Final answer:
In the source-specific tree approach to multicasting, each router must construct an individual tree for every source-group pair, optimizing the path for bandwidth efficiency but requiring more router resources.
Step-by-step explanation:
In the source-specific tree approach to multicasting, each router needs to create a separate tree for each source-group pair. This approach allows for optimized paths and can be beneficial when it comes to efficiency and bandwidth usage for that specific source and group. Nevertheless, it requires more memory and processing power from the routers since each one must maintain a unique tree for each source.
Options like shared tree multicast approaches may use less memory as they rely on a single distribution tree shared by all sources, but they can be less efficient regarding the path taken by the data. The shortest path approach generally results in trees that provide the shortest path from the source to the receivers, which may overlap but are not specific to each source-group pair.