The java application Builder then takes these files and builds a global view of the entire multicast session. However, since the multicast distribution tree changes as receivers join and leave the group, there is no single tree that represents the entire session. Rather, the end result is a graph in which the edges have explicit active periods. As time progresses, the tree changes according to receiver activity. Once the tree is built, the java application Animator is used to inspect the tree.
Animator takes a list of visitors on the command-line.
State can be stored at each node, in the links between nodes and cumulative results can be collected and passed back along the visiting path. Different visitors can be combined to perform separate passes on the tree, preparing state on one pass that can be used by subsequent visitors during their analysis. Evaluators provide an abstraction which can be implemented to introduce different semantics for activity. In some cases, a strict semantic is intended where a receiver is active only if a valid RTCP interval includes the current walk instance. For other studies, random activity is preferred.