Specifications
310 Glossary
ICMP Internet Control Message Protocol. A message control and error-reporting
protocol used between host servers and gateways. For example, some Internet
software applications use ICMP to send a packet on a round trip between two hosts to
determine round-trip times and discover problems on the network.
image See disk image.
IMAP Internet Message Access Protocol. A client-server mail protocol that allows users
to store their mail on the mail server rather than downloading it to the local computer.
Mail remains on the server until the user deletes it.
IP Internet Protocol. Also known as IPv4. A method used with Transmission Control
Protocol (TCP) to send data between computers over a local network or the Internet.
IP delivers data packets and TCP keeps track of data packets.
IP address A unique numeric address that identifies a computer on the Internet.
IP subnet A portion of an IP network, which may be a physically independent network
segment, that shares a network address with other portions of the network and is
identified by a subnet number.
IPP Internet Printing Protocol. A client-server protocol for printing over the Internet.
The Mac OS X printing infrastructure and the Mac OS X Server print service that’s built
on it support IPP.
IPSec A security addition to IP. A protocol that provides data transmission security for
L2TP VPN connections. IPSec acts at the network layer, protecting and authenticating IP
packets between participating IPSec nodes.
IPv4 See IP.
IPv6 Internet Protocol version 6. The next-generation communication protocol to
replace IP (also known as IPv4). IPv6 allows a greater number of network addresses and
can reduce routing loads across the Internet.
ISO International Standards Organization. The international standards body. ISO-
published standards have the status of international treaties.
ISP Internet service provider. A business that sells Internet access and often provides
web hosting for e-commerce applications as well as mail services.
KB Kilobyte. 1,024 (2
10
) bytes.
KDC Kerberos Key Distribution Center. A trusted server that issues Kerberos tickets.