SIP allows for sending and receiving messages, voice calls, and video calls between two or more devices over the internet, facilitating human-to-human conversations. It operates similarly to old telephone networks, acting as an operator to connect users. SIP is an application layer protocol that guides data between different systems, making it flexible and adaptable to various protocols such as UDP, TCP, and SCTP. Its scalability and efficiency are compared to unicast streams, which can be more bandwidth-intensive but also more efficient in terms of scaling. To use SIP, one needs a provider account and a SIP client, allowing users to connect with others and establish calls. The protocol differs from VoIP technology, allowing for sending media types like messages, videos, and pictures beyond voice communication. SIP can be implemented as an out-of-the-box solution or integrated into applications using telephony APIs, enabling real-time or asynchronous functionality.