A communications manager provides communication services for an activity-based collaboration system, in which data change requests comprising deltas are communicated over a network between network-capable devices. The communications manager is operable on a local network capable device for sending locally-generated deltas over the network to at least one remote network-capable device and for receiving remotely-generated deltas over the network from the at least one remote network-capable device. The communications manager can send the deltas via unicasting, multicasting, or broadcasting techniques. The communications manager is responsive to network connection status information indicating that the remote network-capable device is connected to the network for sending the local deltas directly to an address for the remote network-capable device. A presence mechanism maintains and distributes, on request, the network connection status information, which it acquires from each of the network-capable devices. The communications manager is also responsive to the network connection status information indicating that the remote network-capable device is disconnected from the network for sending the local deltas to an address of a relay. The relay stores deltas until the relay is notified that the remote network-capable device has reconnected to the network, and then the relay sends the deltas to the reconnected remote network-capable device.