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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 5837

Internet                                                   A. Atlas, Ed.
Internet-Draft                                              Google, Inc.
Expires: January 7, 2008                                       R. Bonica
                                                        Juniper Networks
                                                              JR. Rivers
                                                           Nuova Systems
                                                                 N. Shen
                                                                 E. Chen
                                                           Cisco Systems
                                                            July 6, 2007


           Extending ICMP to Identify the Receiving Interface
                     draft-atlas-icmp-unnumbered-03

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
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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on January 7, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This memo defines ICMP extensions through which an router or host can
   explicitly identify the interface upon which an undeliverable



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   datagram arrived.  The incoming interface can be identified by
   ifIndex, name, and/or address.  The extensions defined herein are
   particularly useful when troubleshooting networks with unnumbered
   interfaces, parallel interfaces and/or asymmetric routing.


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  . . . .  4
     4.2.  Interface Name 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



























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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 devices use the Internet Control Message Protocol (ICMP) [RFC0792]
   (ICMPv6) [RFC4443] to convey control information.  In particular,
   when an IP device receives a datagram that it cannot forward, it
   sends an ICMP message to the datagram's originator.  Network
   operators and higher level protocols use these ICMP messages to
   detect and diagnose network issues.

   In the nominal case, the source address of the ICMP message
   identifies the interface upon which the non-forwardable datagram
   arrived.  However, in many cases, the incoming interface is not
   identified by the ICMP message at all.  Details follow:

   According to RFC1812 [RFC1812], when a router generates an ICMP
   message, the source address of that ICMP message MUST be one of the
   following:

   o  one of the IP addresses associated with the physical interface
      over which the ICMP message is transmitted
   o  if that interface has no IP addresses associated with it, the
      device's router-id or host-id is used instead.

   If the following conditions are true, the source address of the ICMP
   message identifies the interface upon which the non-forwardable
   datagram arrived:

   o  the device originates an ICMP message through the same interface
      upon which the non-forwardable datagram was received.
   o  that interface is numbered.

   However, the transmitting and incoming interfaces may be different
   due to an asymmetric return path, which can occur due to asymmetric
   link costs, parallel links or ECMP.  When a network uses unnumbered
   interfaces, it is also not possible to identify the incoming
   interface.  The extensions defined in this memo permits an ICMP
   originator to identify the interface through which the datagram that
   elicited the ICMP messages arrived.

   Using the extension defined herein, IP device can explicitly identify
   the incoming interface by any or all of the following:



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   o  IPv4 address
   o  IPv6 address
   o  name
   o  ifIndex


3.  Application to TRACEROUTE

   ICMP extensions defined in this memo support enhancements to
   TRACEROUTE (the reasons are discussed in [RFC4884]).  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 [RFC4884].  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 name string of no more than 31 bytes MAY be
       included.

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.





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   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 the ifIndex of the interface
           is included.  When clear, the ifIndex is not included.

       2 : When set, this indicates an IPv4 address of the interface
           is included.  When clear, no IPv4 address is included.

       1 : When set, this indicates an IPv6 address of the interface
           is included.  When clear, no IPv6 address is included.

       0 : When set, this indicates an Interface Name Sub-object for
           the interface is included.  When clear, it is not included.


                C-Type for the Interface Information Object

4.2.  Interface Name Sub-Object

   The Interface Name 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 interface name SHOULD be the MIB-II
   ifName [RFC2863] but MAY be some other human-meaningful name of the
   interface.

   The Interface Name 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 name.



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   byte       0          1                    31
        +--------------+----..............-------+
        | charset type |    interface name       |
        +--------------+----..............-------+

                         Interface Name Sub-Object

   charset type 0 : This indicates that the human-readable interface
   name MUST be provided in the US-ASCII charset [US-ASCII] using the
   Default Language [RFC2277].

   charset type 1 : This indicates that the human-readable interface
   name 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 [RFC4884].

   Although all examples show an Interface Name Sub-object of length 32,
   this is only for illustration and depicts the maximum allowable
   length.

             Class-Num = 2

     Example 1: Interface with only interface name

             C-Type = 00000001b   // Indicates incoming interface
             Length = 36 (4 + 32)

              0             1             2            3
      +--------------+--------------+--------------+--------------+
      |                Interface Name, word 1                     |
      +--------------+--------------+--------------+--------------+
     ...                                                         ...
      +--------------+--------------+--------------+--------------+
      |                Interface Name, word 8                     |
      +--------------+--------------+--------------+--------------+


     Example 2: Interface with only ifIndex

             C-Type = 00001000b   // Indicates incoming interface
             Length = 8 (4 + 4)

              0             1             2            3



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      +--------------+--------------+--------------+--------------+
      |                    Interface ifIndex                      |
      +--------------+--------------+--------------+--------------+


     Example 3: Unnumbered Interface with ifIndex and interface name

             C-Type = 00001001b   // Indicates incoming interface
             Length = 40 (4 + 4 + 32)

              0             1             2            3
      +--------------+--------------+--------------+--------------+
      |                    Interface ifIndex                      |
      +--------------+--------------+--------------+--------------+
      |                Interface Name, word 1                     |
      +--------------+--------------+--------------+--------------+
     ...                                                         ...
      +--------------+--------------+--------------+--------------+
      |                Interface Name , word 8                    |
      +--------------+--------------+--------------+--------------+


     Example 4: IPv4 interface with ifIndex and interface name

             C-Type = 00001101b   // Indicates incoming interface
             Length = 44 (4 + 4 + 4 + 32)

              0             1             2            3
      +--------------+--------------+--------------+--------------+
      |                    Interface ifIndex                      |
      +--------------+--------------+--------------+--------------+
      |                    IPv4 address                           |
      +--------------+--------------+--------------+--------------+
      |                Interface Name, word 1                     |
      +--------------+--------------+--------------+--------------+
     ...                                                         ...
      +--------------+--------------+--------------+--------------+
      |                Interface Name, word 8                     |
      +--------------+--------------+--------------+--------------+


     Example 5: IPv4 interface with ifIndex

             C-Type = 00001100b   // Indicates incoming interface
             Length = 12 (4 + 4 + 4)

              0             1             2            3
      +--------------+--------------+--------------+--------------+



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      |                    Interface ifIndex                      |
      +--------------+--------------+--------------+--------------+
      |                    IPv4 address                           |
      +--------------+--------------+--------------+--------------+


     Example 6: IPv4 interface with interface name

             C-Type = 00000101b   // Indicates incoming interface
             Length = 40 (4 + 4 + 32)

              0             1             2            3
      +--------------+--------------+--------------+--------------+
      |                    IPv4 address                           |
      +--------------+--------------+--------------+--------------+
      |                Interface Name, word 1                     |
      +--------------+--------------+--------------+--------------+
     ...                                                         ...
      +--------------+--------------+--------------+--------------+
      |                Interface Name , word 8                    |
      +--------------+--------------+--------------+--------------+


     Example 7: IPv6 interface with ifIndex and interface name

             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 Name, word 1                     |
      +--------------+--------------+--------------+--------------+
     ...                                                         ...
      +--------------+--------------+--------------+--------------+
      |                Interface Name, word 8                     |
      +--------------+--------------+--------------+--------------+





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     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 interface name

             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 Name, word 1                     |
      +--------------+--------------+--------------+--------------+
     ...                                                         ...
      +--------------+--------------+--------------+--------------+
      |                Interface Name , word 8                    |
      +--------------+--------------+--------------+--------------+



                  Figure 3: Interface Information Object







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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 interface name 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
   interface name 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.
   Bit 6 and 7 form the Interface Role field.  Value 0 should be
   allocated for incoming interface; value 1 should be allocated for



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   outgoing interface.  Values 2 and 3 are unallocated and IANA should
   allocate those with a requirement for standards action.
   Additionally, the Interface Name Sub-Object has a 1 byte charset type
   field.  IANA should create a registry from it and allocate 0 for
   names in ASCII and 1 for names 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

   [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.

   [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.

   [RFC4884]  Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
              "Extended ICMP to Support Multi-Part Messages", RFC 4884,
              April 2007.

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.




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   [US-ASCII]
              "Coded Character Set -- 7-bit American Standard Code for
              Information Interchange, ANSI X3.4-1986".


Authors' Addresses

   Alia K. Atlas (editor)
   Google, Inc.
   One Broadway, 7th Floor
   Cambridge, MA  02142
   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




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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   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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Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





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