draft-ietf-ipngwg-icmp-v3-01.txt   draft-ietf-ipngwg-icmp-v3-02.txt 
INTERNET-DRAFT A. Conta, Transwitch INTERNET-DRAFT A. Conta, Transwitch
IPNG Working Group S. Deering, Cisco Systems IPNG Working Group S. Deering, Cisco Systems
Internet Control Message Protocol (ICMPv6) Internet Control Message Protocol (ICMPv6)
for the Internet Protocol Version 6 (IPv6) for the Internet Protocol Version 6 (IPv6)
Specification Specification
<draft-ietf-ipngwg-icmp-v3-01.txt> <draft-ietf-ipngwg-icmp-v3-02.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet- Drafts as reference time. It is inappropriate to use Internet- Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This internet draft will expire on January 19, 2002. This internet draft will expire on May 21, 2002.
Abstract Abstract
This document specifies a set of Internet Control Message Protocol This document specifies a set of Internet Control Message Protocol
(ICMP) messages for use with version 6 of the Internet Protocol (ICMP) messages for use with version 6 of the Internet Protocol
(IPv6). (IPv6).
Table of Contents Table of Contents
1. Introduction........................................3 1. Introduction........................................3
2. ICMPv6 (ICMP for IPv6)..............................3 2. ICMPv6 (ICMP for IPv6)..............................3
2.1 Message General Format.......................3 2.1 Message General Format.......................3
2.2 Message Source Address Determination.........4 2.2 Message Source Address Determination.........5
2.3 Message Checksum Calculation.................5 2.3 Message Checksum Calculation.................6
2.4 Message Processing Rules.....................5 2.4 Message Processing Rules.....................6
3. ICMPv6 Error Messages...............................8 3. ICMPv6 Error Messages...............................9
3.1 Destination Unreachable Message..............8 3.1 Destination Unreachable Message..............9
3.2 Packet Too Big Message......................10 3.2 Packet Too Big Message......................11
3.3 Time Exceeded Message.......................11 3.3 Time Exceeded Message.......................12
3.4 Parameter Problem Message...................12 3.4 Parameter Problem Message...................14
4. ICMPv6 Informational Messages......................14 4. ICMPv6 Informational Messages......................16
4.1 Echo Request Message........................14 4.1 Echo Request Message........................16
4.2 Echo Reply Message..........................15 4.2 Echo Reply Message..........................17
5. Security Considerations............................17 5. Security Considerations............................19
6. References.........................................19 6. References.........................................21
7. Acknowledgments....................................19 7. Acknowledgments....................................21
8. Authors' Addresses.................................20 8. Authors' Addresses.................................22
Appendix A - Changes since RFC 2463...................20 Appendix A - Changes since RFC 2463...................22
1. Introduction 1. Introduction
The Internet Protocol, version 6 (IPv6) is a new version of IP. IPv6 The Internet Protocol, version 6 (IPv6) is a new version of IP. IPv6
uses the Internet Control Message Protocol (ICMP) as defined for IPv4 uses the Internet Control Message Protocol (ICMP) as defined for IPv4
[RFC-792], with a number of changes. The resulting protocol is [RFC-792], with a number of changes. The resulting protocol is
called ICMPv6, and has an IPv6 Next Header value of 58. called ICMPv6, and has an IPv6 Next Header value of 58.
This document describes the format of a set of control messages used This document describes the format of a set of control messages used
in ICMPv6. It does not describe the procedures for using these in ICMPv6. It does not describe the procedures for using these
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The type field indicates the type of the message. Its value The type field indicates the type of the message. Its value
determines the format of the remaining data. determines the format of the remaining data.
The code field depends on the message type. It is used to create an The code field depends on the message type. It is used to create an
additional level of message granularity. additional level of message granularity.
The checksum field is used to detect data corruption in the ICMPv6 The checksum field is used to detect data corruption in the ICMPv6
message and parts of the IPv6 header. message and parts of the IPv6 header.
The subclass of ICMPv6 messages used for reporting errors, i.e.,
those with a Type value between 0 and 127, inclusive, all have the
following, more specific format:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| type-specific data (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| As much of invoking packet |
+ as will fit without the ICMPv6 packet +
| exceeding the minimum IPv6 MTU [IPv6] |
2.2 Message Source Address Determination 2.2 Message Source Address Determination
A node that sends an ICMPv6 message has to determine both the Source A node that sends an ICMPv6 message has to determine both the Source
and Destination IPv6 Addresses in the IPv6 header before calculating and Destination IPv6 Addresses in the IPv6 header before calculating
the checksum. If the node has more than one unicast address, it must the checksum. If the node has more than one unicast address, it must
choose the Source Address of the message as follows: choose the Source Address of the message as follows:
(a) If the message is a response to a message sent to one of the (a) If the message is a response to a message sent to one of the
node's unicast addresses, the Source Address of the reply must node's unicast addresses, the Source Address of the reply must
be that same address. be that same address.
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(e.3) a packet destined to an IPv6 multicast address (there are (e.3) a packet destined to an IPv6 multicast address (there are
two exceptions to this rule: (1) the Packet Too Big two exceptions to this rule: (1) the Packet Too Big
Message - Section 3.2 - to allow Path MTU discovery to Message - Section 3.2 - to allow Path MTU discovery to
work for IPv6 multicast, and (2) the Parameter Problem work for IPv6 multicast, and (2) the Parameter Problem
Message, Code 2 - Section 3.4 - reporting an unrecognized Message, Code 2 - Section 3.4 - reporting an unrecognized
IPv6 option that has the Option Type highest-order two IPv6 option that has the Option Type highest-order two
bits set to 10), or bits set to 10), or
(e.4) a packet sent as a link-layer multicast, (the exception (e.4) a packet sent as a link-layer multicast, (the exception
from e.2 applies to this case too), or from e.3 applies to this case too), or
(e.5) a packet sent as a link-layer broadcast, (the exception (e.5) a packet sent as a link-layer broadcast, (the exception
from e.2 applies to this case too), or from e.3 applies to this case too), or
(e.6) a packet whose source address does not uniquely identify (e.6) a packet whose source address does not uniquely identify
a single node -- e.g., the IPv6 Unspecified Address, an a single node -- e.g., the IPv6 Unspecified Address, an
IPv6 multicast address, or an address known by the ICMP IPv6 multicast address, or an address known by the ICMP
message sender to be an IPv6 anycast address. message sender to be an IPv6 anycast address.
(f) Finally, in order to limit the bandwidth and forwarding costs (f) Finally, in order to limit the bandwidth and forwarding costs
incurred sending ICMPv6 error messages, an IPv6 node MUST limit incurred sending ICMPv6 error messages, an IPv6 node MUST limit
the rate of ICMPv6 error messages it sends. This situation may the rate of ICMPv6 error messages it sends. This situation may
occur when a source sending a stream of erroneous packets fails occur when a source sending a stream of erroneous packets fails
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of ways of implementing the rate-limiting function, for example: of ways of implementing the rate-limiting function, for example:
(f.1) Timer-based - for example, limiting the rate of (f.1) Timer-based - for example, limiting the rate of
transmission of error messages to a given source, or to transmission of error messages to a given source, or to
any source, to at most once every T milliseconds. any source, to at most once every T milliseconds.
(f.2) Bandwidth-based - for example, limiting the rate at which (f.2) Bandwidth-based - for example, limiting the rate at which
error messages are sent from a particular interface to error messages are sent from a particular interface to
some fraction F of the attached link's bandwidth. some fraction F of the attached link's bandwidth.
(f.3) Token-bucket based - for example, allowing up to B back-
to-back error messages to be transmitted in a burst, but
limiting the average rate of transmission to N messages
per second.
The limit parameters (e.g., T or F in the above examples) MUST The limit parameters (e.g., T or F in the above examples) MUST
be configurable for the node, with a conservative default value be configurable for the node, with a conservative default value
(e.g., T = 1 second, NOT 0 seconds, or F = 2 percent, NOT 100 (e.g., T = 0.5 second, NOT 0 seconds, or F = 2 percent, NOT 100
percent). percent).
NOTE: THE RESTRICTIONS UNDER (e) AND (f) ABOVE TAKE PRECEDENCE OVER NOTE: THE RESTRICTIONS UNDER (e) AND (f) ABOVE TAKE PRECEDENCE OVER
ANY REQUIREMENT ELSEWHERE IN THIS DOCUMENT FOR SENDING ICMP ERROR ANY REQUIREMENT ELSEWHERE IN THIS DOCUMENT FOR SENDING ICMP ERROR
MESSAGES. MESSAGES.
The following sections describe the message formats for the above The following sections describe the message formats for the above
ICMPv6 messages. ICMPv6 messages.
3. ICMPv6 Error Messages 3. ICMPv6 Error Messages
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address) and the packet cannot be delivered to the destination address) and the packet cannot be delivered to the destination
without leaving the scope of the source address (e.g., without without leaving the scope of the source address (e.g., without
leaving the source's site, in the case of a site-local source leaving the source's site, in the case of a site-local source
address). address).
If there is any other reason for the failure to deliver, e.g., If there is any other reason for the failure to deliver, e.g.,
inability to resolve the IPv6 destination address into a inability to resolve the IPv6 destination address into a
corresponding link address, or a link-specific problem of some sort, corresponding link address, or a link-specific problem of some sort,
then the Code field is set to 3. then the Code field is set to 3.
One specific case in which a Destination Unreachable message with a
code 3 is sent is in response to a packet received by a router from a
point-to-point link, destined to an address within a subnet assigned
to that same link (other than one of the receiving router's own
addresses). In such a case, the packet MUST NOT be forwarded back
onto the arrival link.
A destination node SHOULD send a Destination Unreachable message with A destination node SHOULD send a Destination Unreachable message with
Code 4 in response to a packet for which the transport protocol Code 4 in response to a packet for which the transport protocol
(e.g., UDP) has no listener, if that transport protocol has no (e.g., UDP) has no listener, if that transport protocol has no
alternative means to inform the sender. alternative means to inform the sender.
Upper layer notification Upper layer notification
A node receiving the ICMPv6 Destination Unreachable message MUST A node receiving the ICMPv6 Destination Unreachable message MUST
notify the upper-layer process. notify the upper-layer process.
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and ignored by the receiver. and ignored by the receiver.
Description Description
If a router receives a packet with a Hop Limit of zero, or a router If a router receives a packet with a Hop Limit of zero, or a router
decrements a packet's Hop Limit to zero, it MUST discard the packet decrements a packet's Hop Limit to zero, it MUST discard the packet
and send an ICMPv6 Time Exceeded message with Code 0 to the source of and send an ICMPv6 Time Exceeded message with Code 0 to the source of
the packet. This indicates either a routing loop or too small an the packet. This indicates either a routing loop or too small an
initial Hop Limit value. initial Hop Limit value.
An ICMPv6 Time Exceeded message with Code 1 is used to report
fragment reassembly timeout, as specified in [IPv6, Section 4.5].
The rules for selecting the Source Address of this message are The rules for selecting the Source Address of this message are
defined in section 2.2. defined in section 2.2.
Upper layer notification Upper layer notification
An incoming Time Exceeded message MUST be passed to the upper-layer An incoming Time Exceeded message MUST be passed to the upper-layer
process. process.
3.4 Parameter Problem Message 3.4 Parameter Problem Message
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[IPv6-ESP] Kent, S., R. Atkinson, "IP Encapsulating Security [IPv6-ESP] Kent, S., R. Atkinson, "IP Encapsulating Security
Protocol (ESP)", RFC 2406, November 1998. Protocol (ESP)", RFC 2406, November 1998.
7. Acknowledgments 7. Acknowledgments
The document is derived from previous ICMP drafts of the SIPP and The document is derived from previous ICMP drafts of the SIPP and
IPng working group. IPng working group.
The IPng working group and particularly Robert Elz, Jim Bound, Bill The IPng working group and particularly Robert Elz, Jim Bound, Bill
Simpson, Thomas Narten, Charlie Lynn, Bill Fink, Scott Bradner, Simpson, Thomas Narten, Charlie Lynn, Bill Fink, Scott Bradner,
Dimitri Haskin, and Bob Hinden (in chronological order) provided Dimitri Haskin, Bob Hinden, Jun-ichiro Itojun Hagino, Tatuya Jinmei,
extensive review information and feedback. and Brian Zill (in chronological order) provided extensive review
information and feedback.
Bob Hinden was the document editor for this document. Bob Hinden was the document editor for this document.
8. Authors' Addresses 8. Authors' Addresses
Alex Conta Stephen Deering Alex Conta Stephen Deering
Transwitch Corporation Cisco Systems, Inc. Transwitch Corporation Cisco Systems, Inc.
3 Enterprise Drive 170 West Tasman Drive 3 Enterprise Drive 170 West Tasman Drive
Shelton, CT 06484 San Jose, CA 95134-1706 Shelton, CT 06484 San Jose, CA 95134-1706
US US US US
phone: +1 408 527-8213 phone: +1 408 527-8213
email: aconta@txc.com email: deering@cisco.com email: aconta@txc.com email: deering@cisco.com
Appendix A - Changes from RFC 2463 Appendix A - Changes from RFC 2463
The following changes were made from RFC 2463: The following changes were made from RFC 2463:
- Corrected typos in section 2.4, where references to sub-bullet e.2
were supposed to be references to e.3.
- Added token-bucket method as an example rate-limiting mechanism
for ICMP error messages, and changed default value for the fixed
timer approach, parameter T, from 1 second to 0.5 second.
- Added specification that all ICMP error messages shall have
exactly 32 bits of type-specific data, so that receivers can
reliably find the embedded invoking packet even when they don't
recognize the ICMP message Type.
- In the description of Destination Unreachable messages, Code 3,
added rule prohibiting forwarding of packets back onto point-to-
point links from which they were received, if their destination
addresses belong to the link itself ("anti-ping-ponging" rule).
- Added description of Time Exceeded Code 1 (fragment reassembly
timeout).
- Added "beyond scope of source address" message to the family of - Added "beyond scope of source address" message to the family of
"unreachable destination" type ICMP error messages (section 3.1). "unreachable destination" type ICMP error messages (section 3.1).
- Added a NOTE in section 2.4, that specifies ICMP message - Added a NOTE in section 2.4, that specifies ICMP message
processing rules precedence. processing rules precedence.
- Added ICMP REDIRECT to the list in Section 2.4 e) of cases in - Added ICMP REDIRECT to the list in Section 2.4 e) of cases in
which ICMP error messages are not to be generated. which ICMP error messages are not to be generated.
- Made minor editorial changes in Section 2.3 on checksum - Made minor editorial changes in Section 2.3 on checksum
calculation, and in Section 5.2. calculation, and in Section 5.2.
- Clarified in section 4.2, regarding the Echo Reply Message, that - Clarified in section 4.2, regarding the Echo Reply Message, that
the source address of an Echo Reply to an anycast Echo Request the source address of an Echo Reply to an anycast Echo Request
should be a unicast address, as is the case of multicast. should be a unicast address, as in the case of multicast.
 End of changes. 

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