• Supported Platforms
• MX Series

• Related Topics
• CoS for Subscriber Access Overview
• Configuring Static Hierarchical Scheduling and Queuing in a Dynamic Profile for Subscriber Access
• Configuring Dynamic Hierarchical Scheduling and Queuing in a Dynamic Profile for Subscriber Access
• Configuring Per-Unit Scheduling in a Dynamic Profile for Subscriber Access
• For information about static CoS configurations, see the Junos Class of Service Configuration Guide

Guidelines for Configuring Dynamic CoS for Subscriber Access

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

Hardware Requirements for Dynamic CoS

Table 1 lists the hardware requirements based on subscriber interface type for the hierarchical scheduling and per-unit scheduling dynamic CoS configurations.

Guidelines for Configuring Aggregated Ethernet Interfaces for Dynamic CoS

Keep the following guidelines in mind when configuring static or dynamic CoS for a subscriber interface on a VLAN stacked on a two-link aggregated Ethernet logical interface:

• Configure the aggregated Ethernet logical interface over two physical interfaces capable of performing hierarchical scheduling. For more information, see Table 1.
• Configure the aggregated Ethernet logical interface with both underlying links operating in link-protect mode.
• You can apply static or dynamic CoS characteristics to a scheduler node at the aggregated Ethernet logical interface or its underlying physical interface, but not at an interface set.

Configuration Considerations for Scheduling and Queuing

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

• 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.
• 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.

Configuration Guidelines for 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 2 lists the classification rule configuration for an IP demux subscriber interface with a VLAN underlying interface.

    Table 2: IP Demux Classification Rules

    	IP Demux Interface Classifier Configuration
    	—	Layer 3
    VLAN Underlying Interface Classifier Configuration	Resulting Classifier Configuration
    Layer 2	VLAN Layer 2	Demux Layer 3
    Layer 3	Default	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 3 lists the rewrite rule configuration for an IP demux subscriber interface with a VLAN underlying interface.

    Table 3: IP Demux Rewrite Rules

    	IP Demux Interface Rewrite Rule Configuration
    	—	Layer 3
    VLAN Underlying Interface Rewrite Rule Configuration	Resulting Rewrite Rule Configuration
    Layer 2	VLAN Layer 2	VLAN Layer 2 and demux Layer 3
    Layer 3	Default	Demux Layer 3

Guidelines for Configuring Excess Bandwidth Distribution Parameters

When you configure excess bandwidth distribution parameters for subscriber access, consider the following guidelines:

For queues, you cannot configure the excess rate or excess priority in these cases:

• When the transmit-rate exact statement is configured. In this case, the shaping rate is equal to the transmit rate and the queue does not operate in the excess region.
• When the scheduling priority is configured as strict-high. In this case, the queue gets all available bandwidth and never operates in the excess region.
• When logical interface units are configured in peak information rate (PIR) mode. The excess rate distributes excess bandwidth once the scheduling nodes reach their guaranteed rate. In PIR mode, none of the scheduling nodes have guaranteed rates configured, so you do not need to configure the excess rate.