Re: [9fans] IL and NAT

[geoff@x.bell-labs.com]

NAT routers generally have to rewrite port numbers (not just IP
addresses) for protocols that use them, and ports numbers are at
different offsets and of potentially different sizes in different
protocol's headers.  IL's port numbers appear later than TCP's and
UDP's, for example.  NAT routers will generally understand the headers
of TCP, UDP and ICMP at minimum, but I haven't encountered one yet
that understood IL (even Lucent's own).

Contrary to what Scott just said, it's not each application that has
to be added to a NAT router, but each protocol that rides directly on
IP (or beside it).