Tunneling X.25 in TCP/IP (X.25 over TCP/IP, XOT)

X.25 Packet Switching Data Networks (PSDN) are disappearing nowadays. However, there are many applications that depend on X.25 hardware and software. Migrating these applications (that run on legacy systems or mainframes) to use modern networks is a major effort. Thus, replacing X.25 networks with TCP/IP is a fast growing market. Many customers choose XOT (RFC 1613), unaware of other possible solutions. Branch offices use terminals emulators connected to terminal controllers through LANs. Their terminal emulation software is far simpler to change than the central applications. Besides, eliminating the X.25 equipment and its maintenance results in large savings. In this section you will find XOT and some alternate solutions to this challenge using our PXS: XOT RFC 1613 Cisco-Cisco XOT RFC 1613 Cisco-PXS or PXS-PXS XOT RFC 1613 Cisco-XOT LayGO Client aXOT PXS-aXOT LayGO Client (Advanced XOT) Remote Procedure Calls (RPC) X.25 to TCP/IP Gateway

A Typical Legacy X.25 Network

For example, for a Pacific Bell (SBC) project in 1998 we used an XOT client to communicate to more than 400 Cisco routers (XOT servers) connected to Nortel DMS/100 and Lucent 5ESS phone switches, using a configuration similar to the one depicted in the "XOT RFC 1613 Cisco-XOT LayGO Client" section. This was a suitable solution since SBC uses the same application to access other switches through standard 19.2 kbps RS-232 X.25 connections. Our LayGO API is not aware that the underlying X.25 uses LAPB, LAPD or TCP/IP.

In another example, in 2004 we used our newly-released PXS (Protocol eXchange Server) in a project for Cable & Wireless Europe. We replaced nine Cisco XOT routers and nine AFT/X.25/XOT CDR file collectors with the PXS. We now terminate the AFT/X.25 at the nine DMS/100E using a file client/server module to transfer CDR files from the nine DMS/100Es to only one collector. This project uses the same design principles explained in "X.25 TCP/IP Gateway"

We recommend terminating the X.25 protocol at the mainframe site and switching the data onto a TCP/IP connection. This may require modifying the current application to replace the proprietary X.25 API with a socket interface, but this investment is worth the effort.