SIP Trunking SIP Enablement Services connects Communication Manager and IP Office systems to carrier-based SIP trunks, providing a more cost-effective option for PSTN terminations. For Communication Manager, SIP trunking can be deployed with a much smaller hardware footprint compared to traditional T1 and analog trunks, significantly reducing recurring operational and maintenance expenses. SIP Enablement Services is a Linux-based software application that is deployed as a network appliance on the Avaya S85xx Series Servers or as an embedded component of Communication Manager 5.0 (and later on the Avaya S8300C Server.) Multiple SIP Enablement Services servers can be deployed within the enterprise IP communications network. Each server is licensed to operate in one of three modes: Home, Edge, or Combo.