Low latency queuing (LLQ) adds a priority queue to CBWFQ from which delay-sensitive traffic, such as voice traffic, can be transmitted ahead of packets in other queues. By configuring the quality of service (QoS), you can provide preferential treatment to specific types of traffic at the expense of other traffic types. Without QoS, the device offers best-effort service for each packet, regardless of the packet contents or size. The device sends the packets without any assurance of reliability, delay bounds, or throughput.
The following are specific features provided by QoS:
Low latency

Bandwidth guarantee

Buffering capabilities and dropping disciplines

Traffic policing

Enables the changing of the attribute of the frame or packet header

Relative services

Modular QoS Command-Line Interface

Supported QoS Features for Wired Access

Hierarchical QoS