Reliable Event Logging Protocol (RELP) is a protocol for reliable delivery of event messages to remote logging servers. This protocol is used in environments which cannot afford to tolerate loss of event messages during transit.
RELP uses TCP for event message transmission. Using TCP provides basic protection for message loss. However, it does not guarantee message delivery under all circumstances. TCP cannot reliably detect that the last message sent has actually reached the destination. However, RELP uses a different method to convey information back to the sender about the messages processed by the receiver. This ensures that the both the sender and receiver always know which messages have been transmitted and which have been received at all points of time, even in case of a connection loss.