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RE: PCSAT - dumb questions



Hello Norm

Phil said...

> > What I can't figure out is why a satellite command link even requires
> > a "connection" in the first place, not to mention why only one such
> > "connection" can exist at a time, or why it is possible for an
> > unauthorized person to create such a "connection".

Then Norm said...

> I think you've missed the point of PCsat. It's an extremely simple device,
> made up from storebought bits by satellite first-timers, and kids at that.
> There is no onboard Computer as such, only those imbeded in the TNCs. As I
> see it, and Bob-the-Builder will no doubt correct me if I'm wrong,
> functions of the TNC are used to exercise command and control. For this to
> happen, the TNC must be put into Command Mode using the "remote Op" feture
> of the TNC itself.

Exactly.

As Phil touched on, if one can perform sufficient authentication for each
packet, a connectionless protocol could be used. But there's no IHU on PCSat
to do this. Of course, someone could have re-written the TNC's firmware
instead, but then that in itself opens up a whole new ballgame (and bugs
with it). After all, the existing TNC's firmware had already been tested in
the field by thousands of satified customers.

But IMHO a connectionless continual authentication would be a help in future
designs. A thought though: considering the type of data we are talking about
here, the authentication may well take up more space than the data itself...

73 Howard G6LVB

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