[IPv6] ICMPv6

ICMPv6

Like IPv4, the specification for the Internet Protocol version 6 (IPv6) header and extension headers does not provide facilities for reporting errors. Instead, IPv6 uses an updated version of the Internet Control Message Protocol (ICMP) named ICMP version 6 (ICMPv6). ICMPv6 has the common IPv4 ICMP functions of reporting delivery and forwarding errors and providing a simple echo service for troubleshooting. ICMPv6 is defined in RFC 4443 and is required for an IPv6 implementation.

The ICMPv6 protocol also provides a packet structure framework for the following:

■ Neighbor Discovery     Neighbor Discovery (ND) is a series of five ICMPv6 messages that manage node-to-node communication on a link. ND replaces Address Resolution Protocol (ARP), ICMPv4 Router Discovery, and the ICMPv4 Redirect message. ND is described in more detail in Chapter 6, “Neighbor Discovery.”
■ Multicast Listener     Discovery Multicast Listener Discovery (MLD) is a series of three ICMPv6 messages that are equivalent to the Internet Group Management Protocol (IGMP) for IPv4 for managing subnet multicast membership.

  * ICMPv6 Header Structure

   

Type     Indicates the type of ICMPv6 message. The size of this field is 8 bits. In ICMPv6 error messages, the high-order bit is set to 0. In ICMPv6 informational messages, the high-order bit is set to 1.

Code     Differentiates among multiple messages within a given message type. The size of this field is 8 bits. For the first, or only, message for a given type, the value of the Code field is 0.

Checksum     Stores a checksum of the ICMPv6 message. The size of this field is 16 bits. The IPv6 pseudo-header is added to the front of the ICMPv6 message when calculating the checksum.

Message body     Contains ICMPv6 message-specific data.

  * ICMPv4와 ICMPv6 메시지의 비교