Our recent testing for Session Initiation Protocol compatibility with messaging programs has, at least for the time being, found a working solution. But getting there took some help along the way.In particular, we\u2019ve been testing the Intertex IX66 SIP-enabled router\/firewall. The unit works well, and all functions seem to perform as designed. Nevertheless, it took some expert help, which we received from the tech support staff at Intertex\u2019s sister company, Ingate.Here are just a few of the issues we encountered along the way, shared so that perhaps it will smooth the path for you.SIP registrar: Your SIP client is in most cases registered with a SIP registrar. Further, any firewalls and\/or network address translation devices in the path must be SIP-aware. But how do you do this? Simplest way that we found was to use an internal registrar in the IX66, then to use dyndns.org to direct traffic to the IX66.Messaging client: On the surface, Windows Messenger and MSN Messenger appear to be the same program with a different interface. However, it turns out that Windows Messenger is SIP-compliant, and MSN Messenger is not.Misleading error messages: OK, so nobody ever accused Microsoft of having the most helpful error messages. But some that we encountered were downright misleading. Now we just said that MSN Messenger was not SIP-compliant - well, some of the error messages are. In particular, when we had problems connecting for voice and application sharing with a different router\/firewall, the error message that we repeatedly received was \u201cSIP transaction timed out.\u201d The solution was to use Windows Messenger, which has a place in the configuration window to enter your SIP information. But, in the interest of making sure it\u2019s not too user-friendly, SIP is not mentioned.This reminds us of Steve\u2019s frequent assertion from his student days that all physics problems are either trivial or impossible. If you know what the right procedure is, then the problem is trivial. But if you don\u2019t know the secret combination\u2026The bottom line is that the IX66 worked fine. Windows Messenger seems to be a somewhat usable SIP client. And we\u2019ll continue testing and letting you know what we find out.