Network Working Group Sami Boutros (Ed.) Internet Draft Siva Sivabalan (Ed.) Intended status: Standards Track Cisco Systems, Inc. Expires: March
2,15, 2012 Rahul Aggarwal (Ed.) Juniper Networks,Arktan, Inc. Martin Vigoureux (Ed.) Alcatel-Lucent Xuehui Dai (Ed.) ZTE Corporation September 2,15, 2011 MPLS Transport Profile lock Instruct and Loopback Functions draft-ietf-mpls-tp-li-lb-04.txtdraft-ietf-mpls-tp-li-lb-05.txt 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/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 March 2,15, 2012. Abstract This document specifies one function and describes a second function which are applicable to MPLS transport networks. The first function enables an operator to lock a transport path while the second enables an operator to set, in loopback, a given node along a transport path. This document also defines the extension to MPLS operation, administration, and maintenance (OAM) to perform the lock function. Table of Contents 1. Introduction...................................................2 2. Terminology....................................................4 3. Lock Message...................................................5 3.1. Message Identification....................................5 3.2. LI Message Format.........................................5 4. Lock, Loopback and maintenance operations......................6 5. Operation......................................................6 5.1. Lock Operation............................................6 5.2. UnLock Operation..........................................7 5.3. General Procedures........................................7 5.4. Example Topology..........................................7 5.5. Locking a transport path..................................8 5.6. UnLocking a transport path................................8 6. Security Considerations........................................8 7. IANA Considerations............................................9 7.1. Pseudowire Associated Channel Type........................9 8. Acknowledgements...............................................9 9. References.....................................................9 9.1. Normative References......................................9 9.2. Informative References...................................10 Author's Addresses...............................................10 Full Copyright Statement.........................................11 Intellectual Property Statement..................................12 1. Introduction This document specifies one function and describes another function which are applicable to MPLS transport networks. The first function enables an operator to lock a transport path. The second function enables an operator to set that transport path in loopback at a specified node along the path. This document also defines the extensions to the MPLS operation, administration and maintenance (OAM) to perform the lock function. The Lock function pertains to Label Switched Paths (LSPs), Pseudowires(including multi-segment Pseudowires) and Sections. As per RFC 5860 , lock is an administrative state in which it is expected that no client traffic may be carried. However, test traffic and OAM messages dedicated to the transport path can be mapped on that transport path. Taking the example of an LSP, lock is initiated by an operator. Typically when an LSP is locked, both ends of the LSP are independently locked by the operator. It is often difficult to coordinate these lock operations within a tight window. This document defines a new OAM message, Lock Instruct (LI) in order to provide the desired tight coordination. When an endpoint of an LSP or PW is locked by an operator, the MEP sends LI messages to its peer MEP. An endpoint considers the LSP to be locked when either it receives an external operator command or when it receives an LI message. The Lock function can be performed using an extension to the MPLS OAM as described in the next sections. This is a common mechanism to lock PWs, LSPs and Sections. The Lock function can as well be realized using a management plane. The Loopback function is operated by NMS from MEP to MEP on bidirectional (associated and co-routed) Label Switched Paths (LSPs), Pseudowires (including multi-segment Pseudowires) and Sections. The Loopback function is additionally operated from MEP to MIP on co- routed bidirectional LSPs, on multi-segment Pseudowires and Sections. The Loopback is a function that enables a MEP to request a MEP or a MIP to enter a loopback state. This state corresponds to the situation where, at a given node, a forwarding plane loop is configured and the incoming direction of a transport path is cross- connected to the outgoing reverse direction. Therefore, except in the case of early TTL expiry, traffic sent by the source will be received by that source. Note that before setting a given node in Loopback for a specific transport path, this transport path MUST be locked. Data plane loopback is an out-of-service function, as required in section 2.2.5 of RFC 5860 . This function loops back all traffic (including user data and OAM). The traffic can be originated from one internal point at the ingress of a transport path within an interface or inserted from input port of an interface using an external test equipment. The traffic is looped back unmodified (other than normal per hop processing such as TTL decrement) in the direction of the point of origin by an interface at either an intermediate node or a terminating node. It should be noted that data plane loopback function itself is applied to data plane loopback points that can resides on different interfaces from MIPs/MEPs. All traffic (including both payload and OAM) received on the looped back interface is sent on the reverse direction of the transport path. If the data plane loopback point is set somewhere at an intermediate point in bidirectional transport path, the side of loop back function (one side or both side) needs to be configured. A management system can configure one side or both sides to loopback at an intermediate point. The Loopback can be performed using a management plane. Management plane MUST insure that the two MEPs are locked before performing the loopback function. The Lock function is based on a new G-ACH message using a new channel type as well as an existing TLV. When an LSP is locked, the management or control function is expected to lock both ends. The purpose of the Lock instruct LI message is to ensure the tight coordination of locking and unlocking the two ends. Lock Instruct messages may be lost during looping or maintenance operations, thus locking both ends is required, before such operations occur. 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 . 2. Terminology ACH: Associated Channel Header LSR: Label Switching Router MEP: Maintenance Entity Group End Point MIP: Maintenance Entity Group Intermediate Point. MPLS-TP: MPLS Transport Profile MPLS-OAM: MPLS Operations, Administration and Maintenance MPLS-TP LSP: Bidirectional Label Switch Path NMS: Network Management System TLV: Type Length Value TTL: Time To Live LI: Lock Instruct Transport path: MPLS-TP LSP or MPLS Pseudowire. 3. Lock Message 3.1. Message Identification The proposed mechanism uses a new code point in the Associated Channel Header (ACH) described in . The LI channel is identified by the ACH as defined in RFC 5586  with the Channel Type set to the LI code point = 0xHH. [HH to be assigned by IANA from the PW Associated Channel Type registry] The LI Channel does not use ACH TLVs and MUST NOT include the ACH TLV header. The LI ACH Channel is shown below. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 1|Version|Reserved | 0xHH (LI) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: ACH Indication of LI The LI Channel is 0xHH (to be assigned by IANA) 3.2. LI Message Format The format of an LI Message is shown below. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vers | Reserved | Refresh Timer | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MEP Source ID TLV | ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: MPLS LI Message Format Version: The Version Number is currently 1. (Note: the version number is to be incremented whenever a change is made that affects the ability of an implementation to correctly parse or process the message. These changes include any syntactic or semantic changes made to any of the fixed fields, or to any Type-Length-Value (TLV) or sub- TLV assignment or format that is defined at a certain version number. The version number may not need to be changed if an optional TLV or sub-TLV is added.) Refresh Timer: The maximum time between successive LI messages specified in seconds. The default value is 1. The value 0 is not permitted. When a lock is applied, a refresh timer is chosen. This value MUST NOT be changed for the duration of that lock. MEP Source ID TLV: This is the "CC/CV MEP ID TLV" defined in . 4. Lock, Loopback and maintenance operations When an LSP is locked, the management or control function is expected to lock both ends. The purpose of the LI message is to ensure the tight coordination of locking and unlocking the two ends. LI messages may be lost during looping or maintenance operations, thus locking both ends is required, before such operations occur. When a transport path is put in loopback, traffic sent from the sender MEP will be looped back to that sender MEP. OAM packets not intercepted by TTL expiry will as well be looped back. The use of traffic to measure packet loss, delay and delay variation is outside the scope of this document. 5. Operation 5.1. Lock Operation Lock is used to request a MEP to take a transport path out of service so that some form of maintenance can be done or other administrative reasons. When performing a lock, a sender MEP in response to a management system request MUST take the transport path out of service and MUST send LI messages periodically to the target MEP at the end of the transport path. LI messages will be sent once every refresh time interval. The receiver MEP, will lock the transport path as long as it is receiving the periodic LI messages. The receiver MEP once locked, MUST take the transport path out of service. A MEP can be locked because it was requested by NMS to lock and as such it is sending LI OAM messages, and/or it is receiving OAM LI messages from the other MEP. 5.2. UnLock Operation Unlock is used to request a MEP to bring the previously locked transport path back in service. When a MEP is unlocked via management or control it MUST cease sending LI messages. Further, it must have stopped receiving LI messages for a period of 3.5 times the previously received refresh timer before it brings the transport path back in service. A MEP would unlock transport path and put it back to service if and only if there is no management request to lock the path and it is not receiving in-band LI messages. A MEP is unlocked when there is no NMS request to Lock and no LI OAM messages are received. 5.3. General Procedures When taking a transport path out of service, the operation MUST first be preceded by a lock operation. 5.4. Example Topology The next sections discuss the procedures for locking, Unlocking a transport path. Assume a transport path traverses nodes A <--> B <-- > C <--> D. We will refer to the Maintenance Entities involved as MEP-A, MIP-B, MIP-C, and MEP-D respectively. Suppose a maintenance operation invoked at MEP-A requires to lock the transport path. The following sections describe MEP-A setting and unsetting a lock at MEP-D. 5.5. Locking a transport path 1. MEP-A sends an in-band LI Message in response to a Management system request to lock the transport path. The message will include the source MEP-ID TLV. 2. Upon receiving the LI message, D uses the received label stack and the source MEP-ID as per  to identify the transport path. If no label binding exists or there is no associated transport path back to the originator, or if the source MEP-ID does not match, the event is logged. Processing ceases. Otherwise the message is processed. 5.6. UnLocking a transport path 1. In response to a Management system request to unlock the transport path MEP-A stops sending LI Messages. 2. After 3.5 times the refresh timer, both sender MEP A and receive MEP D unlock the transport path and put the transport path back in service. 6. Security Considerations MPLS-TP is a subset of MPLS and so builds upon many of the aspects of the security model of MPLS. MPLS networks make the assumption that it is very hard to inject traffic into a network, and equally hard to cause traffic to be directed outside the network. The control plane protocols utilize hop-by-hop security, and assume a "chain-of-trust" model such that end-to-end control plane security is not used. For more information on the generic aspects of MPLS security, see . This document describes a protocol carried in the G-ACh , and so is dependent on the security of the G-ACh, itself. The G-ACh is a generalization of the Associated Channel defined in . Thus, this document relies heavily on the security mechanisms provided for the Associated Channel and described in those two documents. A specific concern for the G-ACh is that is can be used to provide a covert channel. This problem is wider than the scope of this document and does not need to be addressed here, but it should be noted that the channel provides end-to-end connectivity and SHOULD NOT be policed by transit nodes. Thus, there is no simple way of preventing any traffic being carried between in the G-ACh consenting nodes. A good discussion of the data plane security of an associated channel may be found in . That document also describes some mitigation techniques. It should be noted that the G-ACh is essentially connection-oriented so injection or modification of control messages specified in this document require the subversion of a transit node. Such subversion is generally considered hard in MPLS networks, and impossible to protect against at the protocol level. Management level techniques are more appropriate. 7. IANA Considerations 7.1. Pseudowire Associated Channel Type LI OAM requires a unique Associated Channel Type which is assigned by IANA from the Pseudowire Associated Channel Types Registry. Registry: Value Description TLV Follows Reference ----------- ----------------------- ----------- --------- 0xHHHH LI No (Section 3.1) 8. Acknowledgements The authors would like to thank Loa Andersson, Yoshinori Koike, D'Alessandro Alessandro Gerardo, Shahram Davari, Greg Mirsky, Yaacov Weingarten, Liu Guoman, Matthew Bocci, Stewart Bryant and Adrian Farrel for their valuable comments. 9. References 9.1. Normative References  Vigoureux, M., Ward, D., and M. Betts, "Requirements for Operations, Administration, and Maintenance (OAM) in MPLS Transport Networks", RFC 5860, May 2010.  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.  D. Allan, et. al., Proactive Connectivity Verification, Continuity Check and Remote Defect indication for MPLS Transport Profile draft-ietf-mpls-tp-cc-cv-rdi-06, work in progress, June 2010  Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic Associated Channel", RFC 5586, June 2009.  T. Nadeau, C. Pignataro, "Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires", RFC 5085, Dec 2007. 9.2. Informative References  L. Fang, "Security Framework for MPLS and GMPLS Networks", RFC 5920, July 2010.  S. Bryant, G. Swallow, L. Martini "Pseudowire Emulation Edge- to-Edge (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, Feb 2006. Author's Addresses Sami Boutros Cisco Systems, Inc. Email: email@example.com Siva Sivabalan Cisco Systems, Inc. Email: firstname.lastname@example.org Rahul Aggarwal Juniper Networks.Arktan, Inc EMail: email@example.com_1@yahoo.com Martin Vigoureux Alcatel-Lucent. Email: firstname.lastname@example.org Xuehui Dai ZTE Corporation. Email: email@example.com George Swallow Cisco Systems, Inc. Email: firstname.lastname@example.org David Ward Juniper Networks. Email: email@example.com Stewart Bryant Cisco Systems, Inc. Email: firstname.lastname@example.org Carlos Pignataro Cisco Systems, Inc. Email: email@example.com Eric Osborne Cisco Systems, Inc. Email: firstname.lastname@example.org Nabil Bitar Verizon. Email: email@example.com Italo Busi Alcatel-Lucent. Email: firstname.lastname@example.org Lieven Levrau Alcatel-Lucent. Email: email@example.com Laurent Ciavaglia Alcatel-Lucent. Email: firstname.lastname@example.org Bo Wu ZTE Corporation. Email: email@example.com Jian Yang ZTE Corporation. Email: firstname.lastname@example.org Full Copyright Statement Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. 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