Allied Telesis AT-S63 - Manual (Page 322)

Chapter 16: Quality of Service
322 Section II: Advanced Operations
5 - DSCP value
Specifies a replacement value to write into the DSCP (TOS) field of the
packets. The range is 0 to 63.
A new DSCP value can be set at all three levels: flow group, traffic
class, and policy. A DSCP value specified in a flow group overrides a
DSCP value specified at the traffic class or policy level. A DSCP value
specified at the traffic class level is used only if no value has been
specified at the flow group level. It will override any value set at the
policy level.
6 - Max Bandwidth
Specifies the maximum bandwidth available to the traffic class. This
parameter determines the maximum rate at which the ingress port
accepts data belonging to this traffic class before either dropping or
remarking occurs, depending on option 3, Exceed Action. If the sum of
the maximum bandwidth for all traffic classes on a policy exceeds the
(ingress) bandwidth of the port to which the policy is assigned, the
bandwidth for the port takes precedence and the port discards packets
before they can be classified. The range is 0 to 1016 Mbps.
The value for this parameter is rounded up to the nearest Mbps value
when this traffic class is assigned to a policy on a 10/100 port, and up
to the nearest 8 Mbps value when assigned to a policy on a gigabit
port (for example, on a gigabit port, 1 Mbps is rounded to 8 Mbps, and
9 is rounded to 16).
Note
If this option is set to 0 (zero), all traffic that matches that traffic class
is dropped. However, a access control list can be created to match
the traffic that is marked for dropping, or a subset of it, and given an
action of permit, to override this. This functionality can be used to
discard all but a certain type of traffic. For more information about
configuring access control lists, see Chapter 14, “Access Control
Lists” on page 269.
7 - Burst Size
Specifies the size of a token bucket for the traffic class. The token
bucket is used in situations where you have set a maximum bandwidth
for a class, but where traffic activity may periodically exceed the
maximum. A token bucket can provide a buffer for those periods where
the maximum bandwidth is exceeded.
Tokens are added to the bucket at the same rate as the traffic class’
maximum bandwidth, set with option 6, Max Bandwidth. For example,
a maximum bandwidth of 50 Mbps adds tokens to the bucket at that
rate.
If the amount of traffic flow matches the maximum bandwidth, no traffic
is dropped because the number of tokens added to the bucket