Brocade Fabric OS Administrators Guide (Supporting Fabric OS v7.3.0) - Manual (Page 383)

QoS on E_Ports
In addition to configuring the hosts and targets in a zone, you must also enable QoS on individual
E_Ports that might carry traffic between the host and target pairs. Path selection between the
"host,target" pairs is governed by FSPF rules and is not affected by QoS priorities. For example, in the
following figure, QoS should be enabled on the encircled E_Ports.
NOTE
By default, QoS is enabled on 8-Gbps or higher ports, except for long-distance 8-Gbps ports. QoS is
disabled by default on all 4-Gbps ports and long-distance 8-Gbps ports.
FIGURE 51 QoS with E_Ports enabled
You must enable QoS on the E_Ports on both ISLs between domain 3 and domain 4, because either
path might be selected to carry the traffic.
You do not need to enable QoS on the E_Ports on the ISLs between domain 1 and domain 2 and
between domain 2 and domain 3, because these are not the shortest paths between the hosts and the
targets. However, if the ISL between domain 1 and domain 3 is broken, then the path through domain 2
would be used.
To guarantee traffic priority, you should enable QoS on all possible E_Ports. Alternatively, you could
use a TI zone to limit the E_Ports that carry the traffic between a "host,target" pair and enable QoS on
only those E_Ports.
If QoS is not enabled on an E_Port, the traffic prioritization stops at that point. For example, in the
above figure if you disabled QoS on E_Ports "3,12" and "3,13," then the traffic from H1 and H2 to S3
would be low priority from the hosts to domain 3, but would change to the default (medium) priority from
domain 3 to the target S3.
QoS over FC routers
QoS over FC routers uses QoS traffic prioritization between devices in edge fabrics over an FC router.
Refer to
Using FC-FC Routing to Connect Fabrics on page 533 for information about FC routers,
phantom switches, and the FC-FC Routing Service.
To establish QoS over FC routers, you must perform the following tasks:
QoS on E_Ports
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