CoS for Subscriber Access Overview
This topic describes class-of-service (CoS) functionality for dynamic subscriber access.
JUNOS CoS enables you to divide traffic into classes and offer various levels of throughput and packet loss when congestion occurs. This allows packet loss to happen according to rules that you configure. The JUNOS CoS features provide a set of mechanisms that you can use to provide differentiated services when best-effort traffic delivery is insufficient.
In a subscriber access environment, service providers want to provide video, voice, and data services over the same network for subscribers. Subscriber traffic is delivered from the access network, through a router, through a switched Ethernet network, to an Ethernet digital subscriber line access multiplexer (DSLAM). The DSLAM, in turn, forwards the subscriber’s traffic to the residential gateway over a digital subscriber line (DSL). An MX Series router that is installed in a subscriber access network as an edge router can perform subscriber management functions that include subscriber identification and per-subscriber CoS.
In a subscriber access network, a subscriber is an authenticated user—a user that has logged into the access network at a subscriber interface and then been verified by the configured authentication server and subsequently granted initial CoS services. Subscribers can be identified statically or dynamically. In this network, subscribers are mapped to VLANs, IP demux, or PPPoE interfaces.
You can configure the router to provide hierarchical scheduling for subscribers by dynamically modifying queues when subscribers require services. 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.
Depending on your deployment, you configure CoS parameters in the static [edit class-of-service] hierarchy and in the [edit dynamic profiles class-of-service] hierarchy.
