xStack
®
DGS-3400 Series Layer 2 Gigabit Ethernet Managed Switch
175
• Priority 0 is assigned to the Switch’s Q2 queue.
• Priority 1 is assigned to the Switch’s Q0 queue.
• Priority 2 is assigned to the Switch’s Q1 queue.
• Priority 3 is assigned to the Switch’s Q3 queue.
• Priority 4 is assigned to the Switch’s Q4 queue.
• Priority 5 is assigned to the Switch’s Q5 queue.
• Priority 6 is assigned to the Switch’s Q6 queue.
• Priority 7 is assigned to the Switch’s Q6 queue.
For strict priority-based scheduling, any packets residing in the higher priority classes of service are transmitted first. Multiple
strict priority classes of service are emptied based on their priority tags. Only when these classes are empty, are packets of lower
priority transmitted.
For weighted round-robin queuing, the number of packets sent from each priority queue depends upon the assigned weight. For a
configuration of 8 CoS queues, A~H, with their respective weight value: 8~1. When each queue has 10 outbound packets, they are
sent in the following sequence:
A1, B1, C1, D1, E1, F1, G1, H1,
A2, B2, C2, D2, E2, F2, G2,
A3, B3, C3, D3, E3, F3,
A4, B4, C4, D4, E4,
A5, B5, C5, D5,
A6, B6, C6,
A7, B7,
A8,
A9, B8, C7, D6, E5, F4, G3, H2,
A10, B9, C8, D7, E6, F5, G4
B10, C9, D8, E7, F6,
C10, D9, E8,
D10,
E9, F7, G5, H3,
E10, F8, G6,
F9,
F10, G7, H4,
G8,
G9, H5,
G10, H6 ~ H10
For weighted round-robin queuing, if each CoS queue has the same weight value, then each CoS queue has an equal opportunity
to send packets just like round-robin queuing.
For weighted round-robin queuing, if the weight for a CoS is set to 0, then it will continue processing the packets from this CoS
until there are no more packets for this CoS. The other CoS queues that have been given a nonzero value, and depending upon the
weight, will follow a common weighted round-robin scheme.
Remember that the xStack
®
DGS-3400 switch series has 7 configurable priority queues (and seven Classes of Service) for each
port on the Switch.
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