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Network Working Group                                           M. Shore
Internet-Draft                                      No Mountain Software
Expires: January 10, 2013                                   C. Pignataro
                                                     Cisco Systems, Inc.
                                                            July 9, 2012

         An Acceptable Use Policy for New ICMP Types and Codes


   Some recent proposals to add new Internet Control Message Protocol
   (ICMP) types and/or codes have highlighted a need to describe
   policies for when adding new features to ICMP is desirable and when
   it is not.  In this document we provide a basic description of ICMP's
   role in the IP stack and some guidelines for the future.

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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 10, 2013.

Copyright Notice

   Copyright (c) 2012 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
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  ICMP's role in the internet  . . . . . . . . . . . . . . . . .  4
   3.  Management vs control  . . . . . . . . . . . . . . . . . . . .  5
   4.  Where ICMP fits  . . . . . . . . . . . . . . . . . . . . . . .  6
   5.  Security considerations  . . . . . . . . . . . . . . . . . . .  7
   6.  IANA considerations  . . . . . . . . . . . . . . . . . . . . .  8
   7.  Informative references . . . . . . . . . . . . . . . . . . . .  9
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10

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1.  Introduction

   There have been some recent proposals to add new message types and
   codes to ICMP [RFC792] (see, for example, [templin]).  Not all of
   these proposal are consistent with the design and intent of ICMP, and
   so we attempt to lay out a description of when (and when not) to move
   functionality into ICMP.

   This document is the result of discussions within the IETF Operations
   area "ICMP Society," and concerns expressed by the OPS area

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2.  ICMP's role in the internet

   ICMP was originally intended to be a mechanism for routers to report
   error conditions back to hosts [RFC792].  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, it was and is not used
   as a routing protocol.

   Most likely because of the presence of the word "control" in the
   protocol name, ICMP is often understood to be a control protocol,
   borrowing some terminology from circuit networks and the PSTN.  That
   is probably not correct - it might be more correct to describe it as
   being closer to a management plane protocol, given the data plane/
   control plane/ management plane taxonomy often used in describing
   telephony protocols.  However, layering in IP networks is not very
   clean and there's often some intermingling of function that can tend
   to lead to confusion about where to place new functions.

   This document provides some background on the differences between
   control and management traffic, and finishes by proposing that any
   future additional ICMP types or codes be limited to what in telephony
   networks would be considered management plane traffic.

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3.  Management vs control

   In this section we attempt to draw a distinction between management
   and control planes, acknowledging in advance that this may serve to
   muddle the differences even further.  Ultimately the difference may
   not matter that much for the purpose of creating a policy for adding
   new types to ICMP, but because that terminology has become
   ubiquitous, even in IETF discussions, and because it has come up in
   prior discussions of ICMP policies, it seems worthwhile to take a few
   paragraph to describe what they are and what they are not.

   The terms "management plane" and "control plane" came into use to
   describe one aspect of layering in telecommunications networks.  It
   is particularly important, in the context of this discussion, to
   understand that "control plane" in telecomm networks almost always
   refers to 'signaling,' or call control and network control
   information.  This includes "call" establishment and teardown, route
   establishment and teardown, requesting QoS or other parameters, and
   so on.

   "Management," on the other hand, tends to fall under the rubric
   "OAM," or "Operations, Administration, and Management." typical
   functions include fault management and performance monitoring
   (Service Level Agreement [SLA] compliance), discovery, etc.

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4.  Where ICMP fits

   The correct answer to the question of where ICMP fits into the
   management/control/data taxonomy is that it doesn't, at least not
   neatly.  While some of the message types are unambiguously management
   message (ICMP type 3, or "unreachable" messages), others are less
   clearly identifiable.  For example, the "redirect" (ICMP type 5)
   message can be construed to contain control (in this case, routing)
   information, even though it is in some very real sense an error

   At this time,

   o  there are many, many other protocols that can be (and are) used
      for control traffic, whether they're routing protocols, telephony
      signaling protocols, QoS protocols, middlebox protocols, AAA
      protocols, etc.

   o  the transport characteristics needed by control traffic can be
      incompatible with the ICMP protocol standard -- for example, they
      may require reliable delivery, very large payloads, or have
      security requirements that cannot be met.

   and because of thiswe propose that any future message types added to
   ICMP must stay within the "management plane" domain, and in
   particular that it would not be appropriate or desirable for control
   (or signaling) messages to be conveyed by ICMP.

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5.  Security considerations

   This document attempts to describe 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,
   specific security considerations are outside the scope of this paper.

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6.  IANA considerations

   There are no actions required by IANA.

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7.  Informative references

              September 1981.

   [templin]  Templin, F., "Asymmetric Extended Route Optimization
              (AERO)", draft-templin-aero-08 (work in progress),
              February 2012.

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Authors' Addresses

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

   Phone: +1 907 322 9522
   Email: melinda.shore@nomountain.net

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

   Email: cpignata@cisc.com

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