Internet A. Atlas Internet-Draft JR. Rivers Expires: June 12, 2006 Google, Inc. R. Bonica Juniper Networks December 9, 2005 ICMP Extensions for Unnumbered Interfaces draft-atlas-icmp-unnumbered-00 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 June 12, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This memo defines extensions to ICMP that permit identification of unnumbered interfaces. The interface the IP packet was received upon can be identified by appending an ifIndex and/or a string describing the interface. These extensions are defined to facilitate troubleshooting in network with unnumbered interfaces and parallel links. Atlas, et al. Expires June 12, 2006 [Page 1] Internet-Draft ICMP Unnumbered December 2005 Table of Contents 1. Conventions Used In This Document . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Application to TRACEROUTE . . . . . . . . . . . . . . . . . . . 4 4. Interface Object . . . . . . . . . . . . . . . . . . . . . . . 4 5. Interface Description Object . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 8. Normative References . . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Intellectual Property and Copyright Statements . . . . . . . . . . 8 Atlas, et al. Expires June 12, 2006 [Page 2] Internet-Draft ICMP Unnumbered December 2005 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 [4]. 2. Introduction IP routers use the Internet Control Message Protocol (ICMP) [1] to convey control information to source hosts. Network operators use this information to diagnose routing problems. When a router generates an ICMP message, the source IP address can be any address of the router. In common implementations, the IP address selected is that of the incoming interface of the packet that triggered the ICMP message. This allows easy identification of specific interface and is very useful for troubleshooting connectivity issues. When a network uses unnumbered interfaces and parallel links, it is not currently possible to identify the specific incoming interface of a packet based upon the responding ICMP message. This memo defines two extensions to ICMP that permit an operator to identify the specific incoming interface traversed by a packet that triggered an ICMP message. These two extensions are motivated by the desire for similar information to that for numbered interfaces. In the case of traceroute, the ICMP message contains the interfaces's IP address; then that IP address is commonly resolved via DNS to provide a meaningful name for the interface that is easier for humans. One extension permits a router to include the interface's ifIndex; this can be used in combination with the source IP address for management tasks. The second extension permits a router to include an interface description string. The inclusion of an interface description may also be useful for numbered interfaces that use a private IP address that DNS cannot resolve for supported users of traceroute and other ICMP message triggers. The ICMP message MUST include the IP header and leading payload octets of the original datagram. As described in [2], an ICMP Extension Structure Header MUST follow the octets from the original datagram and come before any ICMP Extension Objects. Atlas, et al. Expires June 12, 2006 [Page 3] Internet-Draft ICMP Unnumbered December 2005 3. 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 incoming interface on which the original packet arrived, even when that interface is unnumbered. 4. Interface Object This section defines an ICMP extention object that can be appended to the ICMP Time Exceeded and Destination Unreachable messages. One or more Interface Objects can be appended to these messages. Figure 1 depicts the Interface Object. It must be preceded by an ICMP Extension Structure Header and an ICMP Object Header. Both are defined in [2]. The ifIndex included is that assigned to the interface by the router in as specified by the Interfaces Group MIB [3]. Interface Class-Num = 2, C-Type = 1 (Incoming Interface) 0 1 2 3 +-------------+-------------+-------------+-------------+ | Interface ifIndex | +-------------+-------------+-------------+-------------+ Figure 1: Interface Object 5. Interface Description Object This section defines an ICMP extention object that can be appended to the ICMP Time Exceeded and Destination Unreachable messages. One or more Interface Description Objects can be appended to these messages. Figure 2 depicts the Interface Description Object. It must be preceded by an ICMP Extension Structure Header and an ICMP Object Header. Both are defined in [2]. Atlas, et al. Expires June 12, 2006 [Page 4] Internet-Draft ICMP Unnumbered December 2005 Interface Class-Num = 3, C-Type = 1 (Incoming Interface Description encoded in ASCII) 0 1 2 3 +-------------+-------------+-------------+-------------+ | Interface Description | +-------------+-------------+-------------+-------------+ Figure 2: Interface Description Object Interface Description: This field MUST have a length that is a multiple of 4 bytes; the string should be padded with zeroes as necessary. The description can be either the same content as the MIB-II ifDescription field or some other human-meaningful description of the interface. 6. Security Considerations These extensions can provide the user of traceroute with additional network information that is not currently available. It may be desirable to provide this information to a particular network's operators and not to others. If such policy controls are desirable, then an implementation could determine what extensions to include based upon the destination IP address of the ICMP message. For instance, there could be an interface description that is appropriate for all potential recipients; a more detailed description and the ifIndex could be included as well if the destination IP address is a management address of the network that has administrative control of the router. 7. IANA Considerations IANA should should reserve from the ICMP Extension Object registry: 2 for the Interface Object and 3 for the Interface Description Object. IANA should reserve from the Interface Object's C-type the value 1 for Incoming Interface. IANA should reserve from the Interface Description Object's C-type the value 1 for Incoming Interface Description in ASCII. 8. Normative References [1] Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, September 1981. [2] Bonica, R., "Extending the Internet Control Message Protocol (ICMP)", draft-bonica-internet-icmp-00 (work in progress), Atlas, et al. Expires June 12, 2006 [Page 5] Internet-Draft ICMP Unnumbered December 2005 September 2005. [3] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB using SMIv2", RFC 2233, November 1997. [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Atlas, et al. Expires June 12, 2006 [Page 6] Internet-Draft ICMP Unnumbered December 2005 Authors' Addresses Alia K. Atlas Google, Inc. 1600 Amphitheatre Parkway Mountain View, CA 94043 USA Email: akatlas@google.com J.R. Rivers Google, Inc. 1600 Amphitheatre Parkway Mountain View, CA 94043 USA Email: jrrivers@google.com Ronald P. Bonica Juniper Networks 2251 Corporate Park Drive Herndon, VA 20171 US Email: rbonica@juniper.net Atlas, et al. Expires June 12, 2006 [Page 7] Internet-Draft ICMP Unnumbered December 2005 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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Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Atlas, et al. Expires June 12, 2006 [Page 8]