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CompTIA A+ Certification All-in-One Exam Guide

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the default gateway and .2 through .9 for servers.

TCP/UDP

When moving data from one system to another, the TCP/IP protocol suite

needs to know if the communication is connection-oriented or

connectionless. When you want to be positive that the data moving between

two systems gets there in good order, use a connection-oriented application.

If it’s not a big deal for data to miss a bit or two, then connectionless is the

way to go. The connection-oriented protocol used with TCP/IP is called the

Transmission Control Protocol (TCP). The connectionless one is called the

User Datagram Protocol (UDP).

Let me be clear: you don’t choose TCP or UDP. The people who

developed the applications decide which protocol to use. When you fire up

your Web browser, for example, you’re using TCP because Web browsers

use a protocol called HTTP. HTTP is built on TCP.

EXAM TIP Expect a question on the CompTIA A+ 1001 exam about TCP

vs. UDP. Think connection-oriented vs. connectionless and you’ll get the

right answer.

Over 95 percent of all TCP/IP applications use TCP. TCP gets an

application’s data from one machine to another reliably and completely. As a

result, TCP comes with communication rules that require both the sending

and receiving machines to acknowledge the other’s presence and readiness to

send and receive data.

UDP is the “fire and forget” missile of the TCP/IP protocol suite. UDP

doesn’t possess any of the extras you see in TCP to make sure the data is

received intact. UDP works best when you have a lot of data to send that

doesn’t need to be perfect or when the systems are so close to each other that

the chances of a problem occurring are too small to bother worrying about. A

few dropped frames on a Voice over IP (VoIP) call, for example, won’t make

much difference in the communication between two people. So there’s a

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