Brocade Fabric OS Administrator's Guide Supporting Fabric OS v6.3.0 (53-1001336-02, November 2009)

428 Fabric OS Administrator’s Guide
53-1001336-02
QoS: SID/DID traffic prioritization
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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
Figure 65, QoS should be enabled on the encircled E_Ports.
NOTE
By default, QoS is enabled on 8 Gbps 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 65 QoS with E_Ports enabled
You need to 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
Figure 65 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 switch to the default (medium) priority
from Domain 3 to the target S3.
QoS over FC routers
QoS over FCR is QoS traffic prioritization between devices in edge fabrics over an FC router. See
Chapter 21, “Using the FC-FC Routing Service,” for information about FC routers, phantom
switches, and the FC-FC Routing Service.
To establish QoS over FC routers, you must do the following:
• Define QoS zones in each edge fabric.
7
12
3
14
15
16
8
13
Domain 1 Domain 3
Domain 4
Domain 2
H1
19
S3
S2
S1
H2
= High priority
= Medium priority
= Low priority
= E_Ports with
QoS enabled