Topic Last Modified: 2010-11-08

How you implement the service provider side of a SIP trunk connection varies from one ITSP to another. For deployment information, contact your service provider. For a list of certified SIP trunking service providers, see the Microsoft Unified Communications Open Interoperability Program website at

For details about Microsoft certified SIP trunking providers, contact your Microsoft representative.

You must use a Microsoft certified service provider to ensure that your ITSP supports all of the functionality that traverses the SIP trunk (for example, setting up and managing sessions and supporting all of the extended VoIP services). Microsoft technical support does not extend to configurations that use non-certified providers. If you currently use an Internet service provider that is not certified for SIP trunking, you can opt to continue using that provider as your ISP and use a Microsoft certified provider for SIP trunking.