Extreme Networks ExtremeWare XOS 11.1, Manual

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QoS Profiles
ExtremeWare XOS 11.1 Concepts Guide
205
QoS Profiles
QoS profiles are configured differently on the Aspen 8810 switch and on the BlackDiamond 10K switch.
QoS Profiles on the Aspen 8810 Switch Only
The Aspen 8810 switch has two default queues, QP1 and QP8, which are based on traffic flows. QP1 has
the lowest priority, and QP8 has the highest priority. You can configure up to six additional QoS
profiles, or queues, on the switch, QP2 through QP7. Creating a queue dynamically will not cause loss
of traffic. You can also modify the default parameters of each QoS profile. The names of the QoS
profiles, QP1 through QP8, are not configurable.
The parameters that make up a QoS profile on the Aspen 8810 switch include:
●
Buffer—This parameter is the maximum amount of packet buffer memory available to all packets
associated with the configured QoS profile within all affected ports. All QoS profiles use 100% of
available packet buffer memory by default. You can configure the buffer amount from 1 to 100%, in
whole integers. Regardless of the maximum buffer setting, the system does not drop any packets if
any packet buffer memory remains to hold the packet and the current QoS profile buffer use is
below the maximum setting.
NOTE
Use of all 8 queues on all ports may result in insufficient buffering to sustain 0 packet loss throughput during
full-mesh connectivity with large packets.
●
Weight—This parameter is the relative weighting for each QoS profile; 1 through 16 are the available
weight values. The default value for each QoS profile is 1, giving each queue equal weighting. When
you configure a QoS profile with a weight of 4, that queue is serviced 4 times as frequently as a
queue with a weight of 1. However, if you configure all QoS profiles with a weight of 16, each queue
is serviced equally but for a longer period of time.
Finally, you configure the scheduling method that the entire switch will use to empty the queues. The
scheduling applies globally to the entire switch, not to each port. You can configure the scheduling to be
strict priority, which is the default, or weighted round robin. In the strict priority method, the switch
services the higher-priority queues first. As long as a queued packet remains in a higher-priority queue,
any lower-priority queues are not serviced. If you configure the switch for weighted-round-robin
scheduling, the system services all queues based on the weight assigned to the QoS profile. The
hardware services higher-weighted queues more frequently, but lower-weighted queues continue to be
serviced at all times.
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 210 ). 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 213 ).