[95480] in North American Network Operators' Group
Re: TCP and WAN issue
daemon@ATHENA.MIT.EDU (Steve Meuse)
Tue Mar 27 21:41:29 2007
Date: Tue, 27 Mar 2007 21:40:07 -0400
From: "Steve Meuse" <smeuse@gmail.com>
To: "Lincoln Dale" <ltd@interlink.com.au>
Cc: "Philip Lavine" <source_route@yahoo.com>, nanog <nanog@merit.edu>
In-Reply-To: <044901c770d7$cbe1f050$046f09cb@ltdbeast>
Errors-To: owner-nanog@merit.edu
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On 3/27/07, Lincoln Dale <ltd@interlink.com.au> wrote:
>
>
> even on "default settings" on a modern TCP stack, getting close to
> path-line-rate on a 80msec RTT WAN @ DS3 speeds with a single TCP stream
> should
> not be that difficult.
>
> the Windows TCP stack as of Windows XP SP2 has some fairly decent
> defaults. it
> will do RFC1323 / large windows / SACK., but all of these can be tuned
> with
> registry settings if you wish.
>
I was under the impression that XP's default window size was 17,520 bytes,
rfc1323 options disabled.
Assuming 80ms and 45Mb/s, I come up with a window size of 440Kbytes required
to fill the pipe. At windows default I would only expect to see 220Kbs over
that same path.
I think even modern *nix OSs tend to have default window sizes in the 64kB
region, still not enough for that Bandwidth/delay.
--
-Steve
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<br><br><div><span class="gmail_quote">On 3/27/07, <b class="gmail_sendername">Lincoln Dale</b> <<a href="mailto:ltd@interlink.com.au">ltd@interlink.com.au</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>even on "default settings" on a modern TCP stack, getting close to<br>path-line-rate on a 80msec RTT WAN @ DS3 speeds with a single TCP stream should<br>not be that difficult.<br><br>the Windows TCP stack as of Windows XP SP2 has some fairly decent defaults. it
<br>will do RFC1323 / large windows / SACK., but all of these can be tuned with<br>registry settings if you wish.<br></blockquote></div><br>I was under the impression that XP's default window size was 17,520 bytes, rfc1323 options disabled.
<br><br>Assuming 80ms and 45Mb/s, I come up with a window size of 440Kbytes required to fill the pipe. At windows default I would only expect to see 220Kbs over that same path. <br><br>I think even modern *nix OSs tend to have default window sizes in the 64kB region, still not enough for that Bandwidth/delay.
<br><br>-- <br><br>-Steve
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