There are a couple of unused bits in the IPv4 header that one could use. I thought of this during the last "paper" to expand address space that circulated this summer on nanog.
Unfortunately, the real problem is deployment. Once you decide to change the protocol in any way that is not completely downward compatible, everyone has to deploy the modification. I'm going to hazard a guess that IPv6 will really be widely deployed by tunneling it in IPv4. And I'll hazard that much of the IPv6 traffic will just contain tunnelled "private" IPv4 traffic. Tunnel inside tunnel. So much for header compression.
--Dean
Around 01:13 PM 10/18/1999 -0400, rumor has it that jeanlou.dupont@na.marconicomms.com said: