I don't think it was very standardized; I've been working on the Internet since 1977, and this is the very first I ever recall hearing of it! :-) Again, that was not standardized at an early stage, but was, as best I can now recall, just adopted by general usage (i.e. without any formal discussion). There were other ways of specifying a IP address numerically, initially; e.g. for a while at MIT we were using w,x,y,z (with w-z in octal - note the ','s, which were a syntatic tag for the octal form), which was easier to interpret when looking at a packet dump on a PDP-11. Here: http://ana-3.lcs.mit.edu/~jnc/tech/unix/arc/tftp.c.1 is the source for a user command (from July, 1979) which allowed host addresses to be given in that form. I'm not sure who came up with the dotted decimal form; I suspect you'd need to find some really old email archives, and look in that. There was, early on, a list called "tcp-ip", used by people who were getting their machines ready for the NCP->TCP/IP conversion. However, I suspect the 'dotted quad' predates that; there was an even earlier mailing list, used in early experimental work, by the group working on internet technology, whose name escapes me (it was something like "internet working group"). It's possible that an IEN: https://www.rfc-editor.org/ien/ien-index.html might mention the 'dotted quad' syntax; TCP and IP meeting minutes would be a good place to start. Noel PS: The A/B/C addresses are actually a moderately late stage of IP addresses. At the very start, they were all '8 bits network numbers, and 24 bits of 'rest''.