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:
Figure 8.11: ICMP version 6 packet structure
The ICMP type field contains the message type (approximate classification of the message) and the ICMP code field specifies the detailed classification of the message.
RFC 2461 and RFC 2463 specify types and codes of ICMP messages that are listed in Table 8.3:
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Type |
Code |
Description... |
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