Brocade Network Advisor SAN User Manual v11.1x (53-1002167-01, May 2011)

352 Brocade Network Advisor SAN User Manual

53-1002167-01

QoS configuration

QoS configuration involves configuring packet classification, mapping the priority and traffic class,

controlling congestion, and scheduling. The configuration of these QoS entities consist of DCB Map

and Traffic Class Map configuration.

In a Data Center Bridging (DCB) configuration, Enhanced Transmission Selection (ETS) and

Priority-based flow control (PFC) are configured by utilizing a priority table, a priority group table,

and a priority traffic table. The Traffic Class Map is the mapping of user priority to traffic class.

Enhanced Transmission Selection

Enhanced Transmission Selection (ETS) allows lower priority traffic classes to use available

bandwidth not being used by higher priority traffic classes and maximizes the use of available

bandwidth.

Priority-based flow control

Priority based flow control (PFC) is an enhancement to the existing pause mechanism in Ethernet.

PFC creates eight separate virtual links on the physical link and allows any of these links to be

paused and restarted independently, enabling the network to create a no-drop class of service for

an individual virtual link.

Table 28 shows examples of how priority grouping might be allocated in a 15-priority group

scenario.

TABLE 28 Ppriority grouping allocated in a 15-priority group example

Priority group ID Bandwidth (%) Priority flow control

055 on

125 on

20 off

30 off

45 off

50 off

615 on

70 off

15.0-15.7 Strict priority

No bandwidth % configuration

allowed