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Hierarchical Class of Service for Subscriber Management Overview

The hierarchical class-of-service (HCoS) architecture as supported on fine-grained queuing MPCs is a powerful feature designed to provide a flexible and scalable CoS solution in broadband network gateway (BNG) subscriber access applications where triple-play or business class offerings are enabled through IP CoS.

Hierarchical CoS enables you to apply traffic scheduling and queuing parameters (which can include a delay-buffer bandwidth) and packet transmission scheduling parameters (which can include buffer management parameters) to an individual subscriber interface rather than to all interfaces configured on the port. HCoS enables you to dynamically modify queues when subscribers require services.

The logical interface set construct in a five-level scheduler hierarchy is the key feature that enables HCoS. The interface set feature allows you to group subscribers into aggregate classes with specific guaranteed and peak rates that map to service classes. Service classes ultimately map to how much you can charge for the differentiated service levels.

HCoS can be applied dynamically through the use of dynamic traffic profiles and RADIUS vendor-specific attributes (VSAs).

Dynamic traffic profiles are used to dynamically apply CoS to individual subscribers or groups of subscribers. This enables you, as a service provider, to deploy a BRAS solution without having to manually provision each customer. In a dynamic traffic profile, variables are used to represent the values for things like shaping rate and drop priority.

Dynamic traffic profiles are used in conjunction with dynamic profiles. Dynamic profiles allow you to dynamically provision IP service definitions by creating a template configuration and having the specific variable values assigned in real time when the subscriber authenticates to the network.


For a complete list of the Junos OS system variables, see: Junos OS Predefined Variables.

To learn more about how to use HCoS in conjunction with dynamic traffic control profiles for subscriber management, read the Day One: Dynamic Subscriber Management book. Note that you will need to have a login and password to access this document.

In addition, the following topics are very helpful:

Before applying dynamic HCoS on your network, you should learn about HCoS, define your needs, plan how you want to implement HCoS, and test the operation in a simulated environment.