TCP and WAN issue

Steve Meuse smeuse at
Wed Mar 28 01:40:07 UTC 2007

On 3/27/07, Lincoln Dale <ltd at> 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.


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