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
draft-shore-icmp-aup-00
Abstract
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.
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This Internet-Draft will expire on January 10, 2013.
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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
leadership.
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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
message.
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
[RFC792] Postel, J., "INTERNET CONTROL MESSAGE PROTOCOL", RFC 792,
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
US
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
US
Email: cpignata@cisc.com
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