Re: Port numbers in the network layer?

* Joe Touch | 2013-04-25 11:46:38 [-0700]:
>Consider that ethernet ethertype 0x0800 was originally intended to
>mean "IP", allowing the IP version number to be determined at the IP
>layer, but packet demuxing efficiency concerns resulted in a new
>ethertype for IPv6 (0x86DD). So the ethertype includes not only the
>upper layer protocol, but it's redundant with the version at the next
>layer.
>
>Similarly we could allocate a new ethertype to "IPv4:TCP" or "IPv4:SCTP".
>
>So any "mix and match" architecture needs to have some indication of
>what the particular mix is, but it need not be cascaded
>layer-by-layer.

In theory, but in practice this do not work because not every link is Ethernet
and you may end up re-parsing the packet to determine the transport protocol
at each hop.

Limit the ethertype to the next layer was fine. The redundant information in
Ethernet/IP header comes from the fact that we don't life in a perfect world
and things evolve over time.


Hagen