Defining CoS Forwarding Classes

Queues 0 through 7 are for unicast traffic and queues 8 through 11 are for multicast traffic. Forwarding classes mapped to unicast queues must carry unicast traffic, and forwarding classes mapped to multidestination queues must carry multidestination traffic. There are four default unicast forwarding classes and one default multidestination forwarding class.

The default forwarding classes, except on NFX Series devices, are:

• best-effort—Best-effort traffic

• fcoe—Guaranteed delivery for Fibre Channel over Ethernet traffic (do not use on OCX Series switches)

• no-loss—Guaranteed delivery for TCP no-loss traffic (do not use on OCX Series switches)

• network-control—Network control traffic

The default multidestination forwarding class, except on QFX10000 switches and NFX Series devices, is:

• mcast—Multidestination traffic

The NFX Series devices have the following default forwarding classes:

• best-effort (be)—Provides no service profile. Loss priority is typically not carried in a CoS value.

• expedited-forwarding (ef)—Provides a low loss, low latency, low jitter, assured bandwidth, end-to-end service.

• assured-forwarding (af)—Provides a group of values you can define and includes four subclasses: AF1, AF2, AF3, and AF4, each with two drop probabilities: low and high.

• network-control (nc)—Supports protocol control and thus is typically high priority.

You can map forwarding classes to queues using the class statement. You can map more than one forwarding class to a single queue. You cannot mix unicast and multicast forwarding classes on the same queue.

All of the forwarding classes mapped to the same queue must have the same packet drop attribute: either all of the forwarding classes must be lossy or all of the forwarding classes must be lossless. This is important because the default fcoe and no-loss forwarding classes have the no-loss drop attribute.

One example is to create a forwarding class named be2 and map it to queue 1:

Another example is to create a lossless forwarding class named fcoe2 and map it to queue 5:

Note:

On switches that do not run ELS software, use the default forwarding-class-to-queue mapping for the lossless fcoe and no-loss forwarding classes. If you explicitly configure the lossless forwarding classes, the traffic mapped to those forwarding classes is treated as lossy (best-effort) traffic and does not receive lossless treatment unless you include the optional no-loss packet drop attribute.