X.25 is an ITU (CCITT) standard for packet switching networks. Basicly like IP (or better TCP/IP, since it is connection orientated), and in fact, before the IP boom of the last 5 years X.25 networks have been the mayor carriers. They are still common, and the infra- structure ist still available around the world. There are PADs (Packed Assembly/Dissasembly) units to offer async (and sometimes sync) connetions for 'dump' (non X.25) units, or you have to use a interface, capable of X.25. X.25 connections are leases lines in most cases, while connections via a PAD was leasd line or dial up connections. To build up a connection a NUA (Network User Address) is used, which is structured like a international telephone number (maximum 15 digits). When using a dial up line, a terminal had to be identified by a NUI (Network User ID) and a password. Connection speed run from 300 to 2400 Bd for dial ups and 1200 to 64 for leased line (at least here in Germany) - more than 64K waspossible, but not afordable :) For performance, security and scalability, X.25 outperforms TCP/IP clearly as an wide area network. on a simple view, X.25 could be compared to ATM networks (althrough the QOS was less controlable). Beside this (worldwide) public X.25 Networks, that behavied like the telephone system (from a users view), private X.25 Networks are very common in use at telcos and power (network) companies for internal/controll purposes. There are still new installations. Gruss H. -- Ich denke, also bin ich, also gut HRK