The Internet Protocol, IP for short, is the control protocol of the TCP/IP family.
IP is an unreliable datagram protocol, meaning that all it does is receive packets from and dump packets to the network. IP does not guarantee that the packets will ever reach their destination. IP does, however, check each packet for errors and discard packets which have been damaged in transit.
The most important concept in IP is the IP address. Each computer connected to a TCP/IP network is assigned a four-byte IP address, which is used to control the flow of packets.
When your Mac talks to another computer, TOPS TCP/IP sends IP packets to the IP address associated with the other computer. The other computer figures out the IP address of your Mac from the packets that you sent, so it can answer you back. Every IP packet has a "return address" as well as a destination address.
Depending on your local network, you may have to set up the IP address of your computer, or it may be set automatically for you.
When you are specifying a new computer description in TOPS Terminal, you will have to provide the IP address of the computer, just as you would have to supply a phone number before a computer could be called over the phone.
Each physical network (for instance, Appletalk and Ethernet) has its own ideas about how addresses should look, and IP has to map between the abstract IP addresses it uses and the low-level network addresses required by the physical network. It uses the Address Resolution Protocol to perform this mapping.
Most network applications, such as file transfer and terminal emulation, require more powerful services than IP directly offers. The Transmission Control Protocol uses IP to manage the details of packet addresssing, and adds a way of reliably sending data regardless of errors that may occur in transit.
