# Retrieval of DSL Line Rate Information from Access Nodes Overview

You can retrieve updated DSL line rate information from the Access Node Control Protocol (ANCP) and report this information to the SRC software with corresponding COPS messages. ANCP is also known as Layer 2 Control (L2C). To enable the router that functions as the SRC client to obtain updated line rate parameters from ANCP and transmit them to the COPS server, use the sscc update-policy-request enable command in Global Configuration mode. You can configure this setting on a per-virtual-router basis.

In networks with digital subscriber line access multiplexers (DSLAMs), after a connection is established between an subscriber and a routing gateway, the access node or DSLAM obtains the line rate information of the subscriber using a synchronization process. The line rate parameters are transferred in the COPS interface request by using the ANCP topology discovery message to the router that functions as the network access server (NAS). Typically, a COPS interface request is sent from the access node to the SRC client whenever an interface becomes operational.

You can configure the SRC client to obtain the line rate details from the access node whenever any change in the values of the parameters occurs. The capability to receive line rate data, when it changes on the access node, is disabled by default on the SRC client.

The access node passes the DSL line rate parameters, whenever they change, to the SRC client. The SRC client appends updated parameters to the COPS messages that it sends to the COPS server or SRC server. A COPS server processes the following topology parameters that it receives from the SRC client in the updated COPS messages:

- JunosEIpInterfaceMode
- JunosEIpInterfaceUpstreamRate
- JunosEIpInterfaceDownstreamRate
- JunosEIpInterfaceMinimumDataRateUpstream
- JunosEIpInterfaceMinimumDataRateDownstream
- JunosEIpInterfaceAttainableDataRateUpstream
- JunosEIpInterfaceAttainableDataRateDownstream
- JunosEIpInterfaceMaximumDataRateUpstream
- JunosEIpInterfaceMaximumDataRateDownstream
- JunosEIpInterfaceMinimumLowPowerDataRateUpstream
- JunosEIpInterfaceMinimumLowPowerDataRateDownstream
- JunosEIpInterfaceMaximumInterleavingDelayUpstream
- JunosEIpInterfaceActualInterleavingDelayUpstream
- JunosEIpInterfaceMaximumInterleavingDelayDownstream
- JunosEIpInterfaceActualInterleavingDelayDownstream
- JunosEIpInterfaceDSLlinestate

A COPS server that runs an SRC software release earlier than Release 3.0.0 does not support and process the preceding topology parameters that are appended to the COPS messages. Such COPS servers analyze the information, other than the parameters that describe updated DSL line rate details, that they receive in the COPS messages for policy management. Therefore, the COPS-PR operation ensures backward compatibility of the SRC clients with the COPS servers running SRC software releases earlier than Release 3.0.0 by ignoring the received line rate details.

When you configure the sscc update-policy-request enable command, a warning message is displayed, prompting you to confirm whether you want to enable the router that functions as the SRC client to forcibly send line rate information parameters to the COPS server, which is running a release of SRC software earlier than Release 3.0.0 that is not compatible with the line rate message format.

Even if you confirm the prompt to enable the SRC client to forcibly send updated DSL line rate parameters to the COPS server, the COPS server that is running a release of SRC software earlier than Release 3.0.0 ignores the updated line rate details that it receives and processes only the other information in the COPS messages.

The Policy Information Base (PIB) is modified to extend the JunosEIpInterfaceEntry object. ANCP now notifies the SRC software about any change in the ANCP parameters. If this change in rate is greater than 10 percent or a change in mode, SRC software reports this upgrade to the service activation engine (SAE) in SRC version 3.0.0 and later.

#### Related Documentation

- Configuring the SRC Client
- Monitoring SRC Client Connection Status
- sscc update-policy-request enable