18c2ecf20Sopenharmony_ci# SPDX-License-Identifier: GPL-2.0-only 28c2ecf20Sopenharmony_ci# 38c2ecf20Sopenharmony_ci# CCITT X.25 Packet Layer 48c2ecf20Sopenharmony_ci# 58c2ecf20Sopenharmony_ci 68c2ecf20Sopenharmony_ciconfig X25 78c2ecf20Sopenharmony_ci tristate "CCITT X.25 Packet Layer" 88c2ecf20Sopenharmony_ci help 98c2ecf20Sopenharmony_ci X.25 is a set of standardized network protocols, similar in scope to 108c2ecf20Sopenharmony_ci frame relay; the one physical line from your box to the X.25 network 118c2ecf20Sopenharmony_ci entry point can carry several logical point-to-point connections 128c2ecf20Sopenharmony_ci (called "virtual circuits") to other computers connected to the X.25 138c2ecf20Sopenharmony_ci network. Governments, banks, and other organizations tend to use it 148c2ecf20Sopenharmony_ci to connect to each other or to form Wide Area Networks (WANs). Many 158c2ecf20Sopenharmony_ci countries have public X.25 networks. X.25 consists of two 168c2ecf20Sopenharmony_ci protocols: the higher level Packet Layer Protocol (PLP) (say Y here 178c2ecf20Sopenharmony_ci if you want that) and the lower level data link layer protocol LAPB 188c2ecf20Sopenharmony_ci (say Y to "LAPB Data Link Driver" below if you want that). 198c2ecf20Sopenharmony_ci 208c2ecf20Sopenharmony_ci You can read more about X.25 at <https://www.sangoma.com/tutorials/x25/> and 218c2ecf20Sopenharmony_ci <http://docwiki.cisco.com/wiki/X.25>. 228c2ecf20Sopenharmony_ci Information about X.25 for Linux is contained in the files 238c2ecf20Sopenharmony_ci <file:Documentation/networking/x25.rst> and 248c2ecf20Sopenharmony_ci <file:Documentation/networking/x25-iface.rst>. 258c2ecf20Sopenharmony_ci 268c2ecf20Sopenharmony_ci One connects to an X.25 network either with a dedicated network card 278c2ecf20Sopenharmony_ci using the X.21 protocol (not yet supported by Linux) or one can do 288c2ecf20Sopenharmony_ci X.25 over a standard telephone line using an ordinary modem (say Y 298c2ecf20Sopenharmony_ci to "X.25 async driver" below) or over Ethernet using an ordinary 308c2ecf20Sopenharmony_ci Ethernet card and the LAPB over Ethernet (say Y to "LAPB Data Link 318c2ecf20Sopenharmony_ci Driver" and "LAPB over Ethernet driver" below). 328c2ecf20Sopenharmony_ci 338c2ecf20Sopenharmony_ci To compile this driver as a module, choose M here: the module 348c2ecf20Sopenharmony_ci will be called x25. If unsure, say N. 35