I am trying to commission a network of Cisco Call Manager Express systems with (mainly) Cisco 521 phones connected to a private IP network for a corporate client. Prior to the "proper" solution being introduced a temporary solution using Asterisk with Grandstream GX-2000 phones was installed to provide limited service. Both solutions are using SIP between the sites, G729 codecs and run over the same IP network. The IP network is satellite so the latency is large and there is quite a lot of jitter.
My problem is that even though the systems are connected to the same network, the Asterisk/Grandstream solution sounds so much better than the Cisco/Cisco solution. Heavily used satellite IP networks are never going to provide perfect voice quality.
Is this just the way it is? If so how to I explain it to the client?