Network Working Group A. Conta (Digital Equipment Corporation) INTERNET-DRAFT S. Deering (Xerox PARC) February 1995 | ICMP for the Internet Protocol Version 6 (IPv6) draft-ietf-ipngwg-icmp-01.txt | Status of this Memo This document is an Internet Draft. Internet Drafts are working documents of the Internet Engineering Task Force (IETF), its Areas, and its Working Groups. Note that other groups may also distribute working documents as Internet Drafts. Internet Drafts are draft documents valid for a maximum of six months. Internet Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a "working draft" or "work in progress." To learn the current status of any Internet-Draft, please check the ``1id-abstracts.txt'' listing contained in the Internet- Drafts Shadow Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). Distribution of this memo is unlimited. Abstract This document specifies a set of Internet Control Message Protocol (ICMP) messages for use with version 6 of the Internet Protocol (IPv6). The Internet Group Management Protocol (IGMP) messages specified in RFC-1112 have been merged into ICMP, for IPv6, and are included in this document. Conta & Deering Expires in six months [Page 1] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 Table of Contents 1. Introduction........................................3 | 2. ICMP for IPv6.......................................3 | 3. ICMP Error Messages.................................7 | 3.1 Destination Unreachable Message..............7 | 3.2 Packet Too Big Message.......................8 | 3.3 Time Exceeded Message........................9 | 3.4 Parameter Problem Message...................11 | 4. ICMP Informational Messages........................12 | 4.1 Echo Request Message........................12 | 4.2 Echo Reply Message..........................13 | 4.3 Group Membership Messages...................15 | 5. References.........................................16 | 6. Acknowledgements...................................17 | 7. Security Considerations............................17 | 8. Authors' Addresses.................................17 | Conta & Deering Expires in six months [Page 2] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 1. Introduction | The Internet Protocol, version 6 (IPv6) is a new version of IP. IPv6 uses the Internet Control Message Protocol (ICMP) as defined for IPv4 [RFC-792], with a number of changes. The Internet Group | Membership | Protocol (IGMP) specified for IPv4 [RFC-1112] has also been revised and has been absorbed into ICMP for IPv6. This document describes the format of a set of control messages used in ICMP for IPv6. It does not describe the procedures for using these | messages to achieve functions like Path MTU discovery or multicast | group membership maintenance; such procedures are described in other | documents (e.g., [RFC-1112, RFC-1191]). Other documents may also | introduce additional ICMP message types, such as Neighbor Discovery | messages [IPv6-DISC], subject to the general rules for ICMP messages | given in section 2 of this document. | Terminology defined in the IPv6 specification [IPv6] and the IPv6 Routing and Addressing specification [IPv6-ADDR] applies to this document as well. 2. ICMP for IPv6 IPv6 ICMP is used by IPv6 nodes to report errors encountered in processing packets, and to perform other internet-layer functions, such as diagnostics (ICMP "ping") and multicast | membership reporting. IPv6 ICMP is an integral part of IPv6 and MUST be implemented by every IPv6 node. ICMP messages are grouped into two classes: error messages and | informational messages. Error messages are identified as such by | having a zero in the high-order bit of their message Type values. | Thus, error messages have message Types from 0 to 127; informational | messages have message Types from 128 to 255. | This document defines the message formats for the following IPv6 ICMP | messages: | Conta & Deering Expires in six months [Page 3] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 ICMP error messages: | 1 Destination Unreachable (see section 3.1) | 2 Packet Too Big (see section 3.2) | 3 Time Exceeded (see section 3.3) | 4 Parameter Problem (see section 3.4) | ICMP informational messages: | 128 Echo Request (see section 4.1) | 129 Echo Reply (see section 4.2) | 130 Group Membership Qeury (see section 4.3) | 131 Group Membership Report (see section 4.3) | 132 Group Membership Termination (see section 4.3) | Every IPv6 ICMP message is preceded by an IPv6 header and zero or | more | IPv6 extension headers. The ICMP header is identified by a Next | Header value of in the immediately preceding header. (NOTE: | this is different than the value used to identify ICMP for IPv4.) | The IPv6 ICMP messages have the following general 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | + Message Body + | | | | The type field indicates the type of the message. Its value | determines the format of the remaining data. | The code field depends on the message type. It is used to create an additional level of message granularity. The checksum is the 16-bit one's complement of the one's complement sum of the IPv6 Source Address, the IPv6 Destination Address (the final destination, if a Routing Header is being used), | the IPv6 Payload Length, the Next Header type that identifies IPv6 | ICMP(), and the entire ICMP message starting with the ICMP | message type. For | computing the checksum, the checksum field is set to zero. (NOTE: the inclusion of the IPv6 header fields in the ICMP checksum | is a change from IPv4; see [IPv6] for the rationale for this change.) | Conta & Deering Expires in six months [Page 4] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 Implementation Notes: | A node that sends an ICMP message has to determine both | the Source and Destination IPv6 Addresses in the IPv6 header before calculating the checksum. If the node has more than one unicast address, it must choose the | Source Address of the message as follows: | If the message is a response to a message sent to one of the | node's unicast address, the Source Address of the reply must be | that same address. | If the message is a response to a message sent to a multicast | group in which the node is a member, the Source Address of the | reply must be a unicast address belonging to the interface on | which the multicast packet was received. | Otherwise, the node's routing table must be examined to determine | which interface will be used to transmit the message to its | destination, and a unicast address belonging to that interface | must be used as the Source Address of the message. | Implementations MUST observe the following rules when processing IPv6 ICMP messages (from [RFC-1122]): (a) If an IPv6 ICMP message of unknown type is received, it MUST be silently discarded. (b) Every IPv6 ICMP error message (the first four messages in the above list) includes as much of the IPv6 offending (invoking) packet (the packet that causes the error) as will fit without making the error message packet exceed 576 octets. (c) In those cases where the Internet layer is required to pass a | IPv6 ICMP error message to the transport layer, the IPv6 | Transport | Protocol is extracted from the original header (contained in | the body of the IPv6 ICMP error message) and used to select the appropriate transport protocol entity to handle the error. (d) An IPv6 ICMP error message MUST NOT be sent as a result of receiving: (d.1.)an IPv6 ICMP error message, or | Conta & Deering Expires in six months [Page 5] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 (d.2.)a packet destined to an IPv6 multicast address (an | exception to this rule is the Packet Too Big Message - Section 3.2 - to allow Path MTU discovery to work for IPv6 multicast), or (d.3.) | a packet sent as a link-layer multicast, (the exception | from d.2. applies to this case too) or | (d.4.) a packet sent as a link-layer broadcast, (the exception | from d.2. applies to this case too) or | (d.5.)a packet whose source address does not uniquely identify a single node -- e.g., the IPv6 Unspecified Address, or an IPv6 multicast address. (e) Finally, to each sender of an erroneous data packet, an IPv6 node MUST limit the rate of ICMP error messages sent, in order to | limit the bandwidth and forwarding costs incurred by the the | error messages when a generator of erroneous packets does | not respond to those error messages by ceasing its | transmissions. There are a variety of ways of implementing | the rate-limiting function, for example: | (e.1.)Timer-based - for example, limiting the rate of | transmission of error messages to a given source, or to | any source, to at most once every T milliseconds. | (e.2.)Bandwidth-based - for example, limiting the rate at | which error messages are sent from a particular interface | to some fraction F of the attached link's bandwidth. | The limit parameters (e.g., T or F in the above examples) | MUST be configurable for the node, with a conservative | default value (e.g., T = 1 second, NOT 0 seconds, or F = 2 | percent, NOT 100 percent). | The following sections describe the message formats for the above IPv6 ICMP messages. Conta & Deering Expires in six months [Page 6] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 3. ICMP Error Messages 3.1. Destination Unreachable Message 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Unused | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | As much of invoking packet | + as will fit without ICMP packet + | | exceeding 576 octets | + + | | | IPv6 Fields: | Destination Address | Copied from the Source Address field of the invoking | packet. | IPv6 ICMP Fields: | Type 1 | Code 0 - no route to destination | 1 - communication with destination | administratively prohibited | 3 - address unreachable | 4 - port unreachable | Unused This field is unused for all code values. It must be initialized to zero by the sender and ignored by the receiver. Description A Destination Unreachable message SHOULD be generated by a router, or | by the IPv6 layer in the originating node, in response to a packet | that cannot be delivered to its destination address for reasons other | than congestion. (If a packet is dropped due to congestion, no ICMP | error message is generated.) 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 (NOTE: this error can occur only in | Conta & Deering Expires in six months [Page 7] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 routers that do not hold a "default route" in their routing tables). | If the reason for the failure to deliver is administrative | prohibition, e.g., a "firewall filter", the Code field is set to 1. | If there is any other reason for the failure to deliver, e.g., | inability to resolve the IPv6 destination address into a | corresponding link address, or a link-specific problem of some sort, | then the Code field is set to 3. | A destination node SHOULD send a Destination Unreachable message 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 | alternative means to inform the sender. | Upper layer notification | A node receiving the ICMP Destination Unreachable message MUST notify | the upper layer. | 3.2. | Packet Too Big Message | 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MTU | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | As much of invoking packet | + as will fit without ICMP packet + | | exceeding 576 octets | + + | | | IPv6 Fields: | Destination Address | Copied from the Source Address field of the invoking | packet. | Conta & Deering Expires in six months [Page 8] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 IPv6 ICMP Fields: | Type 2 | Code 0 MTU The Maximum Transmission Unit of the next-hop link. | Description 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 the outgoing link. The information in this | message is used as part of the Path MTU Discovery process [RFC-1191]. | Sending a Packet Too Big Message makes an exception to the rules of | when to send an ICMP error message, in that unlike other messages, it | is sent in response to a packet received with an IPv6 multicast | destination address, or a link-layer multicast or link-layer | broadcast address. | Upper layer notification An incoming Packet Too Big message MUST be passed to the transport layer. 3.3. Time Exceeded Message | 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Unused | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | As much of invoking packet | + as will fit without ICMP packet + | | exceeding 576 octets | + + | | | Conta & Deering Expires in six months [Page 9] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 IPv6 Fields: | Destination Address | Copied from the Source Address field of the invoking | packet. | IPv6 ICMP Fields: | Type 3 | Code 0 - hop limit exceeded in transit 1 - fragment reassembly time exceeded Unused This field is unused for all code values. | It must be initialized to zero by the sender | and ignored by the receiver. | Description If a router receives a packet with a Hop Limit of zero, or a router decrements a packet's Hop Limit to zero, it discards the packet and sends an IPv6 ICMP Time Exceeded message with Code 0 to the source of the packet. This indicates either a routing | loop or too small an initial | Hop Limit value. IPv6 systems are expected to avoid fragmentation by implementing Path MTU discovery. However, IPv6 defines an end-to-end fragmentation function for backwards compatibility with existing higher-layer | protocols. All IPv6 implementations are required to support | reassembly | of IPv6 fragments. There MUST be a reassembly timeout. The reassembly timeout SHOULD be a fixed value. It is recommended that this value lie between 60 and 120 seconds. If the timeout expires, the partially-reassembled packet MUST be discarded. If the fragment | with offset zero was received, the destination host SHOULD also send an IPv6 ICMP Time Exceeded message with Code 1 to the source of the | fragment. | Conta & Deering Expires in six months [Page 10] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 Upper layer notification An incoming Time Exceeded message MUST be passed to the transport layer. 3.4. | Parameter Problem Message 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Pointer | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | As much of invoking packet | + as will fit without ICMP packet + | | exceeding 576 octets | + + | | | IPv6 Fields: | Destination Address | Copied from the Source Address field of the invoking | packet. | IPv6 ICMP Fields: | Type 4 | Code 0 - erroneous header field encountered | 1 - unrecognized Next Header type encountered | 2 - unrecognized IPv6 option encountered | Pointer identifies the octet offset within the invoking packet where the error was detected. | The pointer will point beyond the end of the ICMP | packet if the field in error is beyond what can fit | in the 576-byte limit of an ICMP error message. | Description Conta & Deering Expires in six months [Page 11] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 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 | processing the packet, it MUST discard the packet and SHOULD send an | ICMP Parameter Problem message to the packet's source, indicating the | type and location of the problem. | Upper layer notification A node receiving this ICMP message MUST notify the upper layer. 4. | ICMP Informational Messages | 4.1. Echo Request Message | 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+- IPv6 Fields: | Destination Address | Any legal IPv6 address. | | IPv6 ICMP Fields: Type 128 | Code 0 Identifier If code = 0, an identifier to aid in matching | Echo Replies to this Echo Request. May be zero. | Sequence If code = 0, a sequence number to aid in matching | Number Echo Replies to this Echo Request. May be zero. | Data If code = 0, zero or more octets of arbitrary data. | Conta & Deering Expires in six months [Page 12] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 Description Every node MUST implement an ICMP Echo responder function that | receives Echo Requests and sends corresponding Echo Replies. A node SHOULD also implement an application-layer interface for sending Echo Requests and receiving Echo Replies, for | diagnostic purposes. Upper layer notification | A node receiving this ICMP message MAY notify the upper layer. | 4.2. | Echo Reply Message | 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+- IPv6 Fields: | Destination Address | Copied from the Source Address field of the invoking | Echo Request packet. | IPv6 ICMP Fields: | Type 129 | Code 0 Identifier If code = 0, the identifier from the invoking | Echo Request message. | Sequence If code = 0, the sequence number from the invoking | Number Echo Request message. | Data If code = 0, the data from the invoking | Echo Request message | Conta & Deering Expires in six months [Page 13] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 Description Every node MUST implement an ICMP Echo responder function that | receives Echo Requests and sends corresponding Echo Replies. A node SHOULD also implement an application-layer interface for sending Echo Requests and receiving Echo Replies, for | diagnostic purposes. The source address of an Echo Reply sent in response to a unicast | Echo Request message MUST be the same as the destination address of | that Echo Request message. | An Echo Reply SHOULD be sent in response to an Echo Request message | sent | to an IPv6 multicast address. The source address of the reply MUST be a unicast address belonging to the interface on which the multicast Echo Request message was received. | The data received in the ICMP Echo Request message MUST be returned | entirely and unmodified in the ICMP Echo Reply message, unless the | Echo Reply would exceed the MTU of the path back to the Echo | requester, in which case the data is truncated to fit that path MTU. | Upper layer notification Echo Reply messages MUST be passed to the ICMP user interface, unless the corresponding Echo Request originated in the IP layer. Conta & Deering Expires in six months [Page 14] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 4.3. | Group Membership Messages | The ICMP Group Membership Messages have the following 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 | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Maximum Response Delay | Unused | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | Multicast | + + | Address | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IPv6 Fields: | Destination Address | In a Group Membership Query message, the multicast | address of the group being queried, or the Link-Local | All-Nodes multicast address. | In a Group Membership Report or a Group Membership | Termination message, the multicast address of the | group being reported or terminated. | Hop Limit 1 | Conta & Deering Expires in six months [Page 15] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 IPv6 ICMP Fields: Type 130 - Group Membership Query | 131 - Group Membership Report | 132 - Group Membership Termination | Code 0 | Maximum Response Delay | In Query messages, the maximum time that responding | Report messages may be delayed, in milliseconds. | In Report and Termination messages, this field is | is initialized to zero by the sender and ignored by receivers. Unused Initialized to zero by the sender; ignored by receivers. Multicast Address The address if the multicast group about which the message is being sent. In Query messages, the Multicast Address field may be zero, implying a query for all groups. Description The ICMP Group Membership messages are used to convey information | about | multicast group membership from nodes to their neighboring routers. The details of their usage is given in [RFC-1112]. 5. References | [IPv6]R. Hinden, "Internet Protocol Version 6 Specification", | February 1995 | [IPv6-ADDR] R. Hinden, "IP Next Generation Addressing Architecture", | February 1995 | Conta & Deering Expires in six months [Page 16] INTERNET-DRAFT ICMP for IPv6 February 27, 1995 [IPv6-DISC] W. A. Simpson, "IPv6 Neighbor Discovery", February 1995 | [RFC-792] | J. Postel, "Internet Control Message Protocol", RFC 792. | [RFC-1112] | S. Deering, "Host Extensions for IP Multicasting", RFC 1112. | [RFC-1122] | R. Braden, "Requirements for Internet Hosts - Communication | Layers", RFC 1122. | [RFC-1191] | J. Mogul and S. Deering, "Path MTU Discovery", RFC 1191. | 6. Acknowledgements | The document is derived from the "ICMP and IGMP for SIPP" document published as a draft by Ramesh Govindan and Steve Deering in March 1994. The working group and particularly Robert Elz, Jim Bound, and Bill | Simpson provided extensive review information and feedback. | 7. Security Considerations | Security considerations are not discussed in this memo. Authors' Addresses: Alex Conta Stephen Deering Digital Equipment Corporation Xerox Palo Alto Research Center 110 Spitbrook Rd 3333 Coyote Hill Road Nashua, NH 03062 Palo Alto, CA 94304 +1-603-881-0744 +1-415-812-4839 email: conta@zk3.dec.com email: deering@parc.xerox.com Conta & Deering Expires in six months [Page 17] INTERNET-DRAFT ICMP for IPv6 February 27, 1995