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For the rest of this section, we assume that there exists a unique host identifier that never changes. We note that the IP address may not be a good use when Dynamic Host Control Protocol (DHCP) is used since a host's IP address may change over time. For smaller networks, a simple solution such as using DNS names as unique identifiers and dynamically updating the changes of IP addresses may be sufficient [26]. This problem of assigning a unique identifier to each host within enterprise networks is beyond the scope of this paper.

The connection habits of a host may change as a result of the following events: i) new host arrivals, ii) existing host removals, and iii) role changes by existing hosts. Due to a combination of these events, some existing hosts may communicate with different sets of hosts and thus the results of the grouping algorithm before and after these events may be different as: i) new groups are formed, ii) existing groups are deleted, iii) the member compositions of some groups change, and iv) the connection sets of some groups change. The changes affect not only the hosts directly involved in the aforementioned events but also to other hosts whose connection habits have not changed in a logical sense.

Hypothetically, if we know the exact sequence of every single change event that happened between two executions of the role classification algorithm, the results of the first execution could be incrementally updated to achieve the new results. Having such a change log, although not impossible, can complicate the network data gathering process. More importantly, a detailed change log cannot always lead to correct ID correlations.

Consider the example network in Figure 1. Assume that Sales-1 and Eng-1 switch roles as a result of personnels switching jobs or changing machines. Sales-1 now communicates with SourceRevisionControl whereas Eng-1 communicates with SalesDatabase. From the change log, it would seem that the connection sets of both SourceRevisionControl and SalesDatabase change whereas in reality, their logical roles never changed. The difficulty here is in distinguishing which changes in connection patterns are the primary causes that result in differences in group formations between two executions of the grouping algorithm. Furthermore, there may also be natural changes in connection patterns of many nodes. For instance, an existing server machine may be replaced by two new machines that do load sharing among client machines. The logical roles of the client machines have not changed but their observed connection patterns have. The rest of this section describes the role correlation algorithm that does not rely on the change log but rather uses the same set of information (i.e. only connection sets) made available to the grouping algorithm.

next up previous
Next: The Role Correlation Algorithm Up: Role Correlation Previous: Role Correlation
Godfrey Tan 2003-04-01