What QoS architecture prioritizes and forwards data packets based on a DSCP value?

• A. Diffserv (Differentiated Services)
• B. DNS
• C. Dial-ups
• D. Differential Backup

Answer: (A)

This is testing how QoS uses packet marking to guide how traffic is handled across the network. Differentiated Services architecture marks packets with a DSCP value in the IP header, and routers apply Per-Hop Behaviors based on that value to decide queuing, priority, and forwarding treatment. Because the DSCP code point travels with the packet and tells each hop how to treat it, this architecture scales well from edge to core—traffic is classified and marked at the edge, then the core enforces the chosen behavior without keeping per-flow state.

The DSCP value is a 6-bit field in the IP header (in the DS field, formerly the ToS field), and different values map to different forwarding behaviors (for example, expedited forwarding for real-time traffic). The other options don’t describe an architecture that prioritizes and forwards data based on DSCP marks: DNS is simply a name-resolution service, dial-ups describe a connection type, and differential backup is a backup strategy.