The Internet protocol (IP) moves data from one node to another; however, for IP to perform this task successfully, there are other functions that need to be performed: error reporting, router discovery, diagnostics, and others. In IPv6, all these tasks are carried out by the Internet Control Message Protocol (ICMPv6).

In addition, ICMPv6 provides a framework for Multicast Listener Discovery (MLD) and Neighbor Discovery (ND), which carry out the tasks of conveying multicast group membership information (the equivalent of the IGMP protocol in IPv4) and address resolution (performed by ARP in IPv4).