Scott, if memory serves you and I wanted the high-order 2 bits of the IPng address to select between 64, 128, 192, and 256-bit addresses -- and when we couldn't get that we got folks to agree on 128-bit addresses instead of 64-bit, which is what had been on the table. On Feb 14, 2012, at 1:37 39PM, Bradner, Scott wrote: > in the case of IPng, the router people wanted variable length but the host people (or at least some of them) did not > > Scott > > Scott O Bradner > Senior Technology Consultant > > Harvard University Information Technology > Innovation & Architecture > (P) +1 (617) 495 3864 > 29 Oxford St. Rm 407 > Cambridge, MA 02138 > > > > On Feb 14, 2012, at 1:34 PM, Steve Crocker wrote: > >> The word alignment issue was very strong and the router people had considerably more influence than the host folks. I tried to propose variable length addressing using four bit nibbles in August 1974 and I got no traction at all. >> >> Steve >> >> Sent from my iPhone >> >> On Feb 14, 2012, at 6:31 PM, Bob Braden <braden@xxxxxxx> wrote: >> >>> On 2/13/2012 7:53 PM, Noel Chiappa wrote: >>>>> From: Brian E Carpenter<brian.e.carpenter@xxxxxxxxx> >>>> >>>>> The design error was made in the late 1970s, when Louis Pouzin's advice >>>>> that catenet addresses should be variable length, with a format prefix, >>>>> was not taken during the design of IPv4. >>>> >>>> Ironically, TCP/IP had variable length addresses put in _twice_, and they were >>>> removed both times! (You can't make this stuff up! :-) >>> Noel, >>> >>> You probably remember this, but... >>> >>> Within the ARPA-funded Internet research program that designed IP and TCP, Jon Postel and >>> Danny Cohen argued strenuously for variable length addresses. (This must have been >>> around 1979. I cannot name most of the other 10 people in the room, but I have >>> a clear mental picture of Jon, in the back of the room, fuming over this issue. Jon believed >>> intensely in protocol extensibility.) >>> >>> However, Vint Cerf, the ARPA program manager, rules against variable length addresses and >>> decreed the fixed length 32 bit word-aligned addresses of RFC 791. His argument was that >>> TCP/IP had to be simple to implement if it were to succeed (and survive the juggernaut >>> of the ISO OSI protocol suite). >>> >>> System programmers of that day were familiar with word-aligned data >>> structures with fixed offsets, and variable length addresses seemed to be (and in fact >>> would be) harder to program and would make packet dumps harder to interpret. >>> >>> It was a political as much as a technical judgment, and Vint may have been right ... we >>> can never know. We do know that IP eventually succeeded and OSI failed, but it >>> was a near thing for awhile. Of course, there were other factors in the success >>> of IP, such as Berkeley Unix. >>> >>> It is to be noted that when it came time to define IPv6 some 20 years later, the IETF >>> stuck with fixed length internet addresses. >>> >>> Bob Braden >>> >>> _______________________________________________ >>> Ietf mailing list >>> Ietf@xxxxxxxx >>> https://www.ietf.org/mailman/listinfo/ietf >> _______________________________________________ >> Ietf mailing list >> Ietf@xxxxxxxx >> https://www.ietf.org/mailman/listinfo/ietf > > _______________________________________________ > Ietf mailing list > Ietf@xxxxxxxx > https://www.ietf.org/mailman/listinfo/ietf --Steve Bellovin, https://www.cs.columbia.edu/~smb _______________________________________________ Ietf mailing list Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf