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Configuring CoS Hierarchical Schedulers

In metro Ethernet environments, a VLAN typically corresponds to a customer premises equipment (CPE) device and the VLANs are identified by an inner VLAN tag on Ethernet frames (called the customer VLAN, or C-VLAN, tag). A set of VLANs can be grouped at the DSL access multiplexer (DSLAM) and identified by using the same outer VLAN tag (called the service VLAN, or S-VLAN, tag). The service VLANs are typically gathered at the Broadband Remote Access Server (BRAS) level, which can be (among other devices) an SRX-series device. On SRX 5600 and SRX 5800 devices, hierarchical schedulers let you provide shaping and scheduling at the service VLAN level as well as other levels, such as the physical interface. In other words, you can group a set of logical interfaces and then apply scheduling and shaping parameters to the logical interface set as well as other levels.

This basic architecture is shown in Figure 95. You can apply class-of-service (CoS) parameters at the premises on the CPE, on the customer or service VLANs, at the BRAS level, or at all levels.

Figure 95: An SRX-series Device in a Hierarchical Scheduler Architecture

Image g016864.gif

On SRX 5600 and SRX 5800 devices, you can apply CoS shaping and scheduling at one of four different levels, including the VLAN set level.

The supported scheduler hierarchy is as follows:

The physical interface (level 1)
The service VLAN (level 2 is unique to SRX-series devices)
The logical interface or customer VLAN (level 3)
The queue (level 4)

You can specify a traffic control profile (output-traffic-control-profile) that can specify a shaping rate, a guaranteed rate, and a scheduler map with transmit rate and buffer delay. The scheduler map contains the mapping of queues (forwarding classes) to their respective schedulers (schedulers define the properties for the queue). Queue properties can specify a transmit rate and buffer management parameters such as buffer size and drop profile. For more information, see Defining Schedulers.

To configure CoS hierarchical schedulers, include the following statements at the [edit class-of-service interfaces] and [edit interfaces] hierarchy levels:



[edit class-of-service interfaces]
interface-set interface-set-name {
excess-bandwith-share (proportional value | equal);
internal-node;
output-traffic-control-profile profile-name;
output-traffic-control-profile-remaining profile-name;
}



[edit interfaces]
hierarchical-scheduler;
interface-set interface-set-name {



ethernet-interface-name {
(interface-parameters);
}


}

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