ICMPv6

The ICMPv6 (Internet Control Message Protocol Version 6) is an integral part of the IPv6 architecture2 and must be completely supported by all IPv6 implementations. ICMPv6 combines functions previously subdivided among different protocols, such as ICMP (Internet Control Message Protocol version 4), IGMP (Internet Group Membership Protocol)4, and ARP (Address Resolution Protocol), and it introduces some simplifications by eliminating obsolete types of messages no longer in use.

ICMPv6 is a multipurpose protocol; for example, it is used for reporting errors encountered in processing packets, performing diagnostics, performing Neighbor Discovery, and reporting multicast memberships. For this reason, ICMPv6 messages are subdivided into two classes: error messages and information messages. ICMP messages are transported within an IPv6 packet in which extension headers can also be present. An ICMP message is identified by a value of 58 in the Next Header field of the IPv6 header or of the preceding Header.

Packets Format

ICMPv6 packets have the format Type, Code, Checksum & Message Body. The 8-bit Type field indicates the type of the message. If the highorder bit has value zero (values in the range from 0 to 127), it is an error message; if the high-order bit has value 1 (values in the range from 128 to 255), it is an information message. The 8-bit Code field content depends on the message type, and it is used to create an additional level of message granularity. The Checksum field is used to detect errors in the ICMP message and in part of the IPv6 message.

Types of ICMP messages

Type - Meaning
1 - Destination Unreachable
2 - Packet Too Big
3 - Time Exceeded
4 - Parameter Problem
128 - Echo Request
129 - Echo Reply
130 - Group Membership Query
131 - Group Membership Report
132 - Group Membership Reduction
133 - Router Solicitation
134 - Router Advertisement
135 - Neighbor Solicitation
136 - Neighbor Advertisement
137 - Redirect

Contribution: Protocolos3 - Universidad Galileo (Guatemala)
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