Patton electronic 2800 user manual Introduction to Scheduling, Priority, Weighted fair queuing WFQ

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.

Local applications (CLI, Web Server)

Routing

IPSec encryption/ decryption

Access control list (ACL)

Network address translation (NAT)

Link Scheduler

Sequence of processing stages passed by a routed packet

To/from network port (Ethernet, PPPoE,

Frame relay, etc.)

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.

Configuring quality of service (QoS) 96