Which protocol is widely used by Avaya Aura for call signaling?

Session Initiation Protocol (SIP) is the correct answer because it is specifically designed for initiating, maintaining, and terminating real-time sessions that include voice, video, and messaging applications. SIP is a fundamental protocol within the Avaya Aura architecture, facilitating call signaling and establishing communication sessions over the internet or private networks. It allows endpoints to discover each other and negotiate the parameters necessary for real-time communication.

SIP supports many essential features of modern telephony, such as the ability to create conference calls, handle user presence, and manage call features like forwarding and transferring. This makes it particularly suitable for integrated communications environments where both voice and data services need to coexist smoothly.

The other protocols listed do not fulfill the same role as SIP within the context of Avaya Aura. For instance, Hypertext Transfer Protocol (HTTP) is used primarily for data exchange over the web, while File Transfer Protocol (FTP) is designed for transferring files between clients and servers. Simple Mail Transfer Protocol (SMTP) is used for sending and routing email messages. None of these protocols are intended for call signaling or real-time session management in a telecommunication environment, highlighting the unique and specialized function of SIP in the Avaya ecosystem.