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December 15, 1997

Multilinking may provide additional modem bandwidth

Speeding up your modem and its access to the Internet is of great interest to lots of Windows users. In my Nov. 24 column (see Drag and drop Net files with FTP tool), I promised you a report on multilinking. This is a relatively new feature of Windows Dial-Up Networking (DUN) that can combine two modems into a single communications session. This could double the speed at which you can download Web pages.

More and more PC users have two modems available. One reason is that some applications now support more than one concurrent connection. If you have modems on COM1 and COM2, for example, Symantec's WinFax Pro 8.0 can simultaneously transmit faxes on both modems.

Microsoft originally added multilink features to DUN 1.1 to support ISDN. I recommended in my July 28 column that Windows 95 users install the DUN 1.1 upgrade that Microsoft referred to at the time as ISDN Accelerator Pack 1.1. (See Tools can help you monitor your Net download speed.) This upgrade let two 64Kbps B channels on an ISDN link be combined into a single link for faster downloads, but it also improved other features of DUN.

The latest version is DUN 1.2, and the term ISDN Accelerator Pack has been dropped. You should download DUN 1.2 from Microsoft's Web site at Click the link that says, "Download PPTP for Windows 95" (a reference to the Point to Point Tunneling Protocol, a feature of DUN 1.2).

To use DUN 1.2, you also need to install an updated version of Microsoft WinSock. This process is detailed on the same Web page that you download DUN 1.2 from.

Caveat 1: Installing the new WinSock may interfere with applications that modify the features of WinSock, such as Microsoft Proxy Server. You may need to reinstall such applications after upgrading WinSock.

Caveat 2: DUN 1.2 includes an uninstall module in the Control Panel, but this module doesn't return you to DUN 1.1 if needed. It deletes Dial-Up Networking entirely from your system, which disables your modem. This is explained in a document called Windows\Dun12.doc that isn't available to read until after you've run the upgrade. Sheesh.

When you've finished installing the upgrades, right-click an icon in your DUN folder, then click on Properties. There should be a new multilink tab in the dialog box. Windows NT 4.0 users already have this tab present for their dial-up connections.

Most ISPs, unfortunately, don't yet offer multilink support. Reader J. Schultz of Network Services Group points out that enabling multilink on an NT server allows users to dial in to an unlimited number of modems.

PowerNet Communications is one of the few ISPs I've found that does support multilink ( Owner Tim Black says users have gone over their allotment of lines only once.

Another company called Virtual Motion may have a solution. Its Remote Access Manager limits the number of multilink connections allowed by NT's Remote Access Service. For more information, see and click on the Remote Access Manager link.

I've heard from several people who are using multilink to speed up their Net connections. But Microsoft and ISPs will need to beef up their support before it will aid most users.

Brian Livingston is the co-author of several best-selling Windows books, including the most recent Windows 95 Secrets (IDG Books). Send comments to Unfortunately, he cannot answer individual questions.

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