Introduction To Scheduling; Priority; Weighted Fair Queuing (Wfq); Packet Routing In Iplink - Patton electronics IPLink 3210 Series Getting Started Manual

IPLink 3210 Series Getting Started Guide
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 17 on page 74 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.
IPSec encryption/
decryption
Access control
list (ACL)
Network address
translation (NAT)
Link Scheduler
The QoS features in IPLink 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. IPLink uses the priority scheme to make sure that voice packets generated by the
IPLink 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)
Local applications (CLI, Web Server)
Routing
To/from network port (Ethernet, PPPoE,
Frame relay, etc.)
Figure 17. Packet routing in IPLink
7 • Link scheduler configuration
Sequence of processing stages
passed by a routed packet
74