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

Internet                                                   A. Atlas, Ed.
Internet-Draft                                                        BT
Intended status: Standards Track                               R. Bonica
Expires: May 7, 2009                                    Juniper Networks
                                                              JR. Rivers
                                                           Nuova Systems
                                                                 N. Shen
                                                                 E. Chen
                                                           Cisco Systems
                                                        November 3, 2008


        Extending ICMP for Interface and Next-hop Identification
                     draft-atlas-icmp-unnumbered-06

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
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   Drafts.

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   This Internet-Draft will expire on May 7, 2009.

Abstract

   This memo defines ICMP extensions, using ICMP multi-part messages,
   through which a router or host can explicitly identify an interface
   by ifIndex, name, and/or address, as already used in MIBs and by
   OSPF.  The interfaces so identified can be the interface upon which
   an undeliverable datagram arrived, a sub-IP member of that interface,
   and the interface through which the datagram would have been sent.



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   The nexthop IP address can also be provided as part of the outgoing
   interface information.  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.  Applications . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Application to Traceroute  . . . . . . . . . . . . . . . .  4
     3.2.  Policy and MTU Detection . . . . . . . . . . . . . . . . .  5
   4.  Interface Information Object . . . . . . . . . . . . . . . . .  5
     4.1.  C-type meaning in an Interface Information Object  . . . .  6
     4.2.  Interface Name Sub-Object  . . . . . . . . . . . . . . . .  8
     4.3.  Interface Information Object Examples  . . . . . . . . . .  9
     4.4.  Usage  . . . . . . . . . . . . . . . . . . . . . . . . . . 12
   5.  Network Address Translation Considerations . . . . . . . . . . 12
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 14
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
   Intellectual Property and Copyright Statements . . . . . . . . . . 17
























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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 may
   send 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.

   For ICMPv6, the asymmetric issues need not be an issue, since there
   is more flexibility for ICMPv6, as defined in RFC4443 [RFC4443].  For
   responses to messages sent to addresses that aren't the router's, the
   source address must be chosen as follows:





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   o  the Source Address of the ICMPv6 packet MUST be a unicast address
      belonging to the node.  The address SHOULD be chosen according to
      the rules that would be used to select the source address for any
      other packet originated by the node, given the destination address
      of the packet.  However, it MAY be selected in an alternative way
      if this would lead to a more informative choice of address
      reachable from the destination of the ICMPv6 packet.

   For both ICMP and ICMPv6, when a network uses unnumbered interfaces,
   it is not possible to identify the incoming interface.  The extension
   defined in this memo permit an ICMP originator to identify the
   interface through which the datagram that elicited the ICMP message
   arrived.

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

   o  IPv4 address
   o  IPv6 address
   o  name
   o  ifIndex

   Using the same extension, an IP device can explicitly identify by the
   above the outgoing interface over which a datagram would have been
   forwarded if that datagram had been deliverable.

   The next-hop IP address, over which the datagram would have been
   forwarded, can also be provided via this same extension.  This
   information can be used for creating a downstream map.  The next-hop
   information may not always be available.  There are corner-cases,
   such as point-to-point unnumbered links, where it doesn't exist.
   There may be implementations where it is not practical to provide
   this information.  This specification provides an encoding for
   providing the next-hop IP address when it is available.

   The extension defined herein use the ICMP multi-part message
   framework defined in [RFC4884].  The same backward compatibility
   issues that apply to [RFC4884] apply to this extension.


3.  Applications

3.1.  Application to Traceroute

   ICMP extensions defined in this memo require enhancements ([RFC4884])
   and provide additional capability to traceroute.  The enhanced
   traceroute application, like older implementations, indicates which
   nodes the original datagram visited en route to its destination.  It



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   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.

3.2.  Policy and MTU Detection

   A general application would be to identify which outgoing interface
   triggered a given function for the original packet.  For example, if
   an ACL drops the packet and Dest Unreachable/Admin Prohibited denies
   the packet, being able to identify the outgoing interface might be
   useful.  Another example would be to support PMTU, since this would
   allow identification of which outgoing interface can't support a
   given MTU size.  For example, knowledge of the problematic interface
   would allow an informed request for reconfiguration of the MTU of
   that interface.


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.  If desired, information about a sub-IP member of the
   incoming interface can be included.  An example of such a sub-IP
   member would be a member of an Ethernet Link Aggregation Group that
   forms the incoming interface.  To minimize the use of extra octets
   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.  Alternately, 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.
   2.  The ifIndex of the interface of interest MAY be included.  This
       is the 32-bit ifIndex assigned to the interface by the router as
       specified by the Interfaces Group MIB [RFC2863].
   3.  An Interface Name Sub-Object, containing a string of no more than
       62 octets, MAY be included.  That string, as specified in Section
       Section 4.2, is the interface name and SHOULD be the MIB-II
       ifName [RFC2863], but MAY be some other human-meaningful name of
       the interface.





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   4.  If the interface of interest is the outgoing interface, then if
       the triggering packet was IPv4, a next-hop IPv4 address MAY be
       included.  If the triggering packet was IPv6, a next-hop IPv6
       address MAY be included.

4.1.  C-type meaning in an Interface Information Object

   For this object, the c-type is used to indicate both the role of the
   interface and the information that is included.  This is illustrated
   below.









































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 Bit   7        6        5       4       3       2        1       0
    +-------+-------+-------+-------+-------+-------+---------+-------+
    | Interface Role| Rsvd1 | Rsvd2 | index | IP    | nexthop | name  |
    +-------+-------+-------+-------+-------+-------+---------+-------+


   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 : This object describes a sub-IP member of the
                incoming interface.
            3 : Reserved

    bit :  Field Name : description

     5 : Reserved 1 : This bit is reserved for future use and MUST be
                      set to 0 and MUST be ignored on receipt.

     4 : Reserved 2 : This bit is reserved for future use and MUST be
                      set to 0 and MUST be ignored on receipt.

     3 : ifIndex : When set, this bit indicates the 32-bit ifIndex of
                   the interface is included.  When clear, the ifIndex
                   is not included.

     2 :IP address : When set, this indicates an IP address of the
                     interface is included.  When clear, no IP address
                     is included.  The version of the IP packet
                     containing the ICMP message will indicate the type
                     of IP address.  An IPv4 packet will have an IPv4
                     address; an IPv6 packet will have an IPv6 address.

     1 : Next-hop : This MUST be clear unless the Interface Role is 3,
                   indicating an outgoing interface.  When this flag is
                   set, this indicates that the next-hop IP address is
                   included.  When clear, no IP address is included. The
                   version of the IP packet containing the ICMP message
                   will indicate the type of IP address.  An IPv4 packet
                   will include an IPv4 address and an IPv6 packet will
                   include an IPv6 address.

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





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           Figure 1: C-Type for the Interface Information Object

   With the exception of the Interface Name sub-object, the information
   included does not self-identify, so this specification defines a
   specific ordering for sending the information which must be followed.

   If bit 3 (ifIndex) is set, then the 32-bit ifIndex MUST be sent
   first.  If bit 2 (IP address) is set, then either an IPv4 address or
   an IPv6 address, depending on packet version, MUST be sent next.  If
   bit 0 (Interface Name) is set, then an Interface Name Sub-object MUST
   be sent next.  If bit 1 (Next-hop) is set, then the next-hop is given
   in either an IPv4 address or an IPv6 address, depending on the packet
   version.  The information order is thus: ifIndex, IP address,
   Interface Name sub-object, next-hop; any or all pieces of information
   may be present or absent, as indicated by the c-type.  Any data that
   follows these optional pieces of information MUST be ignored.

   The sender of an Interface Information Object MUST NOT set the
   Interface Role to 3 and an Interface Role value of 3 MUST be ignored
   on receipt and the Interface Information Object discarded.  It is
   valid (though pointless until additional bits are assigned by IANA)
   to receive an Interface Information Object where bits 3, 2, 1 and 0
   are all 0; this MUST NOT generate a warning or error.

4.2.  Interface Name Sub-Object

   The Interface Name Sub-Object MUST have a length that is a multiple
   of 4 octets and MUST NOT exceed 64 octets.  A one octet "charset
   type" and a one octet "length" are required and the interface name
   can be at most 62 octets long.  The interface name SHOULD be the full
   MIB-II ifName [RFC2863], if less than 63 octets, or the first 62
   octets of the ifName, if the ifName is longer.  The interface name
   MAY be some other human-meaningful name of the interface.  It is
   useful to provide the ifName for cross-correlation with other MIB
   information and for human-reader familiarity.

   The Interface Name Sub-Object consists of three fields.  The first
   1-octet field indicates the character set type used by the second
   field.  The second field contains the length of the Interface name
   Sub-object, including the charset type, the length, and the human-
   readable name in octets.  The maximum valid length is 64 octets.  The
   length is constrained to ensure there is space for the start of the
   original packet and additional information.  The third field contains
   the human-readable name.







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   octet      0          1        2                   63
        +--------------+--------+---..............-----------------+
        | charset type | length |   interface name octets 1-62     |
        +--------------+--------+---..............-----------------+


                    Figure 2: 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 Examples

   Figure 3 shows a full ICMPv4 Time Exceeded message, including the
   Interface Information Object, which must be preceded by an ICMP
   Extension Structure Header and an ICMP Object Header.  Both are
   defined in [RFC4884].

   Figure 4 depicts the Interface Information Object, with four of the
   valid permutations.

   Although all examples show an Interface Name Sub-object of length 64,
   this is only for illustration and depicts the maximum allowable
   length.






















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     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |     Code      |          Checksum             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     unused    |    Length     |          unused               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      Internet Header + leading octets of original datagram    |
     |                                                               |
     |                           //                                  |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Ver=2 |      (Reserved)       |           Checksum            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |             Length            |Class-Num=2 | C-Type=00001001b |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Interface ifIndex                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                Interface Name, 32-bit word 1                  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ...                                                              ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                Interface Name , 32-bit word 16                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


     Figure 3: ICMPv4 Time Exceeded message with Interface Information
                                  Object


             Class-Num = 2

     Example 1: 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, 32-bit word 1              |
      +--------------+--------------+--------------+--------------+
     ...                                                         ...
      +--------------+--------------+--------------+--------------+
      |                Interface Name , 32-bit word 16             |
      +--------------+--------------+--------------+--------------+




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     Example 2: IPv4 interface with IPv4 address,
                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, 32-bit word 1              |
      +--------------+--------------+--------------+--------------+
     ...                                                         ...
      +--------------+--------------+--------------+--------------+
      |                Interface Name, 32-bit word 16             |
      +--------------+--------------+--------------+--------------+


     Example 3: IPv6 interface with IPv6 address and ifIndex

             C-Type = 00001100b   // Indicates incoming interface
             Length = 24 (4 + 4 + 16)

              0             1             2            3
      +--------------+--------------+--------------+--------------+
      |                    Interface ifIndex                      |
      +--------------+--------------+--------------+--------------+
      |                    IPv6 address, 32-bit word 1            |
      +--------------+--------------+--------------+--------------+
      |                    IPv6 address, 32-bit word 2            |
      +--------------+--------------+--------------+--------------+
      |                    IPv6 address, 32-bit word 3            |
      +--------------+--------------+--------------+--------------+
      |                    IPv6 address, 32-bit word 4            |
      +--------------+--------------+--------------+--------------+

     Example 4: outgoing IPv4 interface with IPv4 address,
                     next-hop IPv4 address

             C-Type = 10000110b   // Indicates incoming interface
             Length = 44 (4 + 4)

              0             1             2            3
      +--------------+--------------+--------------+--------------+
      |          outgoing interface's IPv4 address                |
      +--------------+--------------+--------------+--------------+



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      |           next-hop IPv4 address                           |
      +--------------+--------------+--------------+--------------+


                  Figure 4: Interface Information Object

4.4.  Usage

   For each interface described by an included Interface Information
   Object, these are the rules for the information to be included.  If
   the interface in question is unnumbered, then the Interface
   Information Object SHOULD include the ifIndex and MUST NOT include an
   IP address.  If the interface in question is numbered, then the
   Interface Information Object SHOULD include the IP address.  Other
   fields MAY be included in the Interface Information Object.

   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.  Network Address Translation Considerations

   [I-D.ietf-behave-nat-icmp] encourages Traditional IP Network Address
   Translators (Traditional NATs, see [RFC3022]) to support ICMP
   extension objects.  This document defines an ICMP extension that
   includes IP addresses and therefore contain realm specific
   information, and consequently describes possible NAT behaviors in
   presence of these extensions.

   In the most general case, a NAT device may choose to transparently
   pass, remove or overwrite this extension.  The action may be
   different for the different fields: The ifIndex can either be
   transparently passed or removed, the Description can be transparently
   passed, removed or re-written (adding some text to the effect that a
   NAT was crossed and the description was removed, as a matter of
   policy or other), and IP addresses can either be passed, removed or
   translated.

   When translating IP address-related fields of the extension defined
   in this document, the behavior should be equivalent to that of the
   treatment of Router-x and Router-y source IP address in Sections
   4.2.1 and 4.2.2 of [I-D.ietf-behave-nat-icmp](respectively).  That
   is:






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   o  For ICMP Error Packets received from an External Realm: IP
      Addresses included in this extension remain unchanged because they
      correspond to the external domain (e.g., correspond to a router
      that generated the ICMP in the external realm).
   o  For ICMP Error Packets received from a Private Realm: This
      extension includes an IP address corresponding to the Private
      realm, let's refer to it as IP-Private, and its translation
      depends on whether Basic NAT or NAPT function ([RFC3022]) is
      enforced by the NAT:
   o
      *  Basic NAT: If the NAT has an active mapping for IP-Private, the
         NAT translate it within the extension with the IP-Public in
         said mapping.  If not, the NAT translates the IP-Private
         address using its own IP address on the external domain.
      *  NAPT: the NAT translates the IP-Private address in the
         extension to its own IP address on the external domain.

   These recommendations allow for the improved troubleshooting offered
   by this extension while not leaking private-realm addresses outside.
   A NAT SHOULD follow the recommendations in this section; it MAY
   choose to pass the extension unaltered.


6.  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 that will
   contain the sub-objects.  The implementation of policy controls could
   also be based upon the mechanisms described in
   [I-D.shen-udp-traceroute-ext] for those limited cases supported.

   For instance, the IP address may be included for all potential
   recipients.  The ifIndex and 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.

   Another example use case would be where the detailed information in
   these extensions may be provided to ICMP destinations within the
   local administrative domain, but only traditional information is
   provided to 'external' or untrusted ICMP destinations.







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7.  IANA Considerations

   IANA should reserve from the ICMP Extension Object registry: 2 for
   the Interface Information Object.

   From the Interface ID Object's c-type, IANA should reserve as
   follows:

   o  Bit 0: Interface Name Sub-Object included
   o  Bit 1: IP next-hop address included
   o  Bit 2: IP address included
   o  Bit 3: ifIndex included
   o  Bit 4: Unallocated - allocatable with Standards Action
   o  Bit 5: Unallocated - allocatable with Standards Action
   o  Bit 6-7: Interface Role field
      *  Value 0: Incoming Interface
      *  Value 1: Outgoing Interface
      *  Value 2: Incoming Interface - Sub-IP Member
      *  Value 3: Unallocated - allocatable with Standards Action

   Additionally, the Interface Name Sub-Object has a 1 octet charset
   type field.  IANA should create a registry for it and allocate as
   follows:

   o  0 : encoded in ASCII
   o  1 : encoded in UTF-8
   o  2-127: Unallocated - allocatable with Standards Action
   o  128-255: Unallocated - allocated on first come basis.


8.  Acknowledgements

   The authors would like to thank Carlos Pignataro, Sasha Vainshtein,
   and Joe Touch for their comments and suggestions.


9.  References

9.1.  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.



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   [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.

9.2.  Informative References

   [I-D.ietf-behave-nat-icmp]
              Srisuresh, P., Ford, B., Sivakumar, S., and S. Guha, "NAT
              Behavioral Requirements for ICMP protocol",
              draft-ietf-behave-nat-icmp-10 (work in progress),
              October 2008.

   [I-D.shen-udp-traceroute-ext]
              Shen, N., Pignataro, C., Asati, R., and E. Chen, "UDP
              Traceroute Message Extension",
              draft-shen-udp-traceroute-ext-01 (work in progress),
              June 2008.

   [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.

   [RFC3022]  Srisuresh, P. and K. Egevang, "Traditional IP Network
              Address Translator (Traditional NAT)", RFC 3022,
              January 2001.

   [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".


Authors' Addresses

   Alia K. Atlas (editor)
   BT

   Email: alia.atlas@bt.com





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   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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