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[ih] internet-history Digest, Vol 37, Issue 6

Vint wrote:

  The first documented split of IP from TCP came with TCP v3 which was  
  published as IEN21 in January 1978. The "internetwork header" showed a  
  variable length (!) source and destination address field among other  
  things, separate from the TCP header. This was subsequently revised in  
  TCP 3.1 in Feb 1978  with IENs 26, 27, 28 and again, in June 1978 with  
  IPv4 and TCPv4 in IENs 40 (TCP) and 41(IP).


I recall rather vividly the variable vs fixed length address discussion. 
Jon Postel and Danny Cohen strongly favored variable length addresses, 
for architectural reasons.  I assume that Jon slipped them into IEN21. 
In your DARPA role, you then decreed (and it was perfectly clear to the 
rest of us that this was non-negotiable) that addresses would be 32 bits 
and fixed length.  Your argument was that it would significantly 
simplify implementations of the protocols, and that would strengthen the 
acceptability of TCP/IP in the struggle with OSI. I have often wondered 
who was right. In the short run, you were probably right about the 
threat of OSI.  In the long run, would variable length addresses have 
avoided the IPv4/IPv6 mess?  I can only speculate.

Bob Braden