In a 15 node network, you’ll likely be connected to all nodes all the time. When requesting a file, you’ll:
- Ask all connected nodes for the first piece (root node) of the file.
- After that, you’ll create what we call a “session” and put all peers that responded in step one into the session.
- Finally, you’ll ask peers in the session for subsequent blocks.
You shouldn’t need to explicitly ask your cluster. If you want to be extra safe, you can explicitly connect to all peers in your cluster before starting to download the file.