Tuning TCP/IP Performance

[Tony Finch]

Joe Abley <jab...@patho.gen.nz> wrote:
>
> If 4.0 (or later 3.x's) support SACK, turn that on here too.

Neither of them does.

Tony.
--
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[Andrzej Bialecki]

On Sat, 4 Mar 2000, Paul Robinson wrote:

> Hi,
>
> I've been trying to get TCP/IP performance as fast as possible by playing
> around with sysctl (playing in the net.inet area) and so on, and was
> wondering if there were any comprehensive resources on this that I've
> missed. Whenever I do a sysctl -d -a to get a list of descriptions, I get
> the following on 3.2-RELEASE:
>
> sysctl: sysctl name -1 1024 2: No such file or directory

Retrieval of descriptions is not implemented yet. I'm afraid you'll need
to resort to grepping through the source...

>
> Any idea as to what's going on here?
>
> Also, I seem to remember hearing about a method used on SunOS to send the
> first four bytes of the data payload back with the SYN ACK which gives the
> appearance of improved performance on benchmarks. Does anybody know as to
> whether this is possible under any version of FreeBSD? I'll move to 4.0 if
> I have to. :)

There was a recent discussion (about a month ago) on -current about
delayed ACKs. It's in the archives.

Andrzej Bialecki

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[Joe Abley]

On Sat, Mar 04, 2000 at 08:21:20PM +0000, Paul Robinson wrote:
> I've been trying to get TCP/IP performance as fast as possible by playing
> around with sysctl (playing in the net.inet area) and so on, and was
> wondering if there were any comprehensive resources on this that I've
> missed.

I haven't heard of any algorithms to tune TCP automagically. When I
work with people who have satellite hops in their network, we usually
have to tune the TCP knobs by hand, trying a large number of transactions
and statistically minimising transaction time.

> Whenever I do a sysctl -d -a to get a list of descriptions, I get
> the following on 3.2-RELEASE:
>
> sysctl: sysctl name -1 1024 2: No such file or directory

I get that too, but I had never noticed because I didn't know about
the "d" flag :) FreeBSD 3.3-RELEASE FreeBSD 3.3-RELEASE #1:
Sat Dec 4 15:21:53 NZDT 1999.

> Any idea as to what's going on here?
>
> Also, I seem to remember hearing about a method used on SunOS to send the
> first four bytes of the data payload back with the SYN ACK which gives the
> appearance of improved performance on benchmarks. Does anybody know as to
> whether this is possible under any version of FreeBSD? I'll move to 4.0 if
> I have to. :)

This is what I generally do before I try to tune anything further:

# turn on RFC1323 extensions (timestamps, PAWS, window scaling, etc) These
# seem to be on by default in 3.3, YMMV for 3.2.

sysctl -w net.inet.tcp.rfc1323=1

# open up the send and receive windows to 131072 bytes; the default
# 16k is too small for people living oceans away from the majority of
# their content

sysctl -w net.inet.tcp.sendspace=131072
sysctl -w net.inet.tcp.recvspace=131072

# If 4.0 (or later 3.x's) support SACK, turn that on here too. SACK is
# cool :) This is what I use on OpenBSD:

sysctl -w net.inet.tcp.sack=1

# If you want to try transactional TCP (T/TCP, RFC1644) which is the
# thing you mentioned with the single segment with SIN, ACK, FIN + payload,
# turn this on:

sysctl -w net.inet.tcp.rfc1644=1

[Paul Robinson]

Hi,

I've been trying to get TCP/IP performance as fast as possible by playing
around with sysctl (playing in the net.inet area) and so on, and was
wondering if there were any comprehensive resources on this that I've

missed. Whenever I do a sysctl -d -a to get a list of descriptions, I get
the following on 3.2-RELEASE:

sysctl: sysctl name -1 1024 2: No such file or directory

Any idea as to what's going on here?

Also, I seem to remember hearing about a method used on SunOS to send the
first four bytes of the data payload back with the SYN ACK which gives the
appearance of improved performance on benchmarks. Does anybody know as to
whether this is possible under any version of FreeBSD? I'll move to 4.0 if
I have to. :)

--
Paul Robinson - Developer/Systems Administrator @ Akitanet Internet