Research In Motion's (RIM's) BlackBerry is a PDA that gives you wireless access to your Exchange Server Inbox and Calendar. The BlackBerry has become one of the more prevalent solutions for providing wireless access to Exchange email and personal information manager (PIM) data. BlackBerry devices provide wireless access to Exchange data through BlackBerry Desktop Software (for one user) or BlackBerry Enterprise Server (for multiple users). Many organizations and government agencies deploy BlackBerry Enterprise Server as an enterprise solution to let emergency workers and other field personnel stay connected. If you have users who rely on BlackBerry devices, you should understand how these handhelds communicate and how to monitor them and troubleshoot their problems.
Links in a Chain
Figure 1, page 2, depicts the chain of components and services in a BlackBerry network—mailboxes on the Exchange server, the BlackBerry Enterprise Server system, the Internet, RIM's Server Routing Protocol (SRP) host, RIM's wireless relays, the Mobile Switching Offices (MSOs), radio cell base stations, and the BlackBerry device. BlackBerry Enterprise Server uses Messaging API (MAPI) Collaboration Data Objects (CDO) to interact with Exchange mailboxes. When BlackBerry Enterprise Server starts to monitor a mailbox, it registers itself with the Exchange server by logging on to the mailbox. When a new message arrives in the mailbox, the Exchange server generates a MAPI-based notification to alert BlackBerry Enterprise Server of the message's arrival. BlackBerry Enterprise Server reads the first 2000 bytes of the message (to save bandwidth, the server sends only the beginning of long messages), encrypts those bytes, and passes them over the Internet to the next link in the chain—the SRP host.
The SRP host is an Internet-accessible RIM server that accepts and authenticates communications sessions from the BlackBerry Enterprise Server system and determines which wireless network to use to communicate with the BlackBerry device. In North America, BlackBerry devices use one of three wireless networks—Mobitex, DataTAC, or General Packet Radio Service (GPRS). In Europe, BlackBerry devices use Global System for Mobile Communication (GSM)/GPRS exclusively. (Most of today's BlackBerry devices don't support roaming on networks outside their home territory. In other words, a US/Canadian BlackBerry doesn't function in Europe and vice versa, even when similar networks are available in both places, because although the networks use the same technology—e.g., GPRS—they use different frequency bands—1900MHz in North America and 900MHz or 1800MHz elsewhere. However, in October, RIM introduced the BlackBerry 6710, which supports international roaming.)
After the SRP host identifies the appropriate network, it routes the message to one of RIM's wireless network relays (i.e., RIM's interfaces to the wireless network providers). Message routers then use MSO location-tracking data to determine which radio cell base station should get the message for the BlackBerry. Figure 2 shows an MSO connected to four base stations, each of which anchors a cell. When a BlackBerry is inside a cell, its embedded transceiver communicates with that cell's antenna. The MSO keeps track of which cell the BlackBerry is in. (The BlackBerry's wireless radio transceiver has a unique serial number issued by the wireless carrier that MSOs use to locate and identify the handheld device when it's active on the wireless network.) As the BlackBerry moves toward the edge of the cell, the transceiver and the base station in the adjacent cell measure signal strength to and from the device. As the BlackBerry moves farther from the center of the current cell, the signal strength diminishes in that cell and increases in the adjacent cell. When the BlackBerry crosses the boundary between the cells, its location is updated within the MSO. This tracking process lets the BlackBerry network route messages to BlackBerry devices, no matter where they move within the network.
The process is almost exactly reversed when a user sends a message or command from the BlackBerry. The base station accepts the message and places it on the wireless network. The network's routers use the MSO to determine how to get the message back to the RIM network. The RIM network then uses routing information specific to the BlackBerry device that sent the message or command to send the message to the BlackBerry Enterprise Server system, which interacts with the Exchange mailbox.
Day-to-Day Operation
After you deploy BlackBerry Enterprise Server, it operates in almost a set-it-and-forget-it manner. The problem you'll hear about most frequently from users is that messages aren't moving to or from their handhelds. Let's look at the events that occur or can occur at points along the communication chain that might prevent messages from moving or give the impression that messages aren't moving, as well as some steps you and your users can take to watch for and mitigate these problems.
BlackBerry Enterprise Server can monitor and support hundreds of accounts at the same time. To accomplish this job, BlackBerry Enterprise Server runs as a multithreaded application that uses MAPI CDO to access accounts on one or more Exchange servers. The number of threads BlackBerry Enterprise Server spawns varies depending on the number of servers and accounts it needs to support, but if the server supports more than a few handhelds, one thread typically services many mailboxes at once. (You can see how many threads BlackBerry Enterprise Server is running in two ways. First, you can use Performance Monitor—select Threads, then look through the instances for the BlackBerryServe/x objects. Second, you can look in the BlackBerry Enterprise Server debug logs described later in this article. When BlackBerry Enterprise Server starts or when you add a handheld device to or remove one from the server, the server makes an entry in the log that shows the number of threads in use.) The threaded process rotates through the mailboxes, usually very quickly, performing necessary tasks such as checking for and forwarding messages to BlackBerry devices or carrying out instructions, such as to compose and send a new message, from the devices.