If your organization does not already use a media gateway to provide connectivity to the public switched telephone network (PSTN), you are not required to deploy a media gateway to support PSTN dial-in conferencing. Instead, you can connect your organization’s voice network to a service provider that offers PSTN origination and termination. This capability, which is known in the telecommunications industry as SIP trunking, means that organizations do not need to deploy IP-PSTN gateways, with or without Mediation Servers, in order to enjoy the benefits of PSTN connectivity. SIP trunking offers your organization the option to route communications directly over a virtual private network (VPN) without using the PSTN.
To deploy SIP trunking, you must complete the steps described in Step 5. Deploy a Mediation Serverin the Enterprise Voice deployment section, including Deploying SIP Trunking (Optional). Also, see the documentation provided by your equipment manufacturer and your SIP trunking service provider.
The SIP trunking provider must also configure the service at its end of the VPN to complete the deployment.