segment
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... IPv6 packets between themselves. In this case, the tunnel spans one
segment of the end-to-end path that the IPv6 packet takes.
...
... destination
IPv6/IPv4 site. This tunnel spans only the last segment of the end-
to-end path.
...
... IPv4
infrastructure. This type of tunnel spans the first segment of the
packet's end-to-end path.
...