SBC, or Session Border Controller, is a network device used in Voice over Internet Protocol (VoIP) communications. It helps manage and secure voice and video calls by controlling the signaling and media streams. SBCs are essential for ensuring quality, security, and interoperability between different networks and devices. In addition to managing calls, SBCs provide features like NAT traversal, which helps devices communicate across different network types. They also protect against various security threats, such as Denial of Service attacks, by monitoring and filtering traffic. Overall, SBCs play a crucial role in modern telecommunications.