Tech-invite3GPPspaceIETF RFCsSIP
9190898887868584838281807978777675747372717069686766656463626160595857565554535251504948474645444342414039383736353433323130292827262524232221201918171615141312111009080706050403020100
in Index   Prev   Next

RFC 5837

Extending ICMP for Interface and Next-Hop Identification

Pages: 18
Proposed Standard

Top   ToC   RFC5837 - Page 1
Internet Engineering Task Force (IETF)                     A. Atlas, Ed.
Request for Comments: 5837                                            BT
Category: Standards Track                                 R. Bonica, Ed.
ISSN: 2070-1721                                         Juniper Networks
                                                       C. Pignataro, Ed.
                                                                 N. Shen
                                                           Cisco Systems
                                                              JR. Rivers
                                                              Consultant
                                                              April 2010


        Extending ICMP for Interface and Next-Hop Identification

Abstract

This memo defines a data structure that can be appended to selected ICMP messages. The ICMP extension defined herein can be used to identify any combination of the following: the IP interface upon which a datagram arrived, the sub-IP component of an IP interface upon which a datagram arrived, the IP interface through which the datagram would have been forwarded had it been forwardable, and the IP next hop to which the datagram would have been forwarded. Devices can use this ICMP extension to identify interfaces and their components by any combination of the following: ifIndex, IPv4 address, IPv6 address, name, and MTU. ICMP-aware devices can use these extensions to identify both numbered and unnumbered interfaces. Status of This Memo This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc5837.
Top   ToC   RFC5837 - Page 2
Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions Used In This Document . . . . . . . . . . . . . . 5 3. Applications . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Application to Traceroute . . . . . . . . . . . . . . . . 5 3.2. Policy and MTU Detection . . . . . . . . . . . . . . . . . 6 4. Interface Information Object . . . . . . . . . . . . . . . . . 6 4.1. C-Type Meaning in an Interface Information Object . . . . 7 4.2. Interface IP Address Sub-Object . . . . . . . . . . . . . 9 4.3. Interface Name Sub-Object . . . . . . . . . . . . . . . . 10 4.4. Interface Information Object Examples . . . . . . . . . . 10 4.5. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5. Network Address Translation Considerations . . . . . . . . . . 14 6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 9.1. Normative References . . . . . . . . . . . . . . . . . . . 16 9.2. Informative References . . . . . . . . . . . . . . . . . . 16
Top   ToC   RFC5837 - Page 3

1. Introduction

IP devices use the Internet Control Message Protocol (ICMPv4 [RFC0792] and ICMPv6 [RFC4443]) to convey control information. In particular, when an IP device receives a datagram that it cannot process, 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 simplest case, the source address of the ICMP message identifies the interface upon which the datagram arrived. However, in many cases, the incoming interface is not identified by the ICMP message at all. Details follow: According to [RFC1812], when a router generates an ICMPv4 message, the source address of that message MUST be one of the following: o one of the IP addresses associated with the physical interface over which the ICMPv4 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 all of the following conditions are true, the source address of the ICMPv4 message identifies the interface upon which the original datagram arrived: o the device sends an ICMPv4 message through the same interface upon which the original datagram was received o that interface is numbered However, the incoming and outgoing interfaces may be different due to an asymmetric return path, which can occur due to asymmetric link costs, parallel links, or Equal Cost Multipath (ECMP). Similarly, [RFC1122] provides guidance for source address selection for multihomed IPv4 hosts. These recommendations, like those stated above, do not always cause the source address of an ICMPv4 message to identify the incoming interface. ICMPv6 is somewhat more flexible. [RFC4443] states that for responses to messages sent to a non-local interface, the source address must be chosen as follows: 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
Top   ToC   RFC5837 - Page 4
      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.

   When a datagram that cannot be processed arrives on an unnumbered
   interface, neither ICMPv4 nor ICMPv6 is currently capable of
   identifying the incoming interface.  Even when an ICMP message is
   generated such that the ICMP source address identifies the incoming
   interface, the receiver of that ICMP message has no way of knowing if
   this is the case.  ICMP extensions are required to explicitly
   identify the incoming interface.

   Using the extension defined herein, a device can explicitly identify
   the incoming IP interface or its sub-IP components by any combination
   of the following:

   o  ifIndex

   o  IPv4 address

   o  IPv6 address

   o  name

   o  MTU

   The interface name SHOULD be identical to the first 63 octets of the
   ifName, as defined in [RFC2863].  The ifIndex is also defined in
   [RFC2863].

   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, to which the datagram would have been
   forwarded, can also be identified using 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
   where it doesn't exist and 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 uses the ICMP multi-part message
   framework defined in [RFC4884].  The same backward compatibility
   issues that apply to [RFC4884] apply to this extension.
Top   ToC   RFC5837 - Page 5

2. 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 RFC 2119 [RFC2119].

3. Applications

3.1. Application to Traceroute

ICMP extensions defined in this memo provide additional capability to traceroute. An enhanced traceroute application, like older implementations, identifies nodes that a datagram visited en route to its destination. It differs from older implementations in that it can explicitly identify the following at each node: o the IP interface upon which a datagram arrived o the sub-IP component of an IP interface upon which a datagram arrived o the IP interface through which the datagram would have been forwarded had it been forwardable o the IP next hop to which the datagram would have been forwarded Enhanced traceroute applications can identify the above listed entities by: o ifIndex o IPv4 address o IPv6 address o name o MTU The ifIndex can be utilized within a management domain to map to an actual interface, but it is also valuable in public applications. The ifIndex can be used as an opaque token to discern whether or not two ICMP messages generated from the same router involve the same interface.
Top   ToC   RFC5837 - Page 6

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 access control list (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 Path MTU Discovery (PMTUD), 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 the Interface Information Object, an ICMP extension object with a Class-Num (Object Class Value) of 2 that can be appended to the following messages: o ICMPv4 Time Exceeded o ICMPv4 Destination Unreachable o ICMPv4 Parameter Problem o ICMPv6 Time Exceeded o ICMPv6 Destination Unreachable For reasons described in [RFC4884], this extension cannot be appended to any of the currently defined ICMPv4 or ICMPv6 messages other than those listed above. The extension defined herein MAY be appended to any of the above listed messages and SHOULD be appended whenever required to identify an unnumbered interface and when local policy or security considerations do not supersede this requirement. A single ICMP message can contain as few as zero and as many as four instances of the Interface Information Object. It is illegal if it contains more than four instances, because that means that an interface role is used more than once (see Section 4.5). A single instance of the Interface Information Object can provide information regarding any one of the following interface roles: o the IP interface upon which a datagram arrived
Top   ToC   RFC5837 - Page 7
   o  the sub-IP component of an IP interface upon which a datagram
      arrived

   o  the IP interface through which the datagram would have been
      forwarded had it been forwardable

   o  the IP next hop to which the datagram would have been forwarded

   The following are examples of sub-IP components of IP interfaces upon
   which a datagram might arrive:

   o  Ethernet Link Aggregation Group Member

   o  Multilink PPP bundle member

   o  Multilink frame relay bundle member

   To minimize the number of octets required for this extension, there
   are four different pieces of information that can appear in an
   Interface Information Object.

   1.  The ifIndex of the interface of interest MAY be included.  This
       is the 32-bit ifIndex assigned to the interface by the device as
       specified by the Interfaces Group MIB [RFC2863].

   2.  An IP Address Sub-Object MAY be included if either of the
       following conditions is true: a) the eliciting datagram is IPv4
       and the identified interface has at least one IPv4 address
       associated with it, or b) the eliciting datagram is IPv6 and the
       identified interface has at least one IPv6 address associated
       with it.  The IP Address Sub-Object is described in Section 4.2
       of this memo.

   3.  An Interface Name Sub-Object, containing a string of no more than
       63 octets, MAY be included.  That string, as specified in
       Section 4.3, is the interface name and SHOULD be the MIB-II
       ifName [RFC2863], but MAY be some other human-meaningful name of
       the interface.

   4.  A 32-bit unsigned integer reflecting the MTU MAY be included.

4.1. C-Type Meaning in an Interface Information Object

For this object, the C-Type [RFC4884] is used to indicate both the role of the interface and the information that is included. This is illustrated in Figure 1.
Top   ToC   RFC5837 - Page 8
   Bit     0       1       2       3       4       5       6       7
       +-------+-------+-------+-------+-------+-------+-------+-------+
       | Interface Role| Rsvd1 | Rsvd2 |ifIndex| IPAddr|  name |  MTU  |
       +-------+-------+-------+-------+-------+-------+-------+-------+

           Figure 1: C-Type for the Interface Information Object

   The following are bit-field definitions for C-Type:

   Interface Role (bits 0-1): These bits indicates the role of the
   interface being identified.  The enumerated values are given below:

      Value 0:  This object describes the IP interface upon which a
                datagram arrived

      Value 1:  This object describes the sub-IP component of an IP
                interface upon which a datagram arrived

      Value 2:  This object describes the IP interface through which the
                datagram would have been forwarded had it been
                forwardable

      Value 3:  This object describes the IP next hop to which the
                datagram would have been forwarded

   Reserved 1 (bit 2): This bit is reserved for future use and MUST be
   set to 0 and MUST be ignored on receipt.

   Reserved 2 (bit 3): This bit is reserved for future use and MUST be
   set to 0 and MUST be ignored on receipt.

   ifIndex (bit 4) : When set, the 32-bit ifIndex of the interface is
   included.  When clear, the ifIndex is not included.

   IP Addr (bit 5) : When set, an IP Address Sub-Object is present.
   When clear, an IP Address Sub-Object is not present.  The IP Address
   Sub-Object is described in Section 4.2 of this memo.

   Interface Name (bit 6): When set, an Interface Name Sub-Object is
   included.  When clear, it is not included.  The Name Sub-Object is
   described in Section 4.3 of this memo.

   MTU (bit 7): When set, a 32-bit integer representing the MTU is
   present.  When clear, this 32-bit integer is not present.

   The information included does not self-identify, so this
   specification defines a specific ordering for sending the information
   that must be followed.
Top   ToC   RFC5837 - Page 9
   If bit 4 (ifIndex) is set, then the 32-bit ifIndex MUST be sent
   first.  If bit 5 (IP Address) is set, an IP Address Sub-Object MUST
   be sent next.  If bit 6 (Name) is set, an Interface Name Sub-Object
   MUST be sent next.  If bit 7 is set, an MTU MUST be sent next.  The
   information order is thus: ifIndex, IP Address Sub-Object, Interface
   Name Sub-Object, and MTU.  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.

   It is valid (though pointless until additional bits are assigned by
   IANA) to receive an Interface Information Object where bits 4, 5, 6,
   and 7 are all 0; this MUST NOT generate a warning or error.

4.2. Interface IP Address Sub-Object

Figure 2 depicts the Interface Address Sub-Object: 0 31 +-------+-------+-------+-------+ | AFI | Reserved | +-------+-------+-------+-------+ | IP Address .... Figure 2: Interface Address Sub-Object The IP Address Sub-Object contains the following fields: o Address Family Identifier (AFI): This 16-bit bit field identifies the type of address represented by the IP Address field. It also determines the length of that field and the length of the entire sub-object. Values for this field represent a subset of values found in the IANA registry of Address Family Numbers (available from <http://www.iana.org>). Valid values are 1 (representing a 32-bit IPv4 address) and 2 (representing a 128-bit IPv6 address). o Reserved: This 16-bit field MUST be set to zero and ignored upon receipt. o IP Address: This variable-length field represents an IP address associated with the identified interface. If the eliciting datagram was IPv4, the IP Interface Sub-Object MUST represent an IPv4 address. Likewise, if the eliciting datagram was IPv6, the IP Interface Sub-Object MUST represent an IPv6 address.
Top   ToC   RFC5837 - Page 10

4.3. Interface Name Sub-Object

Figure 3 depicts the Interface Name Sub-Object: octet 0 1 63 +--------+-----------................-----------------+ | length | interface name octets 1-63 | +--------+-----------................-----------------+ Figure 3: 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. The Length field represents the length of the Interface Name Sub- Object, including the length and the interface 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 second field contains the human-readable interface name. The interface name SHOULD be the full MIB-II ifName [RFC2863], if less than 64 octets, or the first 63 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 MUST be padded with ASCII NULL characters if the object would not otherwise terminate on a 4-octet boundary. The interface name MUST be represented in the UTF-8 charset [RFC3629] using the Default Language [RFC2277].

4.4. Interface Information Object Examples

Figure 4 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]. Although examples show an Interface Name Sub-Object of length 64, this is only for illustration and depicts the maximum allowable length.
Top   ToC   RFC5837 - Page 11
      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=00001010b |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Interface ifIndex                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                Interface Name Sub-Object, 32-bit word 1       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ...                                                             ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                Interface Name Sub-Object, 32-bit word 16      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Figure 4: ICMPv4 Time Exceeded Message with Interface Information
                                  Object

   Figure 5 depicts an Interface Information Object representing an
   incoming interface identified by ifIndex and Name.

            Class-Num = 2
            C-Type = 00001010b   // Indicates incoming interface
            Length = 72 (4 + 4 + 64)

               0              1              2              3
       +--------------+--------------+--------------+--------------+
       |                    Interface ifIndex                      |
       +--------------+--------------+--------------+--------------+
       |    Length    |      Name, word 1                          |
       +--------------+--------------+--------------+--------------+
      ...                                                         ...
       +--------------+--------------+--------------+--------------+
       |                     Name, word 16                         |
       +--------------+--------------+--------------+--------------+

             Figure 5: Incoming Interface: By ifIndex and Name
Top   ToC   RFC5837 - Page 12
   Figure 6 depicts an Interface Information Object representing an
   incoming interface identified by ifIndex, IPv4 Address, and Name.

            Class-Num = 2
            C-Type = 00001110b   // Indicates incoming interface
            Length = 80 (4 + 4 + 8 + 64)

               0              1              2              3
       +--------------+--------------+--------------+--------------+
       |                    Interface ifIndex                      |
       +--------------+--------------+--------------+--------------+
       |             AFI             |          Reserved           |
       +--------------+--------------+--------------+--------------+
       |                    IPv4 address                           |
       +--------------+--------------+--------------+--------------+
       |    Length    |      Name, word 1                          |
       +--------------+--------------+--------------+--------------+
      ...                                                         ...
       +--------------+--------------+--------------+--------------+
       |                     Name, word 16                         |
       +--------------+--------------+--------------+--------------+

     Figure 6: Incoming Interface: by ifIndex, IPv4 Address, and Name

   Figure 7 depicts an Interface Information Object representing an
   incoming interface identified by ifIndex and IPv6 Address.

           Class-Num = 2
           C-Type = 00001100b   // Indicates incoming interface
           Length = 28 (4 + 4 + 20)

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

         Figure 7: Incoming Interface: By ifIndex and IPv6 Address
Top   ToC   RFC5837 - Page 13
   Figure 8 depicts an Interface Information Object representing an
   outgoing interface identified by ifIndex and Name.

          Class-Num = 2
          C-Type = 10001010b   // Indicates outgoing interface
          Length = 72 (4 + 4 + 64)

               0              1              2              3
       +--------------+--------------+--------------+--------------+
       |                    Interface ifIndex                      |
       +--------------+--------------+--------------+--------------+
       |    Length    |      Name, word 1                          |
       +--------------+--------------+--------------+--------------+
      ...                                                         ...
       +--------------+--------------+--------------+--------------+
       |                     Name, word 16                         |
       +--------------+--------------+--------------+--------------+

             Figure 8: Outgoing Interface: By ifIndex and Name

4.5. Usage

Multiple Interface Information Objects MAY be included within a single ICMP message, provided that each Interface Information Object specifies a unique role. A single ICMP message MUST NOT contain two Interface Information Objects that specify the same role. ifIndex, MTU, and name information MAY be included whenever it is available; more than one instance of each of these three information elements MUST NOT be included per Interface Information Object. A single instance of IP Address information MAY be included in an Interface Information Object under the following circumstances: o if the eliciting datagram is IPv4 and an IPv4 address is associated with the identified interface. In this case, if an IP Address Sub-Object is included, it must specify an IPv4 address. o if the eliciting datagram is IPv6 and an IPv6 address is associated with the identified interface. In this case, if an IP Address Sub-Object is included, it must specify an IPv6 address. In all other circumstances, IP address information MUST NOT be included. An ICMP message that does not conform to these rules and contains multiple instances of the same information is considered illegal; specifically, an ICMP message containing more than one Interface
Top   ToC   RFC5837 - Page 14
   Information Object with the same role, as well as an ICMP message
   containing a duplicate information element in a given role are
   considered illegal.  If such an illegal ICMP message is received, it
   MUST be silently discarded.

5. Network Address Translation Considerations

[RFC5508] 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 contains realm-specific information, and consequently describes possible NAT behaviors in the presence of these extensions. NAT devices MUST NOT translate or overwrite the ICMP extensions described herein. That is, they MUST either remove the extension entirely or pass it unchanged. It is conceivable that a NAT device might translate an ICMP header without translating the extension defined herein. In this case, the ICMP message might contain two instances of the same address, one translated and the other untranslated. Therefore, application developers should not assume addresses in the extension are of the same realm as the addresses in the datagram's header. It also is conceivable that a NAT device might translate an ICMPv4 message into ICMPv6 or vice versa. If that were to occur, applications might receive ICMPv6 messages that contain IP Address Sub-Objects that specify IPv4 addresses. Likewise, applications might receive ICMPv4 messages that contain IP Address Sub-Objects that specify IPv6 addresses.

6. Security Considerations

This extension can provide the user of traceroute with additional network information that is not currently available. Implementations SHOULD provide configuration switches that suppress the generation of this extension based upon role (i.e., incoming interface, outgoing interface, sub-IP data). Implementations SHOULD also provide configuration switches that conceal various types of information (e.g., ifIndex, interface name). 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 [TRACEROUTE-EXT] for those limited cases supported.
Top   ToC   RFC5837 - Page 15
   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.

   The intended field of use for the extensions defined in this document
   is administrative debugging and troubleshooting.  The extensions
   herein defined supply additional information in ICMP responses.
   These mechanisms are not intended to be used in non-debugging
   applications.

   This document does not specify an authentication mechanism for the
   extension that it defines.  Application developers should be aware
   that ICMP messages and their contents are easily spoofed.

7. IANA Considerations

IANA has reserved 2 for the Interface Information Object from the ICMP Extension Object Classes registry available from <http://www.iana.org>. From the Interface Information Object's C-Type, IANA has reserved values as follows: o Bit 0-1: Interface Role field o Bit 2: Unallocated - allocatable with Standards Action o Bit 3: Unallocated - allocatable with Standards Action o Bit 4: ifIndex included o Bit 5: IP Address Sub-Object included o Bit 6: Name Sub-Object included o Bit 7: MTU included IANA has reserved the following values for Interface Role: o Value 0: Incoming IP Interface o Value 1: Sub-IP Component of Incoming IP Interface
Top   ToC   RFC5837 - Page 16
   o  Value 2: Outgoing IP Interface

   o  Value 3: IP Next Hop

8. Acknowledgments

The authors would like to thank Sasha Vainshtein, Enke Chen, and Joe Touch for their comments and suggestions. They would also like to thank Dr. Ali Assefi.

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. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003. [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

[RFC1122] Braden, R., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, October 1989. [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.
Top   ToC   RFC5837 - Page 17
   [RFC3022]         Srisuresh, P. and K. Egevang, "Traditional IP
                     Network Address Translator (Traditional NAT)",
                     RFC 3022, January 2001.

   [RFC5508]         Srisuresh, P., Ford, B., Sivakumar, S., and S.
                     Guha, "NAT Behavioral Requirements for ICMP",
                     BCP 148, RFC 5508, April 2009.

   [TRACEROUTE-EXT]  Shen, N., Pignataro, C., Asati, R., and E. Chen,
                     "UDP Traceroute Message Extension", Work in
                     Progress, June 2008.
Top   ToC   RFC5837 - Page 18

Authors' Addresses

Alia K. Atlas (editor) BT EMail: alia.atlas@bt.com Ronald P. Bonica (editor) Juniper Networks 2251 Corporate Park Drive Herndon, VA 20171 USA EMail: rbonica@juniper.net Carlos Pignataro (editor) Cisco Systems 7200-12 Kit Creek Road PO Box 14987 Research Triangle Park, NC 27709 USA EMail: cpignata@cisco.com Naiming Shen Cisco Systems 225 West Tasman Drive San Jose, CA 95134 USA EMail: naiming@cisco.com JR. Rivers Consultant EMail: jrrivers@yahoo.com