Voice over satellite problem

Unanswered Question
Nov 8th, 2007

I have 2 routers 2801&3825 connected back-to-back with ethernet via satellite link. Local networks are routed via GRE tunnel. Problem is in bad voice quality beetwen routers due to bid delay in sattelite path. Is it possible to create FR or PPP tunnel beetwen segments to get RTP compression working to improve voice quality?

I have this problem too.
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lgijssel Thu, 11/08/2007 - 04:31

The most important cause of your problems is the long and very variable delay of the satlink. What little can be gained by using rtp compression is then consumed by the extra overhead that would be needed for the tunnel encapsulation. In the end, you will only be increasing the load on the cpu's.

As I learned by eperience, the two most important issues are:

1: Reduce packet loss. Make sure that an optimal radio path exists to reduce packet loss as far as possible

2: Reduce jitter. Take measures to reduce the jitter such as implementing a suitable queueing scheme.

Overbooking of the sat-bandwidth is a killer for voice also. It costs money but dedicated bandwidth pays off.



Paolo Bevilacqua Thu, 11/08/2007 - 05:32

Which codec are you using, and for which application ?

Do you have voice quality issue all the time, or only in present of concurrent data traffi c?

andrey712 Fri, 11/09/2007 - 23:46

I have used G.723 ad G.729 codecs, but problem is the same. Could you show typical QoS settings for voice aplications and methods to sheck does it work correctly or not.

Paolo Bevilacqua Sat, 11/10/2007 - 01:51


can you detail as asked above, if the problem happens in presence of concurrent data traffic, or all the time. Also, if it happens in both directions, or one only.

The please describe how you are connected to satellite, on both sides (ethern, serias, etc).

In networking, often more info is needed than just "this doesn't work" to make exact recommendations.

andrey712 Tue, 11/13/2007 - 00:16

Main site router 3825 is connected with Ethernet port via optical modems to provider satellite equipment. Remote end connected with Ethernet port to 2801. Voice path from main site is normal, but voice from remote to the main all the time is interrupted. This satellite channel have no data and other concurrent traffic, just using to trnsmit 1 voice speech.

Paolo Bevilacqua Tue, 11/13/2007 - 03:11


this means uplink bandwidth from remote is insufficient. I understand than neither G.723 nor G.720 has worked, which uplink bandwidth the remote satellite site has ?


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