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    Scalability and Redundancy

    To accommodate the substantial amount of authentication, authorization, and accounting (AAA) traffic that can be generated in a 3G/4G mobile network, the AAA implementation on the MobileNext Broadband Gateway is optimized for scalability and redundancy, both in the way the broadband gateway distributes AAA functions to its services PICs, and in the way it sends requests to the external RADIUS servers.


    Each session DPC installed on the broadband gateway contains two services PICs. Each services PIC runs a separate AAA instance, which serves as a Network Access Server (NAS) for mobile subscriber sessions. When a mobile subscriber session requires AAA services, its anchor Modular Port Concentrator (MPC) assigns one of the services PICs to handle interaction with the RADIUS servers for the duration of that session. By installing additional session DPCs, you can increase the number of services PICs providing NAS functionality, and thus increase the number of sessions for which the broadband gateway can provide AAA services.

    Rather than use a single RADIUS server for authentication or accounting, the broadband gateway sends RADIUS requests to a load-balanced group of RADIUS severs called a network element. To broadcast accounting traffic to multiple network elements, you can configure network element groups, consisting of from one to four network elements. The broadband gateway sends accounting messages to one of the network elements in the group, or can broadcast them to all of the network elements in the group.


    Services PICs can be configured in redundant pairs, with one services PIC active and the other standby. In this kind of configuration, the active services PIC synchronizes its pending requests with the backup services PIC. When a switchover occurs, any pending requests are then sent from the new active services PIC.

    The broadband gateway can detect when RADIUS servers in a network element have failed. When the broadband gateway detects a dead server, it automatically starts sending RADIUS requests to a different server in the network element. You can set a priority level for individual RADIUS servers in the network element, so that the AAA traffic fails over to a selected server.

    Published: 2011-11-23