Linux v5.2.1 - x25
# SPDX-License-Identifier: GPL-2.0-only
# CCITT X.25 Packet Layer
tristate "CCITT X.25 Packet Layer"
X.25 is a set of standardized network protocols, similar in scope to
frame relay; the one physical line from your box to the X.25 network
entry point can carry several logical point-to-point connections
(called "virtual circuits") to other computers connected to the X.25
network. Governments, banks, and other organizations tend to use it
to connect to each other or to form Wide Area Networks (WANs). Many
countries have public X.25 networks. X.25 consists of two
protocols: the higher level Packet Layer Protocol (PLP) (say Y here
if you want that) and the lower level data link layer protocol LAPB
(say Y to "LAPB Data Link Driver" below if you want that).
You can read more about X.25 at <http://www.sangoma.com/tutorials/x25/> and
Information about X.25 for Linux is contained in the files
One connects to an X.25 network either with a dedicated network card
using the X.21 protocol (not yet supported by Linux) or one can do
X.25 over a standard telephone line using an ordinary modem (say Y
to "X.25 async driver" below) or over Ethernet using an ordinary
Ethernet card and the LAPB over Ethernet (say Y to "LAPB Data Link
Driver" and "LAPB over Ethernet driver" below).
To compile this driver as a module, choose M here: the module
will be called x25. If unsure, say N.