ATL Telecom R1-SW Ethernet Switch - Manual (Page 181)

Configuring QoS
9-13
previous time, the deficit count becomes 1000byte, and 600byte and 300byte packet are
transmitted. After the transmission, the deficit counter becomes 100 (Picture 4). The rest of
packets are processed as above.
Shaping
Shaping is a function that limits bandwidth with buffering when traffic that is bigger than
target traffic rate flows into a queue.
The traffic that is more than target traffic rate is stored into the buffer. If there is enough
bandwidth to transmit, the stored traffic is transmitted.
This method is more flexible than policing, but is not useful in real-time traffic such as voice
traffic because transfer delay occurs.
WC Scheduler and NWC Scheduler
WC (Work Conserving) scheduler can use whole bandwidth of output port until congestion
occurs. SPQ, WRR, DWRR and WFQ are WC method. On the other hand, even if there is no
congestion, NWC (Non Work Conserving) scheduler does not service more than bandwidth
that is assigned queue. Shaping is this method.
Target Traffic Rate
Offered Traffic
Bandwidth(bps)
time
Rate Shaped Traffic
Bandwidth(bps)
time
Buffered