ProLiant BL p-Class GbE2 Interconnect Switch Application Guide

Quality of Service 73
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 GbE2.
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 GbE2 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 GbE2 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 GbE2 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.
The basic GbE2 QoS model works as follows:
• Classify traffic:
• Read DSCP
• Read 802.1p Priority
• Match ACL filter parameters
• Meter traffic:
• Define bandwidth and burst parameters
• Select actions to perform on in-profile and out-of-profile traffic