"Floyd L. Davidson" <floyd@apaflo.com> wrote in message
news:87ejmkqqem.fld@barrow.com...
> "Dana" <raff242@yahoo.com> wrote:
>>"Andrew Swallow" <am.swallow@btopenworld.com> wrote:
>>> Dana wrote:
>>>
>>>> As for the delay, that will still be there, as you have to get up and
>>>> back to the satellite, On VSATS in the field and my own satellite
>>>> connection at the house here in Alaska, I have seen delays up to 2
>>>> doing
>>>> ping.
>>>
>>> If done properly routing in the satellite will half the delay.
>>>
>>> Previous systems did it one of two ways.
>>>
>>> 1. Subscribe A to satellite and the satellite broadcast the data to
>>> everyone.
>>> 2. Or Subscriber A to satellite, satellite forwards data to a military
>>> base somewhere. The routing computer at the military base decides
>>> which one of its satellites to send the data to. Base sends data
>>> to satellite and the satellite forwards data to Subscriber B.
>>> This requires four 36,000 mile hops and 4 radio frequencies.
>>>
>>> The new satellite appears to contain its own routing computer.
>>> New way. Subscriber A to satellite. Satellite examines the Call
>>> Request and looks in its data base for Subscriber B. If B is
>>> within the foot print then the satellite calls Subscriber B.
>>> This requires two 36,000 mile hops and 2 radio frequencies.
>>>
>
> This is the IP equivalent of DAMA (Demand Access Multiple
> Assignment) for switched circuit networking (the PSTN).
>
> Subscriber A now is talking to a ground based router via one
> satellite link, and Subscriber B is talking to the same ground
> based router via a different satellite link. Two hops to the
> satellite are used for A and B to communicate. Each hop adds
> approximately 400-500ms of latency, even though A and B could
> literally be in adjacent buildings.
>
> The "new" idea is to have a router in the satellite, there will
> be only one hop, as each subscriber still has a link to the
> satellite, but no second link to a ground station is required
> (for the data path, at least, but I would expect that most of
> the router's smarts will be ground based, and only the switching
> fabric will be in the satellite).
>
> That has practical application in Alaska, just the same as DAMA
> used for voice switched networking for the PSTN. Using DAMA
> reduces the use of very expensive satellite bandwidth almost
> half, and provides the customer with a significantly higher
> quality service.
>
> Consider the problems that state agencies, schools, and health
> care organizations all have with existing private networking.
> For example, one network based in Bethel (the Yukon/Kuskokwim
> Delta region of southwestern Alaska) had to put their main
> network routing center in Seattle just because it would have
> been a killer to double hop all traffic that did connect
> outside, whereas there is much less traffic between the
> villages, so village-to-village traffic had to tolerate the
> higher latency.
>
> With a router in the satellite, they would be able to move the
> main operation to their building in Bethel and have much better
> administrative control and at the same time provide better
> technical service to their end users in each village.
>
>>> The is only a small advantage in having tactical routers but big
>>> advantages in strategic and logistics routers. The front line
>>> Lieutenant can send an email back to the USA.
>
> But that is *not* significant for email! That's a store and
> forward system that might have hours of latency! But video
> conferencing, or even just voice calls/conferencing, would be
> significantly better with lower latency. Schools and health
> care providers in particular would find it useful.
>
> Of course the military would also be able to deploy a much more
> effective remote controlled tactical battle team, with the
> remote control being in the field and mobile. With low latency
> between each user the Command Post could actually be dispersed,
> with potentially each user participating.
>
>>They are doing that with VSATS, and have been for years.
>
> Where?

SW asia for starters.
I put in VSAT systems while I was over there.

I thought all of them were using common base to
> subscriber links and multiple subscriber to base links. That
> requires a ground based router, and communications between any
> two satellite subscribers requires a double hop.

I was replying to the part about sending emails from the field via sat comm,
they have had that capability for quite some time now.
Iridium has been routing between Sats from the get go.
>
> --
> Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
> Ukpeagvik (Barrow, Alaska) floyd@apaflo.com