Network Working Group M. Shore
Internet-Draft No Mountain Software
Expires: January 14, 2013 C. Pignataro
Cisco Systems, Inc.
July 13, 2012
An Acceptable Use Policy for New ICMP Types and Codes
draft-shore-icmp-aup-01
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.
Status of this Memo
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This Internet-Draft will expire on January 14, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Acceptable use policy . . . . . . . . . . . . . . . . . . . . 4
2.1. Classification of existing message types . . . . . . . . . 4
3. ICMP's role in the internet . . . . . . . . . . . . . . . . . 8
4. Management vs control . . . . . . . . . . . . . . . . . . . . 9
5. Security considerations . . . . . . . . . . . . . . . . . . . 11
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 12
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
8. Informative references . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
There have been some recent proposals to add new message types and
codes to ICMP [RFC792]. 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. Acceptable use policy
In this document we describe a proposed acceptable use policy for new
ICMP message types and codes, and provide some background behind the
proposed policy.
In summary, we propose that 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 on-link routers and hosts
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.
IPV4 forwarding plane anomaly reporting
3: Destination unreachable
4: Source quench (deprecated)
5: Redirect
6: Alternate host address
11 Time exceeded
12 Parameter problem
31: Datagram converson error
32: Mobile host redirect
41: ICMP messages utilized by experimental mobility protocols,
such as Seamoby
IPv4 router or host discovery
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0: Echo reply
8: Echo
9: Router advertisement
10: Router solicitation
13: Timestamp
14: Timestamp reply
15: Information request
16: Information reply
17: Address mask request
18: Address mask reply
30: Traceroute
33: IPv6 Where-Are-You
34: IPv6 I-Am-Here
35: Mobile registration request
36: Mobile registration reply
37: Domain name request
38: Domain name reply
39: SKIP
40: Photuris
41: ICMP messages utilized by experimental mobility protocols,
such as Seamoby
IPv6 forwarding plane anomaly reporting
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1: Destination unreachable
2: Packet too big
3: Time exceeded
4: Parameter problem
137: Redirect message
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
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
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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
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3. 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.
In following sections we provide some background on the differences
between control and management traffic.
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4. 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.
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 this we propose that any future message types added to
ICMP must conform to the policy proposed in Section 2. ICMP should
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not be used as a routing or network management protocol.
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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. Acknowledgments
This document was originally proposed by, and received substantial
review and suggestions from, Ron Bonica.
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8. Informative references
[RFC792] Postel, J., "INTERNET CONTROL MESSAGE PROTOCOL", RFC 792,
September 1981.
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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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