1*4882a593Smuzhiyun# SPDX-License-Identifier: GPL-2.0-only 2*4882a593Smuzhiyun# 3*4882a593Smuzhiyun# CCITT X.25 Packet Layer 4*4882a593Smuzhiyun# 5*4882a593Smuzhiyun 6*4882a593Smuzhiyunconfig X25 7*4882a593Smuzhiyun tristate "CCITT X.25 Packet Layer" 8*4882a593Smuzhiyun help 9*4882a593Smuzhiyun X.25 is a set of standardized network protocols, similar in scope to 10*4882a593Smuzhiyun frame relay; the one physical line from your box to the X.25 network 11*4882a593Smuzhiyun entry point can carry several logical point-to-point connections 12*4882a593Smuzhiyun (called "virtual circuits") to other computers connected to the X.25 13*4882a593Smuzhiyun network. Governments, banks, and other organizations tend to use it 14*4882a593Smuzhiyun to connect to each other or to form Wide Area Networks (WANs). Many 15*4882a593Smuzhiyun countries have public X.25 networks. X.25 consists of two 16*4882a593Smuzhiyun protocols: the higher level Packet Layer Protocol (PLP) (say Y here 17*4882a593Smuzhiyun if you want that) and the lower level data link layer protocol LAPB 18*4882a593Smuzhiyun (say Y to "LAPB Data Link Driver" below if you want that). 19*4882a593Smuzhiyun 20*4882a593Smuzhiyun You can read more about X.25 at <https://www.sangoma.com/tutorials/x25/> and 21*4882a593Smuzhiyun <http://docwiki.cisco.com/wiki/X.25>. 22*4882a593Smuzhiyun Information about X.25 for Linux is contained in the files 23*4882a593Smuzhiyun <file:Documentation/networking/x25.rst> and 24*4882a593Smuzhiyun <file:Documentation/networking/x25-iface.rst>. 25*4882a593Smuzhiyun 26*4882a593Smuzhiyun One connects to an X.25 network either with a dedicated network card 27*4882a593Smuzhiyun using the X.21 protocol (not yet supported by Linux) or one can do 28*4882a593Smuzhiyun X.25 over a standard telephone line using an ordinary modem (say Y 29*4882a593Smuzhiyun to "X.25 async driver" below) or over Ethernet using an ordinary 30*4882a593Smuzhiyun Ethernet card and the LAPB over Ethernet (say Y to "LAPB Data Link 31*4882a593Smuzhiyun Driver" and "LAPB over Ethernet driver" below). 32*4882a593Smuzhiyun 33*4882a593Smuzhiyun To compile this driver as a module, choose M here: the module 34*4882a593Smuzhiyun will be called x25. If unsure, say N. 35