Issue TOC Print full article Print this page Download as PDF E-Mail this URL Flame the author     In this article Introduction IP Packet Architecture Throughput Versus Latency But Is It Secure? Executive Summary GPRS: Problem-Free Connections Verizon Wireless' 1XRTT: Safe At Almost Any Speed

WLAN security, or lack thereof, has received a huge amount of attention, but cellular networks are a different story. First, operators employ rigorous authentication mechanisms to protect against fraud. As for encryption, CDMA networks do not encrypt data traffic, but it is inherently difficult to eavesdrop because CDMA's spread-spectrum signal is intended to look like low-level noise. However, it is not impossible. GPRS, meanwhile, has a reasonably effective encryption option, but only some operators use it. Both 1XRTT and GPRS would require sophisticated equipment that's not yet readily available to try and monitor user traffic, but most corporations are likely to employ their remote-access VPNs with these networks anyway. Even if the wireless link is protected, the data traffic may still pass across the Internet, and the VPN is probably required to access the corporate network. Traditional VPNs work fine over GPRS and 1XRTT, but are not as efficient as some new wireless-optimized VPNs from companies such as NetMotion Wireless and Ecutel.

Although these new networks support IP, you need to read the fine print. One item to watch is session maintenance. To conserve networking resources, such as IP addresses, operators time out inactive sessions. With Verizon Wireless, time-outs occur in as few as five minutes. A user who has just spent a couple of minutes establishing a VPN connection won't be happy to lose that connection five minutes later just because he or she ponders over an e-mail. You may need to adjust keep-alive timers in the VPN accordingly. In contrast, AT&T Wireless (GPRS) has its time-out set at one hour. You will need to ask about this or test it directly. When your session times out, you lose the IP address you had, which can also complicate server-initiated communications, such as for dispatch or other forms of notifications. Also, there simply aren't enough IP addresses for the new world of mobile users. Most operators employ NAT (Network Address Translation) in their networks and issue users private (nonroutable) IP addresses. This lets multiple private addresses map to a single public IP address. Because this does not work with all applications, including most VPNs unless they are configured appropriately, operators also offer public IP addresses as a service option.