What does "call transfer" involve in SIP communications?

Call transfer in SIP communications involves redirecting an ongoing call from one endpoint to another. This means that the original caller is not disconnected; instead, the session is rerouted to a different recipient or device. This functionality is crucial in various scenarios, such as when a user needs to pass a call to a colleague or when a customer service representative must forward a caller to a specialist.

In SIP, transferring a call can be achieved through mechanisms such as the REFER method or by using a series of INVITE and BYE requests to establish the handoff. This approach ensures that the flow of communication remains seamless for the user, which is a core feature of sophisticated telecommunication systems.

Other options, while related to call management, do not accurately describe transfer. Ending a call and starting a new one creates a break in communication, and placing a call on hold interrupts the flow. Similarly, adding a third party to a call refers to a conferencing feature rather than transferring the call itself.