Implementing CoA/DM Support

Step 1: Develop a Deployment Plan

As a mobile or wire-line operator, you can configure the CoA/DM functionality to offer dynamic service changes to reinforce your current service offerings. Before you begin to customize the CoA/DM settings, develop a comprehensive deployment plan based on the solution your company offers to its customers. Have your network architect or someone who has detailed knowledge of your network access servers and service offerings develop this plan.

Depending on the complexity of the services you want to provide, you may need to customize other aspects of your network. For example, if you want to offer a prepaid service, then include in the deployment plan all of the different types of disconnect messages and change of authorization messages that are required to support control of data services where usage is metered by time or traffic volume. When users exhausts their prepaid service quota, the CoA/DM feature can disconnect the users, or redirect them to a subscriber page to ensure that subscribers do not exceed their purchased limit and allow them to purchase more time or data in mid-session.

Note: This type of service interacts with other devices in your network that may require customization beyond the scope of this guide. Make sure your deployment plans take into consideration all aspects of the services you want to provide.

Step 2: Consult Your NAS-Specific Documentation

The information required to identify a session and to process CoA/DM requests depends on the NAS devices in your network. To determine a NAS’s capabilities, you must consult the documentation for each NAS, find its make and model, and determine the appropriate attribute packing list (containing the list of attribute-value pairs). What actions is the NAS capable of supporting? What attributes does the NAS require in the request? What attributes does the NAS include in the response? You need to know what type of information the NAS supports because if the list of AVPs cannot satisfy a request, then the request cannot be sent.

You must configure the deviceModels.xml file to support your specific NAS according the NAS capabilities, and the specific actions you want to support.

Step 3: Configure Each NAS as a Client in Steel-Belted Radius Carrier

Each device in your network sending requests to the server must be defined as a client in Steel-Belted Radius Carrier. To support RFC 3576 Change of Authorization (CoA), Disconnect Message (DM), or the Cisco proprietary Packet of Disconnect (PoD), you need to configure the following parameters for the client:

• RFC 3576 CoA/DM port and RFC 3576 CoA/DM Shared secret
• POD port and POD Shared secret

  Note: For CoA/DM or PoD ports, you must specify the shared secret for the CoA/DM functionality to work. If you do not specify port numbers, Steel-Belted Radius Carrier uses the defaults from the deviceModels.xml file.

  Note: If a NAS client is configured without saving the shared secret, you are prompted to enter the shared secret when the client is subsequently viewed. If unexpected results such as invalid signatures occur, ensure that the shared secret is set correctly.

  Note: CoA/DM and POD messages do not work for the <ANY> RADIUS client.

For complete details on configuring clients in Steel-Belted Radius Carrier, see Administering RADIUS Clients and Client Groups.

Step 4: Configure the deviceModels.xml File

The deviceModels.xml file contains a list of device models for each controlled device object associated with your NAS clients, and defines the actions supported by each NAS. The actions supported by each NAS can vary. For example, some devices may use different AVPs as keys when referring to a session, such as Acct-Session-Id, NAS-Port, and NAS-Port-Type. As a result, you need to customize the deviceModels.xml file to support the specific NAS and their associated CoA/DM capabilities.

For information about configuring the deviceModels.xml file, see Configuring the deviceModels.xml File.

Step 5: Configure the Current Sessions Table (CST) for Your Environment

To ensure that CoA/DM requests get processed properly, you need to customize the current sessions table (CST) for your network environment. The CST must be customized to include the attributes in session queries that your NAS devices require in a CoA/DM (action) request, and for what SBR Carrier requires in the NAS response. Customizing the CST to include the proper attributes ensures that the session data, returned from a Query, includes the appropriate attributes your NAS device requires to process CoA/DM requests.

If you do not customize the CST, then you need to ensure that each DM-Request or CoA-Request includes the appropriate attribute packing list for the request.

For details on customizing the CST, see the SBR Carrier Installation Guide.