Determining Normal System Behavior

To establish a proper and accurate baseline for your system, there are two types of requirements you need to consider: explicit requirements, which are those mandated by your users or your company’s management; and derived (or implicit) requirements, which mainly stem from the explicit requirements. For example, you may be required to make all reasonable efforts to have service restored within 15 minutes of downtime. The 15-minute window is an explicit requirement. However, you may also require that your systems have hot-swap hard drives so that you can indeed switch out a dead disc within 15 minutes. Your hot-swap requirement is derived from the explicit requirements.

Let’s take a look at each of these now.

Explicit requirements

Some RADIUS implementations must deal with a constant, heavy stream of users needing its services. In this case, a measurement called packets per second is used, which quite obviously is a threshold of how many packets per second can be received and processed by the server systems. A few calculations are in order to determine what this qualification should be.

  1. First, determine the number of packets that will be processed in order to start and stop one transaction. In RADIUS, this involves four packets to start the transaction and two to stop it.

  2. Next, consider the average load of your system. For this example, say you have a capacity of 12,000 ports. Assume that normal operating load is about 40% of capacity, which means ...

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