Building trustworthy systems: lessons from the PTN and Internet

The public telephone network (PTN) and Internet are two large and complex networked information systems (NISs). The PTN and the Internet shed light on the technical problems faced by the developers and operators of other NISs. In some ways, the two networks are very similar. No single entity owns, manages, or can even have a complete picture of either. Both networks involve large numbers of subsystems operated by different organizations. The number and intricate nature of the interfaces that exist at the boundaries of these subsystems are one source of complexity; the increasing popularity of advanced services is a second source. This article discusses vulnerabilities in the PTN and Internet, identifying ways new research might help to eliminate those vulnerabilities.