Network Plus 2005 In Depth

782 Glossary

gateway—A combination of networking hardware and software that connects two dissimilar kinds of networks. Gateways perform connectivity, session management, and data translation, so they must operate at multiple layers of the OSI Model.

gateway router—See border router.

GEO (geosynchronous orbit or geostationary orbit)—The term used to refer to a satellite that maintains a constant distance from a point on the equator at every point in its orbit. Geosynchronous satellites are the type used to provide satellite Internet access.

geostationary orbit—See GEO.

geosynchronous—See GEO.

ghost—A frame that is not actually a data frame, but rather an aberration caused by a device misinterpreting stray voltage on the wire. Unlike true data frames, ghosts have no starting delimiter.

giant—A packet that exceeds the medium’s maximum packet size. For example, any Ethernet packet that is larger than 1518 bytes is considered a giant.

Gigabit Ethernet—A type of Ethernet network that is capable of 1000 Mbps, or 1 Gbps, throughput. Examples of Gigabit Ethernet include 1000BASE-T and 1000BASE-CX.

global group—A group on a Windows Server 2003 network that allows members of one domain to access resources within that domain as well as resources from other domains in the same forest.

globally unique identifier—See GUID.

GNU—The name given to the public software project to implement a complete, free source code implementation of UNIX. It also refers to the collection of UNIX-inspired utilities and tools that are included with Linux distributions. The term “GNU” is an acronym within an acronym that stands for “GNU’s Not UNIX.”

grandfather-father-son—A backup rotation scheme that uses daily (son), weekly (father), and monthly (grandfather) backup sets.

graphical user interface—See GUI.

group—A means of collectively managing users’ permissions and restrictions applied to shared resources. Groups form the basis for resource and account management for every type of network operating system, not just Windows Server 2003. Many network administrators create groups according to department or, even more specifically, according to job function within a department.

GroupWise—An application from Novell that runs on NetWare servers and provides e-mail, messaging, scheduling, and collaboration services.

Guest—A user account with very limited privileges that is created during the installation of a network operating system.

GUI (graphical user interface)—A pictorial representation of computer functions and elements that, in the case of network operating systems, enables administrators to more easily manage files, users, groups, security, printers, and other issues.

GUID (globally unique identifier)—A 128-bit number generated and assigned to an object upon its creation in the Windows Server 2003 Active Directory. Network applications and services use an object’s GUID to communicate with it.

Glossary 783

hacker—A person who masters the inner workings of operating systems and utilities in an effort to better understand them. A hacker is distinguished from a cracker in that a cracker attempts to exploit a network’s vulnerabilities for malicious purposes.

half-duplex—A type of transmission in which signals may travel in both directions over a medium, but in only one direction at a time.

handshake protocol—One of several protocols within SSL, and perhaps the most significant. As its name implies, the handshake protocol allows the client and server to authenticate (or introduce) each other and establishes terms for how they securely exchange data during an SSL session.

hardware address—See MAC address.

Hardware Compatibility List—See HCL.

hardware RAID—A method of implementing RAID that relies on an externally attached set of disks and a RAID disk controller, which manages the RAID array.

HCL (Hardware Compatibility List)—A list of computer components proven to be compatible with Windows Server 2003. The HCL appears on the same CD as your Windows Server 2003 software and on Microsoft’s Web site.

head-end—A cable company’s central office, which connects cable wiring to many nodes before it reaches customers’ sites.

hertz (Hz)—A measure of frequency equivalent to the number of amplitude cycles per second.

heuristic scanning—A type of virus scanning that attempts to identify viruses by discovering “virus-like” behavior.

HFC (hybrid fiber-coax)—A link that consists of fiber cable connecting the cable company’s offices to a node location near the customer and coaxial cable connecting the node to the customer’s house. HFC upgrades to existing cable wiring are required before current TV cable systems can provide Internet access.

HFS+—The primary file system used in Mac OS X Server.

hierarchical file system—The organization of files and directories (or folders) on a disk in which directories may contain files and other directories. When displayed graphically, this organization resembles a treelike structure.

High-Speed Token Ring—See HSTR.

home directory—A directory on a server associated with a particular user account. A user has full access privileges to files and subdirectories within his home directory.

hop—A term used to describe each trip a unit of data takes from one connectivity device to another. Typically, “hop” is used in the context of router-to-router communications.

host—A computer that enables resource sharing by other computers on the same network.

host file—A text file that associates TCP/IP host names with IP addresses.

host name—A symbolic name that describes a TCP/IP device.

784 Glossary

hosts—Name of the host file used on UNIX, Linux, and Windows systems. On a UNIXor Linuxbased computer, hosts is found in the /etc directory. On a Windows-based computer, it is found in the %systemroot%\system32\drivers\etc folder.

hot site—A place where the computers, devices, and connectivity necessary to rebuild a network exist, and all are appropriately configured, updated, and connected to match your network’s current state.

hot spare—In the context of RAID, a disk or partition that is part of the array, but used only in case one of the RAID disks fails. More generally, “hot spare” is used as a synonym for a hot swappable component.

hot spot—An area covered by a wireless access point that provides visitors with wireless services, including Internet access.

hot swappable—A characteristic that enables identical components to be interchanged (or swapped) while a machine is still running (hot). After being installed, a hot swappable component automatically assumes the functions of its counterpart.

HSTR (High-Speed Token Ring)—A standard for Token Ring networks that operate at 100 Mbps.

HTML (Hypertext Markup Language)—The language that defines formatting standards for Web documents.

HTTP (Hypertext Transfer Protocol)—An Application layer protocol that formulates and interprets requests between Web clients and servers.

HTTP over Secure Sockets Layer—See HTTPS.

HTTP Secure—See HTTP over Secure Sockets Layer.

HTTPS (HTTP over Secure Sockets Layer)—The URL prefix that indicates that a Web page requires its data to be exchanged between client and server using SSL encryption. HTTPS uses the TCP port number 443, rather than port 80 (the port that normal HTTP uses).

hub—A connectivity device that retransmits incoming data signals to its multiple ports. Typically, hubs contain one uplink port, which is used to connect to a network’s backbone.

hybrid fiber-coax—See HFC.

hybrid topology—A physical topology that combines characteristics of more than one simple physical topology.

Hypertext Markup Language—See HTML.

Hypertext Transfer Protocol—See HTTP.

IAB (Internet Architecture Board)—A technical advisory group of researchers and professionals interested in overseeing the Internet’s design, growth, standards, and management.

IANA (Internet Assigned Numbers Authority)—A nonprofit, U.S. government-funded group that was established at the University of Southern California and charged with managing IP address allocation and the domain name system. The oversight for many of IANA’s functions was given to ICANN in 1998; however, IANA continues to perform Internet addressing and domain name system administration.

ICA (Independent Computing Architecture) client—The software from Citrix Systems, Inc. that, when installed on a client, enables the client to connect with a remote access server and exchange key-

Glossary 785

strokes, mouse clicks, and screen updates. Citrix’s ICA client can work with virtually any operating system or application.

ICANN (Internet Corporation for Assigned Names and Numbers)—The nonprofit corporation currently designated by the U.S. government to maintain and assign IP addresses.

ICMP (Internet Control Message Protocol)—A core protocol in the TCP/IP suite that notifies the sender that something has gone wrong in the transmission process and that packets were not delivered.

ICS (Internet Connection Sharing)—A service provided with Windows 98, Me, 2000 and 32-bit versions of XP operating systems that allows one computer, the ICS host, to share its Internet connection with other computers on the same network.

ICS host—On a network using the Microsoft Internet Connection Sharing service, the computer whose Internet connection other computers share. The ICS host must contain two network interfaces: one that connects to the Internet and one that connects to the LAN.

IEEE (Institute of Electrical and Electronics Engineers)—An international society composed of engineering professionals. Its goals are to promote development and education in the electrical engineering and computer science fields.

IEEE 1394—See FireWire.

IETF (Internet Engineering Task Force)—An organization that sets standards for how systems communicate over the Internet (for example, how protocols operate and interact).

ifconfig—A utility that establishes and allows management of TCP/IP settings on UNIX-type of systems.

IGMP (Internet Group Management Protocol or Internet Group Multicast Protocol)—A TCP/IP protocol used to manage multicast transmissions. Routers use IGMP to determine which nodes use IGMP to join or leave a multicast group.

IKE (Internet Key Exchange)—The first phase of IPSec authentication, which accomplishes key management. IKE is a service that runs on UDP port 500. After IKE has established the rules for the type of keys two nodes use, IPSec invokes its second phase, encryption.

iManager—A browser-based tool for managing eDirectory in NetWare 6.x.

IMAP (Internet Message Access Protocol)—A mail retrieval protocol that improves on the shortcomings of POP. The single biggest advantage IMAP4 has relative to POP is that it allows users to store messages on the mail server, rather than always having to download them to the local machine. The most current version of IMAP is version 4 (IMAP4).

IMAP4 (Internet Message Protocol, version 4)—The most commonly used form of the Internet Message Access Protocol (IMAP).

impedance—The resistance that contributes to controlling an electrical signal. Impedance is measured in ohms.

incremental backup—A backup in which only data that has changed since the last full or incremental backup is copied to a storage medium. After backing up files, an incremental backup unchecks the archive bit for every file it has saved.

786 Glossary

Industry Standard Architecture—See ISA.

information node—See i-node.

infrared—A type of data transmission in which infrared light signals are used to transmit data through space, similar to the way a television remote control sends signals across the room. Networks may use two types of infrared transmission: direct or indirect.

Infrared Data Association—See IrDA.

infrastructure WLAN—A type of WLAN in which stations communicate with an access point and not directly with each other.

inherited—A type of permission, or right, that is passed down from one group (the parent) to a group within that group (the child).

i-node (information node)—A UNIX-type file system information storage area that holds all details about a file. This information includes the size, the access rights, the date and time of creation, and a pointer to the actual contents of the file.

Institute of Electrical and Electronics Engineers—See IEEE.

Integrated Services Digital Network—See ISDN.

integrity—The soundness of a network’s files, systems, and connections. To ensure integrity, you must protect your network from anything that might render it unusable, such as corruption, tampering, natural disasters, and viruses.

integrity checking—A method of comparing the current characteristics of files and disks against an archived version of these characteristics to discover any changes. The most common example of integrity checking involves a checksum.

intelligent hub—A hub that possesses processing capabilities and can therefore monitor network traffic, detect packet errors and collisions, poll connected devices for information, and gather the data in database format.

interior router—A router that directs data between nodes on an autonomous LAN.

International Organization for Standardization—See ISO.

International Telecommunication Union—See ITU.

Internet—A complex WAN that connects LANs and clients around the globe.

Internet Architecture Board—See IAB.

Internet Assigned Numbers Authority—See IANA.

Internet Connection Sharing—See ICS.

Internet Control Message Protocol—See ICMP.

Internet Corporation for Assigned Names and Numbers—See ICANN.

Internet Engineering Task Force—See IETF.

Internet Group Management Protocol—See IGMP.

Internet Group Multicast Protocol—See IGMP.

Glossary 787

Internet Key Exchange—See IKE.

Internet Message Access Protocol—See IMAP.

Internet Message Access Protocol, version 4—See IMAP4.

Internet Protocol—See IP.

Internet Protocol address—See IP address.

Internet Protocol Security—See IPSec.

Internet Relay Chat—See IRC.

Internet Service Provider—See ISP.

Internet services—The services that enable a network to communicate with the Internet, including World Wide Web servers and browsers, file transfer capabilities, Internet addressing schemes, security filters, and a means for directly logging on to other computers.

Internet Society—See ISOC.

Internet telephony—The provision of telephone service over the Internet.

internetwork—To traverse more than one LAN segment and more than one type of network through a router.

Internetwork Packet Exchange—See IPX.

Internetwork Packet Exchange/Sequenced Packet Exchange—See IPX/SPX.

interrupt—A circuit board wire through which a device issues voltage, thereby signaling a request for the processor’s attention.

interrupt request—See IRQ.

interrupt request number—See IRQ number.

intranet—A network or part of a network that uses browser-based services to exchange information within an enterprise. Intranets may be contained within a LAN or may be accessible via a WAN or the Internet.

intraNetWare—Another term for NetWare version 4.11, the version in which support for Internet services was first introduced.

IP (Internet Protocol)—A core protocol in the TCP/IP suite that operates in the Network layer of the OSI Model and provides information about how and where data should be delivered. IP is the subprotocol that enables TCP/IP to internetwork.

IP address (Internet Protocol address)—The Network layer address assigned to nodes to uniquely identify them on a TCP/IP network. IP addresses consist of 32 bits divided into four octets, or bytes.

IP datagram—The IP portion of a TCP/IP frame that acts as an envelope for data, holding information necessary for routers to transfer data between subnets.

IP next generation—See IPv6.

IP phone—See IP telephone.

788 Glossary

IP spoofing—A security attack in which an outsider obtains internal IP addresses, then uses those addresses to pretend that he has authority to access a private network from the Internet.

IP telephone—A telephone used for VoIP on a TCP/IP-based network. IP telephones are designed to transmit and receive only digital signals.

IP telephony—See Voice over IP.

ipconfig—The utility used to display TCP/IP addressing and domain name information in the Windows NT, Windows 2000, and Windows XP operating systems.

IPng—See IPv6.

IP-PBX—A private switch that accepts and interprets both analog and digital voice signals (although some IP-PBXs do not accept analog lines). It can connect with both traditional PSTN lines and data networks. An IP-PBX transmits and receives IP-based voice signals to and from other network connectivity devices, such as a router or gateway.

IPSec (Internet Protocol Security)—A Layer 3 protocol that defines encryption, authentication, and key management for TCP/IP transmissions. IPSec is an enhancement to IPv4 and native to IPv6. IPSec is unique among authentication methods in that it adds security information to the header of all IP packets.

IPv4 (IP version 4)—The current standard for IP addressing that specifies 32-bit addresses composed of four octets.

IPv4LL (IP version 4 Link Local)—A protocol that manages automatic address assignment among locally connected nodes. IPv4LL is part of the Zeroconf group of protocols.

IPv6 (IP version 6)—A newer standard for IP addressing that will replace the current IPv4 (IP version 4). Most notably, IPv6 uses a newer, more efficient header in its packets and allows for 128-bit source and destination IP addresses. The use of longer addresses will allow for many more IP addresses to be in circulation.

IPX (Internetwork Packet Exchange)—A core protocol of the IPX/SPX suite that operates at the Network layer of the OSI Model and provides routing and internetwork services, similar to IP in the TCP/IP suite.

IPX address—An address assigned to a device on an IPX/SPX-based network.

IPX/SPX (Internetwork Packet Exchange/Sequenced Packet Exchange)—A protocol originally developed by Xerox, then modified and adopted by Novell in the 1980s for the NetWare network operating system.

IRC (Internet Relay Chat)—A protocol that enables users running special IRC client software to communicate instantly with other participants in a chat room on the Internet.

IrDA (Infrared Data Association)—A nonprofit organization founded in 1994 to develop and promote standards for wireless communication using infrared signals. IrDA is also used to denote the type of wireless technology this group has developed.

IRQ (interrupt request)—A message sent to the computer that instructs it to stop what it is doing and pay attention to something else. IRQ is often used (informally) to refer to the interrupt request number.

IRQ number—The unique number assigned to each interrupt in a computer. Interrupt request numbers range from 0 to 15, and many PC devices reserve specific numbers for their use alone.

Glossary 789

ISA (Industry Standard Architecture)—The original PC bus type, developed in the early 1980s to support an 8-bit and later 16-bit data path and a 4.77-MHz clock speed.

ISDN (Integrated Services Digital Network)—An international standard that uses PSTN lines to carry digital signals. It specifies protocols at the Physical, Data Link, and Transport layers of the OSI Model. ISDN lines may carry voice and data signals simultaneously. Two types of ISDN connections are used in North America: BRI (Basic Rate Interface) and PRI (Primary Rate Interface). Both use a combination of bearer channels (B channels) and data channels (D channels).

ISO (International Organization for Standardization)—A collection of standards organizations representing 146 countries with headquarters located in Geneva, Switzerland. Its goal is to establish international technological standards to facilitate the global exchange of information and barrier-free trade.

ISOC (Internet Society)—A professional organization with members from more than 180 countries that helps to establish technical standards for the Internet.

ISP (Internet Service Provider)—A business that provides organizations and individuals with Internet access and often other services, such as e-mail and Web hosting.

ITU (International Telecommunication Union)—A United Nations agency that regulates international telecommunications and provides developing countries with technical expertise and equipment to advance their technological bases.

J1—A digital carrier standard used in Japan that offers 24 channels and 1.544-Mbps throughput.

J3—A digital carrier standard used in Japan that offers 480 channels and 32.064-Mbps throughput.

jabber—A device that handles electrical signals improperly, usually affecting the rest of the network. A network analyzer will detect a jabber as a device that is always retransmitting, effectively bringing the network to a halt. A jabber usually results from a bad NIC. Occasionally, it can be caused by outside electrical interference.

jamming—A part of CSMA/CD in which, upon detecting a collision, a station issues a special 32-bit sequence to indicate to all nodes on an Ethernet segment that its previously transmitted frame has suffered a collision and should be considered faulty.

Java System Directory Server Enterprise Edition—The Sun Microsystems implementation of LDAP.

jumper—A small, removable piece of plastic that contains a metal receptacle that fits over a pair of pins on a circuit board to complete a circuit between those two pins. By moving the jumper from one set of pins to another set of pins, you can modify the board’s circuit, thereby giving it different instructions on how to operate.

KDC (Key Distribution Center)—In Kerberos terminology, the server that runs the authentication service and the Ticket-granting service to issue keys and tickets to clients.

Kerberos—A cross-platform authentication protocol that uses key encryption to verify the identity of clients and to securely exchange information after a client logs on to a system. It is an example of a private key encryption service.

kernel—The core of a UNIX-type of system and a NetWare NOS. This part of the operating system is loaded and run when you turn on your computer. It mediates between user programs and the computer hardware.

790 Glossary

kernel module—A portion of the kernel that you can load and unload to add or remove functionality on a running UNIX or Linux system.

key—A series of characters that is combined with a block of data during that data’s encryption. To decrypt the resulting data, the recipient must also possess the key.

Key Distribution Center—See KDC.

key management—The method whereby two nodes using key encryption agree on common parameters for the keys they will use to encrypt data.

key pair—The combination of a public and private key used to decipher data that was encrypted using public key encryption.

L2TP (Layer 2 Tunneling Protocol)—A protocol that encapsulates PPP data, for use on VPNs. L2TP is based on Cisco technology and is standardized by the IETF. It is distinguished by its compatibility among different manufacturers’ equipment, its ability to connect between clients, routers, and servers alike, and also by the fact that it can connect nodes belonging to different Layer 3 networks.

label—A character string that represents a domain (either top-level, second-level, or third-level).

LAN (local area network)—A network of computers and other devices that is confined to a relatively small space, such as one building or even one office.

LAN Emulation—See LANE.

LANE (LAN Emulation)—A method for transporting Token Ring or Ethernet frames over ATM networks. LANE encapsulates incoming Ethernet or Token Ring frames, then converts them into ATM cells for transmission over an ATM network.

last mile—See local loop.

late collision—A collision that takes place outside the normal window in which collisions are detected and redressed. Late collisions are usually caused by a defective station (such as a card, or transceiver) that is transmitting without first verifying line status or by failure to observe the configuration guidelines for cable length, which results in collisions being recognized too late.

latency—The delay between the transmission of a signal and its receipt.

Layer 2 Tunneling Protocol—See L2TP.

Layer 3 switch—A switch capable of interpreting data at Layer 3 (Network layer) of the OSI Model.

Layer 4 switch—A switch capable of interpreting data at Layer 4 (Transport layer) of the OSI Model.

LC (Local Connector)—A connector used with single-mode or multimode fiber-optic cable.

LDAP (Lightweight Directory Access Protocol)—A standard protocol for accessing network directories.

leaf object—An object in an operating system’s directory, such as a printer or user, that does not contain other objects.

lease—The agreement between a DHCP server and client on how long the client can use a DHCPassigned IP address. DHCP services can be configured to provide lease terms equal to any amount of time.

Glossary 791

LEO (low earth orbiting)—A type of satellite that orbits the earth with an altitude between 700 and 1400 kilometers, closer to the earth’s poles than the orbits of either GEO or MEO satellites. LEO satellites cover a smaller geographical range than GEO satellites and require less power.

Level 1—A form of UTP that contains two wire pairs. Level 1 is the type of wire used for older voice networks and is unsuitable for transmitting data.

license tracking—The process of determining the number of copies of a single application that are currently in use on the network and whether the number in use exceeds the authorized number of licenses.

Lightweight Directory Access Protocol—See LDAP.

line printer daemon—See lpd.

line-of-sight—See LOS.

link segment—See unpopulated segment.

Linux—A freely distributable implementation of a UNIX-type of system. Finnish computer scientist Linus Torvalds originally developed it.

LLC (Logical Link Control) sublayer—The upper sublayer in the Data Link layer. The LLC provides a common interface and supplies reliability and flow control services.

load balancing—An automatic distribution of traffic over multiple links, hard disks, or processors intended to optimize responses.

local account—A type of user account on a Windows Server 2003 network that has rights to the resources managed by the server the user has logged on to.

local area network—See LAN.

local collision—A collision that occurs when two or more stations are transmitting simultaneously. Excessively high collision rates within the network can usually be traced to cable or routing problems.

Local Connector—See LC.

local loop—The part of a phone system that connects a customer site with a telecommunications carrier’s switching facility.

logical address—See network address.

Logical Link Control layer—See LLC (Logical Link Control) sublayer.

logical topology—A characteristic of network transmission that reflects the way in which data is transmitted between nodes (which may differ from the physical layout of the paths that data takes). The most common logical topologies are bus and ring.

loopback adapter—See loopback plug.

loopback address—An IP address reserved for communicating from a node to itself (used mostly for troubleshooting purposes). The loopback address is always cited as 127.0.0.1, although in fact, transmitting to any IP address whose first octet is “127” will contact the originating device.