Specifications

110 ExtremeWare XOS 11.0 Concepts Guide
Quality of Service
1 Configure the QoS profile.
QoS profile—A class of service that is defined through minimum and maximum bandwidth
parameters and prioritization settings. The bandwidth and level of service that a particular type of
traffic or traffic grouping receives is determined by assigning it to a QoS profile. The names of the
QoS profiles are QP1 through QP8; these names are not configurable.
2 Create traffic groupings.
Traffic grouping—A classification or traffic type that has one or more attributes in common. These
can range from a physical port to IP Layer 4 port information. You assign traffic groupings to QoS
profiles to modify switch forwarding behavior. Traffic groupings transmitting out the same port that
are assigned to a particular QoS profile share the assigned bandwidth and prioritization
characteristics and hence share the class of service.
3 Monitor the performance of the application with the QoS monitor to determine whether the policies
are meeting the desired results.
The next sections describe each of these QoS components in detail.
QoS Profiles
A QoS profile defines a class of service by specifying traffic behavior attributes, such as bandwidth. The
eight QoS profiles are named QP1 to QP8. The parameters that make up a QoS profile include:
• Minimum bandwidth—The minimum total link bandwidth that is reserved for use by a hardware
queue on a physical port (each physical port has eight hardware queues, corresponding to a QoS
profile). The minimum bandwidth value is configured either as a percentage of the total link
bandwidth or using absolute committed rates in Kbps or Mbps. Bandwidth unused by the queue can
be used by other queues. The minimum bandwidth for all queues should add up to less than 100%.
The default value on all minimum bandwidth parameters is 0%.
• Maximum bandwidth—The maximum total link bandwidth that can be transmitted by a hardware
queue on a physical port (each physical port has eight hardware queues, corresponding to a QoS
profile). The maximum bandwidth value is configured either as a percentage of the total link
bandwidth or using absolute peak rates in Kbps or Mbps. The default value on all maximum
bandwidth parameters is 100%.
• Priority—The level of priority assigned to a hardware egress queue on a physical port. There are
eight different available priority settings and eight different hardware queues. By default, each of the
default QoS profiles is assigned a unique priority. You use prioritization when two or more hardware
queues on the same physical port are contending for transmission on the same physical port, only
after their respective bandwidth management parameters have been satisfied. If two hardware
queues on the same physical port have the same priority, a round-robin algorithm is used for
transmission, depending on the available link bandwidth.
— When configured to do so, the priority of a QoS profile can determine the 802.1p bits used in the
priority field of a transmitted packet (see “Replacing 802.1p priority information” on page 113).
— The priority of a QoS profile determines the DiffServ code point value used in an IP packet when
the packet is transmitted (see “Replacing DiffServ code points” on page 116).
A QoS profile does not alter the behavior of the switch until it is assigned to a traffic grouping. Recall
that QoS profiles are linked to hardware queues. There are multiple hardware queues per physical port.
By default, a QoS profile links to the identical hardware queue across all the physical ports of the
switch.