filePro Printing over a Satellite

[Bill Vermillion]

On Wed, Mar 10, 2004 at 02:43:21PM -0500, Kenneth Brody thus spoke:
> "Brian K. White" wrote:

> > DataDoIt wrote:
> >
> > > * I've most recently have worked with a printer that uses
> > > Satellite, with a remote graphics designer on broadband
> > > attempting to send print jobs directly to a printer behind
> > > the Satellite. We're finding that large jobs (1Mb+) will
> > > almost always time out. That's printing to the printer via
> > > static IP and opening the TCP port on the firewall.

> > That sounds more like someone's mtu or mru isn't set right.
> > A print job shouldn't care about latency, it's just a file
> > trasfer like ftp or http.

> > Then again, if that was your problem, then +1M ftp's would
> > fail too, and presumably they are not or you'd surely have
> > noticed.

> When I had satellite, I would notice that uploads would go in bursts,
> with long delays between.

> For example, an ftp upload would send several hundred K in
> a few seconds, and then stop for 10 to 40 seconds before
> continuing. What rate the receiving side was getting, I can't
> say, but if it too were coming in bursts, I can see how some
> protocols would time out.

Considering that there is usually a limit to the number out
outstanding unacked packets and the minimum round-trip time 
on a satellite link with both up and down coming from the bird
is over 6/10th of a second you can see that you could get delays.

The 10-40 second delay sound like buffering at some location, or
stopping the upflow.

Satellite links up and down have a minimum of 100,000 miles round
trip time.  25 up 25 down for send and then same for receive.

These come under the desicription of 'elephants' - ELFN - Extremly
Long Fat Networks - that is normally associated with long [eg
cross-country] fibre links that can hit 10Gb/sec.  Keeping the pipe
filled and then getting acks back in time was partially solved by
using huge packet sizes.

The problem is such things as satellite don't have the exteme
bandwidth that fibre does and as more people use them there is
going to be more congestion. The early satellite data links were
running only 9600 bps - and I was getting a split usenet feed from
one person locally - we all contributed to his monthly bill.

But that went away when one of the providers lost a bird, and the
people providing data services were not on a guaranteed connections
so the services on the dead bird - such as HBO and other providers
- were moved to that one and the little guys were told to find some
other place to play.

At that time you could get a comlete usenet feed at 9600.  Current
complete feeds would over fill a T3 [ eg over 50Mbps ] on a 24x7
basis.  

As with the old saw about storage where data expands to fill space
available, the same thing applies to transport in many places.  

Bill
-- 
Bill Vermillion - bv @ wjv . com