# SPDX-License-Identifier: GPL-2.0-only # # CCITT X.25 Packet Layer # config X25 tristate "CCITT X.25 Packet Layer" help 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 <https://www.sangoma.com/tutorials/x25/> and <http://docwiki.cisco.com/wiki/X.25>. Information about X.25 for Linux is contained in the files <file:Documentation/networking/x25.rst> and <file:Documentation/networking/x25-iface.rst>. 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.