A communication terminal providing optimal communication services between content providers comprising a property management table with an appraised value registered for each of a predetermined set of communication media properties for various types of communication media, a first user specified priority ranking list and a second priority ranking list specified by an application program provider with rankings for the set of communication media properties, whereby the desired communication medium is selected by adding weightings for priority from the first and second priority ranking lists and adding the appraised value for each item from the property management table and using the highest total to specify the optimum communication medium for use when commencement of communication is specified by a predetermined application program, and establishing communication connections between opposing devices using the selected optimum communication medium. Also disclosed are a communication system, control device and program including the communication terminal's elements.