If you've ever tried to connect sites within Exchange 5.5, you've no doubt noticed that you can use more than one type of connector to get the job done. If you weren't clear on which one to use, you may have used the site connector because of its simplicity. However, even though it works, in the back of your mind you may have wondered if you made the right choice. In this article, I'll discuss two of the most common connectors within Exchange: site connectors and X.400 connectors. As I do, I'll explain the differences between the two and tell you when it's appropriate to use each.
Although an X.400 connector is specific to Exchange, X.400 itself isn't. It's based on the CCITT standard used by many mail systems. An X.400 connector works by sending traffic between sites using an e-mail message format rather than the remote procedure calls normally associated with Exchange.
Because of the way that an X.400 connector works, it doesn't require a permanent connection to the destination server. A low-bandwidth connection such as a modem is perfectly acceptable.
On the other hand, X.400 connectors can be difficult to configure, especially when compared to a site connector. An X.400 connector requires you to fill in information on dozens of fields at each end of the connector. Another downside is that the X.400 connectors aren't natively available with the default Exchange installation. Instead, you must perform a custom Exchange installation and select the option to make the X.400 connector available. If you decide after installing Exchange that you need X.400 support, you must rerun the Setup program and then reapply the service pack. One final disadvantage to X.400 is that it supports a limited number of protocols--the only protocols supported are TCP/IP, TP0/X.25, and TP4/CLNP.
As you can see, X.400 is probably your best choice if you're in a low-bandwidth environment that uses one of these protocols. (According to Microsoft's Tech Support department, X.400 is also a good choice if you're having trouble with your network's reliability.)
Site connectors are totally native to Exchange. They use remote procedure calls to move information between sites. This means that site connectors require permanent, high-bandwidth connections between sites. Site connectors are also easy to configure--simply answer a couple of questions and you're connected. Site connectors support any protocol that works with remote procedure calls, such as TCP/IP, NetBEUI, and IPX / SPX. Therefore, it's appropriate to use site connectors in pure Exchange environments where the sites are hardwired together, such as within campus area networks. //Brien M. Posey is an MCSE who works as a freelance writer and as the Director of Information Systems for a national chain of health care facilities. His past experience includes working as a network engineer for the Department of Defense. You can contact him via e-mail at Brien_Posey@xpressions.com. Because of the extremely high volume of e-mail that Brien receives, it's impossible for him to respond to every message, although he does read them all.