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iLBC or G729 over IPSec VPN using Satellite connection


I’m looking for guidance having to set up a decent VoIP over a satellite connection and will greatly appreciate your input and insight.

Currently, there are 7 UCProxy secure phones at the location (a boat). As we are replacing the current network routers and switches with Cisco devices, we are planning to configure a Cisco 2811 router with a VPN tunnel to connect with our main location and convert the UCProxy phones to “regular” phones. The Satellite link bandwidth is limited to 256 Kbps including all data (Internet) traffic. Maximum of 3 simultaneous phone calls should be supported.

First of, will this setup have any advantages over the UCProxy connection? What is the preferred codec to use in this situation? The UCProxy phones use iLBC. Will iLBC perform better than G729 over the IPSec VPN?

What is the exact bandwidth calculation using the IPSec VPN?

For example, 1 iLBC phone call = 15.2 Kbps + 16 Kbps (IP/UDP/RTP encapsulation) + 16 Kbps (IPSec VPN) = 47.2 Kbps. Do I need to add any additional overhead?

There also is a Riverbed WAN accelerator provided by a third party (a British company – the VSAT provider). Can this device help or shall we let all the (encrypted) VoIP traffic bypass the accelerator?

I’m very interested in your opinions and experiences with similar design.

Thank you.

Petr S

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