Explanation/Reference:
Section: Considerations for Expanding an Existing Network Explanation
Explanation:
Reduced CPU processing load is an advantage of implementing Quality of Service (QoS) in hardware instead of in software. Cisco platforms implement QoS features in either hardware or software, depending on the specific platform. For example, most Cisco switches implement QoS features only in hardware, whereas most Cisco routers implement QoS features in software. A limited number of Cisco platforms can implement QoS features in either hardware or software. Best practice dictates that hardware-based QoS features should be preferred over software-based QoS features when feasible.
When QoS features are implemented in software, the CPU must dedicate a portion of available processing power to the configured QoS policies. Depending on the volume of traffic and the number and complexity of configured QoS policies, it is possible for QoS features to be responsible for a significant portion of the CPU processing load on a software-based QoS platform. If the CPU processing load becomes too high, it could impact other operations on the affected platform, such as responding to network events. In order to ensure that the CPU processing load does not become too high, Cisco recommends using hardware- based QoS features when available. Hardware-based QoS features reduce the CPU processing load by offloading QoS-related processing from the CPU to dedicated hardware, such as QoS-oriented application- specific integrated circuits (ASICs).
Reference:
CCDA 200-310 Official Cert Guide, Chapter 3, Campus LAN QoS Considerations, pp. 111-112 Cisco: Medianet WAN Aggregation QoS Design 4.0: Hardware versus Software QoS