What is the primary purpose of the Cisco Unified Border Element (CUBE)?

• A. Media translation
• B. NAT traversal
• C. SIP normalization and interoperability
• D. QoS signaling

Answer: (C)

CUBE is placed at the network border to connect the enterprise voice network with external SIP domains or the PSTN, and its main job is to make different SIP implementations cooperate smoothly. That means it normalizes SIP signaling, adjusts headers and session descriptions, and reconciles the capabilities and codecs between the two sides so a call can be established and understood end-to-end. This interoperability is the key reason to use CUBE, especially in environments with diverse equipment or service providers.

Media translation (transcoding) is a useful capability when endpoints don’t share a common codec, and NAT traversal is important for calls across networks, but these are supporting features rather than the primary reason CUBE is deployed. QoS signaling isn’t a focus of CUBE’s role.