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Configuring quality of service (QoS) 96
OnSite 2800 Series User Manual 8 • Link scheduler configuration
can be used to mark a specific packet type for the other network nodes. By default the traffic-class tag is empty.
Refer to figure 18 on page 96 when using the ACL to classify traffic. It illustrates the sequence of processing
stages every routed packet passes. Only stages that have been installed in the data path with a “use profile...”
statement in the corresponding interface configuration are present. Both an input direction ACL on the receiv-
ing interface as well as an output ACL on the transmitting interface can be used to classify a packet for special
handling by the output link scheduler on the transmit interface. But as visible from the figure no ACL can be
used for an input link scheduler.
Figure 18. Packet routing in OnSite
The QoS features in OnSite are a combination of an access control list (used for packet classification) and a ser-
vice-policy profile (used by the link arbiter to define the arbitration mode and the order in which packets of
different classes are served).
Introduction to Scheduling
Scheduling essentially means to determine the order in which packets of the different traffic-classes are served.
The following sections describe the ways this arbitration can be done.
Priority
One way of ordering packets is to give priority to one traffic-class and to serve the other traffic-classes when the
first has nothing to send. OnSite uses the priority scheme to make sure that voice packets generated by the
OnSite will experience as little delay as possible.
Weighted fair queuing (WFQ)
This arbitration method assures a given minimal bandwidth for each source. An example: you specify that traf-
fic-class A gets three times the bandwidth of traffic-class B. So A will get a minimum of 75% and B will get a
minimum of 25% of the bandwidth. But if no class A packets are waiting B will get 100% of the bandwidth.
Link Scheduler
Network address
translation (NAT)
Access control
list (ACL)
IPSec encryption/
decryption
Local applications (CLI, Web Server)
To/from network port (Ethernet, PPPoE,
Frame relay, etc.)
Routing
Sequence of processing stages
passed by a routed packet