Furthermore, when the data packet to be sent is larger than the MTU in the data
transmission path, the host will be fragment by itself. This host-fragmented behavior makes it
not necessary for the router to process the fragment and save the resource of the IPv6
router, as well as improve the efficiency of the IPv6 network.
The minimum link MTU is 68 bytes in the IPv4, which means the link of
the path in each data transmission should support the link MTU with 68
bytes at least. The minimum link MTU is 1280 bytes in the IPv6. It is
strongly recommended to use the 1500 link MTU for the link in the IPv6.
32.1.5 IPv6 Neighbor Discovery
The IPv6 neighbor discovery processing makes use of the message of the ICMPv6 and the
multicast addresses of the solicited neighbor to obtain the link layer address of the neighbor
at the same link, and verify the reachability of the neighbor as well as maintain the status of
the neighbor. These types of messages are briefly described respectively below.
32.1.5.1 Neighbor Solicitation Message
When a node is to communicate with another node, the first node must get the link layer
address of the second node. At this time, it should send neighbor solicitation (NS) message
to the second node and the destination address of the message is corresponding to the
requested multicast address of the IPv6 address of the destination node. The sent NS
message also contains the link layer address of itself. After receiving this NS message,
corresponding node will retransmit a response message, referred to as the neighbor
advertisement (NA), whose destination address is the source address of the NS and the
content is the link layer address of the solicited node. After receiving the response message,
the source node can communicate with the destination node.
The following is the neighbor solicitation procedure:
Figure 32-4
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