NetMotion: Mobility 4.0.

(From Network Computing Asian Edition)

Byline: Andy Dornan

Some day, mobile IP will enable seamless roaming between LANs and WANs. Users will remain logged on even as they unplug their Ethernet cables and move in and out of different wireless network coverage areas. That?s still in the future, but the Mobility software from NetMotion (www.nmwco.com) already delivers most of the functionality planned for mobile IP. It also adds features necessary to cope with today?s hardware.

Instead of just handing off connections from one type of network to another, it can keep a connection up if PC cards are swapped, if the device is switched off, or when a user goes under a bridge or tunnel.

A user who?s making a download through a 802.11b (Wi-Fi) hotspot in Singapore can board a flight to Europe, shut down for 12 hours, then reconnect via GPRS and resume the download when the plane lands.

This is achieved by routing data via a proxy server located on the user?s ?home? network, usually a company LAN. On one side, the server keeps track of mobile nodes and tunnels traffic to them. On the other, it provides a fixed ?virtual? IP address, employing techniques such as spoofing and altering the TCP window size to keep applications and higher-level protocols unaware that the user is mobile.

In addition to the proxy server, Mobility requires a client on each mobile node. This automatically selects the best connection method available, though the feature can be over-ridden by users who want to save money or need to swap interface cards.