TCP throttling

TCP throttling

[Al Boldi]

Is there a way to tune the throttling nature of a TCP connection?

i.e:
One TCP connection is slower than two over the same bandwidth limited link.
Can this one TCP connection be tuned to make full use of the link-bandwidth?

Thanks!

--
Al

Re: TCP throttling

[Stephen Hemminger]

You probably need to increase the maximum socket buffer
sizes.  Linux defaults are conservative to avoid running
servers out of memory.

http://www.psc.edu/networking/projects/tcptune/#Linux

Re: TCP throttling

[Al Boldi]

Stephen Hemminger wrote:
> You probably need to increase the maximum socket buffer
> sizes.  Linux defaults are conservative to avoid running
> servers out of memory.
>
> http://www.psc.edu/networking/projects/tcptune/#Linux

Thanks for the great link! It kept me up all night.

I managed to crash the server running out of memory.  Don't ask what numbers 
I used, I just went overboard.  I played with these numbers before, but 
never imagined that their scale would be in the millions.

Could you suggest sane values for 2.4/2.6 on a 100mbit link?

Thanks!

--
Al

Re: TCP throttling

[Arnaldo Carvalho de Melo]

On 9/20/05, Al Boldi <a1426z@gawab.com> wrote:
> Stephen Hemminger wrote:
> > You probably need to increase the maximum socket buffer
> > sizes.  Linux defaults are conservative to avoid running
> > servers out of memory.
> >
> > http://www.psc.edu/networking/projects/tcptune/#Linux
> 
> Thanks for the great link! It kept me up all night.
> 
> I managed to crash the server running out of memory.  Don't ask what numbers
> I used, I just went overboard.  I played with these numbers before, but
> never imagined that their scale would be in the millions.
> 
> Could you suggest sane values for 2.4/2.6 on a 100mbit link?

Well, perhaps the sane, conservative values are the one already calculated
by the kernel? Just add more memory to your machine and the sane values will
go up accordingly? :-)

- Arnaldo

Re: TCP throttling

[Mikael Abrahamsson]

On Tue, 20 Sep 2005, Al Boldi wrote:

> Could you suggest sane values for 2.4/2.6 on a 100mbit link?

Go for approx 2-8 megs of TCP window size and buffers.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: TCP throttling

[Stephen Hemminger]

On Tue, 20 Sep 2005 07:19:03 +0200 (CEST)
Mikael Abrahamsson <swmike@swm.pp.se> wrote:

> On Tue, 20 Sep 2005, Al Boldi wrote:
> 
> > Could you suggest sane values for 2.4/2.6 on a 100mbit link?
> 
> Go for approx 2-8 megs of TCP window size and buffers.

I use the following for testing over 1GE. You want
at least 2x the delay bandwidth product.

/etc/sysctl.conf
# increase Linux TCP buffer limits
net.core.rmem_max = 8388608
net.core.wmem_max = 8388608

# increase Linux autotuning TCP buffer limits
net.ipv4.tcp_rmem = 4096 87380 8388608
net.ipv4.tcp_wmem = 4096 65536 8388608

Re: TCP throttling

[Al Boldi]

Stephen Hemminger wrote:
> On Tue, 20 Sep 2005 07:19:03 +0200 (CEST)
> Mikael Abrahamsson <swmike@swm.pp.se> wrote:
> > On Tue, 20 Sep 2005, Al Boldi wrote:
> > > Could you suggest sane values for 2.4/2.6 on a 100mbit link?
> >
> > Go for approx 2-8 megs of TCP window size and buffers.
>
> I use the following for testing over 1GE. You want
> at least 2x the delay bandwidth product.

ping 10.1 -s56

(RTT=0.250ms) * 100mbit = 3125000 Bytes

How much increase in thruput should be expected?

Thanks!

--
Al