What is the purpose of SIP in communication systems?

The correct answer reflects the core functionality of SIP (Session Initiation Protocol) in communication systems. SIP is specifically designed to establish, maintain, and terminate real-time communication sessions, which can include voice calls, video conferencing, and messaging. Its role is crucial in handling call setup, managing session parameters, and ensuring that sessions can be ended gracefully when completed.

SIP performs these functions by defining the messages that are exchanged between participants, allowing them to initiate, modify, and terminate communication sessions effectively. This capability is fundamental for the operation of VoIP (Voice over Internet Protocol) services and is what differentiates SIP from other protocols that might focus on transporting data or securing networks.

In contrast, other options like transmitting data files, providing network security, or compressing media files don't align with SIP's primary purpose. While there are protocols that handle file transfer, security, and media compression, SIP's unique role is to manage the signaling and control parts of real-time communication.