the simplest topology is a permanent link between two endpoints (the line in the illustration above). switched point-to-point topologies are the basic model of conventional telephony. the value of a permanent point-to-point network is the value of guaranteed, or nearly so, communications between the two endpoints. the value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers, and has been expressed as metcalfe's law.