Kermit FAQ - Kermit Doesn't Work Right with My (RPI) Error-Correcting Modem!

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20 Kermit Doesn't Work Right with My (RPI) Error-Correcting Modem!

When you buy a modern error-correcting, data-compressing, speed-buffering modem, you probably expect the modem to perform those functions, and most do. Unfortunately, some modems that claim to have these features do not have them at all, but require external software that implements them in your computer, rather than in the modem where they belong.

One example of this practice is the Rockwell Protocol Interface (RPI), a proprietary "standard" from Rockwell International Company that allows modem companies to sell modems at a lower price by incorporating Rockwell chips that do not include error-correction or compression capabilities.

This "standard" must be licensed from Rockwell, hence you will only find it implemented in commercial software, such as on the diskette (if any) that came with your modem.

In general, such software is available only for PCs running Microsoft Windows 3.x or Windows 95, or built into proprietary communications packages like Comit.

If your modem documentation says it requires "RPI-compatible" software for error correction and compression, and you want to use it with Kermit, then you are out of luck unless you also have the software driver for the modem and can use it on your computer. Otherwise you bought the wrong modem. Hopefully, you can return it.

It is usually hard to tell by reading the modem box. One user reports: "The RPI bit is hidden on the back of the box: '*Error Control* V.42 and MNP RPI software,' and '*Data Compression* V.42bis RPI software.' The box design is such that, unless you happen to already know what RPI is, you think you're getting a modem with MNP/V.42 LAPM/V.42bis compression built in."

If you can't return the modem, you can still use it without error correction, but then:

Thus, none of the modem's "advanced features" are really there.

Why RPI is a bad idea:

What are the benefits of RPI?

How do I tell if I have an RPI modem?

Is there a list of RPI modems?

Is RPI the only "software driven" modem scheme?

Of course you can't. But what about end users who don't understand any of this? Most of them do not make informed choices when buying modems. And increasingly, many of them make no choice at all -- the modem comes preinstalled in a PC they have bought, and does not even include a manual; sometimes not even a brand name. And now that RPI modems have been out for a while, we are beginning to see how they are passed from hand to hand, installed in or connected to new computers (for use, e.g., with DOS or Linux) and causing a whole new wave of problems.

If you have an RPI or other controllerless modem, and you need to use it in a setting for which a driver is not available -- that is, in most cases, any platform other than a PC running Microsoft Windows -- you are just plain out of luck. Return it and buy a real modem. This way, you will encourage modem manufacturers to continue to make real "platform-independent" modems.

Kermit FAQ / Columbia University /