Just as an ICMP protocol is used for diagnostics and error signaling in IP version 4, IP version 6 uses an ICMP version 6 protocol. For IP version 6, the ICMP protocol is specified by RFC 2463.
The ICMP version 6 protocol offers different functionality than the previous version of ICMP. For example, ICMP version 6 deals with the translation of IP addresses into link addresses. (The IP version 4 protocol uses separate protocols for that purpose, namely, ARP and RARP.)
With regard to packet structure, the ICMP packet has a higher-layer protocol; thus, the base header of the IP protocol as well as Next headers, if necessary, precedes it:
The ICMP type field contains the message ...