Seamless Roaming

In the Windows & .NET Magazine Lab, we test many new products and technologies that perform certain tasks or solve particular problems. Typically, we look at one or more products in a specific category. Sometimes we bring together several vendors' products and test their combined effectiveness as an integrated solution. Having recently collected an array of wireless hardware, portable devices, and specialized mobility software, I found myself in a position to determine whether seamless mobility has finally arrived. I've closely watched the progress of wireless Ethernet, which now offers wireless LAN (WLAN) speeds of 54Mbps in its 802.11a and 802.11g specifications, and I've watched as wireless carriers struggled to implement high-speed, third-generation wireless services. The wireless infrastructure has since matured sufficiently to provide constant connectivity across most travel destinations. Could the right combination of hardware and software make roaming a seamless experience?

If you've attempted to use multiple wireless technologies to stay connected, you know the limitations of such a setup. Rarely can one portable device concurrently host a standard wired Ethernet card, a wireless Ethernet card, and a wireless modem—you need to constantly swap PC Cards, reboot, and reconfigure.

After you have connectivity, how do you reliably and securely access your data? Many mobile users are disappointed by the hassles of switching between wireless networks. Although several vendors have developed products that extend wireless capabilities, no vendor offers an end-to-end solution that makes the transition between networks unnoticeable.

The Test Environment
For me, the ideal roaming experience is the ability to work on my mobile device wherever I am without needing to close active applications, reconfigure network connections, or reboot. To simulate a real-world, seamless-roaming test scenario, I set up several Access Points (APs) on different subnets and separate physical networks. I used standard wired Ethernet and 802.11 connections.

My primary laptop was a Dell Latitude C610 with a mini-PCI 802.11b wireless Ethernet card. I used the two available PC Card slots for a 3Com OfficeConnect LAN Modem combo card. Sprint offers good wireless coverage where I travel, so I chose the Sierra Wireless AirCard 510 wireless modem, the first Code Division Multiple Access (CDMA) modem designed for Sprint networks. I also tested Compaq's latest Pocket PC, the iPAQ 3835, with the PC Card expansion pack for power and flexibility. I used a Compaq WL110 wireless Ethernet card for my WLAN connectivity and the AirCard 510 for wireless WAN connectivity.

I configured my laptop in a dual-boot configuration with Windows XP Professional and Windows 2000 Professional. The iPAQ came with the Pocket PC 2002 OS. I was particularly interested in testing XP's and Pocket PC 2002's enhancements for wireless users.

NetMotion Wireless's NetMotion Mobility provided the final piece I needed. NetMotion Mobility is a client/server product designed to smooth out the rough spots typically associated with switching networks. The client communicates directly with the NetMotion server, which acts as a proxy for your network sessions. The client component resides on the mobile device and simulates a connected state during connectivity interruptions. This product also features strong encryption between the client and server, eliminating a major weakness of Wired Equivalent Privacy (WEP).

My first impression while setting up the test network was that IT departments are in for a headache when attempting to provide a wireless-roaming solution for a large number of mobile users. No particular step was exceptionally difficult, but the cumulative process of configuring the hardware and software, tracking down all the latest firmware and drivers, and preparing the existing network infrastructure isn't without complications.

After I completed the setup process, I worked with several applications on the laptop and Pocket PC, including the Microsoft Office 2000 suite, Web browsers, FTP clients, and Microsoft's Terminal Services client. On the laptop, I also switched between XP Pro and Win2K Pro.

First, the Good Stuff
The AirCard 510, along with the bundled BlueKite compression software, performed reasonably well over the 14.4Kbps connection. Sprint's coverage is good, and I had clean, reliable connections. When you must use wireless WAN connections, you can expect at least usable performance. And because the AirCard could coexist with other PC Cards in my laptop, I could switch networks without swapping hardware.

XP is the OS to use if you want to roam across WLANs. XP's built-in wireless capabilities are impressive. Because XP handles movement between wireless networks behind the scenes, it fulfills a basic prerequisite for seamless roaming.

NetMotion Mobility, although not perfect, let me move between wireless networks with several applications without problems. FTP sessions from within Microsoft Internet Explorer (IE), Telnet sessions, and Terminal Services sessions didn't introduce any problems with latency or disconnected states while I roamed. After I resumed a connection, the sessions picked up where they left off.

The Pocket PC 2002 Terminal Services client is a great addition. Although you can't view the entire desktop at once, I found the client usable on the iPAQ. Performing administrative tasks on a server while riding as a passenger in a car is a plus.

Now, the Not-So-Good Stuff
Despite the good experiences, using Win2K Pro or Pocket PC 2002 to roam between wireless networks isn't seamless. Win2K Pro requires fiddling with configurations, and Pocket PC 2002 often requires a reset before it associates with another wireless AP.

In my tests, NetMotion Mobility didn't fare well with Office 2000 applications or FTP sessions from the command line. Microsoft Word was especially troublesome—it tried to autosave when a network connection wasn't present.

You also need to address security. Encryption with a product such as NetMotion will protect your data, but it isn't a comprehensive security solution. My conclusion is that, although vendors have made good progress, we'll have to wait a while longer before we can roam across networks as if we never left our desk.

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