ATL Telecom R1-SW Ethernet Switch - Manual (Page 180)

R1-SW24L2B User’s Manual
9-12
The DWRR scheduler visits the number 1 of queue, then deficit counter value becomes
1000bytes. 300byte, 100byte and 400byte packets are transmitted through output port. After the
transmission, the deficit counter value becomes 200 (Picture 2).
The DWRR scheduler visits the number 2 of queue. The number 2 of deficit counter set the
value as 500byte, then 500byte packet is transmitted. After the transmission, the deficit counter
value becomes 0. The next time the number 3 of queue should be processed, but the first packet
in the number 3 of queue is 600byte and is bigger than deficit counter of 500byte. In this case,
deficit counter is not changed, and no packet is transmitted.
The DWRR scheduler visits the number 1 of queue again, then the quantum value is added to
the current deficit counter value. In this time, the deficit counter value becomes 1200bytes, and
the number 1 of queue can transmit packets up to 1200byte. 300byte and 200byte packets can be
transmitted, then deficit counter becomes 700 (Picture 3).
There is no packet in the number 1 of queue, so the DWRR scheduler visits the number 2 of
queue. The deficit counter is set as 500byte, and 500byte packet is transmitted in the number 2
of queue, then deficit counter becomes 0. In the num 3 of queue that could not transmit packets
300B 200B 400B 300B 100B
600B 300B 400B
Output Port
DWRR
Scheduler
400B 500B 500B
[Q1] Weight: 2
Quantum=
1000 , DeficiCounter= 0B
[Q2] Weight: 1
Quantum=
500 , DeficitCounter= 0B
[Q3] Weight: 1
Quantum=
500 , DeficitCounter= 0B
300B 200B
600B 300B 400B
Output Port
DWRR
Scheduler
400B 500B 500B
[Q1] Weight: 2
Quantum=1000, DeficiCounter=
200B
[Q2] Weight: 1
Quantum=500, DeficitCounter=
0B
[Q3] Weight: 1
Quantum=500, DeficitCounter=
0B
400B 300B 100B
1000B - 300B - 100B - 400B
[Picture 1]
600B 300B 400B
DWRR
Scheduler
400B 500B
[Q1] Weight: 2
Quantum=1000, DeficiCounter=
700B
[Q2] Weight: 1
Quantum=500, DeficitCounter=
0B
[Q3] Weight: 1
Quantum=500, DeficitCounter=
500B
Output Port
300B 200B
1200B - 300B - 200B
400B
DWRR
Scheduler
400B
[Q1] Weight: 2
Quantum=1000, DeficiCounter=
0B
[Q2] Weight: 1
Quantum=500, DeficitCounter=
0B
[Q3] Weight: 1
Quantum=500, DeficitCounter=
100B
1000B - 600B - 300B
Output Port
600B 300B
[Picture 2]
[Picture 3] [Picture 4]