handshake
    n 1: grasping and shaking a person's hand (as to acknowledge an
         introduction or to agree on a contract) [syn: handshake,
         shake, handshaking, handclasp]

handshaking
handshake

   1. Predetermined hardware or software activity designed to
   establish or maintain two machines or programs in
   synchronisation.  Handshaking often concerns the exchange of
   messages or packets of data between two systems with limited
   buffers.  A simple handshaking protocol might only involve
   the receiver sending a message meaning "I received your last
   message and I am ready for you to send me another one."  A
   more complex handshaking protocol might allow the sender to
   ask the receiver if he is ready to receive or for the receiver
   to reply with a negative acknowledgement meaning "I did not
   receive your last message correctly, please resend it" (e.g. if
   the data was corrupted en route).

   Hardware handshaking uses voltage levels or pulses on wires
   to carry the handshaking signals whereas software
   handshaking uses data units (e.g. ASCII characters) carried
   by some underlying communication medium.

   Flow control in bit-serial data transmission such as
   EIA-232 may use either hardware or software handshaking.

   2. The method used by two modems to establish contact with
   each other and to agreee on baud rate, error correction
   and compression protocols.

   3. The exchange of predetermined signals between agents
   connected by a communications channel to assure each that it
   is connected to the other (and not to an imposter).  This may
   also include the use of passwords and codes by an operator.

   [Jargon File]

   (1995-01-13)