Testing RoamAnywhere Mobility
Agito utilizes several data sources to help make the decision when to roam from the cell network and back to Wi-Fi. At the network level, the Mobility Router can tap into data culled by Cisco's Mobility Services Engine. On the client side, the Mobility client utilizes typical metrics like signal strength, but also leverages location-by comparing a device's location to a series of fingerprints (signal strengths of all detected nearby access points and some cell tower information taken from a designated spot) taken by a system administrator at a building's egress points when the solution is rolled out. I took fingerprints by loading a special calibration application on a supported smart phone, recording three or four measurements just outside each exit point. From the calibration tool, I could measure the accuracy of the fingerprint, walking back and forth through the threshold to ensure that the roam happened where it should. Then I could upload the fingerprint to the Mobility Router, where I could then apply the fingerprint to a location policy object.I tested with two devices-an AT&T Tilt and a Nokia E71-and I indeed found that the fingerprint taken with the E71 worked as expected with the Tilt as well, causing seamless handovers as I walked in and out of the building. However, I also found that with both devices, as I exited the test facility, some unexpected roams back to the Wi-Fi network would also occur well outside of the building if I loitered around for a few seconds. To counter tricky areas where Wi-Fi bleedsoutside the corporate walls, Agito lets administrators fine-tune handover settings for each location in the network. In this way, I could adjust the RSSI (Received Signal Strength Indicator) threshold to ensure that such roams from cell to Wi-Fi only occur inside the building, and then create distinct settings for each building as necessary. The client experience was drastically different between the Nokia and Windows Mobile iterations. On Windows Mobile, Agito has painted its dial application into the native Windows Mobile dialer, whereas the Nokia devices have a separate dial application (called RADialer). This meant that the process of placing calls, looking up corporate contacts from Active Directory or changing forwarding rules was sufficiently different enough between the two that it was a bit confusing to use both. I also noted a significant difference in call quality on the two devices. In both cases, I found calls on the Wi-Fi network sounded significantly clearer than calls placed over the GSM network. This also made it fairly obvious to detect when I switched between networks, even if there were no temporary dropouts or garbles. However, the Windows Mobile devices sounded clearer and more distinct than the Nokia phones over Wi-Fi, likely due to the use of the outstanding codecs from GIPS as part of the Windows Mobile client. Both sets of devices allow the user to place calls in either personal mode-using the cell phone's number-or in corporate mode, using the PBX extension. This dual persona allows the user connected to an enterprise call to accept a second personal call as well, no matter if the first call is connected via Wi-Fi or cellular. The system administrator does have the option of blocking the use of personal mode via central policy. Version 2.0 of the Mobility Router also introduces additional security measures for calls coming in over remote, potentially unknown Wi-Fi networks. When a client connects to a foreign Wi-Fi network, the Agito client automatically engages Secure Remote Voice-in essence, an application layer SSL [Secure Sockets Layer] VPN. The client uses a split tunnel: The encrypted connection to the Mobility Router protects call data, signaling and directory lookups from prying eyes, while any Web browsing or other network activity goes directly to the Internet. Administrators can further tune Secure Remote Voice to only work from approved remote networks such as the user's home network. Secure Remote Voice costs an additional $6,049 for 100 users on the RoamAnywhere 2000, or an additional $27,499 for 500 users on a RoamAnywhere 4000. eWEEK Labs Senior Technical Analyst Andrew Garcia can be reached at firstname.lastname@example.org.
In the background, the Mobility Router also performs a series of heuristics against the fingerprint, to alter fingerprint settings according to known Wi-Fi detection capabilities of different phones than the one used during calibration process. In this way, Agito tries to make one calibration work for every supported device, no matter the differences in radio power or antenna position. The fingerprint also captures some data about the cellular network, allowing Agito to save a bit of battery life for the client because the device won't start scanning Wi-Fi until it detects the device is associated with a cell tower known from the fingerprint.