avoiding tunnel fragmentation

Eric Hoffman (hoffman@cs.washington.edu)
Thu, 29 Oct 1998 15:05:15 -0800 (PST)

1) we can take advantage of the fact that most TCP traffic isn't
"two-way" (ie doesn't have data and acks together) and overload the
acknowledgement number to hold the destination IP address. We could do
the same thing with the sequence number in the ACK direction, but its
unlikely that these packets will be MTU sized.

wont someone have to have the necessary state in order to reconstitute
the correct sequence number before handing it off to the destination
host?

i very much hate to bring up the possibility, but it might be better
to explicitly label flows and recover necessary forwarding state based
on the label, rather than exploit a series of special cases to cram a
few bits here and there in the original packet

of course managing this state (distributed forwarding cache) is a
pretty severe pain pain in the ass