Scaling Issues 195
The problem is that if the interval is too long, information is lost in the average. However, as
the interval gets smaller, it becomes more binary, which is also difficult to interpret.
Specifically, looking at a link over a 24-hour interval clearly highlights the problem. A link that
is full for the entire eight-hour business day, but otherwise unutilized, would show up as 33%
utilization. No hard-and-fast rule exists for selecting intervals.
Figure 8-7 Scalability of Balloons and Home Agents
A busy-hour profile for one or more classes of users needs to encompass all four factors, as
discussed in the sections that follow. You can generally classify users based on the application.
For example, a mobile sales force and a service team likely have different busy-hour usage
profiles, but within each class, the profile is similar. After the classes are established and the
profiles are defined, the two can be merged based on the quantity of users in each profile.
Number of Nodes
The most often asked scalability question is “How many Mobile Nodes are supported by a
specific platform?” This needs to be looked at as a foundation for scalability and not the entire
answer. This number is not only the root of the call model development discussed in the sections
Throughput
Number of Users
Number of Users
Total Throughput

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