Extensions for long fat networks?

[Paul Hyder]

Damien Miller wrote:
> 
> Paul Hyder wrote:
> > Before I get too far in my attempts...
> >
> > Has anyone already implemented support in scp for larger
> > buffers/windows that would take advantage of wscaled TCP
> > windows?
> 
> Shouldn't this be done at the system level? That way all apps would benefit.
> 
> IIRC Linux has something in /proc that one may tweak.
> 
> -d

(Believe this is also what the previous message from Frank was noting.)

Tuning TCP in Linux 2.4.18+ is actually easy and has good documentation.
(/proc/sys/net/core/[rw]mem_{max,default} and /proc/sys/net/ipv4/tcp_[rw]mem)
So getting wscaled connections was fast.

What I've found so far is that ssh has an internal idea of transmission
sizes, seems to be tied to CHAN_TCP_PACKET_DEFAULT/CHAN_TCP_WINDOW_DEFAULT,
and the result is that the underlying large TCP windows are under-utilized.
The answer also doesn't appear to be as easy as increasing
CHAN_TCP_PACKET_DEFAULT above (32*1024).  [But I've just started and
could easily have missed something.]

With encryption requirements and lots of LFN availability I was just
hoping someone else had already run into the low long distance
throughput and fixed it.

Any/all further suggestions and recommendations would be appreciated.
(Particularly the ones that start with "Whatever you do, don't...")
	Paul Hyder
	NOAA Forecast Systems Lab
	Boulder, CO