Re: [tcpm] draft-ietf-tcpm-tcp-uto-02

Wesley Eddy wrote:

> On Fri, Dec 02, 2005 at 08:37:16PM -0800, Fernando Gont wrote:
> 
>>>>>/on a satellite/on a non-geostationary satellite/
>>>>>- All satellites orbit, but the vast majority used for telecoms take an
>>>>>orbit that is goeostationary.
>>>>
>>>>IIRC, this had been a contribution of (NASA's) Wesley Eddy. "Satellite" 
>>>>need not be a communications satellite, but could also be planetary body 
>>>>(i.e., a node operating from the Moon experiences periods of 
>>>>disconnection)
>>>
>>>- Yes and is also a rather bizarre illustration of the point, considering 
>>>the Path RTT >> "normal Internet MSL" ;-)
>>
>>I don't get your point. :-?
>>
> 
> 
> I don't either.  If the "normal Internet MSL" is 2 minutes, then the
> propagation-based RTT between the Earth and Moon of roughly 5.5 seconds
> is well within an MSL.
> 
> I actually think that changing the text to say "geostationary" would be
> an odd example, since from the ground it's rather difficult to go out of
> touch with one of these in comparison to other orbits.  The case of a
> polar orbit (for instance) where you can predict the amount of time when
> the satellite is below the horizon and the time when it'll come back up
> is a better example.  In this case, you can use a combination of UTO (to
> keep the connection alive) and retransmit-now (to kick the connection),
> to gain a little bit of efficiency, and simplify the application by
> letting it use TCP in comparison to CFDP or others.
> 
> -Wes
>  

OK, so the original text was:

    For example, an orbiting node on a satellite might
    experience disconnections due to line-of-sight blocking by other
    planetary bodies.  The disconnection periods of such a node may be
    easily computable from orbital mechanics.

And my original point, was perhaps not clear, but we now seem to have 
come full circle, and so let me try again:

If you think this is a good example of why UTO is useful (and I am not 
sure it really is such a good example), then I would have much prefered 
the I-D to have said something like "non-geostationary satellite" - to 
differentiate it from the more common form of satellite used to provide 
Internet services.

Gorry

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