Using Load Balancing to Add Scalability and Resiliency

Both RAS and RADIUS services work well when load balanced. Because neither service is connection-specific, it doesn't matter which device is actually contacted so long as each of the devices provides the services needed. This is to say that a company could have multiple RAS devices that answer to a single identity. In the case of RAS devices, this could mean either a single phone number that is transferred to the next available line or a load-balanced IP address that contacts the RAS device with the lowest load. Similarly these RAS devices can be pointed to the load-balanced address of multiple RADIUS devices to ensure that connections can be validated .

Windows Server 2003 Enterprise and Datacenter editions have built-in support for load balancing. A less expensive solution for load balancing RAS devices for VPNs is to attach to the device via DNS name. By placing multiple records into DNS for the same name that resolve to each of the IP addresses, the connections can be round-robined to cause each successive request to reach a different RAS device.