To establish a communications link between Messaging and your telephony server, you must ensure that certain parameters for each application role match the equivalent parameter on the telephony server.
Call Control Per Hop Behavior (PHB) and Audio PHB. This information is only relevant if your IP network infrastructure supports these Quality of Service features.
The transport method.
The IP address and port number of each far-end connection, that is, the SIP proxy server.
Domain name. The following domain names must match the application server, telephony server, System Manager, and SIP Enablement Services.
The number of messaging trunks.
(Optional) The type of Secure Real-time Transport Protocol (SRTP) media encryption.
Port number, typically 5060 for TCP transport or 5061 for TLS transport
Domain name