see also - http://www.sobco.com/ipng/big_ten/big_ten_packet_format.txt and http://www.sobco.com/ipng/big_ten/big_ten_address_format.txt variable length addresses were considered for IPng (now IPv6) - for various reasons, including the same issue Int raised of perceived programming complexity in the hosts, the idea was not adopted Scott > On Nov 12, 2016, at 2:44 PM, Bob Braden <braden@xxxxxxx> wrote: > > Brian et al, > > I have not been paying attention to this thread, but Brian's answer got my attention. I was in the room in 1977 when the decision was made to use fixed-length 32 bit IP addresses. I did not have a strong opinion at the time, but at least two members of the Internet research group, Jon Postel and Danny Cohen, strongly urged variable length IP addresses. As manager of ARPA's Internet Research program, Vint Cerf made the call for fixed length addresses. His argument was that if we were to have any hope that the DoD might accept the experimental protocols, TCP must not be too complex to program. He thought that variable-length addresses would scare off our possible customers. > > Incidentally, the OSI folks did adopt variable -length network addresses; this was one of the advantages of OSI that later led the IAB to suggest that the Internet shou ld consider adapting the OSI protocols. Which caused the famous Kobe lynching of the (original) IAB. > > Good heavens, 1977 was 40 years ago! > > Bob Braden > > > > > for a problem, that is IMHO not very clearly described.ally, > >>> how about ipv4 and ipv6 are incompatible on the wire and this >>> has created a multi-decade ipv6 charlie foxtrot? >> Yes, I suggest mentioning that to Vint, Bob and a few others in 1977, >> so that they can design IPv4 with extensible addresses. People in >> 2016 will be grateful. >> >> Brian >> >