Re: tcp slowness update (fwd)

J.H. (
Mon, 8 Mar 1999 15:26:42 -0800 (PST)

> > is a thinnet network. I have had phenomenal problems, with a large range
> > of kernels. In order to try to speed things up a little, I even put a
> including 2.2.2?

Yep, just finished installing 2.2.2 on my client to get rid of that
question mark. Server is 2.2.2 ac3.

> the very low rate is the real rate, once the socket's buffer is filled.
> I presume here that you're looking at the rate estimates given by apps,
> which only know how fast they can write to the socket's buffer...

Correct, but if it takes 10 minutes to transfer a 100K file, something's
going on :-)

> > I have captured some tcpdump output from both ftp and netcat, which I can
> > make available via ftp for anyone who could use them.
> I'm not David Miller, but I'd be happy to take a look. ideally, you'd have
> tcpdumps on both the tx and rx ends (so packet loss is obvious). if it looks
> like there's a real problem with the stack, the net gods are highly motivated
> when presented with bi-directional tcpdumps...

I just finished doing bidirectional tcpdumps on the linux box. I was
getting about 1.5KB/sec tops with both ftp and nc. I have dumps off both
the client and the server.

I also did some transfers with other machines on the same net, got
600KB/sec + . I then rebooted this machine into rusty old NT (haven't
booted it for about 6 months now), and got 745KB/sec on the same file.
Let's see- that's *700 times* better throughput. Looking at the dumps
with the linux client, it looks like there are a lot of retransmits, but
the basic problem HAS TO BE linux. I am using the same linux server for
the server- and ftping from it with a DOS (Lan Workplace), Windows 95,
Windows NT, and linux client. Everything but the linux client gets at
least 400kb/sec (even the 486-33 DOS box). The linux box gets 1.5KB/sec.

I have the bidirectional dumps for both ftp and netcat from the linux
client and server-side dumps for the 700KB/sec ftp with the NT client.

Who wants to tackle this problem?

Brian Pape
Computer Resource Services
University California Los Angeles
voice: (310) 825-9284
fax: (310) 206-6039

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