Allied Telesis AT-8550 - Manual (Page 112)

QoS Profiles and QoS Mode Details
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QoS Profiles and QoS Mode Details
As indicated previously, changing the default QoS mode from
ingress to egress is typically not necessary. In ingress mode, the QoS
profiles qp1 through qp4 are mapped directly to the four hardware
queues on every switch port. Any changes to parameters of the four
pre-defined QoS profiles have the corresponding effect on the ports.
The direct mapping is straight-forward to understand and configure.
In egress mode, there is no fixed mapping of Qos profiles to
hardware queues, except for the default QoS profile
qp1 , which is
mapped to the first of the four hardware queues. Qos profiles qp2
through qp4, and any user-defined QoS profiles, are mapped to the
remaining 3 queues in the order in which they are defined.
The default profiles cannot be deleted, but they can be redefined. If
more than 4 profiles are in use, then the additional profiles share the
existing hardware queues of the same priority. For example, if qp5 is
created with a priority of medium, this causes qp5 to share the same
hardware queue being used by qp3. IPQoS policy-to-hardware
queue mapping occurs when a QoS profile is defined and assigned
to a QoS traffic grouping.
In egress mode, the setting of minimum and maximum bandwidth
parameters on a switch port is managed dynamically. Queue setting
at any instant at a port depends on the QoS profiles associated with
the traffic through that port. The minimum bandwidth is the sum of
all the minimum values of the QoS profiles sharing a queue. The
maximum bandwidth setting is equal to the highest bandwidth
setting of all the profiles that are sharing that queue.