The most common technique for dealing with congestion is to provide sufficient buffering so that large bursts of data can be accommodated. Unfortunately, buffering can introduce jitter in multimedia data streams. The following sections discuss additional techniques for dealing with congestion. The Cisco IOS supports several traffic-shaping techniques that allow multimedia applications to be run over WANs while minimizing jitter. Using the Cisco IOS, network administrators can give priority to certain categories of traffic in order to minimize latency and packet loss in moments of temporary network congestion.
Priority queuing designates certain traffic to always receive priority treatment.
When high-priority traffic is present, other traffic is not allowed to use the link. Custom queuing allows a network administrator to reserve a specified quantity of bandwidth for different categories of traffic. For example, a network administrator could specify that 50 percent of a WAN link should be available for multimedia traffic, leaving the remaining 50 percent reserved for other traffic. If either category of traffic is not present, the other will use the extra available bandwidth. See Appendix A for details of how to configure the Cisco IOS to support traffic-shaping for ProShare conferencing.