Relationships

As shown in the profile relationships diagram (refer back to Figure 11.1), all three of these profiles derive from the serial port profile, or SPP, that was described in the previous chapter. This is not surprising, since the SPP and its associated RFCOMM protocol are intended to allow legacy applications to make use of Bluetooth wireless transports, and all three of these profiles instantiate legacy applications (that is, they define how to do existing tasks without wires). So these profiles are a logical fit as members of the SPP family, which is the basis for the version 1.0 cable-replacement scenarios. They are also a good fit with the SPP technically, since all three profiles involve applications that most likely will include the notion of communicating over a serial port. In the case of dial-up networking and fax, the use of a serial interface is obvious, since both use a modem (or at least the abstraction of a modem) to communicate over a telephony network, and the most prevalent way to access nearly all modems is via a serial port. In the case of LAN access, the use of the serial interface might not be directly evident, since a direct network access cable is not necessarily modeled on a serial port. However, since the version 1.0 LAN access profile uses the point-to-point protocol (PPP), this sort of LAN access tends to resemble dial-up networking, and PPP maps well to a serial communication layer. Thus all three of the profiles derive from the SPP and use a serial port communication model.

The dial-up networking and LAN access profiles together make up the Internet bridge usage model. As described in Chapter 3, two similar yet different methods are defined for using Bluetooth links as a bridge to a larger network like the Internet. Those two methods are defined by the dial-up networking and LAN access profiles, respectively. Curiously, the fax profile has no specific publicized usage model behind it. So in a way the fax profile is not related to any of the other version 1.0 profiles except in being part of the SPP family tree. Indeed the fax profile is an example of the SIG's defining a formal specification for the use of Bluetooth links to perform easily understood usage models. In this respect the fax profile might be more similar to a printing or scanning profile, neither of which exists in the version 1.0 specification although they might be generated in the future. Since it does not derive from a common usage case, the fax profile is related only indirectly to any other version 1.0 profiles. It does, though, have some similarities with the other two networking profiles discussed in this chapter, which is why we include it here.