408 Fabric OS Administrator’s Guide
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QoS zones
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FIGURE 62 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 62 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.
•Define LSAN zones in each edge fabric.
•Enable QoS on the E_Ports (or VE_Ports) in each edge fabric.
•Enable QoS on the EX_Ports (or VEX_Ports) in the backbone fabric.
See “Setting traffic prioritization over FC routers” on page 415 for detailed instructions.
Following are requirements for establishing QoS over FCR:
•QoS over FC routers is supported in Brocade native mode only. It is not supported in
interopmode 2 or interopmode 3.
7
12
3
14
15
16
8
13
Domain 1 Domain 3
Domain 4
Domain 2
H1
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S3
S2
S1
H2
= High priority
= Medium priority
= Low priority
= E_Ports with
QoS enabled