Infrastructure qualified for Lync
http://technet.microsoft.com/en-us/lync/gg131938.aspx
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, Session Border Controllers (SBCs) and IP-PBXs.