Re: Aspera SCP software

[Ed Wilts <ewilts ewilts org>]

On Mon, May 16, 2005 at 02:58:07PM -0400, Tom Sightler wrote:
> On Mon, 2005-05-16 at 17:36 +0100, John Haxby wrote:
> > Ed Wilts wrote:
> > 
> > >It does work well in practise.  The wide-area SAN people use the same
> > >concept.  What appears to happen is that the transfers may go over UDP
> > >instead of TCP so that you're not trying to ack every packet half-way
> > >around the globe but can ack them in bunches.  The end result appears to
> > >be a more consistent data flow.  
> > >  
> > This sounds like windowing to me or am I missing something?  tcp(7) 
> > talks about setting the global read and write windows to deal with high 
> > bandwidth or high latency connections.   With large windows you don't 
> > ack every packet, just every window'th packet don't you? (*)
> 
> I thought the exact same thing.  Are these perhaps Windows clients
> pushing to a Linux system?

Yup.
 
> By default Windows is VERY poorly tuned for performance over even
> moderate latency (50+ ms)/bandwidth links (> 1.5Mbs) links.  This is
> especially true as bandwidth goes up, but latency stays the same.  There
> are plenty of tools out there that can be used to tune the Windows side
> of things if they are the problem.

The other end is in India, so yes, latency is high (300ms).  They've got
a 4mbps pipe to the Internet and we're at 12.  We're trying to minimize
the file transfer times yet throttle the traffic to about 1mbps.

-- 
Ed Wilts, RHCE
Mounds View, MN, USA
mailto:ewilts ewilts org
Member #1, Red Hat Community Ambassador Program