Graceful degradation

Graceful degradation is a property of a computer system whereby it reacts safely and proportionately to erroneous or unexpected circumstances. For example, the TCP protocol is designed to allow reliable two-way communication in a packet-switched network, even in the presence of intermediate nodes which are misconfigured, imperfect, or overloaded. It does this by causing the endpoints of the communication to degrade gracefully in the presence of packet loss, duplication, reordering and corruption.

Data formats may also be designed to degrade gracefully. HTML for example, is designed to be forward compatible, by allowing new HTML entities to be ignored by browsers which do not understand them without causing the document to be unusable.