Unfortunately, competing ISPs often break this hierarchical design. Furthermore, manually configured routing tables may make the problem worse. Only after the packets reach either coast, are they recognized and sent back to the originating location. In this way, keystrokes from a student's virtual terminal session are sent to the west cost before returning to the local university computer. These terms represent the key concepts that allow two computers to communicate via a network.
Network address is a logical address assigned to each host.
All IP addresses are allocated by the Internet Assigned Numbers Authority, and paths to each IP address are manually placed in routers from the top level to the bottom level routers. So even though network addresses are logical, most IP address are geographically fixed. Protocol refers to the manner in which two programs choose to communicate. A virtual circuit protocol requires the communicating programs to go through a series of steps similar to making a telephone call while a datagram is sent out much like dropping a letter into a mail box. Virtual circuits are said to be reliable while datagrams are considered unreliable.