[asterisk-users] VoIP over satellite internet

[David Gibbons]

<snip>
...routing via satellite adds about a quarter second of latency to the path.  Is that too much?
</snip>

Eric,

I believe that you are mistaken. Routing via satellite adds about a quarter second of latency PER TRIP from earth to orbit. This is simply due to the distance a satellite is from the ground and the speed of light (interference not withstanding).

Traceroutes and pings to satellite providers can be misleading because they cache some content on the birds in order to decrease latency. As I recall they even intercept some pings to accomplish the same.

A *real* round trip for a VOIP call and/or non-interfered TCP connection would look like this:

        1. Your device up to the bird (~250ms)
        2. The bird back to the ground (~250ms)
        3. The ground station out to the internet (~Nms)
        4. The internet back to the ground station (~Nms)
        5. The ground station back to the bird (~250ms)
        6. The bird back to your device (~250ms)

As you can see, even the one way udp stream will take approximately 500ms beyond any latency introduced by things such as your wireless network and the internet. VOIP over satellite, as Josh indicated, will be painful. You'll be talking all over one another due to the delay assuming that the stream can even be sustained with that much latency.

-Dave