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Mobile Messaging Gateways: Page 9 of 16

The matter of the final push to the device may seem trivial, as the device has an IP address and you can theoretically just send IP datagrams to it. However, there are complications. For example, most operators time out their data sessions to conserve network resources. If a device has not communicated for an operator-specified number of minutes or hours, the network terminates the data session and the device loses its IP address. If the device initiates another data session, it's likely to get a different IP address. Given that devices can spend more time off or asleep than active, sending unsolicited data to the device is not trivial.

Vendors take two approaches to get around this problem. One is to use SMS to notify the device that new e-mail is available. Operating over the cellular network control channels, SMS pushes small amounts of information) to a mobile device, which then initiates an IP data session if it doesn't already have one and downloads the e-mail. This approach is becoming less popular, mainly because the SMS channel capacity is limited, and operators would prefer to keep it open for revenue-generating applications such as text messaging.

The alternative approach, which RIM and Good Technology already use and other vendors are likely to adopt soon, is for the mobile client to take an active role in monitoring its IP session state. The client makes sure it always has an IP session active, bringing it back up if it expires. Remember that these are packet-data networks, so having a data session active in itself does not consume radio resources. The client then communicates with the wireless e-mail gateway every time its address changes, identifying itself so the gateway knows which IP address to use for the mobile device. This tight coupling between client and gateway increases network chatter, but the result is an effective push mechanism.

With a secure, managed and real-time tunnel in place between the mobile device and the gateway, vendors are now looking at how to extend the range of supported applications. It makes sense to leverage the platform to deliver all types of urgent information to your users. Numerous third-party vendors, including SAP and Salesforce.com, are developing the appropriate hooks. RIM lists 300 ISVs for its platform, and PalmSource and Microsoft are no slouches here either. Some offerings have well-defined APIs you can use yourself with customized development. But there are no standards or consistency among the vendors on how to access nonmessage corporate data. You can provide this access, but don't expect an out-of-the-box implementation.

Our advice: Concentrate on your immediate needs. The market is evolving quickly, as are devices. When you're ready to upgrade your users' PDAs or smartphones, new options will be open to you.