Subject: Re: PPP and flow control
To: None <current-users@NetBSD.ORG>
From: None <is@Beverly.Rhein.DE>
List: current-users
Date: 01/24/1996 01:54:34
Mike Long ( wrote:
: I wrote:
: >I'm still having problems sending data over my PPP link.  I can
: >receive data or send *small* amounts of data without difficulty
: >(e.g. sup works); but any attempt to send a chunk of data over a
: >certain limit fails.  The only possible explanation I think likely is
: >that flow control is broken.  I am running an i386 -current system; my
: >PPP link runs on my 14.4kbps modem.
: Some more details:
: 1) Yes, the crtscts bit is set on the tty. :-)
: 2) It's not a PPP-specific problem because Kermit uploads under NetBSD
:    also fail.
: 3) It is a NetBSD-specific problem because Kermit uploads under DOS
:    *do* work.

I've seen PPP lines on NetBSD-1.1-ix86 producing silo overflows; after
looking at the code, I realized that the damned NS16550 lookalikes don't
have _hardware_ flow control, but only _software_ flow control (that is,
if the interupt isn't serviced fast enough, you loose). 

Not I never saw more tha 0.1% lost packets or bytes, so this is no real
problem (as PPP recognizes broken packets). I wonder, however, why this
shows on certain NetBSD-i386 machines and not on others. Could it be
that the wd driver manages to block serial interupts for more than 1 ms
or 2?

	Ignatios Souvatzis