Session Initiation Protocol (SIP) is an application layer signaling protocol that is used to create, modify, and terminate multimedia sessions. It is modeled after the standard Hyper-Text Transfer Protocol (HTTP). By modeling SIP after HTTP, SIP is able to use a simplified text-based set of instructions and uniform resource indicators (URI). SIP negotiates the means for endpoints to communicate with each other and allows for communications to be established independent of the type of device the end user may be using.