Re: Slow PPP (I had more than one problem)

Steve Davies (
Mon, 1 Apr 1996 10:18:48 +0100 (BST)

On Fri, 29 Mar 1996, Linus Torvalds wrote:

> > Perhaps there is, but WHAT ?????? I've checked the link quality and
> > everything looks perfect. It just seems to be going SLOW... Packets come
> > in, packets go out, LCP stuff is exchanged every few seconds, there are NO
> > errors reported by netstat, pppd-debug or kernel debug.
> What does /proc/net/dev say? Any errors?

I get a FEW errors (30 dropped packets in about 20,000) which I believe
are caused by FCS disagreements, but such a small percentage isn't going
to bother me, particularly as none of them appeared during my throughput

I've solved part of my problem recently by turning bsd_comp back off. It
got turned on by accident when I upgraded to modules-1.3.69 and re-did my
conf.modules incorrectly. By also correcting my asyncmap I can now get
data to stream at full speed. The FTP test I did last week now gives
similar results for both Windows and Linux.

The problem I still get is with "interactive" TCP communications. NNTP
being the best example. My 5.5Kb/s News transfers are down at about
2.4Kb/s, and have been since about the time this problem was reported.
Using tcpdump on various communications seems to show that the begining of
any exchange is constantly troubled with retransmits, but that things
quieten down once data starts to flow one-way (apart from regular acks of
course) - With NNTP, the constant request-send format of the exchange
means that things never seem to settle down.

I forgot to bring the tcpdump output in to work, but if this problem
persists, I'll try and find a good example of this.

> The silly thing is that the 72->73 transition (which people have told me is the
> problematic one) doesn't seem to contain _anything_ that would explain it. It's
> there somewhere, obviously, but certainly not easily seen..
> Linus

I completely agree. As I said in a previous E-mail I've trawled through
kernels 1.3.60+ without finding anything untoward...