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of these players are likely to split their companies accordingly. The model that will be the most successful will depend mostly on its execution, and we will see winners in both camps. The important thing for operators is to actually face the change and set a firm strategy that outlines where they should be in the value chain. We revisit the business aspects of the mobile Internet in Chapter 15, “Getting It All Together.”
Before we plunge deeper into this new architecture and the service network, let’s look at how the applications are typically installed in 2G/2.5G networks.
Today’s Application Architectures
If we use the new way of designing networks, we cannot design them overnight. Many GPRS networks will initially use the old way of integrating applications, putting servers deep within the mobile network. Although all operators have chosen different network designs, the basic outline is often similar. Mostly, there is an application/service LAN connected to the mobile network, as shown in Figure 9.3. We show a GSM system here, but IS-95 and Time Division Multiple Access (TDMA) systems are designed similarly.
In the figure, we see that the LAN where applications reside is tightly connected to the mobile system. The SMS-C, for instance, is connected to both the application LAN and the Signaling System 7 (SS7) signaling network. In other words, there is a high barrier for third-party developers to develop applications for these systems. Not only that, but gaining access to system-specific features such as call control and positioning is close to impossible. (There are no APIs available.) In addition, this network design is not suitable for large subscriber
Figure 9.3 A mobile network and application/service LAN.
bases of applications. An operator that starts with tens of thousands of applications subscribers and suddenly receives millions will run into difficulties. The system scalability will be poor, and adding twice the amount of applications servers will only render a tiny percent increase in capacity. Finally, there is the issue of software upgrades to the components of the service LAN. Will adding a new application mean an interruption of service to other applications on the same application server (or even applications on other servers)? There is clearly a strong need to build the architecture for mobile applications, from the bottom up, in order to handle these challenges.
We expect GPRS to be a transition technology for application architectures in the sense that some operators will start with the old architecture and later migrate to full-blown service networks. Figure 9.4 shows a GPRS system that uses the standard 2G applications solution.
As illustrated in the figure, the GPRS network is closer to the desired IP-based application architecture, with the GGSN (which uses IP) directly connected to both the Internet/ISP and the service LAN without an Inter Working Function (IWF). This approach does not solve the scalability and robustness issues either, however, and the need for a dedicated application architecture (the service network) remains.
Introducing the Service Network
As the mobile Internet becomes pervasive, it also becomes more and more obvious that it is not an isolated network. On the contrary, there will be great synergies in doing some task of an application with a desktop PC (and some with the mobile device). You can book a complicated trip through a travel agency or directly on the Internet by using a desktop PC. At least, the first time that you
Figure 9.4 A GPRS network and application LAN.
perform this action, it requires lots of text entry because the payment and mail information need to be entered. Therefore, a nice 21-inch color monitor with a large keyboard is preferred over a 10-by-2 cm telephone display. Once the itinerary is set and the user is on the move, the lightweight phone is an excellent tool for checking confirmation numbers, hotel addresses, and so on.
As we saw in the previous example, accessibility from a variety of networks (fixed or wireless) is essential to this new architecture. Some of the other drivers are as follows:
Scalability and robustness. The network design should be suitable for any number of users, and it should be convenient to small with just a few nodes and add more nodes as more users join.
Flexibility. The capabilities of the network should be easy to expand in order to include new value -added services as they become available. For instance, one operator might decide to start without location-based services and add support for that later. An application server might initially contain only one application, but later on you might need to install more. This situation should in no way impact the current service to subscribers.
Security. As the applications become logically separated from the mobile network, you must ensure the security,
integrity, and privacy of users and their data. The closed operator environment of 2G systems was what made security easier, and a new open architecture means some new security challenges.