Question

A network engineer is building an LLQ policy on a WAN router to protect UC traffic. Voice RTP is classified into class VOICE and video conferencing RTP into class VIDEO. During periods of congestion, users report that voice remains clear but the video stream occasionally freezes even though there is available bandwidth on the link. Reviewing the policy-map, the engineer sees the VOICE class uses 'priority 1000' and the VIDEO class uses 'bandwidth 2000'. Which statement best explains the behavior and the correct design principle?

Accepted Answer

The 'bandwidth' command guarantees a minimum during congestion but does not provide low-latency priority servicing; real-time video should use its own 'priority' (LLQ) reservation to avoid jitter-induced freezing.

Answer

The VIDEO class is being starved because only one 'priority' queue is allowed; the engineer should change 'bandwidth 2000' to 'priority 2000' so both share the single low-latency queue.

Answer

The 'priority' command in the VOICE class enforces a policer that only drops voice above 1000 kbps during congestion, so VIDEO is unaffected and the freezing is unrelated to the LLQ policy.

Answer

The 'bandwidth 2000' statement caps VIDEO at 2000 kbps at all times, so increasing it to 'bandwidth percent 100' will remove the freezing by allowing video to burst.