Network Working Group George Swallow Internet Draft Cisco Systems, Inc. Category: Standards Track Expiration Date: January 2006 Kireeti Kompella Juniper Networks, Inc. Dan Tappan Cisco Systems, Inc. July 2005 Label Switching Router Self-Test draft-ietf-mpls-lsr-self-test-05.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 is an Internet-Draft and is in full conformance with all provisions of Section 5 of RFC3667. 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 Abstract This document defines a means for a Label-Switching Router (LSR) to verify that its dataplane is functioning for certain key Multi- Protocol Label Switching (MPLS) applications, including unicast Swallow, et al. Standards Track [Page 1] Internet Draft draft-ietf-mpls-lsr-self-test-05.txt July 2005 forwarding based on LDP [LDP] and traffic engineering tunnels based on [RSVP-TE]. A new Loopback FEC type 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 IPv4 Loopback FEC Element ................................. 4 2.2 LDP Procedures ............................................ 5 3 Data Plane Self Test ...................................... 6 3.1 Data Plane Verification Request / Reply Messages .......... 7 3.2 UDP Port .................................................. 8 3.3 Reply-To Object ........................................... 8 3.3.1 IPv4 Reply-To Object ...................................... 9 3.3.2 IPv6 Reply-To Object ...................................... 9 3.4 Sending procedures ........................................ 10 3.5 Receiving procedures ...................................... 11 3.6 Upstream Neighbor Verification ............................ 11 4 Security Considerations ................................... 12 5 IANA Considerations ....................................... 12 6 Acknowledgments ........................................... 13 7 References ................................................ 13 7.1 Normative References ...................................... 13 7.2 Informative References .................................... 13 8 Authors' Addresses ........................................ 14 Swallow, et al. Standards Track [Page 2] Internet Draft draft-ietf-mpls-lsr-self-test-05.txt July 2005 1. Introduction This document defines a means for a Label-Switching Router (LSR) to verify that its dataplane is functioning for certain key Multi-Proto- col 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] mes- sages 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-05.txt July 2005 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. The FEC also carries information to indicate the desired encapsulation should it be the only label in a received label stack. Values are defined for IPv4 and IPv6. An LSR uses a 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 adver- tised, the loopback label is popped and the packet is sent on the interface to which the loopback label was bound. If the label-stack only contains the one loopback label, the encapsulation of the packet is determined by the FEC Type. 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. IPv4 Loopback FEC Element FEC element type 130 is used. The FEC element is encoded as fol- lows: (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 | If & Prot Type| Id Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier | | " | | " | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Swallow, et al. Standards Track [Page 4] Internet Draft draft-ietf-mpls-lsr-self-test-05.txt July 2005 Reserved (Res) Must be set to zero on transmission and ignored on receipt. Interface & Protocol Type # Type Interface Identifier --- ---- -------------------- 1 IPv4 Numbered IPv4 Address 2 IPv4 Unnumbered A 32 bit Link Identifier as defined in [RFC3477] 3 IPv6 Numbered IPv6 Address 4 IPv6 Unnumbered A 32 bit Link Identifier as defined in [RFC3477] .in 9 Note that this type alos indicates the encapsulation type for payloads that have a label stack contain the one loopback label. Identifier Length Length of the interface identifier in octets. The length is 4 bytes for the unnumbered types 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 adver- tisement 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. Swallow, et al. Standards Track [Page 5] Internet Draft draft-ietf-mpls-lsr-self-test-05.txt July 2005 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 LSR-D, 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 LSR-T to obtain the label stack, address and interface information of LSR-D. If FEC verification is required, the MPLS Echo Request and Reply mes- sages are used. The packet flow is shown below. Although the figure shows LSR-D adja- cent to LSR-T it may in some cases be an arbitrary number of hops away. +-------+ +-------+ +-------+ | ,-|-------| | | | | | | | | | | <-|-------| | | | | | +-------+ +-------+ LSR-U LSR-T DPVRq: MPLS Data Plane Verification Request 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, LSR-T 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 This document makes the following codepoint assigments (pending IANA action): Registry Codepoint Purpose UDP Port tbd MPLS Verification Request LSP Ping Message Type 3 MPLS Data Plane Verification Request LSP Ping Message Type 4 MPLS Data Plane Verification Reply LSP Ping Object Type 11 IPv4 Reply-to Object Swallow, et al. Standards Track [Page 12] Internet Draft draft-ietf-mpls-lsr-self-test-05.txt July 2005 LSP Ping Object Type 12 IPv6 Reply-to Object 6. Acknowledgments The authors would like to thank Vanson Lim, Tom Nadeau, and Bob Thomas for their comments and suggestions. 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. Swallow, et al. Standards Track [Page 13] Internet Draft draft-ietf-mpls-lsr-self-test-05.txt July 2005 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 Copyright Notice Copyright (C) The Internet Society (2005). 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. Expiration Date January 2006 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. 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