XOT Overview

XOT (X.25 over TCP/IP) enables X.25 packets to be sent over a TCP/IP network to an XOT-capable router, from where they are transported to the destination over an X.25 connection.

XOT support is provided on most ODEX platforms and allows users to connect to X.25 partners via an XOT router. In many cases, X.25 users prefer to install routers rather than have X.25 calls come directly into their comms applications, since the latter method can have security issues. Routers can be configured to block calls from unknown origins.

Where native X.25 is used, X.25 hardware, which can be costly, has to be connected to the machine on which ODEX is installed. However, where XOT is used, ODEX simply makes a TCP/IP connection to an XOT-capable router such as a Cisco, which can provide a sizeable cost saving.

Using an XOT router, ODEX can communicate with trading partners using either native X.25 or ISDN, depending on the routing rules and configuration of the router.

The example below shows how ODEX Professional, which had native X.25 support, would connect to an X.25 partner. Here the application would need X.25 hardware to be installed and configured. On Windows platforms, the cost of X.25 hardware may not be too great, but on mainframes and Unix machines it can be prohibitive.

ODEX Professional and X.25

XOT scenarios

The diagrams below show a variety of XOT scenarios, using ODEX Enterprise as the example application.

ODEX Enterprise using XOT with an X.25 partner

In this scenario, ODEX Enterprise makes a TCP/IP connection to an XOT-capable device, such as a Cisco router. The router then makes an X.25 call to the destination, according to the information provided in the TCP/IP call.

ODEX Enterprise using XOT with UK and non-UK partners

This example illustrates a possible scenario of a company making calls to UK X.25 partners using a router on their own local network, and making calls to non-UK partners via an XOT router on their partner’s local network.

When connecting to non-UK partners, users can take advantage of a low-cost TCP/IP connection until the call reaches their partner’s network. At this point the XOT router channels the data into the partner’s X.25 lines, which provide the X.25 connection at local rates in that country.

In practice, this solution is likely to be used only by the largest corporations, which can install a router in each foreign location of their operations.

ODEX Enterprise using XOT with an ISDN partner

An XOT-capable router may also be able to handle ISDN calls. In this case, if the router is configured correctly, it can be used to route calls to both X.25 and ISDN partners. However, this is less suitable when a user has many ISDN partners, as each ISDN partner must be configured separately on the router. This is not the case for X.25 partners, as the information needed to make the connection to the partner (the X.25 NUA) is present in the data passed to the router from the ODEX application.

To achieve XOT with ISDN using a Cisco Router, the router requires a BRI (Basic Rate ISDN) interface. A Dialler interface is then configured on the Cisco, which essentially tells the router which number to dial. Further configuration is then required to get the Cisco router to use a particular Dialler interface (for each partner) when it receives a call from the X.25 NUA of the ODEX system. The Cisco then dials the number configured in the Dialler interface and connects over ISDN.