What values does the Type of Service field carry to indicate quality of service?

• A. It carries the destination port
• B. It carries the checksum
• C. It carries DSCP and ECN values to indicate quality of service and congestion notification
• D. It carries the TTL

Answer: (C)

Quality of service in IPv4 is managed by marking packets in the IP header’s Differentiated Services Field. This field carries DSCP (Differentiated Services Code Point) and ECN (Explicit Congestion Notification) values. DSCP uses 6 bits to designate the desired per-hop behavior for QoS, while ECN uses the remaining 2 bits to signal congestion without dropping packets. The combination lets routers apply different handling and let endpoints know when congestion occurs. The other options aren’t QoS markings: the destination port is part of the transport layer, the checksum is for error detection, and the TTL controls hop count rather than service quality.