🚀 go-pugleaf

In article <1993Jan8.122742.3793@hemlock.cray.com>, andyw@aspen32.cray.com (Andy Warner) writes:

  > Huh?  Since when did an interrupt every 13us or so become an unbearable 
  > load?  For well-designed and trim interrupt routines, this is nothing.  I've

  Go ahead, write a trim interrupt routine & PPP stack, you'll
  be a hero.

The ppp stack doesn't have to be trim, only the interrupt routine.

The problem of missing interrupts is a real one.  If your mtu is 1500, then
you have to catch every one of 1500 interrupts in a row.  If you miss even
one, the packet is lost.  While processing an interrupt in 13 us may be
easy, guaranteeing that you can get to it in time is not, at least in a
general purpose computer.

In this day of cheap microcontrollers, it seems to me that what you want is
a controller on the serial io board that knows how to assemble ip packets.
Using a silo helps, but it's less than ideal.  The silo size and timeout
have to be kept short to get reasonable latency.  It would be a lot better
if the processor were interrupted only when a complete packet is assembled.
That's how synchronous (sdlc) boards work.