1. Introduction

The Internet Protocol version 6 (IPv6) uses the Internet Control Message Protocol (ICMP) as defined for IPv4 [RFC-792], with a number of changes. The resulting protocol is called ICMPv6 and has an IPv6 Next Header value of 58.

This document describes the format of a set of control messages used in ICMPv6. It does not describe the procedures for using these messages to achieve functions like Path MTU discovery; these procedures are described in other documents (e.g., [PMTU]). Other documents may also introduce additional ICMPv6 message types, such as Neighbor Discovery messages [IPv6-DISC], subject to the general rules for ICMPv6 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.

This document obsoletes RFC 2463 [RFC-2463] and updates RFC 2780 [RFC-2780].

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC-2119].

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