Internet A. Atlas, Ed. Internet-Draft Google, Inc. Expires: September 5, 2007 R. Bonica Juniper Networks JR. Rivers Nuova Systems N. Shen E. Chen Cisco Systems March 4, 2007 ICMP Extensions for Unnumbered Interfaces draft-atlas-icmp-unnumbered-02 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 September 5, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This memo defines extensions to ICMP that permit identification of unnumbered interfaces. The interface the triggering IPv4 or IPv6 Atlas, et al. Expires September 5, 2007 [Page 1] Internet-Draft ICMP Unnumbered March 2007 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. Additionally, to facilitate debugging of numbered interfaces, an IPv4 or IPv6 address of the interface the triggering IPv4 or IPv6 packet was received upon can be identified by appending an IPv4 or IPv6 address. Table of Contents 1. Conventions Used In This Document . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Application to TRACEROUTE . . . . . . . . . . . . . . . . . . 4 4. Interface Information Object . . . . . . . . . . . . . . . . . 4 4.1. C-type meaning in an Interface Information Object . . . . 5 4.2. Interface Description Sub-Object . . . . . . . . . . . . . 5 4.3. Interface Information Object Description . . . . . . . . . 6 4.4. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 8.1. Normative References . . . . . . . . . . . . . . . . . . . 11 8.2. Informative References . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Intellectual Property and Copyright Statements . . . . . . . . . . 13 Atlas, et al. Expires September 5, 2007 [Page 2] Internet-Draft ICMP Unnumbered March 2007 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 an IPv4 or IPv6 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. The extension defined in this memo permits an operator to identify the specific incoming interface traversed by a packet that triggered an ICMP message. This extension is motivated by the desire for similar information to that for numbered interfaces. In the case of traceroute, the ICMP message contains one of 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 attribute permits a router to include a short interface description string. Another attribute of the extension permits a router to include the interface's ifIndex; this can be used in combination with the source IP address for management tasks. An interface's ifIndex may be used (for example, see Section 12.4.1 of RFC2328 [RFC2328]) when the interface is unnumbered and some identification unique to that router is desired. The inclusion of an interface description may also be useful for numbered interfaces that use a private IP address that DNS cannot Atlas, et al. Expires September 5, 2007 [Page 3] Internet-Draft ICMP Unnumbered March 2007 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 [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 Information Object This section defines an ICMP extension object that can be appended to the ICMPv4 Time Exceeded, ICMPv4 Destination Unreachable, ICMPv4 Parameter Problem, ICMPv6 Time Exceeded, and ICMPv6 Destination Unreachable messages, as described in [I-D.bonica-internet-icmp]. For the description of the Interface Information Object, the incoming interface is the one upon which the packet which triggered the ICMP message was received. To minimize the use of extra bytes required for this extension, there are four different pieces of information that can appear in an Interface Information Object. 1. If the interface of interest has at least one IPv4 address and the triggering packet was IPv4, then one of the interface's IPv4 addresses MAY be included. 2. If the interface of interest has at least one IPv6 address and the triggering packet was IPv6, then one of the interface's IPv6 addresses MAY be included. 3. The ifIndex of the interface of interest MAY be included. This is the ifIndex assigned to the interface by the router in as specified by the Interfaces Group MIB [RFC2863]. 4. An interface description string of no more than 31 bytes MAY be included. Atlas, et al. Expires September 5, 2007 [Page 4] Internet-Draft ICMP Unnumbered March 2007 4.1. C-type meaning in an Interface Information Object For this object, the c-type is split into two fields, a 2-bit interface-role field and a 6-bit included-information field. This is illustrated below. Bit 7 6 | 5 4 3 2 1 0 +-------+-------+-------+-------+-------+-------+-------+-------+ | Interface Role| Rsvd | Rsvd | index | IPv4 | IPv6 | descr | +-------+-------+-------+-------+-------+-------+-------+-------+ Interface Role : This 2-bit field [6:7] indicates the role of the interface being identified. The enumerated values are given below. 0 : This object describes the incoming interface. 1 : This object describes the outgoing interface. 2-3 : Undefined by this memo and to be assigned by IANA Included Information: This 6-bit field [0:5] indicates what information is included in the object. The information must be included in the same order as the bits (from highest to lowest). bit 5 : This bit is reserved for future use and MUST be set to 0. 4 : This bit is reserved for future use and MUST be set to 0. 3 : When set, this bit indicates that the ifIndex of the interface is included. When clear, the ifIndex is not included. 2 : When set, this indicates that an IPv4 address of the interface is included. When clear, no IPv4 address is included. 1 : When set, this indicates that an IPv6 address of the interface is included. When clear, no IPv6 address is included. 0 : When set, this indicates that an Interface Description Sub-object for the interface is included. When clear, it is not included. C-Type for the Interface Information Object 4.2. Interface Description Sub-Object The Interface Description Sub-Object MUST have a length that is a multiple of 4 bytes and MUST NOT exceed 32 bytes; the string should be padded with zeroes as necessary. The description text SHOULD be Atlas, et al. Expires September 5, 2007 [Page 5] Internet-Draft ICMP Unnumbered March 2007 the MIB-II ifName [RFC2863] but MAY be some other human-meaningful description of the interface. The Interface Description Sub-Object consists of two fields. The first 1-byte field indicates the character set type used by the second field. The second field contains the human-readable description text. byte 0 1 31 +--------------+----..............-------+ | charset type | description text | +--------------+----..............-------+ Interface Description Sub-Object charset type 0 : This indicates that the human-readable description text MUST be provided in the US-ASCII charset [US-ASCII] using the Default Language [RFC2277]. charset type 1 : This indicates that the human-readable description text MUST be provided in the UTF-8 charset [RFC3629] using the Default Language [RFC2277]. 4.3. Interface Information Object Description Figure 3 depicts the Interface Information Object, with some valid permutations. It must be preceded by an ICMP Extension Structure Header and an ICMP Object Header. Both are defined in [I-D.bonica-internet-icmp]. Although all examples show an Interface Description Sub-object of length 32, this is only for illustration and depicts the maximum allowable length. Class-Num = 2 Example 1: Interface with only description C-Type = 00000001b // Indicates incoming interface Length = 36 (4 + 32) 0 1 2 3 +--------------+--------------+--------------+--------------+ | Interface Description, word 1 | +--------------+--------------+--------------+--------------+ ... ... +--------------+--------------+--------------+--------------+ | Interface Description , word 8 | Atlas, et al. Expires September 5, 2007 [Page 6] Internet-Draft ICMP Unnumbered March 2007 +--------------+--------------+--------------+--------------+ Example 2: Interface with only ifIndex C-Type = 00001000b // Indicates incoming interface Length = 8 (4 + 4) 0 1 2 3 +--------------+--------------+--------------+--------------+ | Interface ifIndex | +--------------+--------------+--------------+--------------+ Example 3: Unnumbered Interface with ifIndex and description C-Type = 00001001b // Indicates incoming interface Length = 40 (4 + 4 + 32) 0 1 2 3 +--------------+--------------+--------------+--------------+ | Interface ifIndex | +--------------+--------------+--------------+--------------+ | Interface Description, word 1 | +--------------+--------------+--------------+--------------+ ... ... +--------------+--------------+--------------+--------------+ | Interface Description , word 8 | +--------------+--------------+--------------+--------------+ Example 4: IPv4 interface with ifIndex and description C-Type = 00001101b // Indicates incoming interface Length = 44 (4 + 4 + 4 + 32) 0 1 2 3 +--------------+--------------+--------------+--------------+ | Interface ifIndex | +--------------+--------------+--------------+--------------+ | IPv4 address | +--------------+--------------+--------------+--------------+ | Interface Description, word 1 | +--------------+--------------+--------------+--------------+ ... ... +--------------+--------------+--------------+--------------+ | Interface Description , word 8 | +--------------+--------------+--------------+--------------+ Atlas, et al. Expires September 5, 2007 [Page 7] Internet-Draft ICMP Unnumbered March 2007 Example 5: IPv4 interface with ifIndex C-Type = 00001100b // Indicates incoming interface Length = 12 (4 + 4 + 4) 0 1 2 3 +--------------+--------------+--------------+--------------+ | Interface ifIndex | +--------------+--------------+--------------+--------------+ | IPv4 address | +--------------+--------------+--------------+--------------+ Example 6: IPv4 interface with description C-Type = 00000101b // Indicates incoming interface Length = 40 (4 + 4 + 32) 0 1 2 3 +--------------+--------------+--------------+--------------+ | IPv4 address | +--------------+--------------+--------------+--------------+ | Interface Description, word 1 | +--------------+--------------+--------------+--------------+ ... ... +--------------+--------------+--------------+--------------+ | Interface Description , word 8 | +--------------+--------------+--------------+--------------+ Example 7: IPv6 interface with ifIndex and description C-Type = 00001011b // Indicates incoming interface Length = 56 (4 + 4 + 16 + 32) 0 1 2 3 +--------------+--------------+--------------+--------------+ | Interface ifIndex | +--------------+--------------+--------------+--------------+ | IPv6 address, word 1 | +--------------+--------------+--------------+--------------+ | IPv6 address, word 2 | +--------------+--------------+--------------+--------------+ | IPv6 address, word 3 | +--------------+--------------+--------------+--------------+ | IPv6 address, word 4 | +--------------+--------------+--------------+--------------+ | Interface Description, word 1 | Atlas, et al. Expires September 5, 2007 [Page 8] Internet-Draft ICMP Unnumbered March 2007 +--------------+--------------+--------------+--------------+ ... ... +--------------+--------------+--------------+--------------+ | Interface Description , word 8 | +--------------+--------------+--------------+--------------+ Example 8: IPv6 interface with ifIndex C-Type = 00001010b // Indicates incoming interface Length = 24 (4 + 4 + 16) 0 1 2 3 +--------------+--------------+--------------+--------------+ | Interface ifIndex | +--------------+--------------+--------------+--------------+ | IPv6 address, word 1 | +--------------+--------------+--------------+--------------+ | IPv6 address, word 2 | +--------------+--------------+--------------+--------------+ | IPv6 address, word 3 | +--------------+--------------+--------------+--------------+ | IPv6 address, word 4 | +--------------+--------------+--------------+--------------+ Example 9: IPv6 interface with description C-Type = 00000011b // Indicates incoming interface Length = 52 (4 + 16 + 32) 0 1 2 3 +--------------+--------------+--------------+--------------+ | IPv6 address, word 1 | +--------------+--------------+--------------+--------------+ | IPv6 address, word 2 | +--------------+--------------+--------------+--------------+ | IPv6 address, word 3 | +--------------+--------------+--------------+--------------+ | IPv6 address, word 4 | +--------------+--------------+--------------+--------------+ | Interface Description, word 1 | +--------------+--------------+--------------+--------------+ ... ... +--------------+--------------+--------------+--------------+ | Interface Description , word 8 | +--------------+--------------+--------------+--------------+ Atlas, et al. Expires September 5, 2007 [Page 9] Internet-Draft ICMP Unnumbered March 2007 Figure 3: Interface Information Object 4.4. Usage If the incoming interface is unnumbered for the triggering packet type, then an Interface Information Object of c-type 8 or 9 SHOULD be included in the ICMPv4 or ICMPv6 Time Exceeded or ICMPv4 or ICMPv6 Destination Unreachable message. If the triggering packet is IPv4 and the incoming interface has an IPv4 address, then an Interface Information Object of c-type 4, 5, 12, or 13 MAY be included in the ICMPv4 Time Exceeded and ICMPv4 Destination Unreachable messages. If the triggering packet is IPv6 incoming interface has an IPv6 address, then an Interface Information Object of c-type 2, 3, 10, or 11 MAY be included in the ICMPv6 Time Exceeded and ICMPv6 Destination Unreachable messages. In an ICMP message, more than one Interface Information Object with a given interface role MUST NOT be included. Multiple Interface Information Objects, each with a different interface role, MAY be included. 5. Security Considerations This extension 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 sub-objects 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. 6. IANA Considerations IANA should should reserve from the ICMP Extension Object registry: 2 for the Interface Information Object. IANA should reserve from the Interface ID Object's c-type, bit 0 for the inclusion of the description sub-object, bit 1 for inclusion of an IPv6 address, bit 2 for inclusion of an IPv4 address, and bit 3 for inclusion of an ifIndex. Bits 4 and 5 are unallocated and IANA should create a registry to allocate those with a requirement for standards action. Atlas, et al. Expires September 5, 2007 [Page 10] Internet-Draft ICMP Unnumbered March 2007 Bit 6 and 7 form the Interface Role field. Value 0 should be allocated for incoming interface; value 1 should be allocated for outgoing interface. Values 2 and 3 are unallocated and IANA should allocate those with a requirement for standards action. Additionally, the Description Sub-Object has a 1 byte charset type field. IANA should create a registry from it and allocate 0 for descriptions in ASCII and 1 for descriptions in UTF-8. The remaining values should be allocated on a first come basis. 7. Acknowledgements The authors would like to thank Carlos Pignataro, Sasha Vainshtein, and Joe Touch for their comments and suggestions. 8. References 8.1. Normative References [I-D.bonica-internet-icmp] Bonica, R., "Extended ICMP to Support Multi-part Messages", draft-bonica-internet-icmp-16 (work in progress), January 2007. [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. 8.2. 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. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003. [US-ASCII] Atlas, et al. Expires September 5, 2007 [Page 11] Internet-Draft ICMP Unnumbered March 2007 "Coded Character Set -- 7-bit American Standard Code for Information Interchange, ANSI X3.4-1986". Authors' Addresses Alia K. Atlas (editor) Google, Inc. 1600 Amphitheatre Parkway Mountain View, CA 94043 USA Email: akatlas@google.com Ronald P. Bonica Juniper Networks 2251 Corporate Park Drive Herndon, VA 20171 USA Email: rbonica@juniper.net J.R. Rivers Nuova Systems Email: jrrivers@nuovasystems.com 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 September 5, 2007 [Page 12] Internet-Draft ICMP Unnumbered March 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). 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The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Atlas, et al. Expires September 5, 2007 [Page 13]