Supported Platforms
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, and RADIUS Change of Authorization (CoA) after a subscriber is instantiated. Adjustment control profiles are router-wide and apply to both static and dynamic interfaces.
Table 1 describes the terms used to define shaping characteristics.
Table 1: Terms and Definitions for Shaping Characteristics
Term | Definition |
|---|---|
Shaping-rate | The maximum rate of a scheduler node or queue. Also known as Peak Information Rate (PIR). |
Overhead-accounting mode | A class-of-service traffic-control profile attribute that specifies whether the downstream network is a frame-based network, like Ethernet, or a cell-based network, like ATM. Note: The downstream network is not necessarily the directly attached network. In typical broadband services router (BSR) network configurations, the directly attached network is an Ethernet access network, which provides access to either another frame-based network, or a cell-based network. When cell-mode is specified, the Juniper Networks router adjusts rates (like the shaping-rate) to “rate * 48/53” to account for 5-byte ATM AAL5 headers. |
Overhead-accounting bytes | A class-of-service traffic-control profile attribute that specifies the number of bytes per packet to be included or excluded from the shaping mechanism. For example, to properly account for a 4-byte header stripped by the downstream network, set the overhead-accounting bytes to -4. To properly account for a 12-byte header added by the downstream network, set the overhead-accounting bytes to 12. |
Effective-shaping-rate | The shaping-rate resulting from three attributes: shaping-rate, overhead-accounting mode, and overhead-accounting bytes. |
Rate Adjustment | The adjustment that other applications like ANCP, PPPoE tagging, and RADIUS CoA can make when the shaping rate is configured through the CLI or RADIUS. |
Effective Shaping Rate
CoS is responsible for communicating shaping rate information from the Routing Engine to the Packet Forwarding Engine. The shaping-rate, also known as peak information rate (PIR), is the maximum rate for a scheduler node or queue.
The true rate of a subscriber at the access-loop/CPE is a function of:
- The shaping-rate in effect for the subscriber’s household, in bits-per-second.
- Whether the subscriber is connected to a frame-based or
cell-based network. This attribute is known in CoS as the overhead-accounting mode.
- overhead-accounting frame-mode-bytes—When the overhead-accounting mode is set to frame-mode, this is the number of bytes in each frame that are accounted for by the shaper. This value represents the number of bytes that are encapsulated and decapsulated by the downstream equipment.
- overhead-accounting cell-mode-bytes—When overhead-accounting mode is set to cell-mode, this is the number of bytes in each frame that are accounted for by the shaper for a downstream cell-mode network. This value represents the number of bytes that are encapsulated and decapsulated by the downstream equipment.
You configure the values for the shaping-rate and overhead-accounting mode options under either the [edit dynamic-profiles profile-name class-of-service traffic-control-profiles profile-name] hierarchy level or the [edit class-of-service traffic-control-profiles profile-name] hierarchy level. These options are supported on MX Series routers. The applications and specified algorithms configured in the adjustment control profile use the values of these options to adjust the shaping rate for static and dynamically instantiated subscribers.
 | Note: Chassis egress-shaping-overhead is not included in the effective rate. Egress-shaping-overhead accounts for the physical interface overhead (ISO OSI Layer 1). Effective shaping-rate is a Layer 2 (ISO OSI) rate. |
Applications and Associated Algorithms in Adjustment Control Profiles
Table 2 describes the applications and their associated default algorithms that can be configured to perform rate adjustments after the subscriber is instantiated.
Table 2: 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. |
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 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. |
| Note: The lower the priority value, the higher the priority. |
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:
- Adjust-never
- Adjust-always
- Adjust less
- Adjust less than or equal
- Adjust greater
- Adjust greater than or equal
- 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.
