[AusNOG] Why not Symmetric ingress and egress?

[Craig Askings]

Yes the default behavior under windows has been to set tcp window  
scaling for quite some time. However I had the pcap files to prove it  
wasn't being set for that app.

Even with that and other evidence it took a long time for them to come  
around to the idea that latency can actually impact transfer speeds.  
"But it works fast here, it must be your Internet connection" etc.  
Even pointing out that I had over 50 mbit/s of spare outbound didn't  
stop them telling me that repeatedly.

How they managed to overide the default tcp socket settings without  
realising, I will never know. I gave up trying as it wasn't worth my  
time.
A
Craig.



On 19/06/2010, at 7:41 PM, Dmitri Kalintsev <dek735 at gmail.com> wrote:

> Craig,
>
> If I'm not mistaken, Windows isn't any different - tcp window is  
> handled on the OS level, by the TCP stack. Application can't do  
> anything about it.
>
> On Fri, Jun 18, 2010 at 4:56 PM, <craig at askings.com.au> wrote:
> > On Fri, Jun 18, 2010 at 4:24 PM,  <craig at askings.com.au> wrote:
> > Say again?  Don't you set these things in the TCP stack - i.e., the
> > kernel - rather than the application?
> >
> > e.g., echo 1 > /proc/net/ipv4/tcp_window_scaling # linux
>
> It was a Windows desktop app. I could prove using scapy that their  
> servers
> honored window scaling when it was requested, but for some reason  
> their
> app never did.
>
> -- D 
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