Foundry Networks FESX User Manual

Configuring Quality of Service
December 2005 © Foundry Networks, Inc. 13 - 11
The <queue> parameter specifies the hardware forwarding queue to which you are reassigning the priority. The
default queue names are as follows:
• qosp7
• qosp6
• qosp5
• qosp4
• qosp3
• qosp2
• qosp1
• qosp0
Scheduling
Scheduling is the process of mapping a packet to an internal forwarding queue based on its QoS information, and
servicing the queues according to a mechanism.
This section describes the scheduling methods used on the FESX, FSX, and FWSX.
QoS Queuing Methods
The following QoS queuing methods are supported in all IronWare software releases for the FastIron FESX and
FSX.
• Weighted Round Robin (WRR) – WRR ensures that all queues are serviced during each cycle. A weighted
fair queuing algorithm is used to rotate service among the eight queues on FESX, FSX, and FWSX devices.
The rotation is based on the weights you assign to each queue. This method rotates service among the
queues, forwarding a specific number of packets in one queue before moving on to the next one.
WRR is the default queuing method and uses a default set of queue weights.
The number of packets serviced during each visit to a queue depends on the percentages you configure for
the queues. The software automatically converts the percentages you specify into weights for the queues.
NOTE: Queue cycles on the FESX, FSX, and FWSX are based on bytes. These devices service a given
number of bytes (based on the weight) in each queue cycle. FES and BI/FI queue cycles are based on
packets.
The bytes-based scheme is more accurate compared to a packets-based scheme if packets vary greatly in
size.
• Strict Priority(SP) – SP ensures service for high priority traffic. The software assigns the maximum weights
to each queue, to cause the queuing mechanism to serve as many packets in one queue as possible before
moving to a lower queue. This method biases the queuing mechanism to favor the higher queues over the
lower queues.
For example, strict queuing processes as many packets as possible in qosp3 before processing any packets
in qosp2, then processes as many packets as possible in qosp2 before processing any packets in qosp1, and
so on.
Starting with software release 02.2.00, an additional configurable queueing mechanism combines both the strict
priority and weighted round robin mechanisms. The combined method enables the Foundry device to give strict
priority to delay-sensitive traffic such as VOIP traffic, and weighted round robin priority to other traffic types.
By default, when you select the combined SP and WRR queueing method, the Foundry device assigns strict
priority to traffic in qosp7 and qosp6, and weighted round robin priority to traffic in qosp0 through qosp5. Thus, the

Foundry Networks FESX Specifications

General

Brand	Foundry Networks
Model	FESX
Category	Switch
Language	English