[TUHS] History of select(2)

[Paul Ruizendaal]

On 12 Jan 2017, at 4:54 , Clem Cole wrote:

> Paul -- this is a great stuff and fills in some pieces of my memories.

Thanks!

> The point is that while I have no memory of capac(), but I can confirm that I definitely programmed with the empty() system call and Rand ports on a v6 based kernel in the mid-1970s and that it was definitely at places besides Rand themselves.

Thank you for confirming that. If anybody knows of surviving source for these extensions I'd love to hear about it. Although the description in the implementation report is clear enough to recreate it (it would seem to be one file similar to pipe.c and a pseudo device driver similar in size to mem.c), original code is better. It is also possible that the code in pipe.c was modified to drive both pipes and ports -- there would have been a lot of similarity between the two, and kernel space was at a premium.

> [...] confirming something I have been saying for few years and some people have had a hard time believing. The specifications for what would become IP and TCP were kicking around the ARPAnet in the late 1970s.

My understanding is that all RFC's and IEN's were available to all legit users of the Arpanet. By 1979 there were 90 nodes (IMP's) and about 200 hosts connected. I don't get the impression that stuff was always easy to find, with Postel making a few posts about putting together "protocol information binders". Apparently nobody had the idea to put all RFC's in a directory and give FTP access to it.

I am not sure how available this stuff was outside the Arpanet community. I think I should put a question out about this, over on the internet history mailing list.

As an aside: IMHO, conceptually the difference between NCP and TCP wasn't all that big. In my current understanding the big difference was that NCP assumes in-order, reliable delivery of packets (as was the case between IMP's) and that TCP allows for unreliable links. Otherwise, the connection build-up and tear-down and the flow control were similar. See for instance RFC54 and RFC55 from 1970. My point is: yes, these concepts were kicking around for over a decade in academia before BSD.

Paul