Some of these protocols are accompanied by user programs of the same name, such as ftp and telnet. Others, such as SMTP and HTTP, support other programs not named in the same way. And others like UDP, SNMP, and ICMP are hidden behind the scenes, but without their functionality, the Internet would not work at all.

The individual vendors still have their own proprietary systems, but they often provide TCP/IP software so their computers can be hooked to the Internet. It is not uncommon for one computer to have several different sets of networking software and be using all of it simultaneously.

Another set of protocols developed in the 1970s as a rational approach to multi-vendor interoperability was the ISO/OSI model. ISO is the International Standards Organization and OSI stands for Open Systems Interconnect. This set of protocols never quite got off the ground because the programs to implement it were not in place by the late 1980s, when the Internet exploded and TCP/IP became the dominant interoperable networking model. However, the OSI model was incredibly important theoretically and as an ideal to aim for. Everyone believes that TCP/IP's successor will be a cleaner, updated form of OSI.