L19
QoS, shaping and policing
Cram this first — memory hook
Shaping waits; policing enforces the limit. Quality of Service chooses who goes first, not how many lanes exist.
Exam trap
cannot create additional physical bandwidth or repair a damaged cable.
The slide facts
Bandwidth management prioritizes important traffic. The module distinguishes shaping/policing, Quality of Service and Class of Service, and control/data/management planes.
If you have time — extra
Quality of Service () is a collection of classification, queuing and scheduling techniques that manage how traffic receives service. Voice may need timely delivery more than bulk backups. Class of Service () often refers to Layer 2 priority marking, while Differentiated Services () uses Internet Protocol -layer markings and policies. Marking a packet does not help if downstream devices ignore the policy. Traffic shaping usually buffers and delays excess traffic to meet a configured rate; policing commonly drops or remarks traffic that exceeds a limit. Both differ from simply blocking an entire application. The data plane forwards user packets, the control plane determines forwarding behavior, and the management plane supports administration. Their traffic can require distinct protections.
Walkthrough
Identify important applications, classify/mark traffic consistently, apply suitable scheduling and rate policies at the real bottleneck, observe latency/loss and other users' performance, then adjust based on evidence.