Internet as a multiple graph structure: The role of the transport layer

This paper discusses how the transport layer (TCP/UDP/SCTP) divides the Internet into a vertical structure consisting of three domains: IP network domain, terminal equipment domain, and applications domain. This subdivision of the Internet has wide consequences both in the way in which business is carried out on the network and with regard to the vulnerability of society caused by the openness of the network. The Internet may also be modelled as a multiple graph structure. The domains may be viewed as independent entities allowing the different aspects of the Internet to be analysed as single graphs within each domain. Furthermore, the vulnerability of society may also be represented as a multiple graph structure where one of the components is a graph instance in the application domain of Internet representing the problem under study. Information security may then be studied at two levels: the vulnerability of the IP network itself and the vulnerability of the distributed processing taking place in the application domain.