An Internet protocol used for transporting data across a TCP-IP network. Its main advantage is speed. However, it suffers from the fact that it does not provide any facilities for reliability checking. This means that if data is sent using this protocol there is no guarantee that it will arrive correctly, or in the order in which it is sent out. Some applications do use the protocol, but they normally have error checking programmed into them or transport data for which it is unimportant if a small amount is lost, such as voice data. A notable Internet application which uses this protocol is the domain name service.