Topic Last Modified: 2010-04-27
An enterprise-grade VoIP solution must provide for calls to and from the PSTN without any decline in quality of service. In addition, users should not be aware of the underlying technology when they place and receive calls. From the user's perspective, a call between the Enterprise Voice infrastructure and the PSTN should seem like just another SIP session.
For PSTN connections, you can either deploy SIP Trunking or a media gateway (with a PBX, also known as a Direct SIP link, or without a PBX).
SIP Trunking
As an alternative to using media gateways, you can connect your Enterprise Voice solution to the PSTN by using SIP trunking. SIP trunking enables the following scenarios:
- An enterprise user inside or outside the corporate firewall can
make a local or long-distance call specified by an E.164-compliant
number that is terminated on the PSTN as a service of the
corresponding service provider.
- Any PSTN subscriber can contact an enterprise user inside or
outside the corporate firewall by dialing a Direct Inward Dialing
(DID) number associated with that enterprise user.
The use of this deployment solution requires a SIP trunking service provider.
Media Gateways
Media gateways are third-party devices that translate signaling and media between the Enterprise Voice infrastructure and a PSTN or a PBX. Media gateways work with the Mediation Server to present a PSTN or PBX call to an Enterprise Voice client. The Mediation Server also presents calls from Enterprise Voice clients to the media gateway for routing to the PSTN or PBX. For a list of partners who work with Microsoft to provide devices that work with Communications Server, see the Microsoft Unified Communications Partners Web site at http://go.microsoft.com/fwlink/?LinkId=125756.
Private Branch Exchanges
(PBXes)
If you have an existing voice infrastructure that uses a Private Branch Exchange (PBX), you can use your PBX with Communications Server Enterprise Voice.
The supported Enterprise Voice-PBX integration scenarios are as follows:
- IP-PBX that supports DNS load balancing, with a Mediation
Server.
- IP-PBX that supports media bypass, with a Mediation Server.
- IP-PBX that supports both DNS load balancing and media
bypass.
- IP-PBX that requires a standalone IP-PSTN gateway.
- Time division multiplexing (TDM) PBX, with a standalone IP-PSTN
gateway.
For details about partners who offer Enterprise Voice solutions, see the Microsoft Unified Communications Partners page at http://go.microsoft.com/fwlink/?LinkId=125756.
For details about partners who offer Enterprise Voice hardware solutions, including media gateways, see http://go.microsoft.com/fwlink/?LinkId=125757.