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CoS Adjustment Control Profiles Overview

CoS adjustment control profiles control which applications and algorithms can modify a subscriber’s shaping characteristics after a subscriber is instantiated. Subscriber shaping characteristics are configured using the Junos OS CLI or by RADIUS messages. Adjustment control profiles enable subscriber shaping characteristics by to be adjusted by other applications like ANCP, PPPoE tags, DHCP tags, and RADIUS Change of Authorization (CoA) messages after a subscriber is instantiated. Adjustment control profiles are router-wide and apply to both static and dynamic interfaces.

Table 1 describes the applications and their associated default algorithms that can be configured to perform rate adjustments after the subscriber is instantiated.

Table 1: Adjustment Control Profile Applications and Algorithms

Application

Default Priority

Default Algorithm

Description

RADIUS-CoA

1

Adjust-always

RADIUS CoA messages can update the subscriber’s attributes (like shaping rate) after the subscriber is authenticated and QoS parameters (like shaping rate) are assigned.

ANCP

1

Adjust-always

The ANCP application can modify the existing shaping rate for both static and dynamic logical interfaces, and static interface sets. By default, ANCP can override all other applications. The shaping rate must be specified in order to override it.

DHCP

2

Adjust-less

The DHCP application can include DSL Forum VSA attributes in its discovery messages, DHCPDISCOVER for DHCPv4 and SOLICIT for DHCPv6.

The attributes can modify the Junos OS CLI-configured shaping-rate value, as well as the RADIUS-supplied shaping-rate value. By default, these values can be modified by subsequent RADIUS CoA messages and DHCP actions.

The DSL Forum VSAs are conveyed in DHCP option 82, suboption 9 (Vendor-Specific Information suboption) for DHCPv4 and in Option 17 (Vendor-Specific Information option) for DHCPv6.

PPPoE-Tags

2

Adjust-less

The PPPoE IA tag access-rate-downstream can modify the Junos OS CLI-configured shaping-rate value, as well as the RADIUS-supplied shaping-rate value. By default, these values can be modified by subsequent RADIUS CoA messages and ANCP actions. These values are conveyed in PPPoE (PADI) discovery packets.

The lower the priority value, the higher the priority. For example priority 1 is higher than priority 2. By default, the application shaping rates compare as follows:

  • ANCP has priority over all the other applications.

  • RADIUS CoA has priority over DHCP tags or PPPoE IA tags.

  • The DHCP tags or PPPoE IA tags have priority over the shaping rate configured in the traffic control profile.

Applications and Associated Algorithms in Adjustment Control Profiles

You must enable each application to perform rate adjustments. Rate adjustments are global and affect all static and dynamically instantiated subscribers. The following rules apply to adjustment control profiles:

  • If no adjustment control profile is configured, the default adjustment control profile is used.

  • You can configure a maximum of one adjustment control profile; a commit error occurs if you configure more than one adjustment control profile.

  • If an application is not configured with an adjustment control profile, Junos OS uses its default values for priority and algorithm. For example, if ANCP is not configured in the adjustment control profile, the ANCP application is set to a priority of 1 and the algorithm is set to adjust-always.

  • Adjustment control profiles apply to both static and dynamic interfaces.

  • You can configure the algorithm to the following values:

    Note:

    All values can apply to shaping rates. Only adjust-never and adjust always can apply to overhead-accounting attributes.

    • adjust-never—Do not perform rate adjustments.

    • adjust-always—Adjust the shaping rate unconditionally.

    • adjust-less—Adjust the shaping rate if it is less than the configured value.

    • adjust-less-or equal—Adjust the shaping rate if it is less than or equal to the configured value.

    • adjust-greater—Adjust the shaping rate if it is greater than the configured value.

    • adjust-greater-or-equal—Adjust the shaping rate if it is greater than or equal to the configured value.

  • When you modify an adjustment control profile, the changes take effect immediately and the modified profile is used for all further adjustments. However, existing adjustments are not reevaluated when you modify the adjustment control profile.

    For example, if you have an ANCP adjustment that overrides a PPPoE adjustment on interface ge-1/1/0.100, and then you use the adjustment control profile to change the priority so that the ANCP priority is now lower than the PPPoE priority, Junos OS does not go back and reevaluate the adjustment on ge-1/1/0.100.

CoS Shaping Rate Fallback Behavior

When a CoS service profile is deactivated or removed, the CoS shaping rate falls back to the next highest available adjustment source as follows:

  1. Fall back to the ANCP shaping rate if it is present and it has a higher priority than RADIUS CoA, the DHCP tags, or the PPPoE IA tags.

  2. Fall back to the RADIUS CoA shaping rate if it is present and it has a higher priority than the DHCP tags or the PPPoE IA tags.

  3. Fall back to the DHCP tags or the PPPoE IA tags shaping rate, if present.

  4. Fall back to the shaping rate configured in the associated traffic control profile.

When a shaping rate is adjusted by ANCP, if that adjustment is removed, the rate reverts to the PPPoE IA tag rate if it is present. If the tag rate is not present then the shaping rate reverts to the configured rate in the traffic control profile.

When an ANCP adjustment for overhead-accounting mode is removed, the value reverts to the PPPoE IA tag value if it is present. If the tag value is not present, then the mode reverts to the configured value in the traffic control profile.

When an ANCP adjustment for overhead-accounting bytes is removed, the value reverts to the configured value in the traffic control profile; PPPoE IA tags cannot provide this value.

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