H3C S9500 Series Operation Manual page 1031

Operation Manual – QoS
H3C S9500 Series Routing Switches
Packets sent via this
interface
Figure 1-3 Priority queues
SP algorithm is designed for key services. One of the characteristics of key services is
these services should be processed preferentially to minimize response delay in event
of congestion. For example, there are eight output queues at the port, numbered
respectively as 7 to 0, with priority levels in descending order.
In SP mode, the system first sends those packets of higher priority in strict accordance
with priority order. Only when packets in high priority queue are all sent can those in
lower priority queue be sent. This manner of putting key-service packets into high
priority queues and non-key service packets into low priority queues does ensure that
key-service packets are sent first, while non-key service packets are sent during the
interval when no key-service packets need processed.
SP algorithm also has its disadvantages: If high priority queues are full, then packets
from the low priority queues may not be forwarded.
2) WRR algorithm
Each port supports eight output queues except that port of the GV48D/GP48D/XP4
non-wire-speed board only supports four queues. In WRR mode, the system processes
the queues by turn, so every queue can have a service period.
See the case where the port supports eight output queues. Every queue is assigned
with a weight value (respectively numbered as w7, w6, w5, w4, w3, w2, w1, and w0),
which indicates the weight in obtaining resources. For a 100 Mbps port, the weight
values are set as 50, 30, 10, 10, 50, 30, 10 and 10 (corresponding respectively to w7,
w6, w5, w4, w3, w2, w1, and w0). The even the queue with the lowest priority can be
allocated with a 5 Mbps bandwidth.
High priority
Queue 7
Queue 6
Queue 5～2
Classify
Queue 1
Low priority
Queue 0
dequeue
1-4
Chapter 1 QoS Configuration
Packets sent
Sending
queue