[Asterisk-Users] IAX2 trunk mode over satellite

clive18 at webmail.co.za clive18 at webmail.co.za
Tue Mar 30 23:27:59 MST 2004


I have even used H323 over satelite, and beside the lagg,
no trouble.  My only issue is the jitter buffer on IAX2
seems to be broken. On a very jittery connection, I can
hardly make a decent call on IAX2.

Good luck!

On Tue, 30 Mar 2004 10:15:52 -0800
 John Todd <jtodd at loligo.com> wrote:
> Today has been the day for satellite questions,
> apparently, so I'll proxy one out to the rest of the
> community...  I asked this tangentially a month or two
> ago, but I'll put it in a more blunt way:
> If you have IAX2 trunking mode experience over satellite,
> please let us know your experiences with that
> protocol/transport combination.
> I've got several people asking about IAX2 and trunk mode
> over satellite.  I have not experimented with IAX2 over
> satellite (though I have used IAX1 over satellite) and
> I'm wondering if anyone has direct experiences with
> IAX2's jitter buffer control over such long-latency
> connections.
> I've had SIP working very well over satellite (despite
> what some people have found to the contrary on this list)
> and other than the lag there have been no issues that
> have come up on a reasonably-managed satellite segment.
>  However, the IP overhead really starts to cost
> significant amounts of pennies when you add it up on
> multiple SIP RTP sessions over the same link.  Plus,
> packet contention and buffering may (_may_) be an issue
> when pushing multiple simultaneous streams out the same
> transponder.
> It would seem to me that IAX2 in trunk mode would be
> optimal for people on very expensive satellite bandwidth,
> as a G.729 9.6kbps channel starts to actually look like
> 9.6kbps instead of 24kbps. However, I have had mixed
> success with IAX2 in certain circumstances. Before I
> start to ask for favors and get satellite time for
> testing, I'd like to see if anyone else has performed
> this experiment.  If you'd wish to remain anonymous,
> please mail me directly and I'll appropriately trim
> identity information and re-distribute, or re-write as
> appropriate.
> Other hints I have heard/used on VoIP over satellite:
>    - use small transmit cell (packet) sizes on your
> satellite gear
>    - turn off error correction (why use it for VoIP?)
>    - turn off compression (G.729 is already compressed;
> you ARE using 
> G.729, right?)
>    - ensure minimal latency on the terrestrial portions
> of the call
>    - tell your users to suck it up and deal with the
> half-second lag
> JT
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