Q951 How can three servers handle hundreds of connections made to them without a way to prioritize or throttle demand?

A951 The first thing you have to remember about server loading is the bandwidth of a radio channel (packet or pactor) is VERY slow compared to internet bandwidth. Each of the CMSs have at least one T1 connection (1.5 megabits/sec). Most have multiple. Each T1 line would handle roughly 200 simultaneous 9600 baud packet channels running at max throughput. Or something like 1000 Pactor channels. In practice these servers are set up to allow 1000 simultaneous connections but we have rarely seen them go above 20 or so. There are currently four CMSs with distributed DNS servers world wide. All RMS sites now cache actual dotted CMS IP addresses so they don’t require any DNS service. All RMSs automatically rotate through all available CMSs if a connection can’t be made to the initial CMS. If a CMS ever becomes saturated it simply will reject new connections and slow down the throughput to those connected to it. However based on the typical speeds of radio links most users would never even see this throttling.

Each CMS has a firewall and a mechanism of capturing connect attempts and these along with some additional mechanisms can be used to block most Denial of service types of attacks. It might be worth noting that we have had a Central server mechanism used in WL2K for over 9 years and have never had a successful Denial of service attack. Since going to redundant CMSs about 4 years ago we have had virtually 100% availability of the system…even during major disasters such as Katrina, The Tsunami, etc., and hardware/internet failures at a CMS.