Network Working Group Siva Sivabalan INTERNET-DRAFT Sami Boutros Intended Status: Informational Luca Martini Cisco Systems Expires: April 23, 2013 October 20, 2012 Stitching Procedures for Static PW in MPLS-TP Environment draft-ietf-pwe3-mpls-tp-ms-pw-01.txt Abstract The existing procedures for concatenating static and dynamic pseudowires (PWs) do not take into account the PW status Operation, Administration, and Maintenance (OAM) messages defined for static PW. Also, these procedures do not take into account operator functions such Lock Instruct and Loopback introduced as part of MPLS Transport Profile (MPLS-TP). This informational document reiterates stitching procedures for static PW taking into account all the new proposed extensions. This document is a product of a joint Internet Engineering Task Force(IETF) / International Telecommunication Union Telecommunication Standardization Sector (ITU-T) effort to include an MPLS Transport Profile within the IETF MPLS and PWE3 architectures to support the capabilities and functionalities of a packet transport network. Status of this Memo This Internet-Draft is submitted to IETF 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/1id-abstracts.html Sivabalan Expires April 23, 2013 [Page 1] INTERNET DRAFT mpls-tp-ms-pw October 20, 2012 The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Copyright and License Notice Copyright (c) 2012 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 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. Lock Operation . . . . . . . . . . . . . . . . . . . . . . 4 3.1.1. Locking MPLS-TP LSP . . . . . . . . . . . . . . . . . . 4 3.1.1.1. LI originated at T-PE . . . . . . . . . . . . . . . 4 3.1.1.2. LI originated at S-PE . . . . . . . . . . . . . . . 5 3.1.2. Locking PW . . . . . . . . . . . . . . . . . . . . . . 5 3.1.2.1. LI originated at T-PE . . . . . . . . . . . . . . . 5 3.2. Loopback Operation . . . . . . . . . . . . . . . . . . . . 6 3.3. Switching Point PE TLV . . . . . . . . . . . . . . . . . . 6 3.4. VCCV Procedures . . . . . . . . . . . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. Normative References . . . . . . . . . . . . . . . . . . . 6 6.2. Informative References . . . . . . . . . . . . . . . . . . 6 6. Author's Addresses . . . . . . . . . . . . . . . . . . . . . . 7 Sivabalan Expires April 23, 2013 [Page 2] INTERNET DRAFT mpls-tp-ms-pw October 20, 2012 1. Introduction The PWE3 Architecture in [1] defines signaling and encapsulation techniques for establishing Single Segment PW (SS-PW) between a pair of terminating PEs. Procedures for stitching two or more static or dynamic SS-PWs to form Multi-Segment PW (MS-PW) are described in [2]. These procedures make use of PW status messages carried in LDP TLV over dynamic PW established via LDP. [3] defines a new PW status OAM message used to carry PW status in-band over static PW. This message makes it possible to exchange PW status end-to-end over a MS-PW consisting of one or more static PW. [5] specifies operator new Operation, Administration, and Maintenance (OAM) functions Lock Instruct (LI) and Loopback (LB) for associated bi-directional circuits such as MPLS-TP LSP, SS-PW, and MS-PW in an MPLS Transport Profile (MPLS-TP) environment. These functions enable network operators to lock a circuit (LSP and PW) and operate it in loopback mode for testing/management purpose. This informational document describes the application of the existing PW stitching procedures taking into consideration LI, LB, as well as PW status OAM messages. This document is a product of a joint Internet Engineering Task Force (IETF) / International Telecommunication Union Telecommunication Standardization Sector (ITU-T) effort to include an MPLS Transport Profile within the IETF MPLS and PWE3 architectures to support the capabilities and functionalities of a packet transport network. 2. Terminology LDP: Label Distribution Protocol. MEP: Maintenance End Point. MIP: Maintenance Intermediate Point. MPLS: Multi Protocol Label Switching. MPLS-TP: MPLS Transport Profile. MS-PW: Multi- Segment PseudoWire. LB: Loopback. LI: Lock Instruct. LSP: Label Switched Path. OAM: MPLS Operations, Administration and Maintenance. PE: Provide Edge Node. PW: PseudoWire. S-PE: Switching Provider Edge Node of a MS-PW. SS-PW: Single-Segment PseudoWire. TLV: Type, Length, and Value. T-PE: Terminating Provider Edge Node of a MS-PW. 3. Operation In this section, we explain the use of LI/LB mechanisms referring to the MS-PW model shown in Figure 1. The SS-PW segments PW1 and PW2 can be either static or dynamic. We assume that PWs are carried over Sivabalan Expires April 23, 2013 [Page 3] INTERNET DRAFT mpls-tp-ms-pw October 20, 2012 MPLS-TP LSPs (transport LSPs) so that LI/LB mechanisms can be applied at the transport LSP level, as well we consider the application of LI/LB at PW level. PW status is sent via LDP message and PW OAM message respectively over dynamic and static PW segments. Note that even though only two PW segments are considered in the examples below, the described procedures are applicable to MS-PWs with more than two segments. +-------+ (PW1) +-------+ (PW2) +-------+ | |------------->| |-------------->| | | T-PE1 | | S-PE | | T-PE2 | | |<-------------| |<--------------| | +-------+ +-------+ +-------+ Figure 1. Reference Model for LI/LB Mechanism 3.1. Lock Operation 3.1.1. Locking MPLS-TP LSP An MPLS-TP LSP can be taken out of service for maintenance operation using the LI mechanism described in [5]. LI messages are exchanged between MPLS-TP Maintenance End Points (MEPs). In the case of MS-PW, each MPLS-TP LSP associated with a given PW segment can be individually locked for management purpose. This means that, in a MS- PW scenario, a T-PE is always a MEP and an S-PE is a MEP for an MPLS- TP LSP carrying PW segments. 3.1.1.1. LI originated at T-PE Assume that T-PE1 originates an LI request for the MPLS-TP LSP carrying PW1. The intended recipient of the message will be the S-PE. Before locking the MPLS-TP LSP, PW1 and all other PWs associated with the MPLS-TP LSP will be taken out of service. This means that PW1 and all other impacted PWs will no longer carry user data. When S-PE receives an LI request, before locking the MPLS-TP LSP, the S-PE finds all PWs associated with this MPLS-TP LSP and first sends the PW status code 0x00000018 (Local PSN-facing PW Receive/Transmit Faults) on all stitched PWs segments to T-PE2. PW status code is sent over PW OAM message or LDP message depending on whether the segment PW2 is static or dynamic. When T-PE2 receives the PW status codes, it processes them as described in [3] or [4] depending on whether PW2 is dynamic or static. Sivabalan Expires April 23, 2013 [Page 4] INTERNET DRAFT mpls-tp-ms-pw October 20, 2012 If PW2 is a dynamic segment and does not support PW status, S-PE needs to withdraw its labels from T-PE2 before locking the MPLS LSP. For better scalability, S-PE may use the notion of group ID described in [6] to send PW status or withdraw labels all impacted dynamic PWs between itself and T-PE2. Use of group ID with PW status OAM over static PW is TBD. 3.1.1.2. LI originated at S-PE Let's assume that an operator wants to originate an LI request at S- PE for the MPLS-TP LSP carrying PW1. The intended recipient of the LI request is T-PE1. First, S-PE sends PW status code 0x00000018 (Local PSN-facing PW Receive/Transmit Fault) for PW1 as well as all other PWs pinned down to MPLS-TP LSP in question to T-PE1 and PW2 and all other stitched PWs other segments to T-PE2. PW status code is sent over PW OAM message or LDP message depending on whether the segment PW2 is static or dynamic. When T-PE2 receives the PW status codes, it processes them as described in [3] or [4] respectively depending on whether PW2 is dynamic or static. It then sends LI request message to T-PE1, and PW1 is no longer used for carrying regular user data. If PW2 is a dynamic segment and PW status, S-PE needs to withdraw its labels from T-PE1 and T-PE2 before sending LI request to T-PE1. For better scalability, S-PE may use the notion of group ID described in [6] to send PW status or withdraw labels all impacted dynamic PWs. Use of group ID with PW status OAM over static PW is TBD. 3.1.2. Locking PW A given PW can also be taken out of service for maintenance operation without impacting services over other PWs using the LI mechanism described in [5]. 3.1.2.1. LI originated at T-PE In our example, let's assume that, T-PE1 sends an LI request message to lock PW1. S-PE is the intended recipient (based on the TTL value of the PW label). S-PE sends a PW status message with the status code 0x00000018 (Local PSN-facing PW Receive/Transmit Fault) over PW2 to T-PE2, and locks PW1. PW status code is sent over PW OAM message or LDP message depending on whether the segment PW2 is static or dynamic. When T-PE2 receives the PW status codes, it processes them as described in [3] or [4] depending on whether PW2 is dynamic or static. Sivabalan Expires April 23, 2013 [Page 5] INTERNET DRAFT mpls-tp-ms-pw October 20, 2012 3.2. Loopback Operation As described in [5], an MPLS-TP LSP or a PW can be setup to in loopback mode for management purpose, e.g., to test or verify connectivity of the LSP/PW up to a specific node on the path of the MPLS-TP tunnel/PW, and to test the LSP/PW performance with respect to delay/jitter, etc. But, prior to operating in loopback mode, an MPLS- TP LSP or PW must be successfully locked. 3.3. Switching Point PE TLV Switching Point PE TLV (S-PE TLV) is used to record information about S-PE(s) that a PW traverses. An S-PE TLV contains many sub-TLVs as described in [3]. One such sub-TLV carries the FEC of the last traversed PW segment. In the case of MS-PW containing static PW segment(s), if the last traversed PW segment is statically provisioned, a new sub-TLV containing the FEC defined for static PW in [7] can be used to represent the last traversed PW segment. The new sub-TLV type will be defined in [4]. 3.4. VCCV Procedures The same procedures defined in [3] can be used. 4. Security Considerations This document does not introduce any additional security constraints. 5. References 5.1. Normative References [1] Bradner. S, "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March, 1997. 6.2. Informative References [2] Stewart Bryant, et. al, "Pseudowire Emulation Edge-to-Edge (PWE3) Architecture", RFC3985, March 2005. [3] Luca Martini, et. al, "Segmented Pseudowire", draft-ietf-pwe3- segmented-pw-15.txt (work in progress), June 2010. [4] Luca Martini, et. al, "Pseudowire Status for Static Pseudowires", draft-ietf-pwe3-static-pw-status-00.txt (work in Sivabalan Expires April 23, 2013 [Page 6] INTERNET DRAFT mpls-tp-ms-pw October 20, 2012 progress), February 2010. [5] Sami Boutros, et. al, "MPLS Transport Profile Lock Instruct and Loopback Functions", draft-ietf-mpls-tp-li-lb-00.txt (work in progress), June 2010. [6] Luca Martini, et. al, "Pseudowire Setup and Maintenance Using Label Distribution Protocol (LDP)", RFC4447, April 2006. [7] Nitin Bahadur, et. al, "LSP-Ping extensions for MPLS-TP", draft-ietf-mpls-tp-lsp-ping-extensions-01.txt (work in progress), February 2010. 6. Author's Addresses Siva Sivabalan Cisco Systems, Inc. 2000 Innovation Drive Kanata, Ontario, K2K 3E8 Canada Email: msiva@cisco.com Sami Boutros Cisco Systems, Inc. 3750 Cisco Way San Jose, California 95134 USA Email: sboutros@cisco.com Luca Martini Cisco Systems, Inc. 9155 East Nichols Avenue, Suite 400 Englewood, CO, 80112 United States Email: lmartini@cisco.com Sivabalan Expires April 23, 2013 [Page 7]