Qos Supported By The S7500 Series Ethernet Switches - H3C S7500 Series Operation Manual

Operation Manual – QoS
H3C S7500 Series Ethernet Switches
In the RED algorithm, an upper limit and a lower limit are set for each queue, and it is
stipulated that:
When the queue length is smaller than the lower limit, no packet is dropped.
When the queue length is bigger than the upper limit, all received packets all
dropped.
When the queue length is in the range of the upper limit and the lower limit, the
received packets are dropped at random. In this case, a number is assigned to
each received packet and then compared with the drop probability of the current
queue. If the assigned number is bigger than the drop probability, the received
packet is dropped. The longer a queue is, the higher the drop probability is.
However, there is a maximum drop probability.
In the RED algorithm, packets are dropped at random so that global TCP
synchronization is avoided. When packets in a TCP connection are dropped and sent
at a low rate, packets in other TCP connections are still sent at a high rate. In this way,
packets in a part of TCP connections are sent at a high rate in any case. Thus, the
utilization rate of bandwidth is improved.

1.2 QoS Supported by the S7500 Series Ethernet Switches

Table 1-4 QoS features supported by the S7500 series Ethernet switches and related
commands
Priority mapping
Port priority
Priority according to which
a packet is put into an
output queue
TP
Priority marking
Redirect
Queue scheduling
Rate limiting
Guaranteed bandwidth
Congestion avoidance
Traffic statistics
Inbound CAR
QoS Specification
Support only the
802.1p-priority-to-
local-queue
mapping
Supported
Supported
Supported
Supported
Supported
Support SP, RR
and WRR
Supported
Supported
RED operation
Supported
Supported
qos cos-local-precedence-map
priority priority-level
priority-trust
traffic-limit
traffic-priority
traffic-redirect
queue-scheduler
line-rate
traffic-bandwidth
traffic-red
traffic-statistic
inboundcar { enable | disable }
1-11
Chapter 1 QoS Configuration
Related command