Appendix D. Definitions of terms
AFS,Andrew File System
AFSis a more secure way of distributing file systems over a network. If files are mounted over the Internet,
AFSis fairly secure. Normally, AFS uses Kerberos for security management.
ARP
ARP,Address Resolution Protocol, is a protocol for mapping an IP address to a physical machine address in
thelocal network. A thorough description of ARP can be found in RFC 826.
Clientprogram
Aclient program is one that the user runs on her computer. A client program connects to a server. One example
ofa client program is Netscape (a WWW client). One benefit of dividing up a service into server and client
programsis that the server program can be run on a larger computer with better resources, and the users do not
haveto make their own copies of the databases. This allows the client programs to be run on less powerful
computers.
Cracker
Aperson who breaks into computer systems and commits other criminal acts using a computer.
Daemonprogram
Adaemon program is a server program for a service. This kind of program waits for and manages external
calls.A typical example is FTP. A user starts his FTP client. The client connects to the FTP server. Now the
usercan transfer files to his own computer or to the server. See Server.
Denialof Service, DoS
Atype of attack that tries to block a network service by overloading the server.
DHCP
DHCP,Dynamic Host Configuration Protocol, is a protocol for handing out IP addresses and other
configurationinformation to computers without having to log on to every single machine. Instead, the
computersthemselves send out requests about this information at boot, and gets appropriate configuration
parametersfrom a DHCP server. A thorough description of DHCP can be found in RFC 2131.
DMZ
ADMZ is a computer network that is accessible from two other computer networks that have no direct contact
witheach other. Often, one of these networks is the Internet and the other is a local, internal network. There is
nodirect connection between the Internet and the local network, but both of them can access an intermediate
network,a demilitarized zone.
DMZsare often used for special servers, such as web servers, which must be accessible from two separate
networks.
DNS
DomainName System; see Name servers.
Domain
Adomain is a country, organization, or subdivision. All countries have one top domain for the country, except
forthe USA, which is divided into a commercial domain (.com), a non-profit organizational domain (.org), a
universitydomain (.edu), a military domain (.mil), a governmental domain (.gov), and a network domain (.net).
Alldomains are hierarchical and each domain is responsible for the domains directly under it.
Adomain can have several sub-domains, which in turn can have sub-domains and so on. The structure
combinesthe domain name of the organization with the overlying domain name.
Forexample, Stanford University has the domain name stanford, which is under the university domain of
USA,.edu; together they form the domain stanford.edu. The university also has different departments under
stanford.edu.
Thedepartments of a company or organization can request a sub-domain from the domain manager. So if the
techniciansin the company’s service division want their own domain, they can go to their domain manager and
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