MPLS Working Group R. Bonica Internet-Draft D. Gan Intended status:
InformationalStandards Track Juniper Networks Expires: March 30,June 15, 2007 D. Tappan C. Pignataro Cisco Systems, Inc. September 26,December 12, 2006 ICMP Extensions for MultiProtocol Label Switching draft-ietf-mpls-icmp-06draft-ietf-mpls-icmp-07 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. 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 30,June 15, 2007. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This memo defines an extension object that can be appended to selected multi-part ICMP thatmessages. This extension permits Label Switching Routers to append MPLS information to ICMP messages. This extensionmessages, and has already been widely deployed and this memo is introduced to describe existing practice.deployed. Table of Contents 1. Conventions Used In This Document . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Architectural Considerations . . . . . . . . . . . . . . . . . 4 4.Application to TRACEROUTE . . . . . . . . . . . . . . . . . . . 4 5.4. Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6.4 5. MPLS Label Stack EntryObject . . . . . . . . . . . . . . . . . . . . 5 7.6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 8.7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 9.8. Normative References . . . . . . . . . . . . . . . . . . . . . 67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 67 Intellectual Property and Copyright Statements . . . . . . . . . . 89 1. 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 RFC2119 .[RFC2119]. 2. Introduction IP routers use the Internet Control Message Protocol (ICMP) Protocol, ICMPv4 [RFC0792] and ICMPv6 [RFC4443], to convey control information to source hosts. Network operators use this information to diagnose routing problems. When a router receives an undeliverable IP datagram, it can send an ICMP message to the host that originated the datagram. The ICMP message indicates why the datagram could not be delivered. It also contains the IP header and leading payload octets of the "original datagram" to which the ICMP message is a response. MPLS Label Switching Routers (LSR) also use ICMP to convey control information to source hosts. Sections 2.3 and 2.4 of RFC 3032 [RFC3032] describe the interaction between MPLS and ICMP. When an LSR receives an undeliverable MPLS encapsulated datagram, it removes the entire MPLS label stack, exposing the previously encapsulated IP datagram. The LSR then submits the IP datagram to an error processing module. Error processing can include ICMP message generation. The ICMP message indicates why the original datagram could not be delivered. It also contains the IP header and leading octets of the original datagram. The ICMP message, however, contains no information regarding the MPLS label stack that encapsulated the original datagram when it arrived at the LSR. This omission is significant because the LSR would have routedforwarded the original datagram based upon information contained by the MPLS label stack. This memo defines an extension toICMP extension object that permits an LSR to append MPLS label stackinformation to ICMP messages. Selected ICMP messages regarding MPLS encapsulated datagramsSHOULD include the MPLS label stack, as it arrived at the router that is sending the ICMP message. The ICMP message MUST also include the IP header and leading payload octets of the original datagram. The ICMP extensions defined in this document must be preceded by an ICMP Extension Structure Header and an ICMP Object Header. Both are defined in .[I-D.bonica-internet-icmp]. The ICMP extensionsextension defined in this document is equally applicable to ICMPv4 [RFC0792] and ICMPv6 [RFC4443]. Throughout this document, unless otherwise specified, the Internet Control Message Protocol version 6 (ICMPv6) . 3. Architectural Considerations Only layer 3 information should be included inacronym ICMP messages. MPLS information can be included only in so much as MPLS participates in layer 3 routing. Layer 2 information (e.g., ethernet, PPP) should not be included inrefers to multi-part ICMP messages. 4.messages, encompassing both ICMPv4 and ICMPv6. 3. Application to TRACEROUTE The ICMP extensions defined in this memo support enhancements to TRACEROUTE. The enhancedEnhanced TRACEROUTE application,applications, like older implementations, indicatesindicate which nodes the original datagram visited en route to its destination. It differsThey differ from older implementations in that itthey also reflectsreflect the original datagram's MPLS encapsulation status as it arrived at each node. Figure 1 contains sample output from an enhanced TRACEROUTE implementation. > traceroute 192.0.2.1 traceroute to 192.0.2.1 (192.0.2.1), 30 hops max, 40 byte packets 1 192.0.2.13 (192.0.2.13) 0.661 ms 0.618 ms 0.579 ms 2 192.0.2.9 (192.0.2.9) 0.861 ms 0.718 ms 0.679 ms MPLS Label=100048 Exp=0 TTL=1 S=1 3 192.0.2.5 (192.0.2.5) 0.822 ms 0.731 ms 0.708 ms MPLS Label=100016 Exp=0 TTL=1 S=1 4 192.0.2.1 (192.0.2.1) 0.961 ms 8.676 ms 0.875 ms Figure 1: Enhanced TRACEROUTE Sample Output 5.4. Disclaimer This memo does not define the general relationship between ICMP and MPLS. Section 2.3 of RFC3032[RFC3032] defines this relationship. The current memo does not define encapsulation specific TTL manipulation procedures. It defers to Section 5.4 of RFC 3034 [RFC3034] and Section 10 of RFC 3035 [RFC3035] in this matter. When encapsulation specific TTL manipulation procedures defeat the basic TRACEROUTE mechanism, they will also defeat enhanced TRACEROUTE implementations. 6.5. MPLS Label Stack Object The MPLS Label Stack EntryObject This section defines an ICMP extention object thatcan be appended to the ICMP Time Exceeded and Destination Unreachable messages. A single instance of the MPLS EntryLabel Stack Object classrepresents the entire MPLS label stack, formatted exactly as it was when it arrived at the LSR that sends the ICMP message. Figure 2 depicts the MPLS Label Stack EntryObject. It must be preceded by an ICMP Extension Structure Header and an ICMP Object Header. Both are defined in .[I-D.bonica-internet-icmp]. In the object payload, octets 0-3 depict the first member of the MPLS label stack. Each remaining member of the MPLS label stack is represented by another 4 octets that share the same format. MPLS Label Stack EntryClass = 1, C-Type = 1. 0 1 2 3 +-------------+-------------+-------------+-------------+ | Label |EXP |S| TTL | +-------------+-------------+-------------+-------------+ | | | // Remaining MPLS Stack Entries // | | | +-------------+-------------+-------------+-------------+ Figure 2: MPLS Label Stack EntryObject Label: 20 bits Exp: Experimental Use, 3 bits S: Bottom of Stack, 1 bit TTL: Time to Live, 8 bits 7.6. Security Considerations This memo presents no security considerations beyond those already presented by currentdoes not specify the conditions that trigger the generation of ICMP applications (e.g., traceroute). 8. IANA Considerations IANA should should reserveMessages for Labeled IP Packets. It does not define the interaction between MPLS and ICMP. However, this document defines an object classextension that allows an MPLS router to append MPLS information to multi-part ICMP messages, and object typetherefore can provide the user of the traceroute application with additional information. Consequently, a network operator may wish to provide this information selectively based on some policy; for example, only include the MPLS extensions in ICMP messages destined to addresses within the network management blocks with administrative control over the router. An implementation could determine whether to include the MPLS Label Stack Entry Object fromextensions based upon the destination address of the ICMP message, or based on a global configuration option in the router. Alternativelly, an implementation may determine whether to include these MPLS extensions when TTL expires based on the number of label stack entries (depth of the label stack) of the incoming packet. Finally, an operator can make use of the TTL treatment on MPLS Pipe Model LSPs defined in [RFC3443] for a TTL-transparent mode of operation, that would prevent ICMP Time Exceeded altogether when tunneled over the MPLS LSP. 7. IANA Considerations IANA is requested to assign the following object Class-num in the ICMP Extension Object registry. 9.registry: Class-Num Description 1 MPLS Label Stack Class IANA is also requested to establish a registry for the corresponding class sub-type (C-Type) space, as follows: MPLS Label Stack Class Sub-types: C-Type Description 1 Incoming MPLS Label Stack 0xF7-0xFF Reserved for private use C-Type values are assignable on a first-come-first-serve (FCFS) basis [RFC2434]. 8. Normative References [I-D.bonica-internet-icmp] Bonica, R., "Modifying ICMP to Support Multi-part Messages", draft-bonica-internet-icmp-13 (work in progress), December 2006. [RFC0792] Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, September 1981. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.  Postel, J., "Internet Control Message Protocol", STD 5,[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 792, September 1981. 2434, October 1998. [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Encoding", RFC 3032, January 2001.  Bonica, R., "Modifying ICMP to Support Multi-part Messages", draft-bonica-internet-icmp-08 (work in progress), August 2006. [RFC3034] Conta, A., Doolan, P., and A. Malis, "Use of Label Switching on Frame Relay Networks Specification", RFC 3034, January 2001. [RFC3035] Davie, B., Lawrence, J., McCloghrie, K., Rosen, E., Swallow, G., Rekhter, Y., and P. Doolan, "MPLS using LDP and ATM VC Switching", RFC 3035, January 2001. [RFC3443] Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing in Multi-Protocol Label Switching (MPLS) Networks", RFC 3443, January 2003. [RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification", RFC 4443, March 2006. Authors' Addresses Ronald P. Bonica Juniper Networks 2251 Corporate Park Drive Herndon, VA 20171 US Email: firstname.lastname@example.org Der-Hwa Gan Juniper Networks 1194 N. Mathilda Ave. Sunnyvale, CA 94089 US Email: email@example.com Daniel C. Tappan Cisco Systems, Inc. 250 Apollo Drive Chelmsford, MA 01824 US Email: firstname.lastname@example.org@gmail.com Carlos Pignataro Cisco Systems, Inc. 7025 Kit Creek Road Research Triangle Park, N.C. 27709 US Email: email@example.com Full 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. 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