SIP (Session Initiation Protocol) is a "signaling" system for connecting, monitoring and disconnecting connections across the internet. A SIP Trunk is a network interface device that recognizes SIP signals and can process these signals to other SIP devices. SIP Trunking is provided by a Softswitch or SBC-Session Border Controller which provides, among other things, signal processing, protocol conversion, transcoding conversion, call routing, QoS-Quality of Service, AAA-Authorization, Authentication and Accounting functions as well as switching control interface to and from gateways.