Internet A. Atlas Internet-Draft Google, Inc. Expires: August 5, 2006 JR. Rivers Nuova Systems R. Bonica Juniper Networks N. Shen E. Chen Cisco Systems February 2006 ICMP Extensions for Unnumbered Interfaces draft-atlas-icmp-unnumbered-01 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 August 5, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This memo defines extensions to ICMP that permit identification of unnumbered interfaces. The interface the triggering IPv4 packet was Atlas, et al. Expires August 5, 2006 [Page 1] Internet-Draft ICMP Unnumbered February 2006 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. Additionally, to facilitate debugging of numbered interfaces, the IPv4 address of the interface the triggering IPv4 packet was received upon can be identified by appending the IPv4 address. Table of Contents 1. Conventions Used In This Document . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Application to TRACEROUTE . . . . . . . . . . . . . . . . . . . 4 4. Interface ID Object . . . . . . . . . . . . . . . . . . . . . . 4 5. Interface Description Object . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 9.1. Normative References . . . . . . . . . . . . . . . . . . . 6 9.2. Informative References . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 Intellectual Property and Copyright Statements . . . . . . . . . . 9 Atlas, et al. Expires August 5, 2006 [Page 2] Internet-Draft ICMP Unnumbered February 2006 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) [RFC0792] 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, as specified in RFC1812 [RFC1812], MUST be either one of the IP addresses associated with the transmitting interface or, for unnumbered interfaces, the router's router-id. When the transmitting interface is the same as the incoming interface of the packet that triggered the ICMP message and that interface is numbered, this allows easy identification of specific interface and is very useful for troubleshooting connectivity issues. The transmitting and incoming interfaces may be different due to an asymmetric return path, which can occur due to asymmetric link costs or ECMP. This specification provides an extension so that the IPv4 address of the incoming interface can be explicitly reported. 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 additional 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. Atlas, et al. Expires August 5, 2006 [Page 3] Internet-Draft ICMP Unnumbered February 2006 The ICMP message MUST include the IP header and leading payload octets of the original datagram. As described in [I-D.bonica- internet-icmp], an ICMP Extension Structure Header MUST follow the octets from the original datagram and come before any ICMP Extension Objects. 3. Application to TRACEROUTE ICMP extensions defined in this memo support enhancements to TRACEROUTE (the reasons are discussed in [I-D.bonica-internet-icmp]). 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 triggering packet arrived, even when that interface is unnumbered. 4. Interface ID Object This section defines an ICMP extension object that can be appended to the ICMP Time Exceeded and Destination Unreachable messages. An Interface ID Object of c-type 1 can be appended to these messages. The incoming interface is the one upon which the packet which triggered the ICMP message was received. If the incoming interface is unnumbered, then an Interface ID Object of c-type 1 SHOULD be included in the ICMP Time Exceeded or Destination Unreachable message. If the incoming interface has an IPv4 address, then an Interface ID Object of c-type 1 MAY be included in the ICMP Time Exceeded and Destination Unreachable messages; additionally, one or Interface ID Objects of c-type 2 MAY be included in those messages. Figure 1 depicts the Interface ID Object. It must be preceded by an ICMP Extension Structure Header and an ICMP Object Header. Both are defined in [I-D.bonica-internet-icmp]. The ifIndex included is that assigned to the interface by the router in as specified by the Interfaces Group MIB [RFC2863]. Class-Num = 2, C-Type = 1 (Specifies ifIndex of incoming interface) Length = 8 0 1 2 3 +-------------+-------------+-------------+-------------+ | Interface ifIndex | +-------------+-------------+-------------+-------------+ Atlas, et al. Expires August 5, 2006 [Page 4] Internet-Draft ICMP Unnumbered February 2006 Figure 1: Interface ID Object - ifIndex Class-Num = 2, C-Type = 2 Specifies an IPv4 address of the incoming interface. Length = 8 0 1 2 3 +-------------+-------------+-------------+-------------+ | an IPv4 address of the incoming interface | +-------------+-------------+-------------+-------------+ Figure 2: Interface ID Object - IPv4 address 5. Interface Description Object This section defines an ICMP extention object that can be appended to the ICMP Time Exceeded and Destination Unreachable messages. An Interface Description Object with c-type 1 or 2 can be appended to these messages. If the incoming interface is unnumbered, then an Interface ID Object of C-type 1 MAY be included in the ICMP Time Exceeded message and Destination Unreachable messages. Figure 3 depicts the Interface Description Object. It must be preceded by an ICMP Extension Structure Header and an ICMP Object Header. Both are defined in [I-D.bonica-internet-icmp]. Interface Class-Num = 3, C-Type = 1 or 2 0 1 2 3 +-------------+-------------+-------------+-------------+ | Interface Description | +-------------+-------------+-------------+-------------+ // Interface Description, continued // +-------------+-------------+-------------+-------------+ | Interface Description, continued | +-------------+-------------+-------------+-------------+ Figure 3: Interface Description Object C-Type 1: This contains the description of the incoming interface. Human-readable text for this c-type MUST be provided in the US-ASCII charset [US-ASCII] using the Default Language [RFC2277]. Atlas, et al. Expires August 5, 2006 [Page 5] Internet-Draft ICMP Unnumbered February 2006 C-Type 2: This contains the description of the incoming interface. Human-readable text for this c-type MUST be provided in the UTF-8 charset [RFC3629] using the Default Language [RFC2277]. 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 SHOULD be the MIB-II ifName [RFC2863] but MAY be 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, the ifIndex might be appropriate for all potential recipients; the description 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 ID Object and 3 for the Interface Description Object. IANA should reserve from the Interface ID Object's c-type the value 1 for Incoming Interface ifIndex and the value 2 for the Incoming Interface IPv4 address. IANA should reserve from the Interface Description Object's c-type the value 1 for the incoming interface description in ASCII and the value 2 for the incoming interface description in UTF-8. 8. Acknowledgements The authors would like to thank Carlos Pignataro and Sasha Vainshtein for their comments and suggestions. 9. References 9.1. Normative References [I-D.bonica-internet-icmp] Bonica, R., "Extending the Internet Control Message Atlas, et al. Expires August 5, 2006 [Page 6] Internet-Draft ICMP Unnumbered February 2006 Protocol (ICMP)", draft-bonica-internet-icmp-01 (work in progress), January 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. [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB", RFC 2863, June 2000. 9.2. Informative References [RFC1812] Baker, F., "Requirements for IP Version 4 Routers", RFC 1812, June 1995. [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and Languages", BCP 18, RFC 2277, January 1998. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003. [US-ASCII] "Coded Character Set -- 7-bit American Standard Code for Information Interchange, ANSI X3.4-1986". Atlas, et al. Expires August 5, 2006 [Page 7] Internet-Draft ICMP Unnumbered February 2006 Authors' Addresses Alia K. Atlas Google, Inc. 1600 Amphitheatre Parkway Mountain View, CA 94043 USA Email: akatlas@google.com J.R. Rivers Nuova Systems Email: jrrivers@nuovasystems.com Ronald P. Bonica Juniper Networks 2251 Corporate Park Drive Herndon, VA 20171 USA Email: rbonica@juniper.net Naiming Shen Cisco Systems 225 West Tasman Drive San Jose, CA 95134 USA Email: naiming@cisco.com Enke Chen Cisco Systems 170 West Tasman Drive San Jose, CA 95134 USA Email: enkechen@cisco.com Atlas, et al. Expires August 5, 2006 [Page 8] Internet-Draft ICMP Unnumbered February 2006 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. 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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. 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Atlas, et al. Expires August 5, 2006 [Page 9]