Types both Control Word and Router Alert then the S-PE removes the Router Alert CC Type, leaving Control Word unchanged and then passes the modified VCCV parameter to the next S-PE along the path. The far end T-PE (T-PE2) receives the VCCV parameter indicating the Control Word CC Type only if that is supported by the initial T-PE (T-PE1) and all S-PEs along the PW path. The method proposed in this document is a variant to the one described in [PWE3-MS] which is based on defining a new VCCV sub-TLV in the optional PW switching point TLV. The advantages of the proposed method are that it limits the processing of the VCCV messages only to the S-PE/T-PE node which is the target for the message. All other S-PE nodes in between are not required to inspect the VCCV CW and are only required to decrement the TTL of the PW label. Furthermore, it provides a model of operation consistent with the operation of MPLS LSP Ping and LSP Trace. 2.1. Single Hop VCCV adaptation for end to end verification 2.1.1. Inband VCCV using Control Word In Figure 1, if T-PE1, S-PE and T-PE2 support Control Word for VCCV, then as described in section 1 the control plane negotiates the common use of Control Word for VCCV end to end. At the S-PE the data path operations include an outer label pop, inner label swap and new outer label push. Note that there is no requirement for the S-PE to inspect the CW. Thus, the end-to-end connectivity of the multi-segment pseudowire can be verified by: a) setting the PWE Control Word CC Type in the VCCV parameter sent by each T-PE, b) by each S-PE maintaining the Control Word CC Type in the VCCV parameter, and c) inner PW label TTL needs to be set to a large enough value to allow the packet to reach the far end Hart et al. Expires December 19, 2006 [Page 4] Internet-Draft Segmented Pseudo Wire VCCV June 2006 d) by the T-PE sending a VCCV packet that will follow the exact same datapath at each S-PE as that taken by data packets, and that will be diverted to VCCV control processing at the destination T- PE. 2.2. Single Hop VCCV adaptation for partial tracing from T-PE In order to trace part of the multi-segment pseudowire, the TTL of the PW label may be used to force the VCCV message to 'pop out' at an intermediate node. When the TTL expires, the S-PE can determine that the packet is a VCCV packet by checking the control word. If the control word format matches that specified in [VCCV], the packet should be diverted to VCCV processing. In Figure 1, if T-PE1 sends a VCCV message with the TTL of the PW label equal to 1, the TTL will expire at the S-PE. T-PE1 can thus verify the first segment of the pseudo wire. Note that this use of the TTL is subject to the caution expressed in [VCCV]. If a penultimate LSR between S-PEs or between an S-PE and a T-PE manipulates the PW label TTL, the VCCV message may not emerge from the MS-PW at the correct S-PE. It is also a requirement that each S-PE decrement the PW label TTL correctly. 2.3. VCCV between S-PEs Assuming that all nodes along an MS-PW support the Control Word CC Type, VCCV between S-PEs may be accomplished using the PW label TTL as in section 2.2. In Figure-1, the S-PE may verify the path between it and T-PE2 by sending a VCCV message with the PW label TTL set to 1. Given a more complex network with multiple S-PEs, an S-PE may verify the connectivity between it and an S-PE two segments away by sending a VCCV message with the PW label TTL set to 2. 3. Security Considerations Same as security concerns described in [VCCV]. 4. IANA Considerations All the values of the CC, CV and channel types are as described in [VCCV]. 5. Acknowledgments The authors would like to thank Vach Kompella, Kendall Harvey and Michael Hua for their valuable comments and suggestions. Hart et al. Expires December 19, 2006 [Page 5] Internet-Draft Segmented Pseudo Wire VCCV June 2006 References 5.1. Normative References [VCCV] Nadeau, T., et al."Pseudo Wire Virtual Circuit Connection Verification (VCCV)", Internet Draft [PWE3-MS] Martini L., ''Segmented Pseudo Wire'', Internet Draft 5.2. Informative References Author's Addresses Neil Hart Alcatel 600 March Rd Kanata, ON, Canada. K2K 2E6 Email: neil.hart@alcatel.com Tiberiu Grigoriu Alcatel 600 March Rd Kanata, ON, Canada. K2K 2E6 Email: tiberiu.grigoriu@alcatel.com Mustapha Aissaoui Alcatel 600 March Rd Kanata, ON, Canada. K2K 2E6 Email: mustapha.aissaoui@alcatel.com Matthew Bocci Alcatel Voyager Place, Shoppenhangers Rd Maidenhead, Berks, UK SL6 2PJ Email: matthew.bocci@alcatel.co.uk 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 Hart et al. Expires December 19, 2006 [Page 6] Internet-Draft Segmented Pseudo Wire VCCV June 2006 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. 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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 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 Internet Society (2006). 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Hart et al. Expires December 19, 2006 [Page 7]