Skip to main content

An Acceptable Use Policy for New ICMP Types and Codes

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 7279.
Authors Melinda Shore , Carlos Pignataro
Last updated 2018-12-20 (Latest revision 2014-02-03)
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Best Current Practice
Stream WG state (None)
Document shepherd Ron Bonica
Shepherd write-up Show Last changed 2013-10-07
IESG IESG state Became RFC 7279 (Best Current Practice)
Action Holders
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD Benoît Claise
Send notices to (None)
IANA IANA review state Version Changed - Review Needed
IANA action state No IANA Actions
Network Working Group                                           M. Shore
Internet-Draft                                      No Mountain Software
Intended status: BCP                                        C. Pignataro
Expires: August 7, 2014                              Cisco Systems, Inc.
                                                        February 3, 2014

         An Acceptable Use Policy for New ICMP Types and Codes


   In this document we provide a basic description of ICMP's role in the
   IP stack and some guidelines for future use.

   This document is motivated by concerns about lack of clarity
   concerning when to add new Internet Control Message Protocol (ICMP)
   types and/or codes.  These concerns have highlighted a need to
   describe policies for when adding new features to ICMP is desirable
   and when it is not.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   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."

   This Internet-Draft will expire on August 7, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Shore & Pignataro        Expires August 7, 2014                 [Page 1]
Internet-Draft                  ICMP AUP                   February 2014

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Acceptable use policy . . . . . . . . . . . . . . . . . . . . . 3
     2.1.  Classification of existing message types  . . . . . . . . . 3
       2.1.1.  ICMP Use as a Routing Protocol  . . . . . . . . . . . . 5
       2.1.2.  A few notes on RPL  . . . . . . . . . . . . . . . . . . 6
     2.2.  Applications using ICMP . . . . . . . . . . . . . . . . . . 6
     2.3.  Extending ICMP  . . . . . . . . . . . . . . . . . . . . . . 6
     2.4.  ICMPv4 vs. ICMPv6 . . . . . . . . . . . . . . . . . . . . . 6
   3.  ICMP's role in the internet . . . . . . . . . . . . . . . . . . 7
   4.  Security considerations . . . . . . . . . . . . . . . . . . . . 7
   5.  IANA considerations . . . . . . . . . . . . . . . . . . . . . . 8
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 8
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     7.1.  Normative references  . . . . . . . . . . . . . . . . . . . 8
     7.2.  Informative references  . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9

Shore & Pignataro        Expires August 7, 2014                 [Page 2]
Internet-Draft                  ICMP AUP                   February 2014

1.  Introduction

   There has been some recent concern expressed about a lack of clarity
   around when to add new message types and codes to ICMP (including
   ICMPv4 [RFC0792] and ICMPv6 [RFC4443]).  We lay out a description of
   when (and when not) to move functionality into ICMP.

   This document is the result of discussions among ICMP experts within
   the OPS area's IP Diagnostics Technical Interest Group [1] and
   concerns expressed by the OPS area leadership.

   Note that this document does not supercede the IANA Allocation
   Guidelines for Values in the Internet Protocol and Related Headers,
   RFC 2780 [RFC2780], which specifies best practices and processes for
   the allocation of values in the IANA registries but does not describe
   the policies to be applied in the standards process.

2.  Acceptable use policy

   In this document we describe an acceptable use policy for new ICMP
   message types and codes, and provide some background behind the

   In summary, any future message types added to ICMP should be limited
   to two broad categories:

   1.  to inform a datagram's originator that a forwarding plane anomaly
       has been encountered downstream.  The datagram originator must be
       able to determine whether or not the datagram was discarded by
       examining the ICMP message
   2.  to discover and convey dynamic information about a node (other
       than information usually carried in routing protocols), to
       discover and convey network-specific parameters, and to discover
       on-link routers and hosts.

   Normally, ICMP SHOULD NOT be used to implement a general-purpose
   routing or network management protocol.  However, ICMP does have a
   role to play in conveying dynamic information about a network, which
   would belong in category 2 above.

2.1.  Classification of existing message types

   This section provides a rough breakdown of existing message types
   according to the taxonomy described in Section 2 at the time of

   IPv4 forwarding plane anomaly reporting:

Shore & Pignataro        Expires August 7, 2014                 [Page 3]
Internet-Draft                  ICMP AUP                   February 2014

      3:   Destination unreachable
      4:   Source quench (deprecated)
      6:   Alternate host address (deprecated)
      11:  Time exceeded
      12:  Parameter problem
      31:  Datagram conversion error (deprecated)
      41:  ICMP messages utilized by experimental mobility protocols,
           such as Seamoby

   IPv4 router or host discovery:

      0:   Echo reply
      5:   Redirect
      8:   Echo
      9:   Router advertisement
      10:  Router solicitation
      13:  Timestamp
      14:  Timestamp reply
      15:  Information request (deprecated)
      16:  Information reply (deprecated)
      17:  Address mask request (deprecated)
      18:  Address mask reply (deprecated)
      30:  Traceroute (deprecated)
      32:  Mobile host redirect (deprecated)
      33:  IPv6 Where-Are-You (deprecated)
      34:  IPv6 I-Am-Here (deprecated)
      35:  Mobile registration request (deprecated)
      36:  Mobile registration reply (deprecated)
      37:  Domain name request (deprecated)
      38:  Domain name reply (deprecated)
      39:  SKIP (deprecated)
      40:  Photuris
      41:  ICMP messages utilized by experimental mobility protocols,
           such as Seamoby

   Please note that some ICMP message types were formally deprecated by

   IPv6 forwarding plane anomaly reporting:

      1:   Destination unreachable
      2:   Packet too big
      3:   Time exceeded

Shore & Pignataro        Expires August 7, 2014                 [Page 4]
Internet-Draft                  ICMP AUP                   February 2014

      4:   Parameter problem
      150: ICMP messages utilized by experimental mobility protocols,
           such as Seamoby

   IPv6 router or host discovery:

      128: Echo request
      129: Echo reply
      130: Multicast listener query
      131: Multicast listener report
      132: Multicast listener done
      133: Router solicitation
      134: Router advertisement
      135: Neighbor solicitation
      136: Neighbor advertisement
      137: Redirect message
      138: Router renumbering
      139: ICMP node information query
      140: ICMP node information response
      141: Inverse neighbor discovery solicitation message
      142: Inverse neighbor discovery advertisement message
      143: Version 2 multicast listener report
      144: Home agent address discovery request message
      145: Home agent address discovery reply message
      146: Mobile prefix solicitation
      147: Mobile prefix advertisement
      148: Certification path solicitation message
      149: Certification path advertisement message
      150: ICMP messages utilized by experimental mobility protocols,
           such as Seamoby
      151: Multicast router advertisement
      152: Multicast router solicitation
      153: Multicast router termination
      154: FMIPv6 messages
      155: RPL control message

2.1.1.  ICMP Use as a Routing Protocol

   As mentioned in Section 2, using ICMP as a general-purpose routing or
   network management protocol is not advisable, and SHOULD NOT be used
   that way.

   ICMP has a role in the Internet as an integral part of the IP layer.
   This is not as a routing protocol, or as a transport protocol for
   other layers including routing information.  From a more pragmatic
   perspective, some of the key characteristics of ICMP make it a less
   than ideal choice for a routing protocol.  Those include that ICMP is
   frequently filtered, is not authenticated, is easily spoofed, and

Shore & Pignataro        Expires August 7, 2014                 [Page 5]
Internet-Draft                  ICMP AUP                   February 2014

   that specialist hardward processing of ICMP would disrupt the
   deployment of an ICMP-based routing or management protocol.

2.1.2.  A few notes on RPL

   RPL, the IPv6 Routing protocol for low-power and lossy networks (see
   [RFC6550]) uses ICMP as a transport.  In this regard, it is an
   exception among the ICMP message types.  Note that, although RPL is
   an IP routing protocol, it is not deployed on the general Internet,
   but is limited to specific, contained networks.

   This should be considered anomalous and is not a model for future
   ICMP message types.  That is, ICMP is not intended as a transport for
   other protocols and SHOULD NOT be used in that way in future
   specifications.  In particular, while it is adequate to use ICMP as a
   discovery protocol, this does not extend to full routing

2.2.  Applications using ICMP

   Some applications make use of ICMP error notifications, or even
   deliberately create anomalous conditions in order to elicit ICMP
   messages, to then use those ICMP messages to generate feedback to the
   higher layer.  Some of these applications include most widespread
   examples such as PING, TRACEROUTE and Path MTU Discovery (PMTUD).
   These uses are considered acceptable as they use existing ICMP
   message types and do not change ICMP functionality.

2.3.  Extending ICMP

   ICMP multi-part messages are specified in [RFC4884] by defining an
   extension mechanism for selected ICMP messages.  This mechanism
   addresses a fundamental problem in ICMP extensibility.  An ICMP
   multi-part message carries all of the information that ICMP messages
   carried previously, as well as additional information that
   applications may require.

   Some currently defined ICMP extensions include ICMP extensions for
   Multiprotocol Label Switching [RFC4950] and ICMP extensions for
   interface and next-hop identification [RFC5837].

   Extensions to ICMP SHOULD follow [RFC4884].

2.4.  ICMPv4 vs. ICMPv6

   Because ICMPv6 is used for IPv6 Neighbor Discovery, deployed IPv6
   routers, IPv6-capable security gateways, and IPv6-capable firewalls
   normally support administrator configuration of how specific ICMPv6

Shore & Pignataro        Expires August 7, 2014                 [Page 6]
Internet-Draft                  ICMP AUP                   February 2014

   message types are handled.  By contrast, deployed IPv4 routers, IPv4-
   capable security gateways, and IPv4-capable firewalls are less likely
   to allow an administrator to configure how specific ICMPv4 message
   types are handled.  So, at present, ICMPv6 messages usually have a
   higher probability of travelling end-to-end than ICMPv4 messages.

3.  ICMP's role in the internet

   ICMP was originally intended to be a mechanism for gateways or
   destination hosts to report error conditions back to source hosts in
   ICMPv4 [RFC0792], and ICMPv6 [RFC4443] is modeled after it.  ICMP is
   also used to perform IP-layer functions, such as diagnostics (e.g.,

   ICMP is defined to be an integral part of IP, and must be implemented
   by every IP module.  This is true for ICMPv4 as an integral part of
   IPv4 (see the Introduction of [RFC0792]), and for ICMPv6 as an
   integral part of IPv6 (see Section 2 of [RFC4443]).  When first
   defined, ICMP messages were thought of as IP messages that didn't
   carry any higher layer data.  It could be conjectured that the term
   "control" was used given that ICMP messages were not "data" messages.

   The word "control" in the protocol name did not describe ICMP's
   function (i.e. it did not "control" the internet), but rather that it
   was used to communicate about the control functions in the internet.
   For example, even though ICMP included a redirect message type that
   affects routing behavior in the context of a LAN segment, it was and
   is not used as a generic routing protocol.

4.  Security considerations

   This document describes a high-level policy for adding ICMP types and
   codes.  While special attention must be paid to the security
   implications of any particular new ICMP type or code, this
   recommendation presents no new security considerations.

   From a security perspective, ICMP plays a part in the Photuris
   [RFC2521] protocol.  But more generally, ICMP is not a secure
   protocol, and does not include features to be used to discover
   network security parameters or to report on network security
   anomalies in the forwarding plane.

   Additionally, new ICMP functionality (e.g., ICMP extensions, or new
   ICMP types or codes) needs to consider potential ways of how ICMP can
   be abused (e.g., Smurf IP DoS [CA-1998-01]).

Shore & Pignataro        Expires August 7, 2014                 [Page 7]
Internet-Draft                  ICMP AUP                   February 2014

5.  IANA considerations

   There are no actions required by IANA.

6.  Acknowledgments

   This document was originally proposed by, and received substantial
   review and suggestions from, Ron Bonica.  Discussions with Pascal
   Thubert helped clarify the history of RPL's use of ICMP.  We are very
   grateful for the review, feedback, and comments from Ran Atkinson,
   Tim Chown, Joe Clarke, Adrian Farrel, Ray Hunter, Hilarie Orman, Eric
   Rosen, JINMEI Tatuya, and Wen Zhang, which resulted in a much
   improved document.

7.  References

7.1.  Normative references

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC0792]  Postel, J., "Internet Control Message Protocol", STD 5,
              RFC 792, September 1981.

   [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.

7.2.  Informative references

   [RFC2780]  Bradner, S. and V. Paxson, "IANA Allocation Guidelines For
              Values In the Internet Protocol and Related Headers",
              BCP 37, RFC 2780, March 2000.

   [RFC6550]  Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R.,
              Levis, P., Pister, K., Struik, R., Vasseur, JP., and R.
              Alexander, "RPL: IPv6 Routing Protocol for Low-Power and
              Lossy Networks", RFC 6550, March 2012.

   [RFC6918]  Gont, F. and C. Pignataro, "Formally Deprecating Some
              ICMPv4 Message Types", RFC 6918, April 2013.

Shore & Pignataro        Expires August 7, 2014                 [Page 8]
Internet-Draft                  ICMP AUP                   February 2014

   [RFC4950]  Bonica, R., Gan, D., Tappan, D., and C. Pignataro, "ICMP
              Extensions for Multiprotocol Label Switching", RFC 4950,
              August 2007.

   [RFC5837]  Atlas, A., Bonica, R., Pignataro, C., Shen, N., and JR.
              Rivers, "Extending ICMP for Interface and Next-Hop
              Identification", RFC 5837, April 2010.

   [RFC2521]  Karn, P. and W. Simpson, "ICMP Security Failures
              Messages", RFC 2521, March 1999.

              CERT, "Smurf IP Denial-of-Service Attacks", CERT
              Advisory CA-1998-01, January 1998,


   [1]  <>

Authors' Addresses

   Melinda Shore
   No Mountain Software
   PO Box 16271
   Two Rivers, AK  99716

   Phone: +1 907 322 9522

   Carlos Pignataro
   Cisco Systems, Inc.
   7200-12 Kit Creek Road
   Research Triangle Park, NC  27709


Shore & Pignataro        Expires August 7, 2014                 [Page 9]