Handshaking is the process that establishes communication between two networking devices.

What is Handshaking?

The process that establishes communication between two networking devices. For example, when two computers first connect with each other through modems, the handshaking process determines which protocols, speeds, compression, and error-correction schemes will be used during the communication session.

Handshaking is necessary at the start of each session because typically the modems differ in their vendor, model, or hardware/software configuration. The handshake ensures that communication is possible despite these differences.

The term “handshaking” arises from the analogy of two people meeting to conduct business. They first shake hands to greet each other, announcing their name, title, and intentions. They might also “size each other up” to determine the other person’s capacities and capabilities.

How It Works

During the handshaking process, both modems send the other a series of control signals and respond to each other’s signals. Handshaking is also referred to as “flow control” because the process establishes the ground rules for managing the flow of data between the two devices. Some of the parameters that the modems need to negotiate are

  • The maximum transmission speed, taking into consideration the speed of both modems and the quality of the transmission
  • The length of the line delay to apply echo cancellation
  • The communication protocol

Modern modems transmit the control signals in full-duplex mode over the RS-232 interface that connects them to the computers.