[ih] receipts & OS modifications for IMPs [networks]

[Craig Partridge]

John Day raised two points in the discussion of flow control that I
thought I'd lift up to a discussion on their own.

1. John mentioned the jest: how do you interface to an IMP?  Make it
look like a tape drive!  ;-)

This jest points up what was a serious and long-running debate in the
OS and applications community about the abstract interface should be
to both applications and the operating system - a debate that
persisted from the late 1970s into the early 1990s.  The great
innovation of UNIX was to make pipes -- byte streams -- first class OS
objects and then create an ecosystem that leveraged pipes (with
glorious things like grep piped to sed and such like).  TCP fit well
with pipes; UDP (and the short lived RDP, but also ICMP and such)
didn't.  Then there was the issue of how the OS and its supporting
applications (things that brought interfaces up and such) interacted
with network interfaces.  Sockets won this fight, but it was a long
and tricky muddle.

2. John mentioned receipts and issues of who handles flow control and
how acks fit in.

Keep in mind that, again, through the mid-1990s, we did not understand
fully general acknowledgement schemes -- by which I mean, ack schemes
that allowed tracking of packets received out of order, or in order
but with gaps.   Automatic Repeat Request (ARQ) research had worked
out how to handle acks for packets in order and what to do if a single
packet was missing, but beyond those fundamental challenges we took a
long time to figure out what to do.

Craig


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