We set up the multiport analog devices in a remote office near our University of Wisconsin-Madison lab. For connectivity checks, we dialed into a local ISP and into CMP Media's headquarters in Manhasset, N.Y. To rate actual performance, we connected to our San Mateo, Calif., lab, using four 200-MHz Pentium MMX machines to draw Web pages from a Sun Microsystems Ultra 10 server.

On the back end, we used a Cisco Systems AS5300 remote-access server to test the Multi-Tech, Netopia and Ramp products, which support K56flex modem technology. For 3Com's product, the only x2 device we tested, we needed a different server--3Com's NetServer I-modem.

If many users are sharing modem connections, performance is paramount. Emulating a standard remote-office configuration, we used Network Tools' Chisel software to simulate up to eight users browsing the Web. Each client repeatedly downloaded a page of HTML and all of the page's subsequent images. The Web page featured about 4 KB of text and 188 KB of embedded graphics--15 graphics files ranging from 43 bytes to 70 KB. Chisel tracked how long it took each client to download the entire page three times.

We looked at single- and dual-connection performance. Good single-modem performance prevents unnecessary use of two lines. We tested two-line performance to quantify the benefits of the second connection.