The ICMPv6 Header in a Trace File
After reading through all that dry information, you deserve something different. The following screenshot (Figure 4-8) shows what a ping looks like in the trace file and provides details of many of the fields we have discussed so far.

Figure 4-8. Echo Request in a trace file
The two frames in this trace file were captured when my Windows 2000
host issued a ping command to a Linux host. Note that the source
address of the second frame, the Echo Reply, is the same as the
destination address in the first frame, the Echo Request. The IPv6
header provides more information. The Version field indicates that
this is an IPv6 packet. The Next Header field has the value 58, which
is the value for ICMPv6. We can also see source and destination IP
address. The prefix fe80: indicates that these two
addresses are
link-local addresses.
Note the first three fields of the ICMPv6 header. They are the fields that are common for every ICMPv6 message: Type, Code, and Checksum field. The Type field contains the value 128, which is the value for an Echo Request. The Identifier and Sequence Number fields are unique to the Echo Request and Echo Reply message. The Identifier is not used in this case and the sender has set the sequence to 38. It has to be identical in the matching reply that is shown in the following screenshot. The Data field contains arbitrary data that ...