Network Working Group George Swallow Internet Draft Cisco Systems, Inc. Category: Standards Track Expiration Date: August 2004 Kireeti Kompella Juniper Networks, Inc. Dan Tappan Cisco Systems, Inc. February 2004 Label Switching Router Self-Test draft-ietf-mpls-lsr-self-test-02.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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 The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document defines a means of self test for a Label-Switching Router (LSR) to verify that its dataplane is functioning for certain key Multi-Protocol Label Switching (MPLS) applications including unicast forwarding based on LDP [LDP] and traffic engineering tunnels based on [RSVP-TE]. A new Loopback FEC type Swallow, et al. Standards Track [Page 1] Internet Draft draft-ietf-mpls-lsr-self-test-02.txt February 2004 is defined to allow an upstream neighbor to assist in the testing at very low cost. MPLS Echo Request and MPLS Echo Reply messages [LSP-Ping] are extended to do the actual probing. Contents 1 Introduction ........................................... 3 1.1 Conventions ............................................ 3 2 Loopback FEC ........................................... 4 2.1 Loopback FEC Element ................................... 4 2.2 LDP Procedures ......................................... 5 3 Data Plane Self Test ................................... 5 3.1 Data Plane Verification Request / Reply Messages ....... 7 3.2 Downstream Verification Object ......................... 8 3.2.1 IPv4 Downstream Verification Object .................... 8 3.2.2 IPv6 Downstream Verification Object .................... 11 3.3 Reply-To Object ........................................ 13 3.3.1 IPv4 Reply-To Object ................................... 14 3.3.2 IPv6 Reply-To Object ................................... 14 3.4 Sending procedures ..................................... 15 3.5 Receiving procedures ................................... 16 3.6 Upstream Neighbor Verification ......................... 16 4 Security Considerations ................................ 17 5 IANA Considerations .................................... 17 6 Acknowledgments ........................................ 17 7 References ............................................. 18 7.1 Normative References ................................... 18 7.2 Informative References ................................. 18 8 Authors' Addresses ..................................... 18 9 Intellectual Property Notice ........................... 19 10 Full Copyright Statement ............................... 19 Swallow, et al. Standards Track [Page 2] Internet Draft draft-ietf-mpls-lsr-self-test-02.txt February 2004 1. Introduction This document defines a means of self test for a Label-Switching Router (LSR) to verify that its dataplane is functioning for certain key Multi-Protocol Label Switching (MPLS) applications including unicast forwarding based on LDP [LDP] and traffic engineering tunnels based on [RSVP-TE]. MPLS Echo Request and MPLS Echo Reply messages [LSP-Ping] messages are extended to do the actual probing. The pings are sent to an upstream neighbor, looped back through the LSR under test and intercepted, by means of TTL expiration by a downstream neighbor. Extensions to LSP-Ping [LSP-Ping] are defined to allow the down stream neighbor to report the test results. In order to minimize the load on upstream LSRs a new loopback FEC is defined. Receipt of a packet labeled with a loopback label will cause the advertising LSR to pop the label off the label stack and send the packet out the advertised interface. Note that use of a loopback allows an LSR to test label entries for which the LSR is not currently some neighbor's next hop. In this way label entries can be verified prior to the occurrence of a routing change. Some routing protocls, most notably OSPF have no means of exchanging the "Link Local Identifiers" used to identify unnumbered links and components of bundled links. These test procedures can be used to associate the neighbor's interfaces with the probing LSRs interfaces. This is achieved by simply having the TTL of the MPLS Ping expire one hop sooner, i.e. at the testing LSR itself. 1.1. Conventions 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 [KEYWORDS]. Swallow, et al. Standards Track [Page 3] Internet Draft draft-ietf-mpls-lsr-self-test-02.txt February 2004 2. Loopback FEC The Loopback FEC type is defined to enable an upstream neighbor to assist in LSR self-testing at very low cost. This FEC causes the loopback to occur in the dataplane without control plane involvement beyond the initial LDP exchange and dataplane setup. An LSR uses the Loopback FEC to selectively advertise loopback labels to its neighbor LSRs. Each loopback label is bound to a particular interface. For multi-access links, a unique label for each neighbor is required, since the link-level address is derived from the label lookup. When an MPLS packet with its top label set to a loopback label is received from an interface over which that label was advertised, the loopback label is popped and the packet is sent on the interface to which the loopback label was bound. TTL treatment for loopback labels follows the Uniform model. I.e. the TTL carried in the loopback label is decremented and copied to the exposed label or IP header as the case may be. 2.1. Loopback FEC Element FEC element type 130 is used. The FEC element is encoded as follows: (note: 130 is provisionally assigned, the actual value will be assigned by IANA.) 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 130 | Res | Interface Type| Id Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier | | " | | " | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Reserved (Res) Must be set to zero on transmission and ignored on receipt. Swallow, et al. Standards Track [Page 4] Internet Draft draft-ietf-mpls-lsr-self-test-02.txt February 2004 Interface Type # Type Interface Identifier --- ---- -------------------- 0 Unnumbered A 32 bit Link Identifier as defined in [RFC3477] 1 IPv4 Numbered IPv4 Address 2 IPv6 Numbered IPv6 Address Identifier Length Length of the interface identifier in octets. The length is 4 bytes for Unnumbered and IPv4, 16 bytes for IPv6. Address An identifier encoded according to the Identifier Type field. 2.2. LDP Procedures It is RECOMMENDED that loopback labels only be distributed in response to a Label Request message, irrespective of the label advertisement mode of the LDP session. However it is recognized that in certain cases such as OSPF with unnumbered links, the upstream LSR may not have sufficiently detailed information of the neighbor's link identifier to form the request. In these cases, the downstream LSR will need to be configured to make unsolicited advertisements. 3. Data Plane Self Test A self test operation involves three LSRs, the LSR doing the test, an upstream neighbor and a downstream neighbor. We refer to these as LSRs T, U, and D respectively. In order to minimize the processing load on LSRD, two new LSP Ping messages are defined, called the MPLS Data Plane Verification Request and the MPLS Data Plane Verification Reply. These messages are used to allow LSRT to obtain the label stack, address and interface information of LSRD. If FEC verification is required, the MPLS Echo Request and Reply messages are used. The packet flow is shown below. Although the figure shows LSRD adjacent to LSRT it may in some cases be an arbitrary number of hops away. Swallow, et al. Standards Track [Page 5] Internet Draft draft-ietf-mpls-lsr-self-test-02.txt February 2004 +------+ +------+ +------+ | ,-|-------| | | | | <-|-------| | | | | | +------+ +------+ LSRU LSRT Figure 2: Upstream Neighbor Verification No TLVs need to be included in the MPLS Data Plane Verification Request. By noting the Sender's Handle and Sequence Number, as well as the loopback label, LSRT is able to detect that a) the packet was looped, and b) determine (or verify) the interface on which the packet was received. 4. Security Considerations Were loopback labels widely known, they might be subject to abuse. It is therefore RECOMMENDED that loopback labels only be shared between trusted neighbors. Further, if the loopback labels are drawn from the Global Label Space, or any other label space shared across multiple LDP sessions, it is RECOMMENDED that all loopback labels be filtered from a session except those labels pertaining to interfaces directly connected to the neighbor participating in that session. 5. IANA Considerations TBD 6. Acknowledgments The authors would like to thank Vanson Lim, Tom Nadeau, and Bob Thomas for their comments and suggestions. Swallow, et al. Standards Track [Page 17] Internet Draft draft-ietf-mpls-lsr-self-test-02.txt February 2004 7. References 7.1. Normative References [RFC3036] Andersson, L. et al., "LDP Specification", January 2001. [LSP-Ping] Bonica, R. et al., "Detecting MPLS Data Plane Liveness", work-in-progress. [RFC3477] Kompella, K. & Y. Rekhter, "Signalling Unnumbered Links in Resource ReSerVation Protocol - Traffic Engineering (RSVP-TE)", January 2003. [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 7.2. Informative References [RSVP-TE] Awduche, D., et al, "RSVP-TE: Extensions to RSVP for LSP tunnels", RFC 3209, December 2001. 8. Authors' Addresses Kireeti Kompella Juniper Networks, Inc. 1194 N. Mathilda Ave. Sunnyvale, CA 94089 Email: kireeti@juniper.net George Swallow Cisco Systems, Inc. 1414 Massachusetts Ave Boxborough, MA 01719 Email: swallow@cisco.com Dan Tappan Cisco Systems, Inc. 1414 Massachusetts Ave Boxborough, MA 01719 Email: tappan@cisco.com Swallow, et al. Standards Track [Page 18] Internet Draft draft-ietf-mpls-lsr-self-test-02.txt February 2004 9. Intellectual Property Notice The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11 [RFC2028]. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. 10. Full Copyright Statement Copyright (C) The Internet Society (2004). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION Swallow, et al. Standards Track [Page 19] Internet Draft draft-ietf-mpls-lsr-self-test-02.txt February 2004 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Swallow, et al. Standards Track [Page 20]