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VoIP over satellite link?

 
 
Ramon F Herrera
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      08-14-2007

We have a customer in a remote area, relatively near the equator
(their ISP is too). They don't have much voice coverage (no land lines
and scant cell) but they have a satellite-based DSL Internet link. I
would like to try to solve their problem with a VoIP ATA from
Linksys, because its configuration parameters can be tweaked at will.

I have the obvious concerns: how much will the delay affect voice
quality? Is there some TCP/UDP window that should be adjusted? Any
question I haven't addressed?

TIA,

-Ramon F Herrera

 
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Rick Jones
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      08-14-2007
In comp.protocols.tcp-ip Ramon F Herrera <(E-Mail Removed)> wrote:
> We have a customer in a remote area, relatively near the equator
> (their ISP is too). They don't have much voice coverage (no land
> lines and scant cell) but they have a satellite-based DSL Internet
> link. I would like to try to solve their problem with a VoIP ATA
> from Linksys, because its configuration parameters can be tweaked at
> will.


> I have the obvious concerns: how much will the delay affect voice
> quality? Is there some TCP/UDP window that should be adjusted? Any
> question I haven't addressed?


Did you ever use one of those old satelite links for a
long-distance/overseas call? I suspect that VoIP over a
satellite-based DSL link wouldn't even be that good. I have vague
memories of speaking with my grandfather over one of those a few times
and it did not lend itself to a normal flowing dialog.

Assuming we are talking about a geosync satellite here, that is at
least one hop of ~46000 miles each way, which translates to a one-way
latency of ~250 milliseconds. (Handwaving math...) And then add-in
whatever happens once their voice data hits the regular pots (?)
network, and whatever other delays there might be on the IP side at
the ISP or whatnot.

So, your customer would say "boo!" and it would be a full half-second
before you could say "eek!" No tweaking of TCP windows (UDP has no
window) or other stuff could change that. While at first blush half a
second might not sound like a big deal, there was a very compelling
reason the telcos/whatever put all those trans-oceanic links in

rick jones
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these opinions are mine, all mine; HP might not want them anyway...
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...
 
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alt
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      10-19-2007
On Tue, 14 Aug 2007 00:34:27 +0000, Rick Jones wrote:

> In comp.protocols.tcp-ip Ramon F Herrera <(E-Mail Removed)> wrote:
>> We have a customer in a remote area, relatively near the equator
>> (their ISP is too). They don't have much voice coverage (no land
>> lines and scant cell) but they have a satellite-based DSL Internet
>> link. I would like to try to solve their problem with a VoIP ATA
>> from Linksys, because its configuration parameters can be tweaked at
>> will.

>
>> I have the obvious concerns: how much will the delay affect voice
>> quality? Is there some TCP/UDP window that should be adjusted? Any
>> question I haven't addressed?

>
> Did you ever use one of those old satelite links for a
> long-distance/overseas call? I suspect that VoIP over a
> satellite-based DSL link wouldn't even be that good. I have vague
> memories of speaking with my grandfather over one of those a few times
> and it did not lend itself to a normal flowing dialog.
>
> Assuming we are talking about a geosync satellite here, that is at
> least one hop of ~46000 miles each way, which translates to a one-way
> latency of ~250 milliseconds. (Handwaving math...) And then add-in
> whatever happens once their voice data hits the regular pots (?)
> network, and whatever other delays there might be on the IP side at
> the ISP or whatnot.
>
> So, your customer would say "boo!" and it would be a full half-second
> before you could say "eek!" No tweaking of TCP windows (UDP has no
> window) or other stuff could change that. While at first blush half a
> second might not sound like a big deal, there was a very compelling
> reason the telcos/whatever put all those trans-oceanic links in
>
> rick jones


Hi Rick:

I've set up a lot of VoIP-over-Satellite systems. Yes, the latency is a
bit of an issue, but for the most part you can have some well flowing
conversations. And as long as you don't have any packet loss or large
packet jitter, the sound will be very clear and clean because it is
all-digital. I routinely see 300ms-350ms of latency and the customers
don't seem to mind.

That being said, if you can get terrestrial, get it, for all the reasons
you've laid out above.
 
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Stefan Pfefferkorn
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      10-10-2008
wildeyed wrote:

>
> contain;9206800 Wrote:
> > You could just try a standard satellite phone if you can afford the
> > charges, but I should warn you they are not cheap!

>
> This is a VOIP forum not a satellite telephony forum.


This is not a forum - this is a newsgroup

--
"Zwei Dinge sind unendlich: das Universum und die menschliche Dummheit;
aber bei dem Universum bin ich mir noch nicht ganz sicher." (Albert
Einstein (1879-1955))
Mit freundlichen Gren
Stefan "Pfeffi" Pfefferkorn
 
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