On Thu, 2 Apr 1998, Liebowitz, Burt wrote:
> Most current satellites are "bent pipe" repeaters - that is totally
> passive. This is certainly the case for the Orion satellites, of which I
> am most aware. Some of the newer LEO constellations have on- board
> processing, but its not clear if any are router-like.
AFAIK no planned or proposed commercial constellation will be flying
IP routing. IP-wise you could consider the ones actually doing
switching and having intersatellite links as Layer 2/MAC bridge
equivalents at best. Teledesic in particular springs to mind here,
although I don't have anything to cite related to their current
design.
[I've no idea why IP routing gets the thumbs-down and ATM the thumbs
up when ATM and PNNI multicast map so badly to an LEO mesh; I'd vote for
flexibility over speed, and the oft-quoted routing-tables-don't-scale
problem strikes me as movable to the gateways via IP-in-IP
encapsulation or (gack!) address translation; just treat the
satellite backbone mesh as a variant of a private IP network!]
I'm not sure how far up the ATM stack allegedly-ATM-based on-board
processing/switching proposed for a number of constellations extends,
even if they do plan full ATM at the gateways and terminals. Anyone?
In any case, IP tunnelled on top will still consider it all to be
Layer 2, with all the resulting lack of topological flexibility and
throughput control you've come to expect from the MBONE etc.
Well, so much for satellite-sourced quenches (rfc792).
L.
<[email protected]>PGP<http://www.sat-net.com/L.Wood/>+44-1483-300800x3641
> Burt Liebowitz
> Chief Technical Officer
> Loral Orion Network Systems
>
> > ----------
> > From: Tony Hughes[SMTP:[email protected]]
> > Sent: Thursday, April 02, 1998 10:11 AM
> > To: '[email protected]'
> > Subject: Source quench on Satellites
> >
> > Hello Forum,
> > I have been following the forum for a while and do not actually have
> > any "hands on" satellite experience but I try to keep current on
> > things happening.
> > My question is, for IP (using UDP or TCP) over a satellite link,
> > does that satellite perform as a passive, hub like device, or
> > actice like a router? I am just curious if the satellite it self
> > could send a source quench to the sender.
> > Thanks,
> > Tony
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