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WiMAX Prepaid Accounting

Prepaid solutions are generally either single-service or multi-service solutions. This section provides a description of these solutions and describes how to configure SBR Carrier to support them.

Prepaid Scenarios

Single-Service Prepaid Solution

This is a prepaid solution that manages a single service, hence the quota in this solution is only consumed by a single service. Single-service prepaid services range from true prepaid accounts to one-time models like scratch-card and credit card one-time services. This type of solution typically does not require a full-feature prepaid server (PPS), thus greatly simplifying deployment of the solution and reducing your cost. Since only a single service consumes the prepaid quota, in-session quota management is less complex than a multi-service solution. In this case SBR Carrier retrieves the complete quota from the subscriber database on session start, and returns that volume or time based quota to the NAS on authentication. The NAS reports the quota usage through interim accounting and SBR Carrier updates the quota in the subscriber database accordingly. When the session ends, SBR Carrier performs the final update, and any remaining quota is available for the next session.

Multi-Service Prepaid Solution

In true prepaid multi-service scenarios, the subscriber’s quota is consumed by multiple services which requires more sophisticated in-session quota management, as well as a prepaid server to manage that quota. In this scenario, the PPS assigns small portions of the quota when a service is initiated, and the service enforcement point then requests additional quota during the lifetime of that service. There are basically three multi-service prepaid models:

PPS Controlled Prepaid Model

In this model the PPS manages the subscriber’s quota. The NAS has no quota management capabilities at all. The NAS authenticates the subscriber with SBR Carrier, which then triggers the PPS server to start quota management for the session. When the subscriber’s quota on the PPS is depleted, the PPS can trigger SBR Carrier to either:

  • Issue a RADIUS Change of Authorization (CoA) request that redirects the subscriber to a prepaid web portal where they can purchase more time or data for their account.
  • Issue a RADIUS Disconnect Message to disconnect the subscriber from the network.

AAA Proxy Model

In this model the NAS initiates RADIUS Authorize-Only requests or standard Authentication-Requests to obtain portions of quota during the session lifetime. SBR Carrier forwards these requests to the PPS, either by RADIUS proxy or by using one of SBR Carrier’s authentication methods. In this use model the NAS manages the quota which is assigned by the PPS.

Direct PPS Connection

In this model the NAS directly manages the quota assigned by the PPS; the AAA server is not in the quota request path. In this scenario, SBR Carrier identifies the subscriber as being prepaid in their subscriber profile, and assigns a PPS address (or addresses) that the NAS uses to perform quota management for the specific subscriber.

Data Flow for Prepaid Accounting in SBR Carrier

This section provides an overview of the data flow for the prepaid accounting solutions.

Data Flow for Single-Service Prepaid Accounting Model

This option is a simple and cost effective way of implementing a single prepaid service, since it does not require quota management capabilities on the NAS or a PPS system. The NAS receives the entire quota for the subscriber account and can completely consume it without requesting additional quota.

Figure 228 shows an example data flow for the WiMAX single-service prepaid accounting solution using SQL authentication and accounting.

Figure 228: Example Data Flow for WiMAX Single-Service Prepaid Accounting Model

Example Data Flow for WiMAX Single-Service
Prepaid Accounting Model

The following section provides a more detailed discussion of the data flow for the WiMAX single-service prepaid accounting shown in Figure 228.

  1. An operations support systems (OSS) generates subscriber accounts into the subscriber and billing database. These accounts have a predefined quota. There may also be a self-service application in which subscribers are able to increase their quota.
  2. The NAS sends an Access-Request containing the Username the subscriber entered (and the password depending on the authentication method).
  3. SBR Carrier sends an SQL–Request to the subscriber and billing database requesting the subscriber credentials, the subscriber profile (QoS, bandwidth, and so forth) and the available quota. Refer to Configuring SQL Authentication for information about how to configure SQL authentication in SBR Carrier.
  4. The subscriber and billing database sends back the credentials, profile information and quota.
  5. SBR Carrier compares the credentials and if they are acceptable, a final Access-Accept message is sent to the NAS. The Access-Accept message contains the subscriber profile information that is enforced for the lifetime of the subscriber session. SBR Carrier also sends the time or volume based quota to the NAS.
  6. The NAS starts a session for the subscriber and sends an initial Accounting-Start message to SBR Carrier.
  7. SBR Carrier conveys the Accounting-Start information to the subscriber and billing database, updating the session in the database through SQL accounting. Refer to Configuring SQL Accounting for information about how to configure SQL accounting in SBR Carrier.
  8. The NAS sends an Accounting-Interim message to SBR Carrier, containing the time and volume the subscriber has used since starting the session.
  9. SBR Carrier updates the relevant information in the subscriber and billing database.
  10. Steps 8 and 9 are repeated until the NAS detects that either the quota limit is reached for the session, or the subscriber has disconnected. If the subscriber does not disconnect, the NAS disconnects or redirects the subscriber and sends a final Accounting-Stop to SBR Carrier.
  11. SBR Carrier updates the subscriber and billing database using SQL accounting, including the subscriber’s remaining quota.

Data Flow for Multi-Service Prepaid Accounting Models

This section provides an overview of the data flow and configuration for the PPS controlled and AAA proxy prepaid accounting models.

PPS Controlled Prepaid Model

The PPS controlled prepaid accounting model uses a RADIUS extension for dynamic changes during the session called Change of Authorization (CoA) according to RFC 3576. To support this model, the NAS must support the RFC 3576 RADIUS extensions. To enable the RADIUS CoA/DM functionality in SBR Carrier, the optional Session Control module is required on each SBR Carrier instance in a clustered installation requiring the SSR component. For more information about the optional Session Control module, see Managing and Controlling Sessions.

Figure 229 shows an example data flow for the WiMAX PPS controlled prepaid model using SQL authentication and accounting. This example uses SQL to convey session update information to the PPS. Proxy RADIUS can also be used to convey this information.

Figure 229: Example Data Flow for WiMAX PPS Controlled Prepaid Accounting Model

Example Data Flow for WiMAX PPS Controlled
Prepaid Accounting Model

The following section provides a more detailed discussion of the data flow for the WiMAX PPS controlled prepaid accounting shown in Figure 229.

  1. The NAS sends an Access-Request containing the Username the subscriber entered (and the password depending on the authentication method).
  2. SBR Carrier sends an SQL–Request to the subscriber database requesting the subscriber credentials and profile (QoS, bandwidth, and so forth). Refer to Configuring SQL Authentication for information about how to configure SQL authentication in SBR Carrier.
  3. The subscriber database sends back the credentials and profile information.
  4. SBR Carrier compares the credentials and if they are acceptable, a final Access-Accept message is sent to the NAS. The Access-Accept message contains the subscriber profile information that is enforced for the lifetime of the subscriber session.
  5. The NAS starts a session for the subscriber and sends an initial Accounting-Start to SBR Carrier.
  6. SBR Carrier conveys the Accounting-Start information to the PPS, updating the session in the database through SQL accounting. The PPS starts counting down the quota. Refer to Configuring SQL Accounting for information about how to configure SQL accounting in SBR Carrier.
  7. The NAS sends an Accounting-Interim message to SBR Carrier, containing the time and volume the subscriber has used since starting the session.
  8. SBR Carrier updates the relevant information in the PPS through SQL accounting.
  9. Steps 7 and 8 are repeated until the subscriber runs out of quota in the PPS.
  10. When the quota is exhausted, the PPS send’s an HTTPS-XML message to SBR Carrier indicating what to do next. For example, the PPS may send a redirect message to SBR Carrier. The redirect message triggers the server to send a CoA message to the NAS which includes new profile information for the subscriber session. The new profile information may reduce in the subscriber’s bandwidth, or may redirect the subscriber to a web portal where they can renew their quota. Alternatively, when the quota is exhausted, the PPS can send an HTTPS-XML message to SBR Carrier requesting the subscriber be disconnected (by means of a Disconnect-Message (DM)). For more information about how to trigger CoA/DM requests through the HTTPS-XML interface of the Session Control module, see Managing and Controlling Sessions.
  11. SBR Carrier sends the change request from the PPS as either a RADIUS CoA-Message or Disconnect-Message to the NAS with the new profile. To learn how to configure the Session Control module to emit RADIUS CoA/DM requests, see Managing and Controlling Sessions.
  12. The NAS changes the profile for the subscriber, and on success, sends an ACK-Message back to SBR Carrier.
  13. SBR Carrier sends a result code back to the PPS over the HTTPS-XML interface indicating whether the request was successful or not.
  14. The NAS sends an Accounting-Stop message to SBR Carrier to terminate the session.
  15. SBR Carrier sends the Accounting-Stop message as SQL-Update to the PPS so it can calculate the final amount of quota left for the old session. For more information about SQL accounting, see Configuring SQL Accounting.

AAA Proxy Model

In the AAA proxy prepaid accounting model, the NAS manages time or volume based quota which is updated by periodic reauthorization. The reauthorization is handled through RADIUS authentication or RADIUS Authorize-Only messages to the AAA server, which in turn, retrieves portions of the quota from the PPS and encapsulates them in a RADIUS attribute in the authentication/authorization reply.

Figure 230 shows an example data flow for the WiMAX AAA proxy prepaid accounting model. This example uses SQL as a method for communication with a prepaid system, however proxy RADIUS could also be used.

Figure 230: Example Data Flow for WiMAX AAA Proxy Prepaid Accounting Model

Example Data Flow for WiMAX AAA Proxy
Prepaid Accounting Model

The following section provides a more detailed discussion of the data flow for the WiMAX AAA proxy prepaid accounting shown in Figure 230.

  1. The NAS sends an Access-Request containing the Username the subscriber entered (and the password depending on the authentication method).
  2. SBR Carrier sends an SQL–Request to the subscriber database requesting the subscriber credentials and profile (QoS, bandwidth, and so forth). Refer to Configuring SQL Authentication for information about how to configure SQL authentication in SBR Carrier.
  3. The subscriber database sends back the credentials and profile information.
  4. SBR Carrier compares the credentials and if they are acceptable, a final Access-Accept message is sent to the NAS. The Access-Accept message contains the subscriber profile information that is enforced for the lifetime of the subscriber session.
  5. Before starting the session, the NAS requests the initial quota by sending a RADIUS Authorize-Only message to SBR Carrier.
  6. SBR Carrier conveys the request for initial quota to the PPS, updating the session in the database through SQL accounting (this can also be performed through proxy RADIUS). Refer to Configuring SQL Accounting for information about how to configure SQL accounting in SBR Carrier.
  7. The PPS returns a portion of quota in the SQL response.
  8. SBR Carrier conveys that quota to the NAS in the Access-Accept.
  9. The NAS starts the session for the subscriber and sends an initial Accounting-Start to SBR Carrier.

    Note: Steps 5 through 9 can be skipped if initial quota is returned through SQL in the authentication process (steps 1 through 4) and returned in the initial access accept.

  10. The NAS sends interim accounting to SBR Carrier.
  11. When the initial quota is depleted the NAS requests additional quota through a RADIUS Authorize-Only message to SBR Carrier.
  12. SBR Carrier conveys the request for additional quota to the PPS, updating the session in the database through SQL accounting (this can also be performed through proxy RADIUS). For more information about SQL accounting, see Configuring SQL Accounting.
  13. The PPS returns a portion of quota in the SQL response.
  14. SBR Carrier conveys the additional quota to the NAS in the Access-Accept.
  15. The NAS updates the available quota and continues the subscriber session.
  16. The NAS sends interim accounting to SBR Carrier.
  17. When the additional quota is depleted the NAS requests more quota through a RADIUS Authorize-Only message to SBR Carrier.
  18. SBR Carrier conveys the request for additional quota to the PPS, updating the session in the database through SQL accounting (this can also be performed through proxy RADIUS).
  19. The PPS returns a portion of the quota in the SQL response, or as in this case if there is no more quota, the PPS returns no quota.
  20. SBR Carrier subsequently sends a reject message to the NAS.
  21. The NAS terminates (or redirects) the session and sends an Accounting-Stop to SBR Carrier.

Direct PPS Connection Model

In the direct PPS connection model, the NAS performs quota management directly with the PPS; SBR Carrier is not involved in quota management. In this model, SBR Carrier’s involvement is limited to assigning the IP-address of the prepaid server responsible for quota management for the subscriber based on the subscriber’s profile. For more information about managing profiles in, see Administering Profiles.

Modified: 2017-03-07