What is CAC used for in voice networks?

• A. To prioritize video calls over audio.
• B. To prevent oversubscription of WAN links by limiting voice/video calls based on available bandwidth.
• C. To enforce security policies on endpoints.
• D. To convert codecs to save bandwidth.

Answer: (B)

Call Admission Control is about protecting voice quality by managing how much traffic the network agrees to carry. It checks the bandwidth available on a link and the bandwidth required for a new voice (and sometimes video) call. If there’s enough capacity, the call is allowed to proceed; if not, the call setup is blocked or delayed. This prevents oversubscription of WAN links, which would lead to congestion, jitter, and dropped or degraded calls. CAC focuses on making sure there’s enough real-time bandwidth before admitting a new session, rather than prioritizing one type of traffic, enforcing security policies, or converting codecs.