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Trivial Services

TCP/IP offers a host of very simple services that are useful for debugging. Often, no server processes are associated to these servers. Instead, the kernel handles the service directly. Two of the most useful trivial services are:
  1. echo, which simply repeats back whatever you type to it
  2. daytime, which reports, in human-readable form, the machine's idea of the current date and time

Transport Control Protocol/Internet Protocol

(TCP/IP) is a protocol system, a collection of protocols that supports network communications. The answer to the question
What is a protocol?

must begin with the question
What is a network?

This module describes what a network is and shows why networks need protocols. You will also learn what TCP/IP is, what it does, and where it began (and the answer is not Al Gore.) At the completion of this module, you will be able to
  1. Define the term network
  2. Explain what a network protocol suite is
  3. Explain what TCP/IP is
  4. Discuss the of TCP/IP
  5. List some important features of TCP/IP
  6. Identify the organizations that oversee TCP/IP and the Internet
  7. Explain what RFCs are and where to find them
A network is a collection of computers or computer-like devices that can communicate across a common transmission medium.
Often the transmission medium is an insulated metal wire that carries electrical pulses between the computers, but the transmission medium could also be a phone line, or even no line at all in the case of a wireless network.
Regardless of how the computers are connected, the communication process requires that data from one computer pass across the transmission medium to another computer. Computer A must be able to send a message or request to computer B. Computer B must be able to understand the message of computer A and respond to it by sending a message back to computer A.