Not long ago, ISDN was about the only way a small business could get a decent connection to a remote network or the Internet at an affordable price. It was more expensive than using standard phone lines, but promised dramatically improved throughput--up to 128 Kbps--compared with a modem. Now, there's another option: multiport analog routers that aggregate the bandwidth of two or more 56-Kbps modems, making it possible to get near-ISDN throughput at POTS prices.

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We tested four multiport analog routers that connected us to the Internet and remote or central offices faster than the 56 Kbps of a single channel: Multi-Tech Systems' ProxyServer MTPSR3-200, Netopia's Netopia Router with Dual Analog, Ramp Networks' WebRamp M3i and 3Com Corp.'s OfficeConnect Remote Dual Analog. Each device has at least one--and as many as eight--Ethernet ports and two modems that can work together to accelerate downloads. Some routers even include a third internal modem or a serial port to connect an external modem.

We evaluated the routers' features, performance, setup/management, flexibility, price and documentation. Most companies can't afford a dedicated technical support person at each site, so we wanted setup and ongoing management to be easy, preferably handled from a Web browser. Performance is paramount, and flexibility is essential to suit the connectivity needs of every office, whether client machines are routed or proxied via NAT (Network Address Translation) through a PPP connection. While price is important, good performance and flexibility are worth the cost. And because these units are destined for SOHO (small office/home office) environments, we gave documentation some consideration as well.

The devices we tested use one of two methods to aggregate bandwidth: proprietary load-sharing or channel bonding (also known as Multilink PPP, or MLPPP). With MLPPP, data packets travel over the two modem lines, using a single link session. The packets are multiplexed across the two lines. MLPPP requires support at the remote site and the central office or ISP, but it relies on standards to aggregate traffic, and offers more flexible, multiprotocol routing. Multi-Tech, Netopia and 3Com support this protocol.

Load-sharing aggregates two or more TCP sessions. Data from a single source is gathered and transmitted using two simultaneous PPP connections. This method, which Ramp Networks calls COLT (Connection Optimized Link Technology), is the easiest to configure and needs no special support from ISPs or a central office. However, load-sharing requires NAT, and therefore works best for remote sites that don't house many externally accessible servers, since they can address only one of each type of server, such as Web or e-mail. WebRamp M3i uses this method exclusively, and Multi-Tech offers it along with MLPPP.

In our tests, we found no conclusive evidence that one technology delivers better performance than the other when multiple clients use the device; however, many factors influence actual throughput, including phone-line quality, traffic patterns and raw device performance. We measured raw device performance for HTTP traffic (typical for a remote office), and found that performance fluctuated depending on the scenario. For example, Ramp Networks' WebRamp M3i turned in the best performance under a single-modem scenario with four and eight clients, while Multi-Tech's ProxyServer MTPSR3-200 set the pace under a dual-modem scenario with two and four clients. 3Com's OfficeConnect Dual Analog was stressed with four or more clients using a single or dual connection, and Netopia's Router with Dual Analog reaped the most benefit from the addition of a second connection. Activating the devices' second modem generally improved the throughput, but never doubled it.