Subject: Re: problems with ppp
To: bryan collins <>
From: None <>
List: netbsd-users
Date: 09/27/1995 13:02:54
>The remote end is a xylogics annex.

What KIND of xylogics annex?  The only one that has the proper hardware
flow control (as far as I know, and I have admin'd a number of them
from 1990-1994) is the Annex III.

The portmaster has the proper flow control and can run up to 115kbps, the
Annex III has proper flow control and can run at 38.4kbps, the lesser
Annexen can do 38.4kbps, but have no (or limited to only 1 or 2 ports)
flow control.

I don't recall you mentioning if you thought you were dropping packets or
what.  If you are on a lesser annex and see packet loss, I'd consider the

I also don't recall if you mentioned using the i386 architecture or not,
but if you are...

Other observations from my use of PPP on NetBSD (and hearsay about the
other *BSDs) is that they don't throttle the rts/cts lines at the driver
level, they require ioctls from the higher levels to do it (which is IMHO
really stupid, keep the IOCTL support, but when running in hard flow
control mode, do it from the IRQ handler.)  Regrettably (as implied by my
last soapboxing) even if the drivers DID want to employ flow control at
the lowest level, it would have to be done in software somehow, because
the cruddy UARTs used in PCs (including the 16550Xs) have no hardware
support for RTS/CTS flow control.

You mentioned playing with 1.0 and -current...
pppd in 1.0 had a bug that caused it to spin in a while loop somewhere
where it continued to operate, but never slept.  This resulted in adding a
load of 1 to your system... and most probably slowing things down a
little.  There were patches for this bug MANY months ago that worked fine
for me... this bug was in pppd, not the kernel, so it probably impacted
all architectures.  I know the patches for this went into -current because
I have seen them there.

Hope this helps.

! John Winans                     Advanced Photon Source  (Controls)    !
!              Argonne National Laboratory, Illinois !
!                                                                       !
!"The large print giveth, and the small print taketh away." - Tom Waits !