Sun chose UDP for NFS at a point when few if any people believed TCP could
go fast.
I remember (early  80s) being told that one couldn't use TCP/IP in LANs
because they were WAN protocols.  In the late 80s, WAN people were saying
you couldn't use TCP/IP because they were LAN protocols.

But UDP for NFS was more attractive because it was not byte stream
oriented, and didn't require copying to save for retransmissions.  And
there was hope we'd be able to do zero copy transmissions from the servers
- also the reason for inventing Jumbo packets to match the 8K page size of
Sun3 systems.

I did get zero copy serving working with ND (network disk block protocol) -
but it was terribly specific to particular hardware components.

On Thu, Mar 9, 2023 at 4:24 PM ron minnich <rminnich@gmail.com> wrote:

> Ca. 1981, if memory serves, having even small numbers of TCP connections
> was not common.
>
> I was told at some point that Sun used UDP for NFS for that reason. It was
> a reasonably big deal when we started to move to TCP for NFS ca 1990 (my
> memory of the date -- I know I did it on my own for SunOS as an experiment
> when I worked at the SRC -- it seemed to come into general use about that
> time).
>
> What kind of numbers for TCP connections would be reasonable in 1980, 90,
> 2000, 2010?
>
> I sort of think I know, but I sort of think I'm probably wrong.
>