[asterisk-biz] Foip solution

[James Sharp]

Alex Balashov wrote:
> On 03/30/2010 11:49 PM, Trixter aka Bret McDanel wrote:
> 
>> On 03/29/2010 02:10 PM, James Sharp wrote:
>>>>> I suspect that the latency involved in satellite IP connections creates
>>>>> a whole additional level of problem with fax.
>> latency isnt as big of a problem as people pretend it is.  Jitter and
>> packet loss are the real killers.
> 
> I agree;  I did not clearly state it, but meant to imply that the jitter 
> is likely to be highly variable over satellite links.  At least, that's 
> certainly true in my experience, for various reasons.  There is no 
> physical basis for it, but satellite is probably subject to a higher 
> degree of oversubscription.  I don't actually know.

Depends on the satellite link type.  Companies like HughesNet use a
large outgoing transponder (from the main earth station to the end
user), and then a single transponder that gets TDM'd between all of the
customer's return links.  Depending on how loaded the TDM return link
is, latency can be all over the place.

The system I built out used the large outgoing transponder + TDM return
link as well, but when it detected that a latency/jitter/packet loss
sensitive operation (such as a VOIP/FOIP call), it would switch that one
site to a dedicated chunk of space segment that was no longer TDM'd.
After the call(s) dropped, the site would drop back into TDM mode.