Compatibility Tips

Follow the tips in the section to make the best possible use of a network that has systems running both SunNet X.25 7.0 and Solstice X.25.

Point-to-Point Configurations

If you configure an IP point-to-point link between a machine running the current release of Solstice X.25 and a machine running SunNet X.25 7.0, configure the 7.0 machine as the "caller", rather than "called". This role is determined by the value of the mode parameter in the x25mgr configuration file. See page 118 of the SunNet X.25 7.0 System Administration Manual for a description of the mode parameter. Also, you should set the Disconnection Timer to a high value.

The reason for this is the different treatment of IP point-to-point links by SunNet X.25 7.0 and the current release of Solstice X.25. The 7.0 product keeps switched virtual circuits up all of the time in support of point-to-point links, while the current release drops the virtual circuits after a specified period of inactivity. If a 7.0 machine is configured as "called", rather than "caller", it is not able to establish an IP connection with a current-release machine until the latter machine sends a Call Request. This does not occur until the current-release machine has IP packets to send to the 7.0 machine. If the 7.0 machine is configured as "caller" (as it should be), there remains the problem that the current-release machine drops the virtual circuit upon inactivity. When this occurs, the 7.0 machine immediately calls to re-establish the virtual circuit. If your PSDN charges for call setup (as many do), such behavior becomes very expensive. To avoid this, change the Disconnection Timer to a figure that will keep the virtual circuit up long enough to outlast periodic gaps in IP traffic.

Setting the Max. NSDU

If you have an IP/X.25 link between a current-release Solstice X.25 machine and a machine running SunNet X.25 7.0, set Max NSDU to at least 1024. Otherwise IP connections can hang when a high volume of data is sent from the 7.0 machine. If you have two current-release machines on each side of the link, set Max NSDU to be the same on both sides. It can be as high as 8192.