HELP - Increase TCP packet

HELP - Increase TCP packet

Post by Marcelo Muzill » Fri, 25 Oct 2002 06:07:51



Hi all from this NG,

could help me in this question: "what is the command to" and/or "how can
I" increase the size of a TCP packet in a Solaris?

Thanks in advance,

Marcelo Muzilli

 
 
 

HELP - Increase TCP packet

Post by Barry Margoli » Fri, 25 Oct 2002 02:56:51




Quote:>could help me in this question: "what is the command to" and/or "how can
>I" increase the size of a TCP packet in a Solaris?

What do you mean by this?  If you have an Ethernet interface, the maximum
packet size is limited by the Ethernet spec to about 1500 bytes.

--

Genuity, Woburn, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.

 
 
 

HELP - Increase TCP packet

Post by Marcelo Muzill » Fri, 25 Oct 2002 09:58:19


Hi Barry,

I would like to decrease the maximum SLIDING WINDOW of the TCP and I don't know the
command or the way to do this. I think that I was more clear with this.

Regards,

Marcelo Muzilli




> >could help me in this question: "what is the command to" and/or "how can
> >I" increase the size of a TCP packet in a Solaris?

> What do you mean by this?  If you have an Ethernet interface, the maximum
> packet size is limited by the Ethernet spec to about 1500 bytes.

> --

> Genuity, Woburn, MA
> *** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
> Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.

 
 
 

HELP - Increase TCP packet

Post by Michael Halad » Fri, 25 Oct 2002 15:28:17




> Hi Barry,

> I would like to decrease the maximum SLIDING WINDOW of the TCP and I don't
know the
> command or the way to do this. I think that I was more clear with this.

> Regards,

> Marcelo Muzilli




> > >could help me in this question: "what is the command to" and/or "how
can
> > >I" increase the size of a TCP packet in a Solaris?

> > What do you mean by this?  If you have an Ethernet interface, the
maximum
> > packet size is limited by the Ethernet spec to about 1500 bytes.

> > --

> > Genuity, Woburn, MA
> > *** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to
newsgroups.
> > Please DON'T copy followups to me -- I'll assume it wasn't posted to the

group.

You might want to look into the man pages for
1) ndd
2) tcp

check ndd /dev/tcp ? to see a list of possible arguments

Regards

 
 
 

HELP - Increase TCP packet

Post by stor-ste » Fri, 25 Oct 2002 22:33:10


how about these?

tcp_conn_req_max_q0=65535
tcp_conn_req_max_q=65535
tcp_cwnd_max=65535
tcp_max_buf=1073741824
tcp_mss_def_ipv4=1460
tcp_mss_max_ipv4=1460
tcp_recv_hiwat=65535
tcp_wscale_always=1
tcp_xmit_hiwat=65535
udp_recv_hiwat=65535
udp_xmit_hiwat=65535

some ndd settings that could be useful.

Something to consider... My experience has been that you only want to
LOWER the window size if you have a high latency/packet-loss-
prone environment.  If you have a low latency environment, you want your
window size as large as possible.  Under Solaris, you can enable a flag
that permits a >64k window size.  This would be a good thing, given the
right network and traffic types.



Quote:> Hi Barry,

> I would like to decrease the maximum SLIDING WINDOW of the TCP and I
> don't know the command or the way to do this. I think that I was more
> clear with this.

> Regards,

> Marcelo Muzilli

 
 
 

HELP - Increase TCP packet

Post by Rick Jone » Sat, 26 Oct 2002 06:01:38



> Something to consider... My experience has been that you only want
> to LOWER the window size if you have a high latency/packet-loss-
> prone environment.  If you have a low latency environment, you want
> your window size as large as possible.  Under Solaris, you can
> enable a flag that permits a >64k window size.  This would be a good
> thing, given the right network and traffic types.

I think you have that backwards? One of the limits to the performance
of a TCP connection is the window size divided by the round-trip-time
- W/RTT. If you have a low latency environment, you can achieve high
speed with a smaller window.

If there is a lot of packet loss, you want at least some window size
there so there is the chance of getting fast retransmits instead of
retransmits only after a timeout.

rick jones
ftp://ftp.cup.hp.com/dist/networking/briefs/
--
denial, anger, bargaining, depression, acceptance, rebirth...
where do you want to be today?
these opinions are mine, all mine; HP might not want them anyway... :)
feel free to post, OR email to raj in cup.hp.com  but NOT BOTH...

 
 
 

HELP - Increase TCP packet

Post by nor » Sat, 26 Oct 2002 07:42:50



> Hi all from this NG,

> could help me in this question: "what is the command to" and/or "how can
> I" increase the size of a TCP packet in a Solaris?

> Thanks in advance,

> Marcelo Muzilli

I assume you are trying to increase your throughput for
better performance. I have a low cost and free tool which
you can use to monitor your network traffic and determine
whether you have really improved throughput.

http://www.sunperf.com/perfmontools.html

A lot of different things can affect performance, so a
thorough and detailed analysis may be needed.

---------------------------------------------------------
For God makes the sun rise on bad and good alike; Gods
rain falls on the just and the unjust. (Matthew 5:44-45)
http://www.sunperf.com - Performance Monitoring Tools
http://www.justhacked.org - UNIX Security

 
 
 

HELP - Increase TCP packet

Post by stor-ste » Sat, 26 Oct 2002 22:22:29


My own personal testing has shown that in a 100/1000Mbit switched network
with <2ms latency, using the largest possible window size gives the best
throughput.  If the window sized is dropped, throughput drops as TCP
overhead increases.  This may or may not be true for unswitched networks
or lower speed links, but I've never tested that.  What I'm talking about
is a measured transfer rate in the >= 10 Megabytes/sec range.  Of course,
this only takes you so far, and then you have to switch to jumbo frames.
Quote:> I think you have that backwards? One of the limits to the performance
> of a TCP connection is the window size divided by the round-trip-time
> - W/RTT. If you have a low latency environment, you can achieve high
> speed with a smaller window.

> If there is a lot of packet loss, you want at least some window size
> there so there is the chance of getting fast retransmits instead of
> retransmits only after a timeout.

> rick jones
> ftp://ftp.cup.hp.com/dist/networking/briefs/

 
 
 

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