Switch 7700 Configuration Guide, v2

QoS Overview 197
This random number is compared with the discarding probability for the
current queue. Any packet whose random number is greater than the
probability is discarded. The longer the queue, the higher the discarding
probability . However, there is a maximum discarding probability.
Through randomly discarding packets, RED avoids global TCP synchronism. When
some packets of a TCP connection are discarded and the transmission speed is
lowered, other TCP connections can still keep the higher transmission speed. In
this way, there are always some TCP connections with higher transmission speeds,
that make a better use of the line bandwidth.
Configuring QoS QoS configuration includes:
■ Traffic Policing
■ Configure Priority Marking
■ Configure Queue Scheduling
■ Configure the RED Operation
■ Configure Bandwidth Assurance
■ Configure Traffic Statistics
Before configuring these QoS tasks, you must define the corresponding ACL. The
packet filtering function is realized by activating the ACL.
Traffic Policing
Traffic policing is the flow-based rate limit. It takes corresponding actions to deal
with the flows at excessive speed, such as discarding or lowering the priority.
Perform the following configuration in Ethernet port view.
You have to define the corresponding ACL before performing this configuration
task.
The purpose of this configuration task is to implement traffic policing over the
data flow matching the ACL. The traffic beyond the limit will be dealt with in
some other way, such as discarding.
For details about the command, see the Switch 7700 Command Reference Guide.
Configure Priority Marking
Configuring priority-marking creates a policy to tag the priority of the packets so
they match the ACL. The new priority can be filled in the priority field of the
packet header.
Table 10 Configure Rate Limit
Operation Command
Configure the flow-based rate limit traffic-limit { inbound | outbound } { ip-group {
acl-number | acl-name } [ rule rule ] | link-group {
acl-number | acl-name } [ rule rule ] } target-rate
Cancel the configuration of the
flow-based rate limit
undo traffic-limit { inbound | outbound } { ip-group {
acl-number | acl-name } [ rule rule ] | link-group {
acl-number | acl-name } [ rule rule ] }