Which concept describes a QoS approach that classifies and forwards packets based on DSCP markings?

• A. Diffserv (Differentiated Services)
• B. Differentiated Services Code Point (DSCP) value
• C. DNS
• D. Dial-ups

Answer: (A)

Diffserv defines a scalable QoS model where traffic is classified into behavior aggregates and forwarded according to DSCP markings. In this approach, packets are marked at the network edge with a DSCP value that encodes the desired treatment (such as higher priority for Expedited Forwarding or specific classes for different types of traffic). Core routers then apply a small set of Per-Hop Behaviors based on that DSCP value, guiding queuing, latency, and bandwidth decisions without maintaining per-flow state. The DSCP marking communicates the service level, but it’s the DiffServ architecture—edge classification plus DSCP-based forwarding in the core—that makes the approach work. DNS and dial-ups aren’t related to this QoS mechanism, and the DSCP value by itself is just the marking, not the whole QoS method.