Since the database is distributed, the above user-level requirements determine the network requirements. For one user, we can predict the network load that flying will induce under each type of image processing:
We can determine the minimal network required for flying using projected network bandwidths. The following table lists the Optical Carrier (OC) network rates:
We infer from the above two tables that we need more bandwidth than even an OC-12 network can deliver to support just one remote flying user. Since local flying appears to be very difficult under all projected network bandwidths, we will assume remote flying in the rest of this paper.
Network bandwidth will increase further with additional simultaneous users. Figure 1 shows the load predictions for a variable number of users.
Figure 1: Bandwidth versus Number of Simultaneous Users. The curve
is the total bandwidth required. The horizontal lines are various
Optical Carrier (OC) network bandwidths. On this, and subsequent
graphs, the Mbits/second axis is in log 10 scale.
To counteract the huge bandwidth requirements, we can increase the number of servers. If we assume that each user flies through the database for one hour per week, we have an average of 200 simultaneous users (see section 3). Figure 2 shows the load predictions for a variable number of servers.
Figure 2: Bandwidth versus Servers. The curving is
the average bandwidth per server. The horizontal lines are OC network
bandwidths.
With 200 servers, there is, on average, one server per user. We take 200 to be the upper limit on the number of servers. But with 200 servers, each connected to clients by OC-12s, each server can only support one user. Clearly, there is a need to find ways to reduce network load.
