A DX cluster is a network of computers, each running a software package dedicated to gathering, and disseminating, information on amateur radio DX (long-distance contact) activities.
Internet nodes generally connect using the telnet protocol.
The system acts as an aggregator of information, accepting input from various sources, then making that data available to any user who is connected to the network.
The first DX cluster software, PacketCluster[1] was realized by US radio amateur Dick Newell, AK1A in the late 1980s, and quickly became popular as a means of exchanging DX-related information.
When the internet became widely available, the system was expanded to make use of telnet connections to internet nodes, in addition to the already established packet radio nodes.