dCache uses the LocationManager to discover the network topology of the internal communication: to which domains this domain should connect. The domain contacts a specific host and queries the information using UDP port 11111. The response describes how the domain should react: whether it should allow incoming connections and whether it should contact any other domains.

Once the topology is understood, dCache domains connect to each other to build a network topology. Messages will flow over this topology, enabling the distributed system to function correctly. By default, these connections use TCP port 11111.

It is essential that both UDP and TCP port 11111 are firewalled and that only other nodes within the dCache cluster are allowed access to these ports. Failure to do so can result in remote users running arbitrary commands on any node within the dCache cluster.