Technical data

BMD00136, November 2009 97
CHAPTER 7
Quality of Service
Quality of Service features allow you to allocate network resources to mission-critical applications
at the expense of applications that are less sensitive to such factors as time delays or network
congestion. You can configure your network to prioritize specific types of traffic, ensuring that each
type receives the appropriate Quality of Service (QoS) level.
The following topics are discussed in this section:
 “QoS Overview” on page 97
 “Using ACL Filters” on page 99
 “Using DSCP Values to Provide QoS” on page 108
 “Using 802.1p Priorities to Provide QoS” on page 112
 “Queuing and Scheduling” on page 113
QoS Overview
QoS helps you allocate guaranteed bandwidth to the critical applications, and limit bandwidth for
less critical applications. Applications such as video and voice must have a certain amount of
bandwidth to work correctly; using QoS, you can provide that bandwidth when necessary. Also, you
can put a high priority on applications that are sensitive to timing out or cannot tolerate delay by
assigning that traffic to a high-priority queue.
By assigning QoS levels to traffic flows on your network, you can ensure that network resources are
allocated where they are needed most. QoS features allow you to prioritize network traffic, thereby
providing better service for selected applications.
Figure 13 shows the basic QoS model used by the RackSwitch G8000 (G8000).