Ful form of R. S. V.. P

Répondez s'il vous plaît RSVP is a process for a response from the invited person or people. It is derived from the French phrase "Répondez s'il vous plaît" meaning "Please respond". The initialism "RSVP" or the phrase "Répondez s'il vous plaît" are still used in current French to require confirmation of an invitation. (note-source: wikipedia)

Reliable State Update Protocol. Reliable SAP Update Protocol.