Quality of Service
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Quality of Service
Introduction
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:
• Quality of Service Overview
• Using ACL Filters
• Using DSCP Values to Provide QoS
• Using 802.1p Priorities to Provide QoS
• Queuing and Scheduling
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. Traffic for applications that
are sensitive to timing out or cannot tolerate delay can be assigned 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.
The following figure shows the basic QoS model used by the HP 10GbE switch.
Figure 11 QoS model
Ports
ACL
Filter
ACL
Meter
Drop/Pass/
Re-Mark
Classify
Packets
Perform
Actions
Egress
Ingress
COS
Queue
Meter
Traffic
Queue and
Schedule
The switch uses the Differentiated Services (DiffServ) architecture to provide QoS functions. DiffServ
is described in IETF RFCs 2474 and 2475.
With DiffServ, you can establish policies to direct traffic. A policy is a traffic-controlling mechanism
that monitors the characteristics of the traffic, (for example, its source, destination, and protocol) and
performs a controlling action on the traffic when certain characteristics are matched.
The switch can classify traffic by reading the IEEE 802.1p priority value, or by using filters to match
specific criteria. When network traffic attributes match those specified in a traffic pattern, the policy
instructs the switch to perform specified actions on each packet that passes through it. The packets are
assigned to different Class of Service (COS) queues and scheduled for transmission.
