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 MX-series router. 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 15. 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 15: An MX-series Router in a Hierarchical Scheduler Architecture
On MX-series routers, you can apply CoS shaping and scheduling at one of four different levels, including the VLAN set level. You can only use this configuration on MX-series routers.
The supported scheduler hierarchy is as follows:
Users 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.
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);
- }
- }
This chapter discusses the following topics: