Apple Xserve Up Mac OS X Server Specifications download pdf (Page 319)

Glossary 319

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SSL Secure Sockets Layer. An Internet protocol that allows you to send encrypted,

authenticated information across the Internet. More recent versions of SSL are known

as TLS (Transport Level Security).

static IP address An IP address that’s assigned to a computer or device once and is

never changed.

subnet A grouping on the same network of client computers that are organized by

location (for example, different floors of a building) or by usage (for example, all eighth-

grade students). The use of subnets simplifies administration. See also IP subnet.

subnet mask A number used in IP networking to specify which portion of an IP

address is the network number.

systemless client A computer that doesn’t have an operating system installed on its

local hard disk. Systemless computers can start up from a disk image on a NetBoot

server.

TCP Transmission Control Protocol. A method used with the Internet Protocol (IP) to

send data in the form of message units between computers over the Internet. IP

handles the actual delivery of the data, and TCP keeps track of the units of data (called

packets) into which a message is divided for efficient routing through the Internet.

Transmission Control Protocol See TCP.

TTL Time-to-live. The specified length of time that DNS information is stored in a

cache. When a domain name–IP address pair has been cached longer than the TTL

value, the entry is deleted from the name server’s cache (but not from the primary DNS

server).

UDP User Datagram Protocol. A communications method that uses the Internet

Protocol (IP) to send a data unit (called a datagram) from one computer to another on

a network. Network applications that have very small data units to exchange may use

UDP rather than TCP.

UID User ID. A number that uniquely identifies a user within a file system. Mac OS X

computers use the UID to keep track of a user’s folder and file ownership.

Unicode A standard that assigns a unique number to every character, regardless of

language or the operating system used to display the language.

Uniform Resource Locator See URL.

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Apple Xserve Up Mac OS X Server Specifications Page 319