Which DSCP value is recommended for RTP voice?

• A. AF31 (33)
• B. CS4 (32)
• C. AF41 (44)
• D. EF (Expedited Forwarding)

Answer: (D)

RTP voice requires the lowest possible delay and jitter, so it should be marked with the highest-priority DSCP value to ensure it gets expedited forwarding through network devices. Expedited Forwarding maps to DSCP value 46 and is designed to provide minimal queuing delay by giving these packets strict priority in forwarding decisions. In practice, this means voice packets are transmitted first, reducing the likelihood of drops or late arrival that can ruin conversations.

Other markings, like those in the AF (Assured Forwarding) family or CS (Class Selector) ranges, do not guarantee the same level of low-latency treatment. They offer different service guarantees and drop precedences that are more suitable for traffic that can tolerate some delay or for non-real-time control data. Therefore, Expedited Forwarding is the best choice for RTP voice to meet real-time performance requirements.