The UDP monitoring check is a part of the ClouDNS motoring service, which scans the chosen UDP port number on the given IP address. If the connection is unsuccessful, the check is marked as DOWN.
User Datagram Protocol (UDP) is a communications protocol that is primarily used to establish low-latency and loss tolerating connections between applications on the internet.UDP is an alternative to Transmission Control Protocol (TCP). UDP sends messages, called datagrams, and is considered a best-effort mode of communications. This means UDP doesn't provide any guarantees that the data will be delivered or offer special features to retransmit lost or corrupted messages.
UDP is suitable for time-sensitive applications that can’t afford retransmission delays for dropped packets. Examples include Voice over IP (VoIP), online games, and media streaming. Since high performance is needed, UDP permits packets to be dropped instead of processing delayed packets. It speeds up communications by not formally establishing a connection before data is transferred.
Each Monitoring check provides debugging option which you can use to find out where the problem comes from using Traceroute information - The traceroute command is used to determine the path between two connections. Often a connection to another device will have to go through multiple routers. The option can be found in the Monitoring check settings page on the right side of the "Uptime changes section".