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Overview of CoS Upgrade Requirements to Junos OS Release 12.2

 

Before you upgrade to Junos OS Release 12.2, you might need to edit the class-of-service (CoS) configuration, because the way the QFX Series handles lossless forwarding classes has changed in Junos OS Release 12.2.

By default, the fcoe and no-loss forwarding classes are mapped to output queue 3 and output queue 4, respectively. These are the only two forwarding classes (and the only two queues) that support lossless transport.

In Junos OS Release 12.1 and earlier, explicitly setting the lossless fcoe and no-loss forwarding classes resulted in the same CoS behavior as using the default configuration. However, in Junos OS Release 12.2, the behavior when you explicitly configure the lossless forwarding classes differs from the behavior when you use the default forwarding classes.

Note

The default behavior differs from the explicit configuration behavior even if the explicit configuration is exactly the same as the default configuration.

  • If you use the default forwarding class configuration for the lossless queues (the configuration does not include explicit setting of the fcoe or the no-loss forwarding classes), then the fcoe and no-loss queues behave as lossless queues.

    If your CoS configuration does not explicitly configure the fcoe and no-loss forwarding classes, you can upgrade from Junos OS Release 12.1 to Junos OS Release 12.2, and the behavior of the two lossless queues remains the lossless.

  • If your configuration includes statements that explicitly configure the fcoe or the no-loss forwarding class (using the [set class-of-service forwarding-classes class class-name queue-num queue-number] statement), after you upgrade to Junos OS Release 12.2, those queues do not receive lossless treatment and behave as lossy (best-effort) queues.

    If your CoS configuration explicitly configures the fcoe and no-loss forwarding classes, to retain the lossless behavior of those queues, you need to remove the explicit configuration for these two forwarding classes from the CoS configuration before you upgrade.

If you upgrade to Junos OS Release 12.2 and the fcoe and no-loss forwarding classes are explicitly configured, then those two queues continue to be used, but the traffic is treated as lossy traffic, not lossless traffic. To make the queues for these two forwarding classes lossless, you must delete the explicit forwarding class configuration.

Caution

If you explicitly configured the fcoe or the no-loss forwarding class and you upgrade to Junos OS Release 12.2, the system does not return an upgrade error or a commit error, or a generate a syslog message, to notify you that these forwarding classes are no longer lossless. Traffic mapped to these forwarding classes is not treated as lossless traffic until you remove the explicit forwarding class configuration.

Before you upgrade, delete the fcoe and no-loss forwarding classes from the explicit configuration to preserve the lossless behavior of traffic mapped to these forwarding classes.

  • To delete the explicit fcoe forwarding class configuration:

    [edit]

    user@switch# delete class-of-service forwarding-class class fcoe queue-num 3

    user@switch# commit
  • To delete the explicit no-loss forwarding class configuration:

    [edit]

    user@switch# delete class-of-service forwarding-class class no-loss queue-num 4

    user@switch# commit
Note

If you try to delete these forwarding classes and they have not been explicitly configured on the system, the system returns the message warning: statement not found. This simply means that there is no explicit configuration to delete and does not change the lossless behavior of the fcoe and no-loss forwarding classes.

After you delete the explicit configuration for the fcoe and no-loss forwarding classes, traffic mapped to those forwarding classes retains its lossless behavior after the upgrade to Junos OS Release 12.2.