ICMPv6

mhkabir1952  Diamond  (1)
6 years 8 months ago  View: 771  Reply: 1

As one base protocol of IPv6, Internet Control Message Protocol for IPv6 (ICMPv6) generates error messages and informational messages, which are used by IPv6 nodes to report errors and information generated during packet processing. Figure 1 shows the format of an ICMPv6 message.

Figure 1:  Format of an ICMPv6 message

The meanings of the fields in an ICMPv6 message are as follows:

  • Type field: indicates the message type. The values from 0 to 127 indicate the error message type, and values from 128 to 255 indicate the informational message type.
  • Code field: indicates the specific message type.
  • Checksum field: indicates the checksum of an ICMPv6 message.

Classification of ICMPv6 Error Messages

  • Destination Unreachable message

    When an IPv6 node forwards IPv6 packets, if it detects that the destination address of the packets is unreachable, it sends an ICMPv6 Destination Unreachable message to the source node of the packets. Specific causes for the error message are carried in the message. Destination Unreachable messages are classified into the following types:

    • No route to destination
    • Address Unreachable
    • Port Unreachable
  • Datagram Too Big message

    When an IPv6 node forwards IPv6 packets, if it detects that the size of the packets exceeds the path MTU of the outbound interface, it sends an ICMPv6 Datagram Too Big message to the source node of the packets. The path MTU of the outbound interface is carried in the message. Path MTU discovery is implemented based on Datagram Too Big messages.

  • Time Exceeded message

    During the transmission of IPv6 packets, when a router receives a packet with the hop limit being 0 or a router reduces the hop limit to 0, it sends an ICMPv6 Time Exceeded message to the source node of the packets. During the processing of a packet to be fragmented and reassembled, an ICMPv6 Time Exceeded message is also generated when the reassembly time is longer than the specified period.

  • Parameter Problem message

    When a destination node receives an IPv6 packet, it checks the validity of the packet. If it detects the following errors, it sends an ICMPv6 Parameter Problem message to the source node of the packet:

    • A field in the IPv6 basic header or extension header is incorrect.
    • The NextHeader in the IPv6 basic header or extension header cannot be identified.
    • Unknown options exist in the extension header.

Classification of ICMPv6 Informational Messages

ICMPv6 informational messages are classified into Echo Request messages and Echo Reply messages. ICMPv6 messages can be used for network fault diagnosis, path MTU discovery, and neighbor discovery. During the detection of interworking between two nodes, the node that receives an Echo Request message sends an Echo Reply message to the source node. In this manner, packets are transmitted between the two nodes.


foisal  Gold 
6 years 8 months ago

Thanks for your Excellent Post.