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Guidelines for Configuring Dynamic CoS for Subscriber Access

 

This topic describes the guidelines for configuring dynamic CoS in a subscriber access environment.

Configuration Guidelines for Hierarchical CoS and Per-Unit Scheduling

You can configure dynamic CoS with one of the following scheduling configurations:

  • For hierarchical scheduling configurations, you must enable hierarchical scheduling in the static CLI for the interface referenced in the dynamic profile. If not, the dynamic profile fails.

  • For per-unit scheduling configurations, you must enable per-unit scheduling in the static CLI for the interface referenced in the dynamic profile. If not, the dynamic profile fails and schedulers are not attached to the interface.

Junos software supports either per-unit scheduling or hierarchical scheduling on an interface. You cannot run both types of scheduling at the same time. If CoS is active on an interface, and you change the type of scheduling configured on the interface, all traffic is dropped upon egress from the interface.

Configuration Guidelines for Dynamic Scheduling and Queuing

When configuring scheduling and queuing for subscriber access, consider the following guidelines:

  • To improve CoS performance in IPv4, IPv6, and dual-stack networks that use a DHCP access model, we recommend that you use the aggregate-clients replace statement rather than the aggregate-clients merge statement.

  • You configure the traffic scheduling and shaping parameters in a traffic-control profile within the dynamic profile. You can configure the scheduler map and schedulers in a dynamic profile or in the [edit class-of-service] hierarchy. You must statically configure the remaining CoS parameters, such as hierarchical scheduling, classifiers, drop profiles, and forwarding classes, in the [edit class-of-service] hierarchy.

  • You can configure only one traffic-control-profile under a dynamic profile.

  • You must define the output-traffic-control-profile that binds the traffic-control profile to the interface within the same dynamic profile as the interface.

  • We recommend that you provide different names for the schedulers defined in dynamic profiles that are used for access and services. For example, if there are two dynamic profiles, voice-profile and video-profile, provide unique names for the schedulers defined under those profiles.

  • You must use a service dynamic profile with a different profile name for each RADIUS CoA request over the same logical interface.

  • When you configure scheduler and scheduler map sharing in client profiles, schedulers and scheduler maps must use the unique ID format. If the client profile uses the unique ID format and you want to have either scheduler or scheduler map sharing for service activation, you must configure the service profile in unique ID format.

Configuration Guidelines for Dynamic Classifiers and Rewrite Rules

When you configure classifiers and rewrite rules for subscriber access, consider the following guidelines:

  • To apply classifiers and rewrite rules to a subscriber interface in a dynamic profile, you must configure the rewrite rule and classifier definitions in the static [edit class-of-service] hierarchy and reference them in the dynamic profile.

    • If a static classifier or a rewrite rule definition that is referenced by a dynamic subscriber interface does not exist, the configuration is invalid and the subscriber cannot log in.

    • If a network administrator changes the static classifiers and rewrite rules definitions that are referenced in a dynamic profile with an active subscriber interface logged in, the changes are applied to the active subscriber interface immediately.

    • If a network administrator deletes a classifier or a rewrite rule definition that is referenced by an active dynamic subscriber interface, the system removes the classifier or rewrite rule binding from the interface. The classifier is replaced by the default classifier. If the network administrator adds the removed classifier or rewrite rule to the configuration while the dynamic interface is active, the addition does not take effect until the subscriber logs out and then logs in again.

  • IP demux interfaces can only instantiate Layer 3 rules (both rewrite rules and classifiers).

    • An IP demux subscriber interface can implicitly inherit a classifier from the underlying interface. If an IP demux interface is created without a classifier and a Layer 2 classifier is attached to the underlying interface, the IP demux interface also inherits the Layer 2 classifier. The show class-of-service interface interface-name command does not display this attachment.

      Table 1 lists the classification rule configuration for an IP demux subscriber interface with a VLAN underlying interface.

      Table 1: IP Demux Classification Rules

      VLAN Underlying Interface Classifier Configuration

      IP Demux Interface Classifier Configuration

      Resulting Classifier Configuration

      Layer 2

      VLAN Layer 2

      Layer 2

      Layer 3

      Demux Layer 3

      Layer 3

      Default

      Layer 3

      Layer 3

      Demux Layer 3

    • An IP demux subscriber interface explicitly inherits Layer 2 rewrite rules from the underlying interface if a Layer 2 rewrite rule is present. The show class-of-service interface interface-name command displays the attachment.

      Table 2 lists the rewrite rule configuration for an IP demux subscriber interface with a VLAN underlying interface.

      Table 2: IP Demux Rewrite Rules

      VLAN Underlying Interface Rewrite Rule Configuration

      IP Demux Interface Rewrite Rule Configuration

      Resulting Rewrite Rule Configuration

      Layer 2

      VLAN Layer 2

      Layer 2

      Layer 3

      VLAN Layer 2 and demux Layer 3

      Layer 3

      Default

      Layer 3

      Layer 3

      Demux Layer 3

    • An L2TP subscriber interface can implicitly inherit a classifier from the underlying interface.

      Table 3 lists the classification rule configuration for an L2TP LAC subscriber interface with a VLAN underlying interface.

      Table 3: L2TP Classification Rules

      VLAN Underlying Interface Classifier Configuration

      L2TP LAC Classifier Configuration

      Resulting Classifier Configuration

      Layer 2 or Fixed

      Layer 2 or Fixed

      VLAN Layer 2 or Fixed

      Layer 2 or Fixed

      Layer 3

      Demux/PPPoE Layer 3

      Layer 3

      Layer 2 or Fixed

      VLAN Layer 2 or Fixed

      Layer 3

      Layer 3

      Demux/PPPoE Layer 3

    • An L2TP LAC subscriber interface explicitly inherits Layer 2 rewrite rules from the underlying interface if a Layer 2 rewrite rule is present. Table 4 lists the rewrite rule configuration for an L2TP LAC subscriber interface with a VLAN underlying interface.

      Table 4: L2TP LAC Rewrite Rules

      VLAN Underlying Interface Rewrite Rule Configuration

      L2TP Interface Rewrite Rule Configuration

      Resulting Rewrite Rule Configuration

      Layer 2

      Layer 2

      VLAN Layer 2

      Layer 2

      Layer 3

      VLAN Layer 2 and demux/PPPoE Layer 3

      Layer 3

      Layer 2

      VLAN Layer 2 and demux/PPPoE Layer 3

      Layer 3

      Layer 3

      Demux/PPPoE Layer 3