Traffic shaping is a QoS rate-limiting technique. It transmits conforming traffic immediately, buffers exceeding traffic in a separate shaping queue, and releases it later at the permitted rate. Unlike policing, which drops or re-marks excess traffic, shaping smooths the traffic flow. section 10.5 section 10.7
Key operational facts:
- Configure shaping per class, so each traffic class and queue is handled separately, or per interface, applying it to all transmitted or received packets. section 10.5
- Use shaping when a downstream provider polices traffic; buffering at the customer edge prevents packets from exceeding the provider’s permitted rate. section 10.5
- Permit bursts when required: both policing and shaping can allow temporary traffic spikes above the configured average rate. section 10.5
300 Mbps customer connection
An ISP polices incoming customer traffic to 300 Mbps even though both routers use GigabitEthernet. The customer shapes outbound traffic to 300 Mbps, buffering excess packets instead of sending them at interface capacity and having them dropped by the ISP. section 10.5
