Wireless Networks

The following topics are avaialable here under wireless networking. Click on the topic of your interest to read more. WiFi | WiMAX | RFID | BLUETOOTH | UWB | WIRELESS SECURITY

GPRS and Dynamic IP incoming traffic. How do I Secure?

I work on a SCADA system that basically uses a GPRS network to acquire data from remote sites. The 3rd party telecom company providing GPRS allots dynamic IP addresses to the remote devices. We use a cisco router at the perimeter for managing incoming traffic from these remote sites. In such a scenario where IP addresses change over time, how do I secure my SCADA hosts at the control center? I basically want to make sure that only the traffic coming from the remote sites is allowed into the LAN network of the control center.
Thanks
Khaled