Documentation for configuring SIP trunks with Engin and several other providers may be found at https://supportforums.cisco.com/docs/DOC-9830. Amongst other things, this discusses the use of the connection-reuse parameter. And as Luke states above, we are in the process of developing a number of plugins for CCA 1.9 that will allow different providers to be imported into the drop down list on the SIP Trunk page, and will automatically address some of the configuration traps that you might otherwise run into. Keep an eye on the support community for updates, as these plugins will be made available on the community once the are ready for publication.
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