The Network subsystem facilitates communication between the different nodes of the system.
It uses integers (handles) to identify the various connections. When the local system wants to send some data to another node it sends the handle along with the message. The network looks up the connection using the handle and sends the message.
Handles keep the rest of the system from knowing too many of the details of the networking library. They were created during the period when Miranda was switching from Netty to Mina.
The Network subsystems also covers the part of the system that listens for new nodes. When a new node connects, the Network tells Miranda and the Cluster about it.