ATL Telecom R1-SW Ethernet Switch - Manual (Page 178)

R1-SW24L2B User’s Manual
9-10
WRR (Weight Round Robin)
WRR method processed every queue in sequence to remove starvation that happens in SPQ
(Strict Priority Queuing). The packet size that process packets each time can be set for each
queue instead. A value, called weight, is used to set the packet size. The weight represents the
ratio of packets that is serviced through the queues.
If weight values (2, 1, 1) are assigned to each queue as above, the ratio of packets are 2:1:1. It
means that two packets are transmitted through the first queue (Q1), and a packet is
transmitted through the second queue (Q2), then a packet is transmitted through the third
queue (Q3).
WRR method can specify priority to each queue and prohibit starvation as above. The
disadvantage of WRR is not useful in IP network that packet size is variable because weight is
ratio of packets. For example, there are two packets. One is 64byte VoIP packet, and the other is
1500byte data packet. The packets are serviced through two queues that weight is 2:1. Even
though the VoIP packet is serviced through high weight queue, 128bytes are sent each time, but
the 1500byte data packet can be sent through the low weight queue.
[Q1] Weight: 2
[Q2] Weight: 1
[Q3] Weight: 1
300B 200B 400B 300B 100B
600B 300B 400B
WRR Scheduler
400B 500B 500B
Output Port