4 - Internet Control Message Protocol for IPv6

Abstract

The Internet Control Message Protocol for IPv6 (ICMPv6) is similar to Internet Control Message Protocol (ICMP) for IPv4 [RFC792]. [RFC2463] defines the basic ICMPv6 protocol messages. These messages defined in [RFC2463] are for purposes of error reporting and network diagnostics. For example, a node sends ICMPv6 messages to notify a packet source that the node has encountered errors while processing the packet. In addition, a node can utilize the ICMPv6 messages to perform a simple network reachability test. Different from ICMP for IPv4, ICMPv6 provides many important functions that are necessary for the IPv6 protocol operation. For example, the Neighbor Discovery Protocol operates over ICMPv6, which performs a rich set of functions such as automatic address configuration and link-layer address resolution. Therefore, any node that supports IPv6 must fully implement ICMPv6. It is difficult to provide interoperability for ICMP between IPv4 and IPv6. This chapter describes the basic ICMPv6 protocol as defined in [RFC2463]. It explains ICMPv6-related protocol data structures and the implementation. The chapter also describes the Path MTU (Maximum Transmission Unit) discovery mechanism, which is performed using an ICMPv6 error message.