Re: 2.0.6 Networking strangeness

Christoph Lameter (clameter@fuller.edu)
Sun, 14 Jul 1996 09:46:40 -0700 (PDT)


On Sun, 14 Jul 1996, Linus Torvalds wrote:

> > ping waterf -> hur 140-160msec
> > ping waterf -> miriam 1.0-1.6msec
This was evidently wrong. The ping time was 1.0-1.6seconds!!!
> > ping hur -> miriam 0.6-1.1msec
> >
> > Setup:
> >
> > Linux 2.0.6 (waterf)
> > |
> > PPP Link
> > |
> > Linux 2.0.6 (hur)
> > |
> > Ethernet
> > |
> > Linux 2.0.6 (miriam)
> >
> > Sometimes I have doubts that Alan knows what he is doing.
>
> Don't blame alan, blame me. It's the small patch I made to
Sorry just wanted to spice up the message a bit.... I remember having the
same issue around 1.3.73.

> HOWEVER, now that I look a bit more closely at your report, it starts making
> less and less sense. Notably, "ping" doesn't use TCP at all, so the only
> change that is in the 5->6 upgrade simply _cannot_ affect ping latency. And
> the _longer_ trip to miriam from waterf (that still uses PPP) doesn't seem
> affected.
Sorry you are right. Its general latency.
> Anyway, try just reverting on the tcp_output.c patch in 2.0.6 (it's a rather
> small one), and if that fixes the problem then I guess we'll just have to go
> back. However, this behaviour makes me suspect more and more that there is
> something broken in the PPP (or serial code) timings, and that the TCP change
> just happens to make that show up more (so the TCP change itself isn't the
> bug, it just triggers the _real_ bug - not something we want to necessarily
> look into in the 2.0.x series, though).
I downgraded to 2.0.5 and the speed is back.
*
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