!!! Overview
[{$pagename}] is an [ITU-T] standard protocol suite for [Packet switching] [Wide Area Network] ([WAN]) [communication]. [{$pagename}] [network] consists of packet-switching exchange (PSE) nodes as the networking hardware, and leased lines, [Public Switched Telephone Network] connections, or [ISDN] connections as physical links.

!! More Information
There might be more information for this subject on one of the following:
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* [#1] - [X.25|Wikipedia:X.25|target='_blank'] - based on information obtained 2018-08-20-