Handshake (computing)

[2] Handshaking can negotiate parameters that are acceptable to equipment and systems at both ends of the communication channel, including information transfer rate, coding alphabet, parity, interrupt procedure, and other protocol or hardware features.

[6] Handshaking facilitates connecting relatively heterogeneous systems or equipment over a communication channel without the need for human intervention to set parameters.

The Simple Mail Transfer Protocol (SMTP) is the key Internet standard for email transmission.

When a Transport Layer Security (SSL or TLS) connection starts, the record encapsulates a "control" protocol—the handshake messaging protocol (content type 22).

It is therefore very important for the device and charger to first perform a handshake to "agree" on mutually supported charge parameters.

If such a charger can't identify the connected device or determine its compatibility, it will default to normal but much slower charge parameters within the USB standard.