CompTIA A+ Certification All-in-One Exam Guide

NOTE This chapter only covers local area networks, such as a group of
computers in a single office. We’ll save connecting to the Internet for
Chapter 21, “The Internet.” But be ready! You need to understand everything
in this chapter before you can take the next step and connect to the Internet.
1001/1002
TCP/IP
The Ethernet hardware protocol does a fine job of moving data from one
machine to another, as you learned in Chapter 18, “Essentials of
Networking.” But Ethernet alone isn’t enough to make a complete network;
many other functions need to be handled. For example, an Ethernet frame
holds a maximum of 1500 bytes. What if the data being moved is larger than
1500 bytes? Something has to chop up the data into chunks on one end of a
connection and something else needs to reassemble those chunks on the other
end so the data can be put to use.
Another issue arises if one of the machines on the network has its network
card replaced. Up to this point, the only way to distinguish one machine from
another was by the MAC address on the network card. To solve this, each
machine must have a unique name, an identifier for the network, which is
“above” the MAC address. Something needs to keep track of the MAC
addresses on the network and the names of the machines so that frames and
names can be correlated. If you replace a PC’s network card, the network
will, after some special queries, update the list to associate the name of the
PC with the new network card’s MAC address.
Network protocol software takes the incoming data received by the
network card, keeps it organized, sends it to the application that needs it, and
then takes outgoing data from the application and hands it to the NIC to be
sent out over the network. All networks use some network protocol. Over the
years there have been many network protocols, most combining multiple