Glossary

Numbers and Symbols

10Base-T A variant of Ethernet that allows stations to be attached by a twisted-pair cable.

A

access control list (ACL) A list that indicates which users or groups have permission to access or modify a particular file; the Microsoft Windows discretionary access control list (DACL) and system access control list (SACL) are examples of access control lists.

ACL See access control list (ACL).

Active Directory Service Interfaces (ADSI) A Component Object Model (COM)–based directory service model that allows ADSI-compliant client applications to access a wide variety of distinct directory protocols, including Microsoft Windows directory service and Lightweight Directory Access Protocol (LDAP), while using a single standard set of interfaces. ADSI shields the client application from the implementation and operational details of the underlying data store or protocol.

active hub A type of hub that uses electrical power to regenerate and retransmit network data.

active/passive configuration In the Cluster service, an active/passive configuration is a method that you can use to configure your cluster. In this configuration, one node acts as the primary node and another node acts as the secondary node. The secondary node is idle unless failover occurs.

Active Server Pages (ASP) A server-side scripting environment that can be used to create dynamic Web pages or build Web applications. ASP pages are files that contain Hypertext Markup Language (HTML) tags, text, and script commands. ASP pages can call Component Object Model (COM) components to perform tasks, such as connecting to a database or performing a business calculation. With ASP, the user can add interactive content to Web pages or build entire Web applications that use HTML pages as the interface to your customers.

ActiveX An umbrella term for Microsoft technologies that enable developers to create interactive content for the World Wide Web. A set of language­independent interoperability technologies that enable software components written in different languages to work together in networked environments. The core technology elements of ActiveX are the Component Object Model (COM) and distributed COM. These technologies are licensed to The Open Group standards organization and are being implemented on multiple platforms.

ActiveX Controls Reusable software components that incorporate ActiveX technology. These components can be used to add specialized functionality, such as animation or pop-up menus, to Web pages, desktop applications, and software development tools. ActiveX Controls can be written in a variety of programming languages including C, C++, Visual Basic, and Java.

ActiveX Data Objects (ADO) A high-level data access programming interface to an underlying data access technology (such as OLE DB), implemented by using the Component Object Model (COM).

administrative software In the Cluster service, the software that you use to administer the cluster.

ADO See ActiveX Data Objects (ADO).

ADSI See Active Directory Service Interfaces (ADSI).

agile model A type of threading model in which objects are specified as both-threaded.

alias A name that maps part of a Uniform Resource Locator (URL) to a physical directory on the server. In general, an easily remembered name used in place of an Internet Protocol (IP) address, directory path, or other identifier; also called a friendly name.

American National Standards Institute (ANSI) A voluntary, nonprofit organization of U.S. business and industry groups formed in 1918 for the development of trade and communications standards. It provides area charters for groups that establish standards in specific fields, such as the Institute of Electrical and Electronics Engineers (IEEE). ANSI is the U.S. representative of the International Organization for Standardization (ISO) and has developed recommendations for the use of programming languages including FORTRAN, C, and COBOL. Standards approved by ANSI are often called ANSI standards (for example, ANSI C is the version of the C language approved by ANSI). See also American Standard Code for Information Interchange.

American Standard Code for Information Interchange (ASCII) A coding scheme using 7 or 8 bits that assigns numeric values up to 256 characters, including letters, numerals, punctuation marks, control characters, and other symbols. ASCII was developed in 1968 to standardize data transmission among disparate hardware and software systems and is built into most minicomputers and all personal computers.

anonymous File Transfer Protocol (anonymous FTP) An FTP configuration that makes it possible for a user to retrieve documents, files, programs, and other archived data from anywhere on the Internet without having to establish a logon name and password.

ANSI See American National Standards Institute (ANSI).

API See application programming interface (API).

application A computer program, such as a word processor or electronic spreadsheet; or a group of Active Server Pages (ASP) scripts and components that perform such tasks. In Application Center 2000, an application can consist of any combination of Hypertext Markup Language (HTML) and ASP files, COM+ components, Microsoft Windows registry settings, and Internet Information Services (IIS) settings. In COM+, an application is a grouping of COM+ components.

application programming interface (API) A set of routines that an application uses to request and carry out lower-level services performed by a computer’s operating system. Also, a set of calling conventions in programming that defines how a service is invoked through the application.

application state The data maintained by a server application on behalf of its clients.

ASCII See American Standard Code for Information Interchange (ASCII).

ASP See Active Server Pages (ASP).

Asynchronous Transfer Mode (ATM) A network technology capable of transmitting data, voice, video, and frame relay traffic in real time. Data, including frame relay data, is broken into packets containing 53 bytes each, which are switched between any two nodes in the system at rates ranging from 1.5 to 622 megabits per second (Mbps). ATM is defined in the broadband Integrated Services Digital Network (ISDN) protocol at the levels corresponding to levels 1 and 2 of the International Organization for Standardization Open Systems Interconnection (ISO/OSI) model. It’s currently used in local area networks involving workstations and personal computers.

ATM See Asynchronous Transfer Mode (ATM).

auditing The process an operating system uses to detect and record security­related events, such as an attempt to create, access, or delete objects such as files and directories. The records of such events are stored in a file known as the Security log, whose contents are available only to those with the proper clearance.

authentication The process by which the system validates a user’s logon information. A user’s name and password are compared against an authorized list, and if the system detects a match, access is granted to the extent specified in the permission list for the user.

authentication certificate See certificate, authentication.

authorization In relation to computers, especially to remote computers on a network open to more than one person, the right granted to an individual to use the system and the data stored on it. Authorization is typically set up by a system administrator, Web master, or site owner and checked and cleared by the computer. This requires that the user provide some type of identification, such as a code number or a password, that the computer can verify against its internal records. Also called permission or privilege.

availability A measure (from 0 to 100 percent) of the fault tolerance of a computer and its programs. Availability measures whether a particular service is functioning properly. A highly available computer runs 24 hours a day, 7 days a week.

B

back end In a multitiered network environment, this term usually describes the portion of the network that resides behind the Web servers. For example, a SQL Server computer located on a data tier would be considered a back-end server.

bandwidth The capacity of the transmission medium stated in bits per second (bps) or as a frequency measured in hertz (Hz). Generally, a higher bandwidth number indicates faster data-transfer capability. In communications, the difference between the highest and lowest frequencies in a given range. In computer networks, greater bandwidth indicates faster data­transfer capability and is expressed in bps.

bandwidth throttling Setting the maximum portion of total network capacity that a service is allowed to use. An administrator can deliberately limit a server’s Internet workload by not allowing it to receive requests at full capacity, thus saving resources for other programs such as e-mail.

Basic authentication An authentication protocol supported by most browsers, including Internet Explorer. It’s a method of authentication that encodes user name and password data transmissions. Basic authentication is sometimes called clear-text authentication because the Base-64 encoding can be decoded by anyone with a freely available decoding utility. Note that encoding isn’t the same as encryption. See also Integrated Windows authentication; encryption.

baud A measure of data transmission speed. Commonly used to refer to the data transmission speed of a modem.

bits per second (bps) The speed at which data bits are transmitted over a communications medium, such as a transmission wire or a modem.

bridgehead server In the Active Directory service, the bridgehead server is the point at which directory information is exchanged with another site.

browser Also called a Web browser. A client interface that enables a user to view Hypertext Markup Language (HTML) documents on the World Wide Web, another network, or the user’s computer; follow hyperlinks among them; and transfer files. One example is Microsoft Internet Explorer.

C

CA See certification authority (CA).

cache A special memory subsystem in which frequently used data values are duplicated for quick access. A memory cache stores the contents of frequently accessed random access memory (RAM) locations and the addresses where these data items are stored. When the processor references an address in memory, the cache checks to see whether it holds that address. If it does, the data is returned to the processor; if it doesn’t, a regular memory access occurs. A cache is useful when RAM accesses are slow compared with the microprocessor speed, because cached memory is faster than main RAM memory.

capacity planning The process of measuring a Web site’s ability to deliver content to its visitors at an acceptable speed.

cascading failover In the Cluster service, cascading failover refers to a failover process in which a resource group may survive multiple server failures, each time failing over to the next server on its node preference list.

certificate, authentication See certificate, digital.

certificate, client A digital certificate that functions in a way similar to a driver’s license or passport. Client certificates can contain detailed identification information about the user and organization that issued the certificate. See also certificate, digital.

certificate, digital An encrypted file, containing user or server identification information, that’s used to verify identity; also called an authentication certificate. When issued to users, a digital certificate is called a client certificate. When issued to a server administrator, it’s called a server certificate. See also certificate, client; certificate, server.

certificate revocation list A document maintained and published by a certification authority (CA) that lists certificates that have been revoked by the certification authority. See also certification authority.

certificate, server A unique digital identification that forms the basis of a Web server’s Secure Sockets Layer (SSL) security features. Server certificates are obtained from a mutually trusted, third-party organization and provide a way for users to authenticate the identity of a Web site.

certification authority (CA) An entity that issues, manages, and revokes certificates.

CGI See Common Gateway Interface (CGI).

client On a local area network or the Internet, a computer that accesses shared network resources provided by another computer called a server. Also, an application or process that requests a service from some process or component. A client facilitates a connection to server computers and manages and presents information retrieved from those sources. In a client/server environment, the workstation is usually the client computer. When referring to Component Object Model (COM) objects, a program that accesses or uses a service provided by another component.

client affinity In Network Load Balancing (NLB), client affinity refers to a process that allows a client to be mapped to the same host during a session. After the initial client request, which is distributed like any other request, NLB looks at only the source Internet Protocol (IP) address and not the source port information. Therefore, a client with a given IP address will always map to a particular cluster host, and any session state that’s maintained in that cluster host will persist across those connections.

client/server architecture A model of computing whereby client applications running on a desktop or personal computer access information on remote servers or host computers. The client portion of the application is typically optimized for user interaction, whereas the server portion provides centralized, multiuser functionality.

cluster Two or more computers connected for the purpose of providing services to the client. Microsoft Windows 2000 Advanced Server and Datacenter Server support two types of clusters: Network Load Balancing (NLB) clusters and the Cluster service clusters. NLB clusters usually operate on front-end systems to provide core services such as Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP). Cluster service clusters usually operate on the back-end to provide database and file storage services.

cluster adapter The network adapter in a Network Load Balancing (NLB) cluster that handles the network traffic for cluster operations (that is, the traffic for all hosts in the cluster). This adapter is assigned one or more virtual IP addresses and, optionally, a dedicated IP address.

cluster-aware application In the Cluster service, a cluster-aware application is one that supports the Cluster application programming interface (API). These applications can register with the Cluster service to receive status and notification information, and they can use the Cluster API to administer clusters.

cluster name In the Cluster service, the cluster name is the common name under which all members in the cluster are grouped. You can use the cluster name when accessing and managing the cluster.

Cluster service A service in Microsoft Windows 2000 Advanced Server and Datacenter Server that allows you to set up a cluster to support failover functionality. The Cluster service is made up of components on each node that perform cluster-specific activities.

cluster size In Network Load Balancing (NLB), cluster size is the number of hosts participating in the cluster, which can be up to 32.

clustered disk In the Cluster service, the clustered disk is an external disk storage system. Nodes in the cluster share access to cluster resources on the clustered disk.

clustering Connecting two or more computers for the purpose of sharing resources and request load. Each member computer of a cluster is called a node. The nodes in a cluster may either have their own storage devices or share a common device. Typically, clustering will involve support for load balancing, fault tolerance, and failover. See also failover; fault tolerance; load balancing.

clustering software In the Cluster service, clustering software is the software the makes the cluster run.

cluster-unaware application In the Cluster service, a cluster-unaware application is one that doesn’t support the Cluster application programming interface (API). These applications can’t register with the Cluster service to receive status and notification information, and they can’t use the Cluster API to administer clusters.

COM See Component Object Model (COM).

Common Gateway Interface (CGI) A server-side interface for initiating software services; the specification that defines communications between information services, such as a Hypertext Transfer Protocol (HTTP) service, and resources on the server’s host computer, such as databases and other programs. For example, when a user submits a form through a Web browser, the HTTP service executes a program, often called a Common Gateway Interface (CGI) script, and passes the user’s input information to that program through CGI. The program then returns information to the service through CGI. Any software can be a CGI program if it handles input and output according to the CGI standard. CGI applications always run out-of-process.

Component Load Balancing (CLB) A service in Application Center 2000 that provides dynamic load balancing for COM+ application components. In CLB, the COM+ components are located on servers in a separate COM+ cluster. Calls to activate COM+ components are load balanced to different servers within the COM+ cluster.

Component Object Model (COM) The object- oriented programming model that defines how objects interact within a single application or between applications. In COM, client software accesses an object through a pointer to an interface—a related set of functions called methods—on the object. A COM component is a binary file containing code for one or more class factories, COM classes, registry-entry mechanisms, loading code, among others.

concurrency The appearance of simultaneous execution of processes or transactions by interleaving the execution of multiple pieces of work.

connected user A user who is currently accessing one of the services of a Web server.

connection pooling A performance optimization based on using collections of preallocated resources, such as objects or database connections. Pooling results in more efficient resource allocation.

content type The type of file (such as text, graphic, or sound), usually indicated by the file name extension (such as .txt, .gif, or .wav, respectively).

convergence In Network Load Balancing (NLB), convergence is a process in which the hosts exchange heartbeat messages to determine a new, consistent state of the cluster and to elect the host with the highest priority as the new default host.

cookie A means by which, under the Hypertext Transfer Protocol (HTTP) protocol, a server or a script can maintain information on the client computer. A cookie is a small text file that is stored in the user’s browser by the Web server. Cookies contain information about the user such as an identification number, a password, how a user browsed a Web site, or how many times the user visited that site. A Web site can access cookie information whenever the user connects to the server.

CryptoAPI See Microsoft Cryptographic API.

cryptography A field science involving the transmission of information in an encoded form so that only an intended recipient can decode the information and reveal its meaning. Encoded information is commonly said to be encrypted.

D

Data Encryption Standard (DES) A specification for encryption of computer data developed by IBM and adopted by the U.S. government as a standard in 1976. DES uses a 56-bit key to protect against password discovery and playback.

data-dependent routing An application-based method that you can use to access partitioned data. Data-dependent routing uses code to determine where the target data is located.

datagram A self-contained, independent entity of data carrying sufficient information to be routed from the source to the destination computer without reliance on earlier exchanges between the source and destination computer and the transporting network.

data provider Software that implements OLE DB methods and interfaces.

data source The name that applications use to request a connection to an Open Database Connectivity (ODBC) data source. It specifies the computer name and (optionally) database that the data source name (DSN) maps to. A system data source is a data source that’s available to anyone using the computer. Data sources that will be used with a Web server need to be system data sources.

Data Source Name (DSN) The logical name used by Open Database Connectivity (ODBC) to refer to the drive and other information required to access data. The name is used by Internet Information Services (IIS) for a connection to an ODBC data source, such as a SQL Server database.

data source tier A logical layer that represents a computer running a Database Management System (DBMS), such as SQL Server.

deadlock In operating systems or databases, a situation in which two or more processes are prevented from continuing while each waits for resources to be freed by the continuation of the others.

debugger A software tool used to detect the source of program or script errors, by performing step-by-step execution of application code and viewing the content of code variables.

default document Sometimes called a default home page. The file sent by a Web server when it receives a request for a Uniform Resource Locator (URL) that doesn’t specify a filename. This document can be generated automatically by the server, or it can be a custom file placed in that directory by the administrator.

default gateway In Transmission Control Protocol/Internet Protocol (TCP/IP), the intermediate network device on the local network that has knowledge of the network IDs of the other networks in the Internet so it can forward the packets to other gateways until they’re delivered to the one connected to the specified destination.

default host In Network Load Balancing (NLB), the host with the highest priority. It handles all client traffic for the virtual Internet Protocol (IP) addresses that isn’t specifically intended to be load balanced.

dependency In the Cluster service, a resource that depends on another resource to operate. Dependent resources are taken offline before their dependencies, and they’re brought online after their dependencies. Also known as a dependent resource.

dependency tree In the Cluster service, a dependency tree is a series of dependency relationships. A dependent resource and all of its dependencies must be in the same resource group.

dependent resource In the Cluster service, a dependent resource is one that requires another resource, which is known as a dependency.

DES See Data Encryption Standard (DES).

DHCP See Dynamic Host Configuration Protocol (DHCP).

DHCP lease In the Dynamic Host Configuration Protocol (DHCP) Service, the DHCP lease refers to the allocation of Internet Protocol (IP) addressing information to the client computer. The DHCP lease process occurs when Transmission Control Protocol/Internet Protocol (TCP/IP) is initialized on the client, the client requests a specific IP address and is denied, or the client previously leased an IP address but then released it and requires a new one.

DHTML See Dynamic HTML (DHTML).

dial-up Of, pertaining to, or being a connection that uses the public switched telephone network rather than a dedicated circuit or some other type of private network. Also called a slow link.

Digest authentication An authentication method that sends user name and password information over the network as a hash value. See also authentication.

digital certificate See certificate, digital.

digital signature The part of a digital certificate that contains an encryption key that uniquely identifies the holder of the certificate.

direct dependency In the Cluster service, a direct dependency is a resource dependency in which no intermediary resources are between the two dependent resources.

directory browsing A feature that automatically provides a default Web page of available directories and files to browsers that submit a Uniform Resource Locator (URL) that doesn’t specify a particular file.

directory service A network service that identifies all resources on a network and makes them accessible to users and applications. The directory service is the central authority that manages the identities of distributed resources and brokers the relationships between those resources.

disaster Any situation that causes a serious disruption to your system’s services. A disaster can result in data loss or machine failure, making your system unavailable to users and applications.

disk duplexing The process of installing a second controller on a computer so that each disk in a mirrored volume has its own controller.

DLL See dynamic-link library (DLL).

DNS See Domain Name System (DNS).

domain In Microsoft Windows, a collection of computers that share a common domain database and security policy. Each domain has a unique name. In the Active Directory service, resources are organized hierarchically into domains.

domain controller For a Microsoft Windows 2000 Server domain, the server that authenticates domain logons and maintains the security policy and the master database for a domain.

domain, Internet The highest subdivision of a domain name in a network address, which identifies the type of entity owning the address (for example, .com for commercial users or .edu for educational institutions) or the address’s geographic location (for example, .fr for France or .sg for Singapore). The Internet domain is the last part of the address (for example, www.microsoft.com).

domain name An address of a network connection that identifies the owner of that address in a hierarchical format. For example, www.whitehouse.gov identifies the Web server at the White House, which is a government agency. See also Domain Name System (DNS).

domain namespace The names in a Domain Name System (DNS) database that form a hierarchical tree structure.

Domain Name System (DNS) The system by which hosts on the Internet have domain name addresses (such as microsoft.com) and Internet Protocol (IP) addresses (such as 172.21.13.45). The domain name address is used by human users and is automatically translated into the numerical IP address, which is used by the packet­routing software. DNS is also the acronym for Domain Name Service, the Internet utility that implements the Domain Name System. DNS servers, also called name servers, maintain databases containing the addresses and are accessed transparently by the user.

domain naming master In the Active Directory service, the domain naming master controls the addition or removal of domains in the forest.

download In communications, the process of transferring a copy of a file from a remote computer to the requesting computer by means of a modem or network.

DSN See Data Source Name (DSN).

Dynamic Host Configuration Protocol (DHCP) A Transmission Control Protocol/Internet Protocol (TCP/IP) protocol that enables a network connected to the Internet to assign a temporary IP address to a host automatically when the host connects to the network.

dynamic HTML (DHTML) A set of innovative features in Internet Explorer 4 and later that can be used to create Hypertext Markup Language (HTML) documents that dynamically change their content and interact with the user. By using DHTML, authors can provide special effects on a Web page without relying on server-side programs.

dynamic-link library (DLL) A feature of the Microsoft Windows family of operating systems that supports executable routines—usually serving a specific function or set of functions—to be stored separately as files with the file extension name .dll and to be loaded only when called by the program that needs them. This saves memory during program execution and enables code reusability.

E

e-commerce Electronic commerce. The process of buying and selling over the Web—often based on software products such as Microsoft Commerce Server.

e-mail A system whereby a computer user can exchange messages with other computer users (or groups of users) through a communications network. E-mail is one of the most popular uses of the Internet.

encryption A way of making data indecipherable to protect it from unauthorized viewing or use, especially during network transmission or when it’s stored on a transportable magnetic medium while it’s being sent from computer to computer. Encryption can be either symmetric or asymmetric. Symmetric encryption involves the use of the same key to both encrypt and decode the data. Asymmetric encryption uses one key to encrypt and another to decode.

Ethernet A 10 megabits-per-second (Mbps) standard for local area networks (LANs) initially developed by Xerox and later refined by Digital, Intel, and Xerox (DIX). All hosts are connected to a coaxial cable, where they contend for network access.

event Any significant occurrence in the system or in an application that requires an entry to be added to a log.

executable program A program, or collection of programs, forms, data, menus, and other files, that can be run.

exponential failure distribution A measure of how long it’s likely to take a hardware component to fail under normal circumstances and after an initial phase.

F

failback The full restoration of a failed server node to its original state.

failover A process that takes place when one individual computer fails and another automatically takes over its request load. The transition is invisible to the user.

failover clustering Clustering functionality that provides failover service. In failover clustering, if one node fails, the other node takes ownership of its resources. Failover clustering assumes that an application can resume on another computer that’s been given access to the failed system disk subsystem.

failure A departure from the expected behavior on an individual computer system or a system of associated computers and applications. Failures can include behaviors that are outside the defined performance parameters. System failure can be caused by software, hardware, operator and procedural error, and environmental factors.

fat client The client computer in a client/server architecture in which most of an application is run on that computer. Such a configuration yields good client performance but complicates administrative tasks such as software upgrades.

fault tolerance The ability of a computer or an operating system to respond to a catastrophic event or fault, such as a power outage or a hardware failure, in a way that ensures that no data is lost or corrupted. This can be accomplished with a battery-backed power supply, backup hardware, provisions in the operating system, or any combination of these. In a fault-tolerant network, the system has the ability either to continue the system’s operation without loss of data or to shut the system down and restart it, recovering all processing that was in progress when the fault occurred.

file allocation table (FAT) file system The system used by MS-DOS to organize and manage files. FAT is a data structure that MS-DOS creates on the disk when the disk is formatted. When MS-DOS stores a file on a formatted disk, the operating system places information about the stored file in the file system table so that MS-DOS can retrieve the file later when requested. FAT is the only file system MS-DOS can use. See also NT file system (NTFS).

file encryption key (FEK) A symmetric bulk encryption key used by Encrypting File System (EFS) to encrypt the file. The FEK is then encrypted by using the public key taken from the user’s certificate, which is located in the user’s profile.

File Transfer Protocol (FTP) A protocol used for copying files to and from remote computer systems on a network using Transmission Control Protocol/Internet Protocol (TCP/IP), such as the Internet. This protocol also allows users to use FTP commands to work with files, such as listing files and directories on the remote system.

filter In Internet Information Services (IIS), a feature of Internet Server Application Programming Interface (ISAPI) that allows preprocessing of requests and post-processing of responses, permitting site-specific handling of Hypertext Transfer Protocol (HTTP) requests and responses.

filtering, host name Allowing or denying access based on the host name from which the browser is attempting access.

filtering, IP address Allowing or denying access based on the Internet Protocol (IP) address from which the browser is attempting access.

firewall A security system intended to protect an organization’s network against external threats, such as intruders, coming from another network such as the Internet. A firewall prevents computers in the organization’s network from communicating directly with computers external to the network and vice versa. Instead, all communication is routed through a proxy server outside of the organization’s network, and the proxy server decides whether it’s safe to let a particular message or file pass through.

forest In the Active Directory service, a forest groups together one or more domain trees. Although the trees have different naming structures, they share a common schema.

friendly name See alias.

FQDN See fully qualified domain name (FQDN).

front end In a multitiered network environment, this term usually describes the portion of the network that supports the Web services. For example, an Internet Information Services (IIS) computer that hosts a Web site would be considered a front-end server.

FTP See File Transfer Protocol (FTP).

fully qualified domain name (FQDN) A name that uniquely identifies a host’s position within the Domain Name System (DNS) hierarchical tree. For example, a host named mycomputer in the microsoft.com domain would have an FQDN of mycomputer.microsoft.com.

G

gateway A device that connects networks using different communications protocols so that information can be passed from one to the other. A gateway both transfers information and converts it to a form compatible with the protocols used by the receiving network.

GIF See Graphics Interchange Format (GIF).

global catalog A central repository of information about Active Directory service objects in a tree or forest. It stores a full replica of all objects in the directory for its host domain and a partial replica of all objects contained in the directory of every other domain in the forest.

globally unique identifier (GUID) In COM, a 16-byte code that identifies an interface to an object across all computers and networks. Such an identifier is unique because it contains a time stamp and a code based on the network address hard­ wired on the host computer’s local area network (LAN) interface card. These identifiers are generated by a utility program.

graphical user interface (GUI) A type of environment that represents programs, files, and options by means of icons, menus, and dialog boxes on the screen. The user can select and activate these options by pointing and clicking with a mouse or, often, by using a keyboard.

Graphics Interchange Format (GIF) A computer graphics file format developed in the mid-1980s by CompuServe for use in photo-quality graphic image display on computer screens. Now commonly used on the Internet.

GUI See graphical user interface (GUI).

GUID See globally unique identifier (GUID).

H

handshake A series of signals acknowledging that communication or the transfer of information can take place between computers or other devices. A hardware handshake is an exchange of signals over specific wires (other than the data wires), in which each device indicates its readiness to send or receive data. A software handshake consists of signals transmitted over the same wires used to transfer data, as in modem-to-modem communications over telephone lines.

home directory The root directory for a Web site, where the content files are stored. Also called a document root or Web root. In Internet Information Services (IIS), the home directory and all its subdirectories are available to users by default. Also the root directory for an IIS service. The home directory for a site typically contains the home page.

home page The initial page of information for a collection of pages, a Web site, or a section of a Web site.

host A Windows 2000 computer that runs a server program or service used by network or remote clients. For Network Load Balancing (NLB), a cluster consists of multiple hosts connected over a local area network (LAN).

host name The name of a specific server on a specific network within the Internet, leftmost in the complete host specifications. For example, www.microsoft.com indicates the server called "www" within the network at Microsoft Corporation.

hot link See hyperlink.

HTML See Hypertext Markup Language (HTML).

HTTP See Hypertext Transfer Protocol (HTTP).

hub A network-enabled device that joins communication lines at a central location, providing a common connection to all devices on the network. There are two kinds of hubs: passive and active. When a hub receives a transmission, it broadcasts traffic to all ports.

hyperlink A connection between an element in a hypertext document, such as a word, phrase, symbol, or image, and a different element in the document, another hypertext document, a file, or a script. The user activates the link by clicking on the linked element, which is usually underlined or in a color different from the rest of the document. Hyperlinks are indicated in a hypertext document by the use of tags in markup languages such as Standard Generalized Markup Language (SGML) and Hypertext Markup Language (HTML). Users generally can’t see these tags. Also called hot link and hypertext link.

hypertext Text linked together in a complex, nonsequential web of associations in which the user can browse through related topics. The term hypertext was coined in 1965 to describe documents presented by a computer that express the nonlinear structure of ideas as opposed to the linear format of books, film, and speech.

hypertext link See hyperlink.

Hypertext Markup Language (HTML) A simple markup language used to create hypertext documents that are portable from one platform to another. HTML files are simple ASCII text files with codes embedded (indicated by markup tags) to indicate formatting and hypertext links. The formatting language used for documents on the World Wide Web.

Hypertext Transfer Protocol (HTTP) The client/server protocol used to access information on the World Wide Web.

I

ICMP See Internet Control Message Protocol (ICMP).

IETF See Internet Engineering Task Force (IETF).

indirect dependency In the Cluster service, an indirect dependency is a resource dependency in which a transitive relationship exists between resources. In other words, an intermediary resource is between the two dependent resources. For example, if resource A depends on resource B, and resource B depends on resource C, there’s an indirect dependency between resource A and resource C.

infrastructure master In the Active Directory service, the infrastructure master updates the group-to-user references whenever the members of groups are renamed or changed.

inheritance Generally, the ability of a newly created object to automatically have, or inherit, properties of an existing object. For example, a newly created child directory can inherit the access­control settings of the parent directory.

in-process component A component that runs in a client’s process space. This component is typically a dynamic-link library (DLL).

instance An object of a particular component class. Each instance has its own private data elements or member variables. Component instance is synonymous with object. An instance can also refer to the installation of an application that’s completely separate from any other installations of that application.

instantiate To create an instance of an object.

Integrated Services Digital Network (ISDN) Combines voice and digital network services in a single medium, making it possible to offer telephone customers digital data service and voice connection through a single "wire." A dial-up ISDN line can offer speeds of up to 128,000 bits per second (bps). A type of phone line used to enhance wide area network (WAN) speeds, an ISDN line can transmit at speeds of 64 or 128 kilobits per second (Kbps). An ISDN line must be installed by the phone company at both the server site and the remote site.

Integrated Windows authentication A method of authentication in which a server verifies user account information by means of a cryptographic exchange; actual passwords are never transmitted.

interconnect See network.

International Organization for Standardization (ISO) A voluntary, nontreaty organization founded in 1946 that is responsible for creating international standards in many areas, including computers and communications. Its members are the national standards organizations of the 89 member countries, including ANSI for the United States. See also American National Standards Institute (ANSI).

International Organization for Standardization Open Systems Interconnection (ISO/OSI) model A layered architecture (plan) that standardizes levels of service and types of interaction for computers exchanging information through a communications network. The ISO/OSI model separates computer­to-computer communications into seven layers, or levels, each building upon the standards contained in the levels below it. The lowest of the seven layers deals solely with hardware links; the highest deals with software interactions at the application-program level.

Internet Abbreviation for internetwork. A set of dissimilar computer networks joined by means of gateways that handle data transfer and the conversion of messages from the sending network to the protocols used by the receiving networks. These networks and gateways use the Transmission Control Protocol/Internet Protocol (TCP/IP) suite of protocols. Originally part of the Defense Advanced Research Projects Agency (DARPA), operated by the U.S. Department of Defense.

Internet Control Message Protocol (ICMP) An extension to Internet Protocol (IP), ICMP allows for the generation of error messages, test packets, and informational messages related to IP.

Internet Engineering Task Force (IETF) A protocol engineering and development organization focused on the Internet. The IETF is a large, open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. It’s now under the auspices of the Internet Society, a nongovernmental international organization for global cooperation and coordination for the Internet and its internetworking technologies and applications. For more information, see http://www.isoc.org/.

Internet Network Information Center (InterNIC) A coordinator for Domain Name Service (DNS) registration of names in the .com, .net, .org, .edu, .gov, and .mil top-level domains. To register domain names and obtain Internet Protocol (IP) addresses, contact InterNIC at http://internic.net/.

Internet Protocol (IP) The part of Transmission Control Protocol/Internet Protocol (TCP/IP) that routes messages from one Internet location to another. IP is responsible for addressing and sending TCP packets over the network. IP provides a best-effort, connectionless delivery system that doesn’t guarantee that packets arrive at their destination or that they’re received in the sequence in which they were sent.

Internet Protocol address (IP address) A unique address that identifies a host on a network. It identifies a computer as a 32-bit address that’s unique across a Transmission Control Protocol/Internet Protocol (TCP/IP) network. An IP address is usually represented in dotted-decimal notation, which depicts each octet (8 bits, or a byte) of an IP address as its decimal value and separates each octet with a period. For example: 172.16.255.255.

Internet Server Application Programming Interface (ISAPI) An application program interface (API) that resides on a server computer for initiating software services tuned for the Microsoft Windows operating system. It’s an API for developing extensions to Internet Information Services (IIS) and other Hypertext Transfer Protocol (HTTP) services that support the ISAPI interface.

Internet service provider (ISP) Public provider of remote connections to the Internet. A company or educational institution that enables remote users to access the Internet by providing dial-up connections or installing leased lines.

interoperability The ability of software and hardware on multiple computers from multiple vendors to communicate meaningfully.

intranet A network designed for information processing within a company or organization. Its uses include such services as document distribution, software distribution, access to databases, and training. An intranet derives its name from the fact that it usually employs applications associated with the Internet, such as Web pages, Web browsers, File Transfer Protocol (FTP) sites, e-mail, newsgroups, and mailing lists, in this case accessible only to those within the company or organization.

IP See Internet Protocol (IP).

ISAPI See Internet Server Application Programming Interface (ISAPI).

ISDN See Integrated Services Digital Network (ISDN).

ISO/OSI model See International Organization for Standardization Open Systems Interconnection (ISO/OSI) model.

ISP See Internet service provider (ISP).

J

Java An object-oriented programming language developed by Sun Microsystems. Currently, the most widespread use of Java is in programming small applications, or applets, for the World Wide Web.

JavaScript A scripting language developed by Netscape Communications that’s syntactically similar to Java. JavaScript, however, isn’t a true object-oriented language, and it’s limited in performance compared with Java because it’s not compiled. A JavaScript-client Web browser is necessary to run JavaScript code. Now an open standard that has been adopted by the European Computer Manufacturers Association (ECMA) and is known as the ECMA 262 language specification.

K

Kerberos protocol The basis of Microsoft Windows security, for both internal and intranet logon. The Kerberos protocol provides for the secure use of distributed software components.

L

LAN See local area network (LAN).

latency The amount of time a user has to wait for a page to load once a request has been made. In general, static content such as Hypertext Markup Language (HTML) pages doesn’t contribute to latency nearly as much as dynamic content, such as Active Server Pages (ASP) pages.

LDAP See Lightweight Directory Access Protocol (LDAP).

Lightweight Directory Access Protocol (LDAP) A network protocol designed to work on Transmission Control Protocol/Internet Protocol (TCP/IP) stacks to extract information from a hierarchical directory. This gives users a single tool to search through data to find a particular piece of information, such as a user name, e­mail address, security certificate, or other contact information.

load-balanced adapter In Network Load Balancing (NLB), the network adapter on a computer in an NLB cluster that’s used for front-end traffic.

load balancing A process in which a server cluster shares the information requests equally over all of its active nodes. This can be done either statically, by tying clients directly to different back-end servers, or dynamically, by having each client tied to a different back-end server controlled by software or a hardware device. The Network Load Balancing (NLB) feature of Microsoft Windows 2000 Advanced Server provides load balancing for Hypertext Transfer Protocol (HTTP) services.

local area network (LAN) A group of computers and other devices intended to serve an area of only a few square miles or less and connected by a communications link that enables any device to interact with any other on the network. Because the network is known to cover only a small area, optimizations can be made in the network signal protocols that permit data rates of up to 100 megabits per second (Mbps).

log file The file in which logging records are stored. This file can be either a text file or a database file.

log shipping The process of copying transaction logs from a primary SQL Server computer and applying them sequentially to another SQL Server computer. If the primary computer fails, you can direct your application to the backup server.

logging Storing information about events that occurred on a firewall or network.

M

Management Information Base (MIB) Software that describes aspects of a network that can be managed by using the Simple Network Management Protocol (SNMP). The MIB files included in Microsoft Windows can be used by third-party SNMP monitors to enable SNMP monitoring of the Web and File Transfer Protocol (FTP) services of Internet Information Services (IIS).

management-traffic adapter In Network Load Balancing (NLB), the network adapter on a computer in an NLB cluster that’s used for back-end traffic.

MAPI See Messaging Applications Programming Interface (MAPI).

mean time to failure (MTTF) The mean time until a device will fail. By knowing the MTTF of a hardware device, you might be able to predict when that device will enter its failure mode.

mean time to recovery (MTTR) The mean time it takes to recover from a failure.

member scope In the Dynamic Host Configuration Protocol (DHCP) Service, a member scope is a scope that’s added to a superscope.

Message Queuing A server technology that developers can use to build large-scale distributed systems with reliable communications between applications that can continue to operate even when networked systems are unavailable.

Messaging Applications Programming Interface (MAPI) An open and comprehensive messaging interface used by developers to create messaging and workgroup applications—such as e-mail, scheduling, calendaring, and document management. In a distributed client/server environment, MAPI provides enterprise messaging services within Windows Open Services Architecture (WOSA).

metabase A structure for storing Internet Information Services (IIS) configuration settings; the metabase performs some of the same functions as the system registry, but uses less disk space.

metadata Data used to describe other data. For example, Indexing Service must maintain data that describes the data in the content index.

MIB See Management Information Base (MIB).

Microsoft Cryptographic API An application programming interface (API) providing services for authentication, encoding, and encryption in Win32-based applications.

Microsoft Visual Basic for Applications (VBA) The development environment and language found in Microsoft Visual Basic that can be hosted by applications.

Microsoft Visual Basic Scripting Edition (VBScript) A subset of the Microsoft Visual Basic language, VBScript is implemented as a fast, portable, lightweight interpreter for use in World Wide Web browsers and other applications that use ActiveX Controls and Java applets.

middle tier The logical layer between a user interface or Web client and the database. This is typically where the Web server resides and where business objects are instantiated. Also known as application server tier.

middleware The network-aware system software, layered between an application, the operating system, and the network transport layers, whose purpose is to facilitate some aspect of cooperative processing. Examples of middleware include directory services, message-passing mechanisms, distributed transaction processing (TP) monitors, object request brokers, remote procedure call (RPC) services, and database gateways.

mirror A fully redundant or shadow copy of data. Mirror sets provide an identical twin for a selected disk; all data written to the primary disk is also written to the shadow or mirror disk. The user can then have instant access to another disk with a redundant copy of the information on the failed disk. Mirror sets provide fault tolerance.

mirrored volume A RAID-1 configuration in which the same data is written to a volume on each of two physical disks simultaneously. Each volume is considered a member of the mirrored volume.

mirroring In redundant array of independent disks (RAID), the process of providing fault tolerance by using a mirror.

modem A communications device that enables a computer to transmit information over a standard telephone line. Short for modulator/demodulator.

MTTF See mean time to failure (MTTF).

MTTR See mean time to recovery (MTTF).

multihomed host A host that has a connection to more than one physical network. The host may send and receive data over any of the links but won’t route traffic for other nodes.

multihoming The process of installing multiple network interface cards (NICs) on a single server or configuring a single NIC with multiple Internet Protocol (IP) addresses. When multiple NICs are installed, each NIC is assigned a unique IP address.

multimaster replication The replication process used by the Active Directory service. In multimaster replication, all domain controllers for the domain can modify the zone and then replicate the changes to other domain controllers. Any domain controller can send or receive updates of information stored in Active Directory.

Multipurpose Internet Mail Extensions (MIME) mapping A way of configuring browsers to view files that are in multiple formats. An extension of the Internet mail protocol that enables sending 8­bit–based e-mail messages, which are used to support extended character sets, voice mail, facsimile images, and so on.

multithreading Running several processes in rapid sequence within a single program, regardless of which logical method of multitasking is being used by the operating system. Because the user’s sense of time is much slower than the processing speed of a computer, multitasking appears to be simultaneous, even though only one task at a time can use a computer processing cycle.

multitier architecture A technique for building applications generally split into user, business, and data services tiers. These applications are built of component services that are based on an object model such as Component Object Model (COM).

N

N+1 failover A Cluster service cluster configuration in which the node preference lists of all cluster groups identify the standby cluster nodes to which resources should be made during failover. The standby nodes are servers in the cluster that are mostly idle or whose workload can be easily preempted.

name resolution The method of mapping friendly names to Internet Protocol (IP) addresses.

named pipe A high-level interprocess communication mechanism used by network computers to provide connection-oriented messaging.

network In the Cluster service, a network is an object managed by the Cluster service. A network can be private, public, private and public, or neither private nor public. Also called an interconnect.

network interface A card or other network adapter that connects a computer to a network.

network interface card (NIC) A type of network interface that connects a computer to a network. Can be an expansion card or another device. A NIC allows communication to occur between the computer and physical media, such as cabling.

Network Load Balancing (NLB) A service in Microsoft Windows 2000 Advanced Server and Datacenter Server that balances incoming Internet Protocol (IP) traffic across multiple cluster hosts. It automatically detects host failures and redistributes traffic to the surviving hosts. NLB enhances the scalability and availability of mission-critical services such Internet Information Services (IIS).

Network News Transfer Protocol (NNTP) The protocol used to distribute network news messages to NNTP servers and to NNTP clients (news readers) on the Internet. NNTP provides for the distribution, inquiry, retrieval, and posting of news articles by using a reliable stream-based transmission of news on the Internet. NNTP is designed so that news articles are stored on a server in a central database; thus users can select specific items to read. Indexing, cross- referencing, and expiration of old messages are also provided. Defined in RFC 977.

network sniffer A hardware and software diagnostic tool that can also be used to decipher passwords, which may result in unauthorized access to network accounts. Clear-text passwords are susceptible to network sniffers.

NIC See network interface card (NIC).

NNTP See Network News Transfer Protocol (NNTP).

node A computer that’s attached to a network; also called a host. A node is also a junction of some kind. On a local area network (LAN), a node is a device that’s connected to the network and is capable of communicating with other network devices. In the Cluster service, a node is a computer that’s a member of the cluster.

NT file system (NTFS) A file system designed for use specifically with the Microsoft Windows operating system. It supports long file names, full security access control, file system recovery, extremely large storage media, and various features for the Windows Portable Operating System Interface for UNIX( POSIX) subsystem. It also supports object-oriented applications by treating all files as objects with user-defined and system-defined attributes.

NTFS See NT file system (NTFS).

O

Object Linking and Embedding (OLE) A set of integration standards that is used to transfer and share information among client applications. A protocol that enables creation of compound documents with embedded links to applications so that a user doesn’t have to switch among applications in order to make revisions. OLE is based on the Component Object Model (COM) and allows for the development of reusable objects that are interoperable across multiple applications. The technology has been broadly used in business, where spreadsheets, word processors, financial packages, and other applications can share and link disparate information across client/server architectures.

octet Consists of 8 contiguous bits, or a byte. The term was created because some computer systems attached to the Internet used a byte with more than 8 bits.

ODBC See Open Database Connectivity (ODBC).

OLE See Object Linking and Embedding (OLE).

OLE DB Data-access interfaces providing consistent access to SQL and non­SQL data sources across the enterprise and the Internet. See also Structured Query Language (SQL).

Open Database Connectivity (ODBC) An application programming interface that enables applications to access data from a variety of existing data sources. A standard specification for cross-platform database access.

organizational unit (OU) In the Active Directory service, an OU is a container that can contain such objects as users, groups, computers, and other OUs.

OU See organizational unit (OU).

out-of-process component A Component Object Model (COM) component that runs in a process space separate from its client.

P

packet A transmission unit of a fixed maximum size that consists of binary information representing both data and a header containing an ID number, source and destination addresses, and error-control data. A piece of information sent over a network.

parity In redundant array of independent disks (RAID), parity refers to the mathematical method of determining the number of odd and even bits in a number or series of numbers, which you can use to reconstruct data if one number in a sequence of numbers is lost.

parity information In redundant array of independent disks (RAID), parity information is the data generated by the system to reconstruct lost information in case a disk fails.

partitioned In the Cluster service, partitioned refers to two nodes being unable to communicate with each other. After two nodes become partitioned, the Cluster service automatically shuts down on one node to guarantee data consistency.

partitioning The process of distributing data from one table into multiple, identical tables on different servers. Once the data is partitioned, you can use distributed partitioned views to access that data.

passive hub A type of hub that organizes wiring, but, unlike an active hub, it doesn’t regenerate or retransmit network data.

PDC emulator In the Active Directory service, the PDC emulator acts as a Microsoft Windows NT Primary Domain Controller (PDC) if the domain contains computers operating without Microsoft Windows 2000 client software or if it contains Windows NT backup domain controllers.

Point-to-Point Protocol (PPP) A set of industry-standard framing and authentication protocols included with Microsoft Windows remote access to ensure interoperability with third-party remote access software. PPP negotiates configuration parameters for multiple layers of the Open Systems Interconnection (OSI) model. The Internet standard for serial communications, PPP defines how data packets are exchanged with other Internet-based systems using a modem connection.

Point-to-Point Tunneling Protocol (PPTP) A specification for virtual private networks in which some nodes of a local area network are connected through the Internet. PPTP is an open industry standard that supports the most prevalent networking protocols—Internet Protocol (IP), Internetwork Packet Exchange (IPX), and Microsoft Networking (NetBEUI). Companies can use PPTP to outsource their remote dial-up needs to an Internet service provider or other carrier to reduce cost and complexity.

port number A number identifying a certain Internet application. For example, the default port number for the WWW service is 80.

port rule In Network Load Balancing (NLB), a port rule is a configuration setting that describes which traffic to load balance and which traffic to ignore. By default, NLB configures all ports for load balancing.

PPP See Point-to-Point Protocol (PPP).

PPTP See Point-to-Point Tunneling Protocol (PPTP).

preferred node In the Cluster service, a preferred node is a preferred computer on which the resource is configured to run.

primary node In the Cluster service, a primary node supports all clients while its companion node (secondary node) is idle. If the primary node fails, the secondary node immediately picks up all operations and continues to service clients at a rate of performance that’s close or equal to that of the primary node. See also secondary node.

process In Microsoft Windows, an object consisting of an executable program, a set of virtual memory addresses, and threads; in UNIX, a synonym for thread. A process is the largest component of activity in Windows 2000. See also thread.

process isolation Running an application or component out-of-process.

protocol The method by which computers communicate on the Internet. The most common protocol for the World Wide Web is Hypertext Transfer Protocol (HTTP). Other Internet protocols include File Transfer Protocol (FTP), Gopher, and Telnet. The protocol is part of the full Uniform Resource Locator (URL) for a resource.

provider In OLE DB, a provider is any component that allows technologies such as ActiveX Directory Objects (ADO) to access data in a uniform way through the OLE DB interfaces.

proxy A software program that connects a user to a remote destination through an intermediary gateway.

proxy server A firewall component that manages Internet traffic to and from a local area network and can provide other features, such as document caching and access control. A proxy server can improve performance by caching and directly supplying frequently requested data, such as a popular Web page, and can filter and discard requests that the owner doesn’t consider appropriate, such as requests for unauthorized access to proprietary files. See also firewall.

public-key encryption An asymmetric scheme that uses a pair of keys for encryption: the public key encrypts data and a corresponding secret key decrypts it. For digital signatures, the process is reversed: The sender uses the secret key to create a unique electronic number that can be read by anyone possessing the corresponding public key, which verifies that the message is from the sender.

Q

quorum disk In the Cluster service, a single disk in the cluster storage system designated as the quorum resource.

quorum resource In the Cluster service, a special common resource that’s a dedicated physical resource in the common cluster disk array that plays a critical role in the cluster operation.

R

RAID See redundant array of independent disks (RAID).

RAM See random access memory (RAM).

random access memory (RAM) Semiconductor-based memory that can be read and written by the central processing unit (CPU) or other hardware devices. The storage locations can be accessed in any order. Note that various types of read-only memory (ROM) are capable of random access but can’t be written to. The term RAM is generally understood to refer to volatile memory that can be written to as well as read. Information stored in RAM is lost when the user turns off the computer.

redundancy The duplication of network components, paths, and services to provide fault tolerance and avoid any single points of failure in your network. The use of redundant hardware and software is the most effective way to ensure a Web site’s availability.

redundant array of independent disks (RAID) A data storage method in which data, along with information used for error correction, such as parity bits, is distributed among two or more hard disk drives in order to improve performance and reliability. The hard disk array is governed by array management software and a disk controller, which handles the error correction. RAID is generally used on network servers. Several defined levels of RAID offer differing trade­offs among access speed, reliability, and cost. Microsoft Windows includes three RAID levels: Level 0, Level 1, and Level 5.

registry A central hierarchical database in Microsoft Windows used to store information necessary to configure the system for one or more users, applications, and hardware devices. The registry contains information that’s constantly referenced during operation, such as profiles for each user, the applications installed on the computer and the types of documents each can create, property sheet settings for folders and application icons, what hardware exists on the system, and which ports are being used.

relative ID master In the Active Directory service, the relative ID master allocates sequences of relative IDs to each of the various domain controllers in its domain.

reliability A measure of the time that elapses between failures in a system. Hardware and software components have different failure characteristics. As a result, it’s easier to predict hardware reliability than software reliability. With hardware, you can often predict when a component will fail and from there estimate that component’s reliability.

Remote Data Services A Web-based technology that brings database connectivity and corporate data publishing capabilities to Internet and intranet applications.

remote procedure call (RPC) In programming, a call by one program to a second program on a remote system. The second program usually performs a task and returns the results of that task to the first program.

replication Copying from one server node to another of either content or the configuration metabase, or both. This copying can be done either manually or automatically by using replication software. Replication is a necessary function of clustering to ensure fault tolerance.

resource In the Cluster service, a resource is a hardware or software component within the cluster. A resource is any physical or logical component that can be brought online and taken offline, can be managed in a server cluster, and can be hosted by only one node at a time.

resource group In the Cluster service, a resource group is a logical collection of cluster resources. A resource group is usually made up of logically related resources such as applications and their associated peripherals and data.

root domain In Domain Name System (DNS), the root domain is the domain name that the zone is anchored to. A zone contains information about all names that end with the zone’s root domain.

router An intermediary device on a communications network that expedites message delivery. On a single network linking many computers through a mesh of possible connections, a router receives transmitted messages and forwards them to their correct destinations over the most efficient available route. On an interconnected set of local area networks (LANs) using the same communications protocols, a router serves the somewhat different function of acting as a link between LANs, enabling messages to be sent from one to another.

RPC See remote procedure call (RPC).

S

SAN See storage area network (SAN).

scalability A measure of how easily a computer, service, or application can expand to meet increasing performance demands. A scalable system is one that can perform increasing work while sustaining acceptable performance levels. For server clusters, scalability refers to the ability to incrementally add one or more systems to an existing cluster when the cluster’s load exceeds its capabilities.

scaling out The process of adding more servers to your network. Scaling out delivers high performance when an application’s throughput requirements exceed an individual system’s capabilities. Scaling out reduces contention for resources and improves availability.

scaling up The process of adding more resources to a system. Scaling up can include adding memory, processors, and disk drives to your computer.

schema master In the Active Directory service, the schema master controls all updates and modifications to the schema.

script A kind of program that consists of a set of instructions for an application or utility program. A script can be embedded in a Web page.

scripting engine A program that interprets and executes a script. See also script.

secondary node In the Cluster service, a secondary node is the companion node in the cluster that acts as a backup to the primary node. The secondary node is idle unless failover occurs. If the primary node fails, the secondary node immediately picks up all operations and continues to service clients at a rate of performance that’s close to or equal to that of the primary node. See also primary node.

Secure Sockets Layer (SSL) A protocol that supplies secure data communication through data encryption and decryption. SSL uses Rivest-Shamir-Adleman (RSA) public-key encryption for specific Transmission Control Protocol/Internet Protocol (TCP/IP) ports. It’s intended for handling commerce payments. An alternative method is Secure-HTTP (S-HTTP), which is used to encrypt specific Web documents rather than the entire session. SSL is a general-purpose encryption standard. SSL can also be used for Web applications requiring a secure link, such as e-commerce applications, or for controlling access to Web-based subscription services.

security descriptor The access control information associated with an object. Each object in Microsoft Windows 2000 contains a security descriptor. When a user tries to access the object, Windows 2000 examines the security descriptor to determine whether the user is allowed to access the object and what action the user is allowed to take with that object.

Security log A log, generated by a firewall or other security device, that lists events that could affect security, such as access attempts or commands, and the information about the users involved.

server A term that refers to any of the following: a computer on a network that sends files to, or runs applications for, other computers on the network; the software that runs on the server computer and performs the work of serving files or running applications; or, in object-oriented programming, a piece of code that exchanges information with another piece of code upon request.

server certificate See certificate, server.

server cluster A group of server computers that are networked together both physically and with software, in order to provide cluster features such as fault tolerance or load balancing. See also cluster.

server-side include A mechanism for including dynamic text in World Wide Web documents. Server-side includes are special command codes that are recognized and interpreted by the server; their output is placed in the document body before the document is sent to the browser. Server-side includes can be used, for example, to include the date/time stamp in the text of the file.

session key A digital key that’s created by the client, encrypted, and sent to the server. This key is used to encrypt data sent by the client.

session state Client data that’s visible to a particular client for the duration of a session. Session state can span multiple Transmission Control Protocol (TCP) connections, which can be either simultaneous or sequential.

shared-nothing model In the Cluster service, the shared-nothing model refers to how servers in a cluster manage and use local and common cluster devices and resources. In this model, each server owns and manages its local devices. Devices common to the cluster are selectively owned and managed by a single server at any given time.

Simple Mail Transfer Protocol (SMTP) A Transmission Control Protocol/Internet Protocol (TCP/IP) protocol for sending messages from one computer to another on a network. This protocol is used on the Internet to route e­mail.

Simple Network Management Protocol (SNMP) The network management protocol of Transmission Control Protocol/Internet Protocol (TCP/IP). In SNMP, agents, which can be hardware as well as software, monitor the activity in the various devices on the network and report to the network console workstation. Control information about each device is maintained in a structure known as a management information block. See also Management Information Base (MIB).

site In the Active Directory service, consists of one or more Internet Protocol (IP) subnets that are connected by highly reliable and fast links. A site often shares the same boundaries as the local area network (LAN), but a site isn’t a part of the namespace.

slow link A modem connection, usually from 14,400 bits per second (bps) to 56,000 bps. Also called a dial-up.

SMTP See Simple Mail Transfer Protocol (SMTP).

snap-in A program hosted within Microsoft Management Console (MMC) that administrators use to manage network services. MMC provides the environment in which management tools (snap-ins) are hosted; snap-ins provide the actual management behavior necessary to administer network services such as Internet Information Services (IIS).

sniffer See network sniffer.

SNMP See Simple Network Management Protocol (SNMP).

socket An identifier for a particular service on a particular node on a network. The socket consists of a node address and a port number, which identifies the service. For example, port 80 on an Internet node indicates a Web server.

spoofing Impersonating another person or computer, usually by providing a false e-mail name, Uniform Resource Locator (URL), or Internet Protocol (IP) address.

SQL See Structured Query Language (SQL).

SSL See Secure Sockets Layer (SSL).

stager A server on which content is placed prior to being placed on a production server. A stager is also known as a staging computer or staging server.

stateful object An object that holds private state accumulated from the execution of one or more client calls.

stateful system A system (usually on the back end) that maintains data and state across sessions. Data can be stored in flat files, inside other applications, or in a database.

stateless object An object that doesn’t hold private state accumulated from the execution of one or more client calls.

stateless system A system (usually on the front end) that doesn’t store client information across sessions. If client information needs to persist between sessions, you can use techniques such as cookies to maintain the information.

static page Hypertext Markup Language (HTML) pages prepared in advance of the request and sent to the client upon request. This page takes no special action when requested.

sticky session A session in which a client request establishes a server-side state that’s used in subsequent requests during the same session.

storage area network (SAN) A network comprised of one or more storage systems, each capable of providing terabytes of disk storage capacity at very high transfer rates. Most SANs use Fibre Channel technology and are capable of providing input/output (I/O) throughputs in the gigabits-per-second (Gbps) range.

stored procedure A precompiled set of queries that’s stored on the database server. They control which operations are performed and which database fields are accessed.

stripe set Refers to the saving of data across identical partitions on different drives. A stripe set doesn’t provide fault tolerance; however, stripe sets with parity do provide fault tolerance. See also stripe sets with parity.

stripe sets with parity A method of data protection in which data is striped in large blocks across all the disks in an array. Data redundancy is provided by the parity information. This method provides fault tolerance. See also stripe set.

Structured Query Language (SQL) The international standard language for defining and accessing relational databases.

subnet A subdivision of an Internet Protocol (IP) network. Each subnet has its own unique subnetted network ID, which is a subset of the original class-based network ID. Subnetted network IDs are created by using bits from the host ID portion of the original network ID.

subnet mask A Transmission Control Protocol/Internet Protocol (TCP/IP) configuration parameter that extracts the network ID and host ID from an IP address.

subnetting The process of dividing a Transmission Control Protocol/Internet Protocol (TCP/IP) network into subnets.

switch A computer or other network-enabled device that controls routing and operation of a signal path. Rather than broadcast to all ports (as a hub does), a switch establishes a direct path between two ports so that multiple pairs of ports can communicate without collision.

switch flooding In Network Load Balancing (NLB), switch flooding refers to the process in which the switch sends a client request, which contains the cluster media access control (MAC) address, to all ports because it doesn’t recognize the MAC address in the packet.

symmetric encryption See encryption.

T

T1 A U.S. telephone standard for a transmission facility at digital signal level 1 (DS1) with 1.544 megabits per second (Mbps) in North America and 2.048 Mbps in Europe. The bit rate is with the equivalent bandwidth of approximately twenty-four 56-kilobits-per-second (Kbps) lines. A T1 circuit is capable of serving a minimum of 48 modems at 28.8 Kbps, or 96 modems at 14.4 Kbps. T1 circuits are also used for voice telephone connections. A single T1 line carries 24 telephone connections with 24 telephone numbers. When used for voice transmission, a T1 connection must be split into 24 separate circuits.

T3 A U.S. telephone standard for a transmission facility at digital signal level 3 (DS3). Equivalent in bandwidth to 28 T1s. The bit rate is 44.736 megabits per second (Mbps). T3 is sometimes called a 45-meg circuit.

TCP/IP See Transmission Control Protocol/Internet Protocol (TCP/IP).

Telnet A protocol that enables an Internet user to log onto and enter commands on a remote computer linked to the Internet, as if the user were using a text-based terminal directly attached to that computer. Telnet is part of the Transmission Control Protocol/Internet Protocol (TCP/IP) suite of protocols.

thin server A client/server architecture in which most of an application is run on the client computer, which is called a fat client, with occasional data operations on a remote server. Such a configuration yields good client performance but complicates administrative tasks such as software upgrades.

thread The basic entity to which the operating system allocates central processing unit (CPU) time. A thread can execute any part of the appli-cation’s code, including a part currently being executed by another thread. All threads of a process share the virtual address space, global variables, and operating-system resources of the process.

three-tier architecture Divides a networked application into three logical areas: the user interface layer, the business logic layer, and the database layer. Layers may have one or more components. For example, there can be one or more user interfaces in the top tier, each user interface may communicate with more than one application in the middle tier at the same time, and the applications in the middle tier may use more than one database at a time. Components in a tier may run on a computer that’s separate from the other tiers, communicating with the other components over a network.

throttling Controlling the maximum amount of bandwidth dedicated to Internet traffic on a server. This feature is useful if there are other services (such as e-mail) sharing the server over a busy link.

time out A setting that automatically cancels an unanswered client request after a certain period of time.

traffic The interchange of incoming network requests and outgoing responses. In a Web environment, the request is sent by a browser on a client computer through a Transmission Control Protocol (TCP) connection with the server. The server sends out pages in response to the request.

Transmission Control Protocol/Internet Protocol (TCP/IP) A communications standard for all computers on the Internet. On the sending end, TCP breaks the data to be sent into data segments. IP assembles segments into packets that contain data segments, as well as sender and destination addresses. IP then sends packets to the router for delivery. On the receiving end, IP receives the packets and breaks them down into data segments. TCP assembles the data segments into the original data set.

tree In the Active Directory service, a hierarchical grouping of domains. You can create a tree by adding one or more child domains to the parent domain.

U

UNC See Universal Naming Convention (UNC).

Uniform Resource Locator (URL) A naming convention that uniquely identifies the location of a computer, directory, or file on the Internet. The URL also specifies the appropriate Internet protocol, such as Hypertext Transfer Protocol (HTTP) or File Transfer Protocol (FTP). For example: http://www.microsoft.com.

Universal Naming Convention (UNC) The naming convention used for physical directories.

URL See Uniform Resource Locator (URL).

V

VBA See Microsoft Visual Basic for Applications (VBA).

VBScript See Microsoft Visual Basic Scripting Edition (VBScript).

virtual directory A directory name, used in an address, that corresponds to a physical directory on the server; sometimes called URL mapping.

virtual machine Software that mimics the performance of a hardware device, such as a program that allows applications written for an Intel processor to be run on a Motorola processor.

virtual server A virtual computer that resides on a Hypertext Transfer Protocol (HTTP) server but appears to the user as a separate HTTP server. Several virtual servers can reside on one computer, each capable of running its own programs and each with individualized access to input and peripheral devices. Each virtual server has its own domain name and Internet Protocol (IP) address and appears to the user as an individual Web site or File Transfer Protocol (FTP) site. Some Internet service providers use virtual servers for those clients who want to use their own domain names. In clusters, a virtual server appears as a single server to users.

W

W3C See World Wide Web Consortium (W3C).

WAN See wide area network (WAN).

Web application A software program that uses Hypertext Transfer Protocol (HTTP) for its core communication protocol and delivers Web-based information to the user in the Hypertext Markup Language (HTML).

WebDAV See Web Distributed Authoring and Versioning (WebDAV).

Web Distributed Authoring and Versioning (WebDAV) An extension to the Hypertext Transfer Protocol (HTTP) 1.1 standard that facilitates access to files and directories through an HTTP connection. Remote authors can add, search, delete, or change directories and documents and their properties.

Web farm A front-end cluster that provides core services, such as Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP), to the clients. See also cluster.

Web page A World Wide Web document. A Web page typically consists of a Hypertext Markup Language (HTML) file, with associated files for graphics and scripts, in a particular directory on a particular computer (and thus identifiable by a Uniform Resource Locator [URL]).

Web server In general terms, a computer equipped with the server software that uses Internet protocols such as Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP) to respond to Web client requests on a Transmission Control Protocol/Internet Protocol (TCP/IP) network.

wide area network (WAN) A communications network that connects geographically separated areas.

Windows Internet Name Service (WINS) server A server that uses the WINS protocol to map Internet Protocol (IP) addresses to user-friendly names. See also Domain Name System(DNS).

Windows Open Services Architecture (WOSA) Standards for creating cross-platform applications that use Microsoft Windows services.

Windows Script Host (WSH) A language- independent scripting host for ActiveX scripting engines on 32-bit Microsoft Windows platforms.

worker thread A thread that’s created by a component or Internet Server Application Programming Interface (ISAPI) extension or filter to perform asynchronous processing. Using worker threads frees up Internet Information Services (IIS) input/output (I/O) threads to process additional requests.

working directory A term sometimes used to describe the directory in which the Web server software is installed.

working set The RAM allocated to a process in the Microsoft Windows operating system.

World Wide Web (WWW) The most graphical service on the Internet, the Web also has the most sophisticated linking abilities. It’s a set of services that run on top of the Internet, providing a cost-effective way of publishing information, supporting collaboration and workflow, and delivering business applications to connected users all over the world. The Web is a collection of Internet host systems that make these services available on the Internet using the Hypertext Transfer Protocol (HTTP). Web-based information is usually delivered in the form of hypertext and hypermedia using Hypertext Markup Language (HTML).

World Wide Web Consortium (W3C) Founded in 1994 to develop common standards for the World Wide Web, the W3C is an international industry consortium jointly hosted by the Massachusetts Institute of Technology Laboratory for Computer Science (MIT/LCS) in North America, by the Institut National de Recherche en Informatique et en Automatique (INRIA) in Europe, and by the Keio University Shonan Fujisawa Campus in Asia. Initially, the W3C was established in collaboration with the Conseil Européen pour la Recherche Nucléaire (CERN), where the Web originated, with support from the Defense Advanced Research Projects Agency (DARPA) and the European Commission. For more information, see http://www.w3.org/.

WOSA See Windows Open Services Architecture (WOSA).

WSH See Windows Script Host (WSH).

WWW See World Wide Web (WWW).

Z

zone transfer The process of replicating a zone file to multiple name servers. A zone transfer is achieved by copying the zone file information from the master server to the secondary server.