User's Manual

Introduction to Network Security
6 WatchGuard Firebox X Edge
About PPPoE
Some ISPs assign the IP addresses through Point-to-Point Protocol
over Ethernet (PPPoE). PPPoE emulates a standard dial-up connec-
tion to provide some of the features of Ethernet and PPP. This sys-
tem allows the ISP to use the billing, authentication, and security
systems designed for dial-up, DSL modem, and cable modem ser-
vice.
Domain Name Service (DNS)
If you don’t know a person’s street address, you can look it up in the
telephone directory. On the Internet, the equivalent to a telephone
directory is the Domain Name Service, or DNS. You probably use
DNS all the time without knowing it. Whenever you use a “.com”
address such as www.mysite.com (which is actually the site’s
domain
name
) to visit an Internet site, you are using DNS. When you type
the .com address into your Internet browser (such as Internet
Explorer or Netscape), your computer asks its DNS server for the
actual IP address of the site.
A URL (Uniform Resource Locator) identifies each IP address on the
Internet. An example of a URL is:
http://www.watchguard.com/
Services
As the name implies, a service provides some kind of useful function
for you on the computer, such as exchanging e-mail or transferring
files from one computer to another through the network. These ser-
vices are based on specific protocols. Commonly used Internet ser-
vices are:
• World Wide Web access uses Hypertext Transfer Protocol (HTTP)
• E-mail uses Simple Mail Transfer Protocol (SMTP)
• File transfer uses File Transfer Protocol (FTP)
• Resolving a domain name into an Internet address uses Domain
Name Service (DNS)
• Remote terminal access uses Telnet or Secure Shell