draft-ietf-ipngwg-icmp-v3-07.txt   rfc4443.txt 
Internet Draft A. Conta, Transwitch Network Working Group A. Conta
IPv6 Working Group S. Deering, Cisco Systems Request for Comments: 4443 Transwitch
11 July 2005 M. Gupta, Nokia (ed.) Obsoletes: 2463 S. Deering
Updates: 2780 Cisco Systems
Category: Standards Track M. Gupta, Ed.
Tropos Networks
March 2006
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-v3-07.txt>
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2006).
Abstract Abstract
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 (Internet Control Message Protocol). ICMPv6 is the in ICMPv6 (Internet Control Message Protocol). ICMPv6 is the
Internet Control Message Protocol for Internet Protocol version 6 Internet Control Message Protocol for Internet Protocol version 6
(IPv6). (IPv6).
Table of Contents Table of Contents
1. Introduction.....................................................3 1. Introduction ....................................................2
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......................5 2.2. Message Source Address Determination .......................5
2.3 Message Checksum Calculation..............................6 2.3. Message Checksum Calculation ...............................5
2.4 Message Processing Rules..................................6 2.4. Message Processing Rules ...................................5
3. ICMPv6 Error Messages............................................9 3. ICMPv6 Error Messages ...........................................8
3.1 Destination Unreachable Message...........................9 3.1. Destination Unreachable Message ............................8
3.2 Packet Too Big Message...................................12 3.2. Packet Too Big Message ....................................10
3.3 Time Exceeded Message....................................13 3.3. Time Exceeded Message .....................................11
3.4 Parameter Problem Message................................14 3.4. Parameter Problem Message .................................12
4. ICMPv6 Informational Messages...................................16 4. ICMPv6 Informational Messages ..................................13
4.1 Echo Request Message.....................................16 4.1. Echo Request Message ......................................13
4.2 Echo Reply Message.......................................17 4.2. Echo Reply Message ........................................14
5. Security Considerations.........................................19 5. Security Considerations ........................................15
5.1 Authentication and Confidentiality of ICMP messages......19 5.1. Authentication and Confidentiality of ICMP Messages .......15
5.2 ICMP Attacks.............................................19 5.2. ICMP Attacks ..............................................16
6. IANA Considerations.............................................21 6. IANA Considerations ............................................17
6.1 Procedure for new ICMPV6 Type and Code value assignments.22 6.1. Procedure for New ICMPV6 Type and Code Value Assignments ..17
6.2 Assignments for this document............................22 6.2. Assignments for This Document .............................18
7. References......................................................23 7. References .....................................................19
7.1 Normative................................................22 7.1. Normative References ......................................19
7.2 Informative..............................................22 7.2. Informative References ....................................19
8. Acknowledgments.................................................23 8. Acknowledgements ...............................................20
9. Authors' Addresses..............................................23 Appendix A - Changes since RFC 2463................................21
Appendix A - Changes since RFC 2463................................24
1. Introduction 1. Introduction
The Internet Protocol, version 6 (IPv6) uses the Internet Control The Internet Protocol version 6 (IPv6) uses the Internet Control
Message Protocol (ICMP) as defined for IPv4 [RFC-792], with a number Message Protocol (ICMP) as defined for IPv4 [RFC-792], with a number
of changes. The resulting protocol is called ICMPv6, and has an IPv6 of changes. The resulting protocol is called ICMPv6 and has an IPv6
Next Header value of 58. 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
messages to chieve functions like Path MTU discovery; such procedures messages to achieve functions like Path MTU discovery; these
are described in other documents (e.g., [PMTU]). Other documents may procedures are described in other documents (e.g., [PMTU]). Other
also introduce additional ICMPv6 message types, such as Neighbor documents may also introduce additional ICMPv6 message types, such as
Discovery messages [IPv6-DISC], subject to the general rules for Neighbor Discovery messages [IPv6-DISC], subject to the general rules
ICMPv6 messages given in section 2 of this document. for ICMPv6 messages given in Section 2 of this document.
Terminology defined in the IPv6 specification [IPv6] and the IPv6 Terminology defined in the IPv6 specification [IPv6] and the IPv6
Routing and Addressing specification [IPv6-ADDR] applies to this Routing and Addressing specification [IPv6-ADDR] applies to this
document as well. document as well.
This document obsoletes RFC 2463 [RFC2463] and updates RFC 2780 This document obsoletes RFC 2463 [RFC-2463] and updates RFC 2780
[RFC-2780]. [RFC-2780].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC-2119]. document are to be interpreted as described in [RFC-2119].
2. ICMPv6 (ICMP for IPv6) 2. ICMPv6 (ICMP for IPv6)
ICMPv6 is used by IPv6 nodes to report errors encountered in ICMPv6 is used by IPv6 nodes to report errors encountered in
processing packets, and to perform other internet-layer functions, processing packets, and to perform other internet-layer functions,
such as diagnostics (ICMPv6 "ping"). ICMPv6 is an integral part of such as diagnostics (ICMPv6 "ping"). ICMPv6 is an integral part of
IPv6 and the base protocol (all the messages and behavior required by IPv6, and the base protocol (all the messages and behavior required
this specification) MUST be fully implemented by every IPv6 node. by this specification) MUST be fully implemented by every IPv6 node.
2.1 Message General Format 2.1. Message General Format
Every ICMPv6 message is preceded by an IPv6 header and zero or more Every ICMPv6 message is preceded by an IPv6 header and zero or more
IPv6 extension headers. The ICMPv6 header is identified by a Next IPv6 extension headers. The ICMPv6 header is identified by a Next
Header value of 58 in the immediately preceding header. (NOTE: this Header value of 58 in the immediately preceding header. (This is
is different than the value used to identify ICMP for IPv4.) different from the value used to identify ICMP for IPv4.)
The ICMPv6 messages have the following general format: The ICMPv6 messages have the following general format:
0 1 2 3 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 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 | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ Message Body + + Message Body +
| | | |
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.
ICMPv6 messages are grouped into two classes: error messages and ICMPv6 messages are grouped into two classes: error messages and
informational messages. Error messages are identified as such by informational messages. Error messages are identified as such by a
having a zero in the high-order bit of their message Type field zero in the high-order bit of their message Type field values. Thus,
values. Thus, error messages have message Types from 0 to 127; error messages have message types from 0 to 127; informational
informational messages have message Types from 128 to 255. messages have message types from 128 to 255.
This document defines the message formats for the following ICMPv6 This document defines the message formats for the following ICMPv6
messages: messages:
ICMPv6 error messages: ICMPv6 error messages:
1 Destination Unreachable (see section 3.1) 1 Destination Unreachable (see Section 3.1)
2 Packet Too Big (see section 3.2) 2 Packet Too Big (see Section 3.2)
3 Time Exceeded (see section 3.3) 3 Time Exceeded (see Section 3.3)
4 Parameter Problem (see section 3.4) 4 Parameter Problem (see Section 3.4)
100 Private experimentation 100 Private experimentation
101 Private experimentation 101 Private experimentation
127 Reserved for expansion of ICMPv6 error messages 127 Reserved for expansion of ICMPv6 error messages
ICMPv6 informational messages: ICMPv6 informational messages:
128 Echo Request (see section 4.1) 128 Echo Request (see Section 4.1)
129 Echo Reply (see section 4.2) 129 Echo Reply (see Section 4.2)
200 Private experimentation 200 Private experimentation
201 Private experimentation 201 Private experimentation
255 Reserved for expansion of ICMPv6 informational messages 255 Reserved for expansion of ICMPv6 informational messages
Type values 100, 101, 200, and 201 are reserved for private Type values 100, 101, 200, and 201 are reserved for private
experimentation. These are not intended for general use. It is experimentation. They are not intended for general use. It is
expected that multiple concurrent experiments will be done with the expected that multiple concurrent experiments will be done with the
same type values. Any wide scale and/or uncontrolled usage should same type values. Any wide-scale and/or uncontrolled usage should
obtain real allocations as defined in section 6. obtain real allocations as defined in Section 6.
Type value 255 is reserved for future expansion of the type value Type values 127 and 255 are reserved for future expansion of the type
range if there should be a shortage in the future. The details of value range if there is a shortage in the future. The details of
this are left for future work. One possible way of doing this that this are left for future work. One possible way of doing this that
would not cause any problems with current implementations is if the would not cause any problems with current implementations is that if
type equals 255, use the code field for the new assignment. Existing the type equals 127 or 255, the code field should be used for the new
implementations would ignore the new assignments as specified in assignment. Existing implementations would ignore the new
section 2.4, section (b). The new messages using these expanded type assignments as specified in Section 2.4, (b). The new messages using
values, could assign fields in the message body for it's code values. these expanded type values could assign fields in the message body
for its code values.
Sections 3 and 4 describe the message formats for the ICMPv6 error Sections 3 and 4 describe the message formats for the ICMPv6 error
message types 1 through 4 and informational message types 128 and message types 1 through 4 and informational message types 128 and
129. 129.
Inclusion of, at least, the start of the invoking packet is intended Inclusion of, at least, the start of the invoking packet is intended
to allow the originator of a packet that has resulted in an ICMPv6 to allow the originator of a packet that has resulted in an ICMPv6
error message to identify the upper-layer protocol and process that error message to identify the upper-layer protocol and process that
sent the packet. sent the packet.
2.2 Message Source Address Determination 2.2. Message Source Address Determination
A node that originates an ICMPv6 message has to determine both the A node that originates an ICMPv6 message has to determine both the
Source and Destination IPv6 Addresses in the IPv6 header before Source and Destination IPv6 Addresses in the IPv6 header before
calculating the checksum. If the node has more than one unicast calculating the checksum. If the node has more than one unicast
address, it MUST choose the Source Address of the message as follows: address, it MUST 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
be that same address. that same address.
(b) If the message is a response to a message sent to any other (b) If the message is a response to a message sent to any other
address, such as address, such as
- a multicast group address,
- an anycast address implemented by the node, or
- a unicast address which does not belong to the node
the Source Address of the ICMPv6 packet MUST be a unicast
address belonging to the node. The address SHOULD be chosen
according to the rules which would be used to select the source
address for any other packet originated by the node, given the
destination address of the packet, but MAY be selected in an
alternative way if this would lead to a more informative choice
of address which is reachable from the destination of the ICMPv6
packet.
2.3 Message Checksum Calculation - a multicast group address,
- an anycast address implemented by the node, or
- a unicast address that does not belong to the node
the Source Address of the ICMPv6 packet MUST be a unicast address
belonging to the node. The address SHOULD be chosen according to
the rules that would be used to select the source address for any
other packet originated by the node, given the destination address
of the packet. However, it MAY be selected in an alternative way
if this would lead to a more informative choice of address
reachable from the destination of the ICMPv6 packet.
2.3. Message Checksum Calculation
The checksum is the 16-bit one's complement of the one's complement The checksum is the 16-bit one's complement of the one's complement
sum of the entire ICMPv6 message starting with the ICMPv6 message sum of the entire ICMPv6 message, starting with the ICMPv6 message
type field, prepended with a "pseudo-header" of IPv6 header fields, type field, and prepended with a "pseudo-header" of IPv6 header
as specified in [IPv6, section 8.1]. The Next Header value used in fields, as specified in [IPv6, Section 8.1]. The Next Header value
the pseudo-header is 58. (NOTE: the inclusion of a pseudo-header in used in the pseudo-header is 58. (The inclusion of a pseudo-header
the ICMPv6 checksum is a change from IPv4; see [IPv6] for the in the ICMPv6 checksum is a change from IPv4; see [IPv6] for the
rationale for this change.) rationale for this change.)
For computing the checksum, the checksum field is first set to zero. For computing the checksum, the checksum field is first set to zero.
2.4 Message Processing Rules 2.4. Message Processing Rules
Implementations MUST observe the following rules when processing Implementations MUST observe the following rules when processing
ICMPv6 messages (from [RFC-1122]): ICMPv6 messages (from [RFC-1122]):
(a) If an ICMPv6 error message of unknown type is received at its (a) If an ICMPv6 error message of unknown type is received at its
destination, it MUST be passed to the upper-layer process that destination, it MUST be passed to the upper-layer process that
originated the packet that caused the error, where this can be originated the packet that caused the error, where this can be
identified (see Section 2.4(d)). identified (see Section 2.4, (d)).
(b) If an ICMPv6 informational message of unknown type is received, (b) If an ICMPv6 informational message of unknown type is received,
it MUST be silently discarded. it MUST be silently discarded.
(c) Every ICMPv6 error message (type < 128) MUST include as much of (c) Every ICMPv6 error message (type < 128) MUST include as much of
the IPv6 offending (invoking) packet (the packet that caused the the IPv6 offending (invoking) packet (the packet that caused the
error) as possible without making the error message packet error) as possible without making the error message packet exceed
exceed the minimum IPv6 MTU [IPv6]. the minimum IPv6 MTU [IPv6].
(d) In those cases where the internet-layer protocol is required to (d) In cases where the internet-layer protocol is required to pass an
pass an ICMPv6 error message to the upper-layer process, the ICMPv6 error message to the upper-layer process, the upper-layer
upper-layer protocol type is extracted from the original packet protocol type is extracted from the original packet (contained in
(contained in the body of the ICMPv6 error message) and used to the body of the ICMPv6 error message) and used to select the
select the appropriate upper-layer process to handle the error. appropriate upper-layer process to handle the error.
In the cases where it is not possible to retrieve the upper- In cases where it is not possible to retrieve the upper-layer
layer protocol type from the ICMPv6 message, the ICMPv6 message protocol type from the ICMPv6 message, the ICMPv6 message is
is silently dropped after any IPv6-layer processing. One silently dropped after any IPv6-layer processing. One example of
example of such a case is an ICMPv6 message with unusually large such a case is an ICMPv6 message with an unusually large amount
amount of extension headers that does not have the upper-layer of extension headers that does not have the upper-layer protocol
protocol type due to truncation of the original packet to meet type due to truncation of the original packet to meet the minimum
the minimum IPv6 MTU [IPv6] limit. Another example of such a IPv6 MTU [IPv6] limit. Another example is an ICMPv6 message with
case is an ICMPv6 message with ESP extension header where it is an ESP extension header for which it is not possible to decrypt
not possible to decrypt the original packet due to either the original packet due to either truncation or the
truncation or the unavailability of the state necessary to unavailability of the state necessary to decrypt the packet.
decrypt the packet.
(e) An ICMPv6 error message MUST NOT be originated as a result of (e) An ICMPv6 error message MUST NOT be originated as a result of
receiving: receiving the following:
(e.1) an ICMPv6 error message, or (e.1) An ICMPv6 error message.
(e.2) an ICMPv6 redirect message [IPv6-DISC], or (e.2) An ICMPv6 redirect message [IPv6-DISC].
(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
Message - Section 3.2 - to allow Path MTU discovery to (Section 3.2) to allow Path MTU discovery to work for IPv6
work for IPv6 multicast, and (2) the Parameter Problem multicast, and (2) the Parameter Problem Message, Code 2
Message, Code 2 - Section 3.4 - reporting an unrecognized (Section 3.4) reporting an unrecognized IPv6 option (see
IPv6 option (see section 4.2 of [IPv6]) that has the Section 4.2 of [IPv6]) that has the Option Type highest-
Option Type highest-order two bits set to 10), or order two bits set to 10).
(e.4) a packet sent as a link-layer multicast, (the exceptions (e.4) A packet sent as a link-layer multicast (the exceptions
from e.3 apply to this case too), or from e.3 apply to this case, too).
(e.5) a packet sent as a link-layer broadcast, (the exceptions (e.5) A packet sent as a link-layer broadcast (the exceptions
from e.3 apply to this case too), or from e.3 apply to this case, too).
(e.6) a packet whose source address does not uniquely identify (e.6) A packet whose source address does not uniquely identify a
a single node -- e.g., the IPv6 Unspecified Address, an single node -- e.g., the IPv6 Unspecified Address, an IPv6
IPv6 multicast address, or an address known by the ICMP multicast address, or an address known by the ICMP message
message originator to be an IPv6 anycast address. originator 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 by originating ICMPv6 error messages, an IPv6 node MUST incurred by originating ICMPv6 error messages, an IPv6 node MUST
limit the rate of ICMPv6 error messages it originates. This limit the rate of ICMPv6 error messages it originates. This
situation may occur when a source sending a stream of erroneous situation may occur when a source sending a stream of erroneous
packets fails to heed the resulting ICMPv6 error messages. packets fails to heed the resulting ICMPv6 error messages.
Rate-limiting of forwarded ICMP messages is out of scope of this Rate-limiting of forwarded ICMP messages is out of scope of this
specification. specification.
A recommended method for implementing the rate-limiting function A recommended method for implementing the rate-limiting function
is a token bucket, limiting the average rate of transmission to is a token bucket, limiting the average rate of transmission to
N, where N can either be packets/second or a fraction of the N, where N can be either packets/second or a fraction of the
attached link's bandwidth, but allowing up to B error messages attached link's bandwidth, but allowing up to B error messages to
to be transmitted in a burst, as long as the long-term average be transmitted in a burst, as long as the long-term average is
is not exceeded. not exceeded.
Rate-limiting mechanisms which cannot cope with bursty traffic Rate-limiting mechanisms that cannot cope with bursty traffic
(e.g., traceroute) are not recommended; for example a simple (e.g., traceroute) are not recommended; for example, a simple
timer-based implementation, allowing an error message every T timer-based implementation, allowing an error message every T
milliseconds (even with low values for T), is not reasonable. milliseconds (even with low values for T), is not reasonable.
The rate-limiting parameters SHOULD be configurable. In the The rate-limiting parameters SHOULD be configurable. In the case
case of a token-bucket implementation, the best defaults depend of a token-bucket implementation, the best defaults depend on
on where the implementation is expected to be deployed (e.g., a where the implementation is expected to be deployed (e.g., a
high-end router vs. an embedded host). For example, in a high-end router vs. an embedded host). For example, in a
small/mid -sized device, the possible defaults could be B=10, small/mid-size device, the possible defaults could be B=10,
N=10/s. N=10/s.
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 ORIGINATING ICMP ERROR ANY REQUIREMENT ELSEWHERE IN THIS DOCUMENT FOR ORIGINATING 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
3.1 Destination Unreachable Message 3.1. Destination Unreachable Message
0 1 2 3 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 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 | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unused | | Unused |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| As much of invoking packet | | As much of invoking packet |
+ as possible without the ICMPv6 packet + + as possible without the ICMPv6 packet +
skipping to change at page 9, line 31 skipping to change at page 8, line 31
Destination Address Destination Address
Copied from the Source Address field of the invoking Copied from the Source Address field of the invoking
packet. packet.
ICMPv6 Fields: ICMPv6 Fields:
Type 1 Type 1
Code 0 - no route to destination Code 0 - No route to destination
1 - communication with destination 1 - Communication with destination
administratively prohibited administratively prohibited
2 - beyond scope of source address 2 - Beyond scope of source address
3 - address unreachable 3 - Address unreachable
4 - port unreachable 4 - Port unreachable
5 - source address failed ingress/egress policy 5 - Source address failed ingress/egress policy
6 - reject route to destination 6 - Reject route to destination
Unused This field is unused for all code values. Unused This field is unused for all code values.
It must be initialized to zero by the originator It must be initialized to zero by the originator
and ignored by the receiver. and ignored by the receiver.
Description Description
A Destination Unreachable message SHOULD be generated by a router, or A Destination Unreachable message SHOULD be generated by a router, or
by the IPv6 layer in the originating node, in response to a packet by the IPv6 layer in the originating node, in response to a packet
that cannot be delivered to its destination address for reasons other that cannot be delivered to its destination address for reasons other
than congestion. (An ICMPv6 message MUST NOT be generated if a than congestion. (An ICMPv6 message MUST NOT be generated if a
packet is dropped due to congestion.) packet is dropped due to congestion.)
If the reason for the failure to deliver is lack of a matching entry If the reason for the failure to deliver is lack of a matching entry
in the forwarding node's routing table, the Code field is set to 0 in the forwarding node's routing table, the Code field is set to 0.
(NOTE: this error can occur only in nodes that do not hold a "default
route" in their routing tables). (This error can occur only in nodes that do not hold a "default
route" in their routing tables.)
If the reason for the failure to deliver is administrative If the reason for the failure to deliver is administrative
prohibition, e.g., a "firewall filter", the Code field is set to 1. prohibition (e.g., a "firewall filter"), the Code field is set to 1.
If the reason for the failure to deliver is that the destination is If the reason for the failure to deliver is that the destination is
beyond the scope of the source address, the Code field is set to 2. beyond the scope of the source address, the Code field is set to 2.
This condition can occur only when the scope of the source address is This condition can occur only when the scope of the source address is
smaller than the scope of the destination address (e.g., when a smaller than the scope of the destination address (e.g., when a
packet has a link-local source address and a global-scope destination packet has a link-local source address and a global-scope destination
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. without leaving the scope of the source address.
If the reason for the failure to deliver can not be mapped to any of If the reason for the failure to deliver cannot be mapped to any of
other codes, the Code field is set to 3. The example of such cases other codes, the Code field is set to 3. Example of such cases are
are inability to resolve the IPv6 destination address into a an 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.
One specific case in which a Destination Unreachable message with a One specific case in which a Destination Unreachable message is sent
code 3 is sent is in response to a packet received by a router from a with a code 3 is in response to a packet received by a router from a
point-to-point link, destined to an address within a subnet assigned 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 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 addresses). In such a case, the packet MUST NOT be forwarded back
onto the arrival link. onto the arrival link.
A destination node SHOULD originate a Destination Unreachable message A destination node SHOULD originate a Destination Unreachable message
with Code 4 in response to a packet for which the transport protocol with 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.
If the reason for the failure to deliver is that packet with this If the reason for the failure to deliver is that the packet with this
source address is not allowed due to ingress or egress filtering source address is not allowed due to ingress or egress filtering
policies, the Code field is set to 5. policies, the Code field is set to 5.
If the reason for the failure to deliver is that the route to the If the reason for the failure to deliver is that the route to the
destination is a reject route, the Code field is set to 6. This may destination is a reject route, the Code field is set to 6. This may
occur if the router has been configured to reject all the traffic for occur if the router has been configured to reject all the traffic for
a specific prefix. a specific prefix.
Codes 5 and 6 are more informative subsets of code 1. Codes 5 and 6 are more informative subsets of code 1.
For security reasons, it is recommended that implementations SHOULD For security reasons, it is recommended that implementations SHOULD
allow sending of ICMP destination unreachable messages to be allow sending of ICMP destination unreachable messages to be
disabled, preferably on a per-interface basis. disabled, preferably on a per-interface basis.
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 if the relevant process can be notify the upper-layer process if the relevant process can be
identified (see section 2.4(d)). identified (see Section 2.4, (d)).
3.2 Packet Too Big Message 3.2. Packet Too Big Message
0 1 2 3 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 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 | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MTU | | MTU |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| As much of invoking packet | | As much of invoking packet |
+ as possible without the ICMPv6 packet + + as possible without the ICMPv6 packet +
skipping to change at page 12, line 30 skipping to change at page 10, line 36
Destination Address Destination Address
Copied from the Source Address field of the invoking Copied from the Source Address field of the invoking
packet. packet.
ICMPv6 Fields: ICMPv6 Fields:
Type 2 Type 2
Code Set to 0 (zero) by the originator and ignored by the Code Set to 0 (zero) by the originator and ignored by the
receiver receiver.
MTU The Maximum Transmission Unit of the next-hop link. MTU The Maximum Transmission Unit of the next-hop link.
Description Description
A Packet Too Big MUST be sent by a router in response to a packet A Packet Too Big MUST be sent by a router in response to a packet
that it cannot forward because the packet is larger than the MTU of that it cannot forward because the packet is larger than the MTU of
the outgoing link. The information in this message is used as part the outgoing link. The information in this message is used as part
of the Path MTU Discovery process [PMTU]. of the Path MTU Discovery process [PMTU].
Originating a Packet Too Big Message makes an exception to one of the Originating a Packet Too Big Message makes an exception to one of the
rules of when to originate an ICMPv6 error message, in that unlike rules as to when to originate an ICMPv6 error message. Unlike other
other messages, it is sent in response to a packet received with an messages, it is sent in response to a packet received with an IPv6
IPv6 multicast destination address, or a link-layer multicast or multicast destination address, or with a link-layer multicast or
link-layer broadcast address. link-layer broadcast address.
Upper layer notification Upper Layer Notification
An incoming Packet Too Big message MUST be passed to the upper-layer An incoming Packet Too Big message MUST be passed to the upper-layer
process if the relevant process can be identified (see section process if the relevant process can be identified (see Section 2.4,
2.4(d)). (d)).
3.3 Time Exceeded Message 3.3. Time Exceeded Message
0 1 2 3 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 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 | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unused | | Unused |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| As much of invoking packet | | As much of invoking packet |
+ as possible without the ICMPv6 packet + + as possible without the ICMPv6 packet +
skipping to change at page 13, line 28 skipping to change at page 11, line 34
IPv6 Fields: IPv6 Fields:
Destination Address Destination Address
Copied from the Source Address field of the invoking Copied from the Source Address field of the invoking
packet. packet.
ICMPv6 Fields: ICMPv6 Fields:
Type 3 Type 3
Code 0 - hop limit exceeded in transit Code 0 - Hop limit exceeded in transit
1 - Fragment reassembly time exceeded
1 - fragment reassembly time exceeded
Unused This field is unused for all code values. Unused This field is unused for all code values.
It must be initialized to zero by the originator It must be initialized to zero by the originator
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 if a
decrements a packet's Hop Limit to zero, it MUST discard the packet router decrements a packet's Hop Limit to zero, it MUST discard the
and originate an ICMPv6 Time Exceeded message with Code 0 to the packet and originate an ICMPv6 Time Exceeded message with Code 0 to
source of the packet. This indicates either a routing loop or too the source of the packet. This indicates either a routing loop or
small an initial Hop Limit value. too small an initial Hop Limit value.
An ICMPv6 Time Exceeded message with Code 1 is used to report An ICMPv6 Time Exceeded message with Code 1 is used to report
fragment reassembly timeout, as specified in [IPv6, Section 4.5]. fragment reassembly timeout, as specified in [IPv6, Section 4.5].
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 if the relevant process can be identified (see section process if the relevant process can be identified (see Section 2.4,
2.4(d)). (d)).
3.4 Parameter Problem Message 3.4. Parameter Problem Message
0 1 2 3 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 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 | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pointer | | Pointer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| As much of invoking packet | | As much of invoking packet |
+ as possible without the ICMPv6 packet + + as possible without the ICMPv6 packet +
skipping to change at page 14, line 29 skipping to change at page 12, line 35
Destination Address Destination Address
Copied from the Source Address field of the invoking Copied from the Source Address field of the invoking
packet. packet.
ICMPv6 Fields: ICMPv6 Fields:
Type 4 Type 4
Code 0 - erroneous header field encountered Code 0 - Erroneous header field encountered
1 - Unrecognized Next Header type encountered
1 - unrecognized Next Header type encountered 2 - Unrecognized IPv6 option encountered
2 - unrecognized IPv6 option encountered
Pointer Identifies the octet offset within the Pointer Identifies the octet offset within the
invoking packet where the error was detected. invoking packet where the error was detected.
The pointer will point beyond the end of the ICMPv6 The pointer will point beyond the end of the ICMPv6
packet if the field in error is beyond what can fit packet if the field in error is beyond what can fit
in the maximum size of an ICMPv6 error message. in the maximum size of an ICMPv6 error message.
Description Description
If an IPv6 node processing a packet finds a problem with a field in If an IPv6 node processing a packet finds a problem with a field in
the IPv6 header or extension headers such that it cannot complete the IPv6 header or extension headers such that it cannot complete
processing the packet, it MUST discard the packet and SHOULD processing the packet, it MUST discard the packet and SHOULD
originate an ICMPv6 Parameter Problem message to the packet's source, originate an ICMPv6 Parameter Problem message to the packet's source,
indicating the type and location of the problem. indicating the type and location of the problem.
Codes 1 and 2 are more informative subsets of Code 0. Codes 1 and 2 are more informative subsets of Code 0.
The pointer identifies the octet of the original packet's header The pointer identifies the octet of the original packet's header
where the error was detected. For example, an ICMPv6 message with where the error was detected. For example, an ICMPv6 message with a
Type field = 4, Code field = 1, and Pointer field = 40 would indicate Type field of 4, Code field of 1, and Pointer field of 40 would
that the IPv6 extension header following the IPv6 header of the indicate that the IPv6 extension header following the IPv6 header of
original packet holds an unrecognized Next Header field value. the original packet holds an unrecognized Next Header field value.
Upper layer notification Upper Layer Notification
A node receiving this ICMPv6 message MUST notify the upper-layer A node receiving this ICMPv6 message MUST notify the upper-layer
process if the relevant process can be identified (see section process if the relevant process can be identified (see Section 2.4,
2.4(d)). (d)).
4. ICMPv6 Informational Messages 4. ICMPv6 Informational Messages
4.1 Echo Request Message 4.1. Echo Request Message
0 1 2 3 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 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 | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier | Sequence Number | | Identifier | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data ... | Data ...
+-+-+-+-+- +-+-+-+-+-
skipping to change at page 16, line 49 skipping to change at page 14, line 20
Data Zero or more octets of arbitrary data. Data Zero or more octets of arbitrary data.
Description Description
Every node MUST implement an ICMPv6 Echo responder function that Every node MUST implement an ICMPv6 Echo responder function that
receives Echo Requests and originates corresponding Echo Replies. A receives Echo Requests and originates corresponding Echo Replies. A
node SHOULD also implement an application-layer interface for node SHOULD also implement an application-layer interface for
originating Echo Requests and receiving Echo Replies, for diagnostic originating Echo Requests and receiving Echo Replies, for diagnostic
purposes. purposes.
Upper layer notification Upper Layer Notification
Echo Request messages MAY be passed to processes receiving ICMP Echo Request messages MAY be passed to processes receiving ICMP
messages. messages.
4.2 Echo Reply Message 4.2. Echo Reply Message
0 1 2 3 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 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 | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier | Sequence Number | | Identifier | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data ... | Data ...
+-+-+-+-+- +-+-+-+-+-
skipping to change at page 17, line 32 skipping to change at page 15, line 5
Echo Request packet. Echo Request packet.
ICMPv6 Fields: ICMPv6 Fields:
Type 129 Type 129
Code 0 Code 0
Identifier The identifier from the invoking Echo Request message. Identifier The identifier from the invoking Echo Request message.
Sequence The sequence number from the invoking Echo Request Sequence Number
Number message.
The sequence number from the invoking Echo Request
message.
Data The data from the invoking Echo Request message. Data The data from the invoking Echo Request message.
Description Description
Every node MUST implement an ICMPv6 Echo responder function that Every node MUST implement an ICMPv6 Echo responder function that
receives Echo Requests and originates corresponding Echo Replies. A receives Echo Requests and originates corresponding Echo Replies. A
node SHOULD also implement an application-layer interface for node SHOULD also implement an application-layer interface for
originating Echo Requests and receiving Echo Replies, for diagnostic originating Echo Requests and receiving Echo Replies, for diagnostic
purposes. purposes.
skipping to change at page 18, line 8 skipping to change at page 15, line 32
that Echo Request message. that Echo Request message.
An Echo Reply SHOULD be sent in response to an Echo Request message An Echo Reply SHOULD be sent in response to an Echo Request message
sent to an IPv6 multicast or anycast address. In this case, the sent to an IPv6 multicast or anycast address. In this case, the
source address of the reply MUST be a unicast address belonging to source address of the reply MUST be a unicast address belonging to
the interface on which the Echo Request message was received. the interface on which the Echo Request message was received.
The data received in the ICMPv6 Echo Request message MUST be returned The data received in the ICMPv6 Echo Request message MUST be returned
entirely and unmodified in the ICMPv6 Echo Reply message. entirely and unmodified in the ICMPv6 Echo Reply message.
Upper layer notification Upper Layer Notification
Echo Reply messages MUST be passed to the process that originated an Echo Reply messages MUST be passed to the process that originated an
Echo Request message. An Echo Reply message MAY be passed to Echo Request message. An Echo Reply message MAY be passed to
processes that did not originate the Echo Request message. processes that did not originate the Echo Request message.
Note that there is no limitations on the amount of data that can be Note that there is no limitation on the amount of data that can be
put in Echo Request and Echo Reply Messages. put in Echo Request and Echo Reply Messages.
5. Security Considerations 5. Security Considerations
5.1 Authentication and Confidentiality of ICMP messages 5.1. Authentication and Confidentiality of ICMP Messages
ICMP protocol packet exchanges can be authenticated using the IP ICMP protocol packet exchanges can be authenticated using the IP
Authentication Header [IPv6-AUTH] or IP Encapsulating Security Authentication Header [IPv6-AUTH] or IP Encapsulating Security
Payload Header [IPv6-ESP]. Confidentiality for the ICMP protocol Payload Header [IPv6-ESP]. Confidentiality for the ICMP protocol
packet exchanges can be achieved using IP Encapsulating Security packet exchanges can be achieved using the IP Encapsulating Security
Payload Header [IPv6-ESP]. Payload Header [IPv6-ESP].
[SEC-ARCH] describes the IPsec handling of ICMP traffic in detail. [SEC-ARCH] describes the IPsec handling of ICMP traffic in detail.
5.2 ICMP Attacks 5.2. ICMP Attacks
ICMP messages may be subject to various attacks. A complete ICMP messages may be subject to various attacks. A complete
discussion can be found in the IP Security Architecture [IPv6-SA]. A discussion can be found in the IP Security Architecture [IPv6-SA]. A
brief discussion of such attacks and their prevention is as follows: brief discussion of these attacks and their prevention follows:
1. ICMP messages may be subject to actions intended to cause the 1. ICMP messages may be subject to actions intended to cause the
receiver to believe the message came from a different source than receiver to believe the message came from a different source from
the message originator. The protection against this attack can be that of the message originator. The protection against this
achieved by applying the IPv6 Authentication mechanism [IPv6-AUTH] attack can be achieved by applying the IPv6 Authentication
to the ICMP message. mechanism [IPv6-AUTH] to the ICMP message.
2. ICMP messages may be subject to actions intended to cause the 2. ICMP messages may be subject to actions intended to cause the
message or the reply to it go to a destination different than the message or the reply to it to go to a destination different from
message originator's intention. The protection against this that of the message originator's intention. The protection
attack can be achieved by using the Authentication Header against this attack can be achieved by using the Authentication
[IPv6-AUTH] or the Encapsulating Security Payload Header Header [IPv6-AUTH] or the Encapsulating Security Payload Header
[IPv6-ESP]. Authentication Header provides the protection against [IPv6-ESP]. The Authentication Header provides the protection
change for the source and the destination address of the IP against change for the source and the destination address of the
packet. Encapsulating Security Payload Header does not provide IP packet. The Encapsulating Security Payload Header does not
this protection but the ICMP checksum calculation includes the provide this protection, but the ICMP checksum calculation
source and the destination addresses and the Encapsulating includes the source and the destination addresses, and the
Security Payload Header protects the checksum. Therefore, the Encapsulating Security Payload Header protects the checksum.
combination of ICMP checksum and the Encapsulating Security Therefore, the combination of ICMP checksum and the Encapsulating
Payload Header provides the protection against this attack. The Security Payload Header provides protection against this attack.
protection provided by the Encapsulating Security Payload Header The protection provided by the Encapsulating Security Payload
will not be as strong as the protection provided by the Header will not be as strong as the protection provided by the
Authentication Header. Authentication Header.
3. ICMP messages may be subject to changes in the message fields, or 3. ICMP messages may be subject to changes in the message fields, or
payload. The authentication [IPv6-AUTH] or encryption [IPv6-ESP] payload. The authentication [IPv6-AUTH] or encryption [IPv6-ESP]
of the ICMP message is a protection against such actions. of the ICMP message protects against such actions.
4. ICMP messages may be used as attempts to perform denial of service 4. ICMP messages may be used to attempt denial-of-service attacks by
attacks by sending back to back erroneous IP packets. An sending back to back erroneous IP packets. An implementation that
implementation that correctly followed section 2.4, paragraph (f) correctly followed Section 2.4, paragraph (f), of this
of this specifications, would be protected by the ICMP error rate specification, would be protected by the ICMP error rate limiting
limiting mechanism. mechanism.
5. The exception number 2 of rule e.3 in section 2.4 gives the 5. The exception number 2 of rule e.3 in Section 2.4 gives a
opportunity to a malicious node to cause a denial of service malicious node the opportunity to cause a denial-of-service attack
attack to a multicast source. A malicious node can send a to a multicast source. A malicious node can send a multicast
multicast packet with an unknown destination option marked as packet with an unknown destination option marked as mandatory,
mandatory with the IPv6 source address of a valid multicast with the IPv6 source address of a valid multicast source. A large
source. A large number of destination nodes will send ICMP number of destination nodes will send an ICMP Parameter Problem
Parameter Problem Message to the multicast source causing a denial Message to the multicast source, causing a denial-of-service
of service attack. The way multicast traffic is forwarded by the attack. The way multicast traffic is forwarded by the multicast
multicast routers does require the malicious node to be part of routers requires that the malicious node be part of the correct
the correct multicast path i.e. near to the multicast source. multicast path, i.e., near to the multicast source. This attack
This attack can only be avoided by securing the multicast traffic. can only be avoided by securing the multicast traffic. The
The multicast source should be careful while sending multicast multicast source should be careful while sending multicast traffic
traffic with the destination options marked as mandatory because with the destination options marked as mandatory, because they can
they can cause a denial of service attack to themselves if the cause a denial-of-service attack to themselves if the destination
destination option is unknown to a large number of destinations. option is unknown to a large number of destinations.
6. As the ICMP messages are passed to the upper-layer processes, it 6. As the ICMP messages are passed to the upper-layer processes, it
is possible to perform attacks on the upper layer protocols (e.g., is possible to perform attacks on the upper layer protocols (e.g.,
TCP) with ICMP [TCP-attack]. It is recommended for the upper TCP) with ICMP [TCP-attack]. It is recommended that the upper
layers to perform some form of validation of ICMP messages (using layers perform some form of validation of ICMP messages (using the
the information contained in the payload of the ICMP message) information contained in the payload of the ICMP message) before
before acting upon them. The actual validation checks are acting upon them. The actual validation checks are specific to
specific to the upper layers and are out of the scope of this the upper layers and are out of the scope of this specification.
spec. Protecting the upper layer with IPsec mitigates these Protecting the upper layer with IPsec mitigates these attacks.
attacks.
ICMP error messages signal network error conditions that were ICMP error messages signal network error conditions that were
encountered while processing an internet datagram. Depending on encountered while processing an internet datagram. Depending on
the particular scenario, the error conditions being reported might the particular scenario, the error conditions being reported might
or might not get solved in the near term. Therefore, reaction to or might not get solved in the near term. Therefore, reaction to
ICMP error messages may depend not only on the error type and ICMP error messages may depend not only on the error type and code
code, but also on other factors such as the time the error but also on other factors, such as the time at which the error
messages are received, previous knowledge of the network error messages are received, previous knowledge of the network error
conditions being reported, and knowledge of the network scenario conditions being reported, and knowledge of the network scenario
in which the receiving host is operating. in which the receiving host is operating.
6. IANA Considerations 6. IANA Considerations
6.1 Procedure for new ICMPV6 Type and Code value assignments 6.1. Procedure for New ICMPV6 Type and Code Value Assignments
The IPv6 ICMP header [ICMPV6] contains the following fields that The IPv6 ICMP header defined in this document contains the following
carry values assigned from IANA-managed name spaces: Type and Code. fields that carry values assigned from IANA-managed name spaces: Type
Code field values are defined relative to a specific Type value. and Code. Code field values are defined relative to a specific Type
value.
Values for the IPv6 ICMP Type fields are allocated using the Values for the IPv6 ICMP Type fields are allocated using the
following procedure: following procedure:
1. The IANA should allocate and permanently register new ICMPv6 type 1. The IANA should allocate and permanently register new ICMPv6 type
codes from IETF RFC publication. This is for all RFC types codes from IETF RFC publication. This is for all RFC types,
including standards track, informational, and experimental status including standards track, informational, and experimental status,
that originate from the IETF and have been approved by the IESG that originate from the IETF and have been approved by the IESG
for publication. for publication.
2. IETF working groups with working group consensus and area director 2. IETF working groups with working group consensus and area director
approval can request reclaimable ICMPV6 type code assignments from approval can request reclaimable ICMPV6 type code assignments from
the IANA. The IANA will tag the values as "reclaimable in the IANA. The IANA will tag the values as "reclaimable in
future". future".
The "reclaimable in the future" tag will be removed when an RFC is The "reclaimable in the future" tag will be removed when an RFC is
published documenting the protocol as defined in 1). This will published that documents the protocol as defined in 1. This will
make the assignment permanent and update the reference on the IANA make the assignment permanent and update the reference on the IANA
web pages. web pages.
At the point where the ICMPv6 type values are 85% assigned, the At the point where the ICMPv6 type values are 85% assigned, the
IETF will review the assignments tagged "reclaimable in the IETF will review the assignments tagged "reclaimable in the
future" and inform the IANA which ones should be reclaimed and future" and inform the IANA which ones should be reclaimed and
reassigned. reassigned.
3. Requests for new ICMPv6 type value assignments from outside the 3. Requests for new ICMPv6 type value assignments from outside the
IETF are only made through the publication of an IETF document, IETF are only made through the publication of an IETF document,
per 1) above. Note also that documents published as "RFC Editor per 1 above. Note also that documents published as "RFC Editor
contributions" [RFC 3667] are not considered to be IETF documents. contributions" [RFC-3978] are not considered IETF documents.
The assignment of new Code values for the Type values defined in this The assignment of new Code values for the Type values defined in this
document require standards action or IESG approval. The policy for document require standards action or IESG approval. The policy for
assigning Code values for new IPv6 ICMP Types not defined in this assigning Code values for new IPv6 ICMP Types not defined in this
document should be defined in the document defining the new Type document should be defined in the document defining the new Type
values. values.
6.2 Assignments for this document 6.2. Assignments for This Document
The following should update the assignments located at: The following has updated assignments located at:
http://www.iana.org/assignments/icmpv6-parameters http://www.iana.org/assignments/icmpv6-parameters
The IANA is requested to reassign ICMPv6 type 1 "Destination The IANA has reassigned ICMPv6 type 1 "Destination Unreachable" code
Unreachable" code 2, that was unassigned in [RFC-2463], to: 2, which was unassigned in [RFC-2463], to:
2 - beyond scope of source address 2 - Beyond scope of source address
The IANA is requested to assign the following two new codes values The IANA has assigned the following two new codes values for ICMPv6
for ICMPv6 type 1 "Destination Unreachable": type 1 "Destination Unreachable":
5 - source address failed ingress/egress policy 5 - Source address failed ingress/egress policy
6 - reject route to destination 6 - Reject route to destination
The IANA is requested to assign the following new type values: The IANA has assigned the following new type values:
100 Private experimentation 100 Private experimentation
101 Private experimentation 101 Private experimentation
200 Private experimentation 127 Reserved for expansion of ICMPv6 error messages
201 Private experimentation
255 Reserved for expansion 200 Private experimentation
201 Private experimentation
255 Reserved for expansion of ICMPv6 informational messages
7. References 7. References
7.1 Normative 7.1. Normative References
[IPv6] Deering, S., R. Hinden, "Internet Protocol, Version 6, [IPv6] Deering, S. and R. Hinden, "Internet Protocol, Version 6
Specification", RFC2460, December 1998. (IPv6) Specification", RFC 2460, December 1998.
[IPv6-DISC] Narten, T., E. Nordmark, W. Simpson, "Neighbor Discovery [IPv6-DISC] Narten, T., Nordmark, E., and W. Simpson, "Neighbor
for IP Version 6 (IPv6)", RFC2461, December, 1998. Discovery for IP Version 6 (IPv6)", RFC 2461, December
1998.
[RFC-792] Postel, J., "Internet Control Message Protocol", STD 5, [RFC-792] Postel, J., "Internet Control Message Protocol", STD 5,
RFC792, September 1981. RFC 792, September 1981.
[RFC-2463] Conta, A., S. Deering, "Internet Control Message [RFC-2463] Conta, A. and S. Deering, "Internet Control Message
Protocol (ICMPv6) for the Internet Protocol Version 6 Protocol (ICMPv6) for the Internet Protocol Version 6
(IPv6) Specification", RFC2463, December, 1998. (IPv6) Specification", RFC 2463, December 1998.
[RFC-1122] Braden, R., "Requirements for Internet Hosts - [RFC-1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 5, RFC1122, August 1989. Communication Layers", STD 3, RFC 1122, October 1989.
[RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP14, RFC2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2 Informative [RFC-3978] Bradner, S., "IETF Rights in Contributions", BCP 78, RFC
3978, March 2005.
[RFC-2780] Bradner, S., V. Paxson, "IANA Allocation Guidelines For 7.2. Informative References
Values In the Internet Protocol and Related Headers",
RFC 2780, March 2000.
[IPv6-ADDR] Hinden, R., S. Deering, "IP Version 6 Addressing [RFC-2780] Bradner, S. and V. Paxson, "IANA Allocation Guidelines
Architecture", RFC2373, July 1998. For Values In the Internet Protocol and Related
Headers", BCP 37, RFC 2780, March 2000.
[PMTU] McCann, J., S. Deering, J. Mogul, "Path MTU Discovery [IPv6-ADDR] Hinden, R. and S. Deering, "Intpernet Protocol Version 6
for IP version 6", RFC1981, August 1996. (IPv6) Addressing Architecture", RFC 3513, April 2003.
[IPv6-SA] Kent, S., R. Atkinson, "Security Architecture for the [PMTU] McCann, J., Deering, S., and J. Mogul, "Path MTU
Internet Protocol", RFC1825, November 1998. Discovery for IP version 6", RFC 1981, August 1996.
[IPv6-AUTH] Kent, S., "IP Authentication Header", draft-ietf-ipsec- [IPv6-SA] Kent, S. and R. Atkinson, "Security Architecture for the
rfc2402bis-11.txt, work in progress. Internet Protocol", RFC 2401, November 1998.
[IPv6-ESP] Kent, S., "IP Encapsulating Security Payload (ESP)", [IPv6-AUTH] Kent, S., "IP Authentication Header", RFC 4302, December
draft-ietf-ipsec-esp-v3-10.txt, work in progress. 2005.
[SEC-ARCH] Kent, S., K. Seo, "Security Architecture for the [IPv6-ESP] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC
Internet Protocol", draft-ietf-ipsec-rfc2401bis-05.txt, 4203, December 2005.
work in progress.
[TCP-attack] Gont, F., "ICMP attacks against TCP", draft-gont-tcpm- [SEC-ARCH] Kent, S. and K. Seo, "Security Architecture for the
icmp-attacks-03.txt, work in progress. Internet Protocol", RFC 4301, December 2005.
8. Acknowledgments [TCP-attack] Gont, F., "ICMP attacks against TCP", Work in Progress.
The document is derived from previous ICMP drafts of the SIPP and 8. Acknowledgements
The document is derived from previous ICMP documents 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, Bob Hinden, Jun-ichiro Itojun Hagino, Tatuya Jinmei, Dimitri Haskin, Bob Hinden, Jun-ichiro Itojun Hagino, Tatuya Jinmei,
Brian Zill, Pekka Savola, Fred Templin and Elwyn davies (in Brian Zill, Pekka Savola, Fred Templin, and Elwyn Davies (in
chronological order) provided extensive review information and chronological order) provided extensive review information and
feedback. feedback.
Bob Hinden was the document editor for this document. Bob Hinden was the document editor for this document.
9. Authors' Addresses Appendix A - Changes since RFC 2463
Alex Conta The following changes were made from RFC 2463:
Transwitch Corporation
3 Enterprise Drive
Shelton, CT 06484
USA
Email: aconta@txc.com
Stephen Deering - Edited the Abstract to make it a little more elaborate.
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
USA
Mukesh Gupta (ed.) - Corrected typos in Section 2.4, where references to sub-bullet e.2
Nokia were supposed to be references to e.3.
313 Fairchild Drive
Mountain View, CA 94043
US
Phone: +1 650-625-2264
Email: mukesh.k.gupta@nokia.com
Appendix A - Changes since RFC 2463 - Removed the Timer-based and the Bandwidth-based methods from the
example rate-limiting mechanism for ICMP error messages. Added
Token-bucket based method.
The following changes were made from RFC 2463: - 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.
- Edited the Abstract to make it a little more elaborate. - 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).
- Corrected typos in section 2.4, where references to sub-bullet e.2 - Added description of Time Exceeded Code 1 (fragment reassembly
were supposed to be references to e.3. timeout).
- Removed the Timer-based and the Bandwidth-based methods from the - Added "beyond scope of source address", "source address failed
example rate-limiting mechanism for ICMP error messages. Added ingress/egress policy", and "reject route to destination" messages
Token-bucket based method. to the family of "unreachable destination" type ICMP error messages
(Section 3.1).
- Added specification that all ICMP error messages shall have - Reserved some ICMP type values for experimentation.
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 a NOTE in Section 2.4 that specifies ICMP message processing
added rule prohibiting forwarding of packets back onto point-to- rules precedence.
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 - Added ICMP REDIRECT to the list in Section 2.4, (e) of cases in
timeout). which ICMP error messages are not to be generated.
- Added "beyond scope of source address", "source address failed - Made minor editorial changes in Section 2.3 on checksum
ingress/egress policy", and "reject route to destination" messages calculation, and in Section 5.2.
to the family of "unreachable destination" type ICMP error
messages (section 3.1).
- Reserved some ICMP type values for experimentation. - Clarified in Section 4.2, regarding the Echo Reply Message; the
source address of an Echo Reply to an anycast Echo Request should
be a unicast address, as in the case of multicast.
- Added a NOTE in section 2.4, that specifies ICMP message - Revised the Security Considerations section. Added the use of the
processing rules precedence. Encapsulating Security Payload Header for authentication. Changed
the requirement of an option of "not allowing unauthenticated ICMP
messages" to MAY from SHOULD.
- Added ICMP REDIRECT to the list in Section 2.4 e) of cases in - Added a new attack in the list of possible ICMP attacks in Section
which ICMP error messages are not to be generated. 5.2.
- Made minor editorial changes in Section 2.3 on checksum - Separated References into Normative and Informative.
calculation, and in Section 5.2.
- Clarified in section 4.2, regarding the Echo Reply Message, that - Added reference to RFC 2780 "IANA Allocation Guidelines For Values
the source address of an Echo Reply to an anycast Echo Request In the Internet Protocol and Related Headers". Also added a note
should be a unicast address, as in the case of multicast. that this document updates RFC 2780.
- Revised the Security Considerations section. Added the use of - Added a procedure for new ICMPv6 Type and Code value assignments in
Encapsulating Security Payload Header for authentication. Changed the IANA Considerations section.
the requirement of an option of "not allowing unauthenticated ICMP
messages" to MAY from SHOULD.
- Added a new attack in the list of possible ICMP attacks in section - Replaced word "send" with "originate" to make it clear that ICMP
5.2. packets being forwarded are out of scope of this specification.
- Separated References into Normative and Informative. - Changed the ESP and AH references to the updated ESP and AH
documents.
- Added reference to RFC-2780 "IANA Allocation Guidelines For Values - Added reference to the updated IPsec Security Architecture
In the Internet Protocol and Related Headers". Also added a note document.
that this document updates RFC-2780.
- Added a procedure for new ICMPv6 Type and Code value assignments - Added a SHOULD requirement for allowing the sending of ICMP
in the IANA Consideration section. destination unreachable messages to be disabled.
- Replaced word "send" with "originate" to make it clear that ICMP - Simplified the source address selection of the ICMPv6 packet.
packets being forwarded are out of scope of this specification.
- Changed the ESP and AH references to the updated ESP and AH - Reorganized the General Message Format (Section 2.1).
drafts.
- Added reference to the updated IPsec Security Architecture draft. - Removed the general packet format from Section 2.1. It refers to
Sections 3 and 4 for packet formats now.
- Added a SHOULD requirement for allowing the sending of ICMP - Added text about attacks to the transport protocols that could
destination unreachable messages to be disabled. potentially be caused by ICMP.
- Simplified the source address selection of the ICMPv6 packet. Authors' Addresses
- Reorganized the General Message Format (section 2.1). Alex Conta
Transwitch Corporation
3 Enterprise Drive
Shelton, CT 06484
USA
- Removed the general packet format from section 2.1. It refers to EMail: aconta@txc.com
section 3 and 4 for packet formats now.
- Added text about attacks to the transport protocols that could Stephen Deering
potentially be caused by ICMP. Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
USA
Intellectual Property Statement Mukesh Gupta, Ed.
Tropos Networks
555 Del Rey Avenue
Sunnyvale, CA 94085
Phone: +1 408-331-6889
EMail: mukesh.gupta@tropos.com
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