What Is Slip Protocol?

SLIP sends data over a network link.

Serial line internet protocol (SLIP) is a simple data framing system. SLIP was created as a stop-gap to provide data link layer data framing while the point-to-point protocol was still being developed.

Function

A serial transmission sends data one bit at a time over a wire. This is the standard for network data transfer. SLIP performs few functions other than breaking up an internet protocol (IP) datagram into bytes, sending them over the wire and terminating the transmission of the datagram with an "END" signal. The protocol was later modified so that a data frame transmission also starts with an "END" signal. This makes it clear that any data picked up before the real start of the datagram was just noise on the line and should be discarded.

Features

The "END" character is a byte, equivalent to decimal 192. Any byte in the data being transmitted having that value is replaced by two bytes: "219 220." If the data contains a 219. That byte is replaced by a "219 221." The receiving SLIP program knows to make these substitutions.

Evolution

SLIP hasn't evolved at all. It was never intended to be a long-term part of networking technology and most implementations have been replaced by the point-to-point protocol (PPP). However, there are still some implementations of the protocol in use.

References

• The TCP/IP Guide: Serial Line Internet Protocol (SLIP)