AppendixD. Definitions of terms
requesta domain called, for instance, service. Below, we have ‘Company Inc.,’ which consists of three
departments:A sales department, a service department, and a computer department. The computer department
isdivided into an IBM section and a Unisys section.
Contactyour internet service provider to register a domain.
Dynamicrouting
Dynamicrouting is used when the traffic between two computers have several routes available. The route for
thepackets can be changed if a connection is broken or a router is turned off. RIP is a protocol handling
dynamicrouting.
Firewall
Adevice that prevents unauthorized access to a computer network.
Forwarding
SeeRelay.
FTP(File Transfer Protocol)
Imaginethat you have an account on a UNIX machine. You can retrieve and store files on the UNIX machine
withFTP. The program that manages this is called the FTP server. You can also establish an area of files that
areaccessible to others. Anyone can log in as user anonymous and enter his e-mail address as a password.
Theycan then access all files in this area, but nothing else. A computer with an FTP server and a freely
availablearea is usually called an FTP site.
Gateway
Gatewayis an old name for a Router.
Hacker
Aperson who is skilled and knowledgeable about computers and likes to examine the details of a computer
systemand what can be done with it. A hacker is good at programming and achieves good results. A hacker is
notto be confused with a computer criminal; see Cracker.
HTTPS
HTTPSis WWW traffic (HTTP traffic) on an encrypted connection. The encrypted connection is established
withthe SSL protocol.
ICMPprotocol
ICMPis used to forward information, primarily error messages. To see if a computer is running, the ‘ping’
programsends an echo request, which is part of ICMP. If a problem occurs with a connection, a response is
sentthrough ICMP that something is not right (the computer is not responding, the network is down, etc). If
thereare two possible paths for a connection, a router along the way may tell the computer to use the other
path.The router sends an ICMP redirect. ICMP uses the IP protocol to send data over the network.
IPaddress
IPaddresses are the Internet equivalent to telephone numbers. An IP address is divided into four groups, each
ofwhich is a number from 0 to 255. The groups are separated by dots. An example of an IP address is
141