It is ingrained in our behavior that if we are going to take a step toward calling someone on the telephone, we need to ask them “what is your telephone number?” It is is ingrained in our behavior that if we are going to make it possible for someone to call us on the telephone, we need to be able to tell someone “our telephone number”. This world of “having a telephone number” and “calling a telephone number” is the most prominent aspect of the Public Switched Telephone Network (Wikipedia article). One way to think of the PSTN is that it is a collective effort by governments and post offices and landline telephone companies to collect money from people who “dial telephone numbers” and who receive telephone calls from other people who “dial telephone numbers”.
The rise of the Internet has prompted many efforts to find ways that people can talk to each other without paying money to the PSTN. One of those ways is the SIP URI (Wikipedia article). Continue reading