MPLS Working Group R. Bonica Internet-Draft D. Gan Expires:
March 24,September 17, 2006 Juniper Networks D. Tappan Cisco Systems, Inc. September 20, 2005March 16, 2006 ICMP Extensions for MultiProtocol Label Switching draft-ietf-mpls-icmp-04draft-ietf-mpls-icmp-05 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 24,September 17, 2006. Copyright Notice Copyright (C) The Internet Society (2005).(2006). Abstract This memo defines an extension to ICMP that permits Label Switching Routers to append MPLS information to ICMP messages. This extension has already been widely deployed and this memo is introduced to describe existing practice. Table of Contents 1. Conventions Used In This Document . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Architectural Considerations . . . . . . . . . . . . . . . . . 4 4. Application to TRACEROUTE . . . . . . . . . . . . . . . . . . . 4 5. Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . 4 6. MPLS Stack Entry Object . . . . . . . . . . . . . . . . . . . . 5 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 9. Normative References . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Intellectual Property and Copyright Statements . . . . . . . . . . 8 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 . 2. Introduction IP routers use the Internet Control Message Protocol (ICMP)  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  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 routed the original datagram based upon information contained by the MPLS label stack. This memo defines an extension to ICMP that permits an LSR to append MPLS label stack information to ICMP messages. ICMP messages regarding MPLS encapsulated datagrams SHOULD 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 by an ICMP Extension Structure Header and an ICMP Object Header. Both are defined in . 3. Architectural Considerations Only layer 3 information should be included in 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 in ICMP messages. 4. Application to TRACEROUTE ICMP extensions defined in this memo support enhancements to TRACEROUTE. The enhanced TRACEROUTE application, like older implementations, indicates which nodes the original datagram visited en route to its destination. It differs from older implementations in that it also reflects the original datagram's MPLS encapsulation status as it arrived at each node. Figure 1 contains sample output from an enhanced TRACEROUTE implementation. > traceroute 10.100.6.1 traceroute to 10.100.6.1 (10.100.6.1), 30 hops max, 40 byte packets 1 10.1.1.2 (10.1.1.2) 0.661 ms 0.618 ms 0.579 ms 2 10.1.12.2 (10.1.12.2) 0.861 ms 0.718 ms 0.679 ms MPLS Label=100048 Exp=0 TTL=1 S=1 3 10.1.24.2 (10.1.24.2) 0.822 ms 0.731 ms 0.708 ms MPLS Label=100016 Exp=0 TTL=1 S=1 4 10.100.6.1 (10.100.6.1) 0.961 ms 8.676 ms 0.875 ms Figure 1: Enhanced TRACEROUTE Sample Output 5. Disclaimer This memo does not define the general relationship between ICMP and MPLS. Sections 2.3 and 2.4 of RFC3032 define this relationship. The current memo does not define encapsulation specific TTL manipulation procedures. It defers to Section 5.4 of RFC 3034  and Section 10 of RFC 3035  in this matter. When encapsulation specific TTL manipulation procedures defeat the basic TRACEROUTE mechanism, they will also defeat enhanced TRACEROUTE implementations. 6. MPLS Stack Entry Object This section defines an ICMP extention object that can be appended to the ICMP Time Exceeded and Destination Unreachable messages. A single instance of the MPLS Entry Object class represents 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 Stack Entry Object. It must be preceded by an ICMP Extension Structure Header and an ICMP Object Header. Both are defined in . 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 Stack Entry Class = 1, C-Type = 1. 0 1 2 3 +-------------+-------------+-------------+-------------+ | Label |EXP |S| TTL | +-------------+-------------+-------------+-------------+ | | | // Remaining MPLS Stack Entries // | | | +-------------+-------------+-------------+-------------+ Figure 2: MPLS Stack Entry Object Label: 20 bits Exp: Experimental Use, 3 bits S: Bottom of Stack, 1 bit TTL: Time to Live, 8 bits 7. Security Considerations This memo presents no security considerations beyond those already presented by current ICMP applications (e.g., traceroute). 8. IANA Considerations IANA should should reserve an object class and object type for the MPLS Stack Entry Object from the ICMP Extension Object registry. 9. Normative References  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, RFC 792, September 1981.  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., "Extending the Internet Control Message Protocol (ICMP)", draft-bonica-internet-icmp-00draft-bonica-internet-icmp-01 (work in progress), September 2005.January 2006.  Conta, A., Doolan, P., and A. Malis, "Use of Label Switching on Frame Relay Networks Specification", RFC 3034, January 2001.  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. 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 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights 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; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat 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 implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. 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