[ih] Early Unix networking

[pnr at planet.nl (Paul Ruizendaal)]

On 11 Oct 2016, at 21:59 , Jeremy C. Reed wrote:

> The BBN Combined Quarterly Technical Report No. 24 mentions some of BSD 
> changes they knew about but not implemented on BBN's side.

That's an interesting read. Section 8 is indeed a nice summary of how the
BBN code evolved between August 1981 and January 1982.

The notes on local net performance tuning are intriguing:
- byte swapping and check summing in assembly
- tuning timer values
- software interrupts instead of a kernel thread

It would be interesting to find out which of the above made it into the
4.1a release.

As yet, I haven't fathomed why software interrupts would
be more efficient than the kernel thread design.

I've checked the code again and at that time the CSRG mbuf code does
not use external 2048 byte blocks yet; the page allocation algorithm
appears to have changed from the BBN version, but as yet I don't know if
this affected performance much.

In any case, my earlier understanding that larger buffers were used at
that time to boost speed on local nets appears incorrect.