Brocade Network Advisor SAN User Manual v12.0.0 (53-1002696-01, April 2013)

Brocade Network Advisor SAN User Manual 455

53-1002696-01

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.

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

(CoS) for an individual virtual link.

Table 60 shows examples of how priority grouping might be allocated in a 15-priority group

scenario.

Creating a DCB map

This procedure is applicable only for Fabric OS versions earlier than Fabric OS 7.0.

When you create a DCB map, each of the Class of Service (CoS) options (0-7) must be mapped to

at least one of the Priority Group IDs (0-7) and the total bandwidth percentage must equal 100. All

QoS, DCB map, and Traffic Class map configurations apply to all ports in a LAG.

There can be, at the most, 16 entries in the Priority Group table. Eight of the entries are Strict

Priority entries with a Priority Group ID (15.0 - 15.7) and eight are user-definable entries with a

Priority Group ID of 0-7. See Table 60 for an example of priority group configuration.

TABLE 60 Priority 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