Find out more about the Microsoft Unified Communications Open Interoperability Program for enterprise telephony services and infrastructure, including finding qualified SIP Trunking Services, E911 Service Providers, Survivable Branch Appliances, SIP-PSTN gateways, and IP-PBXs at http://technet.microsoft.com/en-us/lync/gg131938.aspx?ocid=soc-n-SA-loc-services-omers