S Reference Point

ISDN reference point that works with a T reference point to convert a 4-wire ISDN network to the 2-wire ISDN network needed to communicate with the ISDN switches at the network provider.

SA, sa (System Administrator)

The default login ID for SQL Server; the global administrator of the SQL Server system. This ID has no restrictions on what it can do within the SQL Server environment. By default, anyone who has logged in to SQL Server will be able to use the SA account unless you change this.

Safe Mode

A Windows Advanced Options menu item that loads the absolute minimum of services and drivers that are needed to start Windows. The drivers that are loaded with Safe Mode include basic files and drivers for the mouse (unless a serial mouse is attached to the computer), monitor, keyboard, hard drive, standard video driver, and default system services. Safe Mode is considered a diagnostic mode. It does not include networking capabilities.

Safe Mode with Command Prompt

A Windows Advanced Options menu item that starts Windows in Safe Mode, but instead of loading the graphical interface, it loads a command prompt.

Safe Mode with Networking

A Windows Advanced Options menu item that starts Windows in Safe Mode, but it adds networking features.

Sag

See Brownout.

SAM

See Security Accounts Manager.

Sampling Rate

The rate at which samples of a specific waveform amplitude are collected within a specified period of time.

SAP

See Service Access Point and Service Advertising Protocol.

Satellite Microwave

Satellite microwave systems relay transmissions through communications satellites that operate in geosynchronous orbits 22,300 miles above the earth.

Scalable

The ability of a system to grow to handle greater traffic, volume, usage, etc.

Scanner

A virus detection program that searches for viruses. See also Anti-Virus Software, On-Demand Scanner, and On-Access Scanner.

Scheduling

The process of determining which threads should be executed according to their priority and other factors. See also Preemptive Multitasking.

Schema

The metadata (data about data) that describes the use of objects within a given structure. In Active Directory, the schema governs the type of objects that can exist and the mandatory and optional attributes of each object. Windows Active Directory has an extensible schema that allows third-parties to create their own object classes. Schemas also exist for other components such as the message transfer agent and information store in Exchange Server.

Schema FSMO

The operations manager that holds the master copy of the directory schema. In other words, the schema FSMO is the only server that can write to the schema.

Schema Master

A Windows server that controls the structure of the AD database. Any updates or modifications made to the database structure must be made on this server first. It will then replicate these changes to the rest of the AD servers in your forest. This ensures that all AD servers are “speaking the same language”. There should never be a case in which one server knows about a new object class or property but another server does not. Also known as the schema FSMO. See also Schema FSMO.

Scope

Contiguous range of addresses.

SCR

See Sustainable Cell Rate.

Script

1. A small program or macro invoked at a particular time. For example, a login script may execute the same specific set of instructions every time a user logs on to a network. A communications script may send user-identification information to an Internet Service Provider (ISP) each time a subscriber dials up the service.
2. A saved query that has an .SQL extension by default. Scripts can be loaded, edited, and run from Query Analyzer or osql. Scripts can also be created by Enterprise Manager for existing databases and objects. Scripts are saved as ASCII text and generally have an .SQL extension.

Script Policy

Setting within Group Policy objects that specifies login, logoff, startup, and shutdown script settings.

Scripting Agent

The Microsoft Exchange Scripting Agent is a component that reads and executes a script attached to a public folder. It can carry out instructions by accessing databases, spreadsheets, gateways, and many other programs and services.

Scroll Bar

The bar that appears at the right side of the File List and Directory sections of the File System screen of DOSSHELL.

SCSI

See Small Computer Systems Interface.

SDLC

See Synchronous Data Link Control.

Sealing

The process of encrypting data.

Search Engine

Web sites dedicated to responding to requests for specific information, searching massive locally stored databases of Web pages, and responding with the URLs of pages that fit the search phrase. See also World Wide Web and Uniform Resource Locator.

Secondary DNS Server

Pulls DNS information from the specified master server. Secondary DNS servers receive a read-only copy of zone files. The secondary DNS server can resolve queries from this read-only copy, but cannot make changes or updates.

Secret Key

A security key that can be used to encrypt data and that is only known by a sender and the recipients the sender informs.

Secret Key Encryption

An encryption technique that works with keys that are shared between two parties, but are unknown to an external party. The keys are exchanged via a secure channel. See also Public Key Encryption.

Sector

Disk space, normally 512 bytes long.

Sector Viruses

See Boot Sector Infector and Master Boot Sector Virus.

Secure MIME (S/MIME)

An extension to the Multipurpose Internet Mail Extension (MIME) e-mail standard that adds security in the form of the RSA public-key algorithm.

Secure Sockets Layer (SSL)

An Internet protocol that provides secure and authenticated TCP/IP connections. A client and server establish a “handshake” whereby they agree on a level of security they will use, such as authentication requirements and encryption. SSL can be used to encrypt sensitive data for transmission.

Security

The process of giving “rights” or “permissions” to groups or users, so that they can access resources on the network. Different network operating systems use different terms to describe these types of security issues. See also Security Identifiers and Security Accounts Manager.

Security Accounts Manager (SAM)

The module of the Windows NT executive that authenticates a username and password against a database of accounts, generating an access token that includes the user’s permissions. See also Security, Security Identifiers, and Access Tokens.

Security Association (SA)

Provides all the information needed for two computers to communicate securely. It contains a policy agreement that controls which algorithms and key lengths the two machines will use, plus the actual security keys used to securely exchange information.

Security Configuration and Analysis

A Windows utility used for creating security profiles and managing security settings across multiple machines.

Security Configuration and Analysis Tool

A Windows utility that is used to analyze and to help configure a computer’s local security settings. Security Configuration and Analysis works by comparing the computer’s actual security configuration to a security template configured with the desired settings.

Security Group

A type of group that can be created on a Windows 2000 domain controller in the Active Directory. A security group is a logical group or users who need to access specific resources. Security groups are used to assign permissions to resources. See also Domain Controller and Active Directory.

Security Identifiers (SIDs)

Unique codes that identify a specific user to the Windows NT security system. Security identifiers contain a complete set of permissions for that user.

Security Log

A log that tracks events that are related to Windows auditing. The Security log can be viewed throught the Event Viewer utility. See also Event Viewer.

Security Method

A pre-specified encryption algorithm with a negotiated key length and key lifetime.

Security Option Policies

Policies used to configure security for the computer. Security option policies apply to computers rather than to users or groups. These policies are set through Local Computer Policy. See also Local Computer Policy.

Security Principals

An Active Directory object that is used for the assignment and maintenance of security settings. The primary security principals are Users, Groups, and Computers.

Security Services

A service that provides security on the network.

Security Templates

Files used by the Security Configuration and Analysis tool for defining and enforcing security settings across multiple computers.

Seed Router

In an AppleTalk network, the router that is equipped with the network number or cable range in its port descriptor. The seed router specifies the network number or cable range for other routers in that network section and answers to configuration requests from nonseed routers on it connected AppleTalk network, permitting those routers to affirm or modify their configurations accordingly. Every AppleTalk network needs at least one seed router physically connected to each network segment.

Segmentation

The process of splitting a larger network into two or more segments linked by bridges or routers.

Segmentation and Reassembly Sublayer

Abbreviated SAR. One of two sublayers that make up the ATM Adaptation Layer, the other being the convergence sublayer (CS). The SAR is the lower of the two sublayers, packages variable-sized data packets into fixed-sized cells at the transmitting end, and repackages the cells at the receiving end. SAR is also responsible for locating and managing lost cells and cells that are received out of sequence. See also ATM Adaptation Layer and Convergence Sublayer.

Self-Encrypting Virus

Self-encrypting viruses attempt to conceal themselves from anti-virus programs. Most anti-virus programs attempt to find viruses by looking for certain patterns of code (known as virus signatures) that are unique to each virus. Self-encrypting viruses encrypt these text strings differently with each infection to avoid detection. See also Encrypted Virus and Self-Garbling Virus.

Self-Extracting Files

A self-extracting file decompresses part of itself into one or more parts when executed. Software authors and others often use this file type to transmit files and software via the Internet since the compressed files conserve disk space and reduce download time. Some anti-virus products may not search self-extracting file components. To scan these components, you must first extract the files and then scan them.

Self-Garbling Virus

A self-garbling virus attempts to hide from anti-virus software by garbling its own code. When these viruses spread, they change the way their code is encoded so anti-virus software cannot find them. A small portion of the virus code decodes the garbled code when activated. See also Self-Encrypting Virus and Polymorphic Virus.

Send Form

A stand-alone form that is sent from one user to another user.

Separate Clock Signal

A method of synchronous communication in which a separate channel carries clocking information.

Separator Page

A page used at the beginning of each document to identify the user who submitted the print job. When users share a printer, separator pages can be useful for distributing print jobs.

Sequenced Packet Exchange (SPX)

A Transport layer protocol that extends IPX to provide connection-oriented service with reliable delivery. Reliable delivery is ensured by retransmitting packets in the event of an error.

Serial

A method of communication that transfers data across a medium one bit at a time, usually adding stop, start, and check bits to ensure quality transfer. See also COM Port and Modem.

Serial Interface

An interface that transfers data as individual bits; each operation has to be completed before the next starts.

Serial Line Internet Protocol (SLIP)

This is a standard for moving data across a telephone line using the TCP/IP transport protocol. See also Point-to-Point Protocol and Internet Protocol.

Serial Tunnel (STUN)

A technology used to connect an HDLC link to an SDLC link over a serial link.

Server

A computer dedicated to servicing requests for resources from other computers on a network. Servers typically run network operating systems such as Windows Server or NetWare. See also Windows NT, NetWare, and Client/Server.

Server Cluster

Two or more computers working together to provide higher availability, reliability, and scalability than can be obtained by using a single system.

Server Manager

Utility in the Administrative Tools group used to manage domains and computers.

Server Messaging Blocks (SMB)

Microsoft’s equivalent to NCP packets. Like NCP packets, SMBs operate at the Application layer of the OSI model. SMBs allow machines on a Microsoft network to communicate with one another. Through the use of SMBs, file and print services can be shared. SMBs can use TCP/IP, NWLink (IPX/SPX), or NetBEUI.

Server Mirroring

The capability to have one server completely mirrored in all forms to another server. This would mean that if Server A went down for any reason whatsoever, such as a failed hard drive, a failed network card, or even a blown motherboard, the mirrored Server B would take over the duties of Server A.

Server Push

A mechanism used on the Internet whereby a client application, usually a Web browser, maintains an open connection to a Web site, and the Web server provides new content to the client automatically, as soon as the new content becomes available. This process continues until the server decides to close the connection. See also Client Pull.

Server Service

A service on Microsoft computers that provides file and print services.

Service

A process dedicated to implementing a specific function for other processes. Most Windows components are services used by user-level applications.

Service Access Point (SAP)

A field specified by IEEE 802.2 that is part of an address specification.

Services

A Windows utility used to manage the services installed on the computer.

Service Advertising Protocol (SAP)

The Service Advertising Protocol (SAP) provides location information by a device indicating what services it is offering. Devices can see each other on the network by listing the SAPs each server issues.

Service Group

A Windows special group that includes users who log on as a user account that is only used to run a service. See also Special Group and Service.

Service Pack

A group of bug fixes and enhancements offered by Microsoft on a (semi) regular basis. There are various Service Packs for different applications.

Service Profile Identifier (SPID)

A number assigned by service providers or local telephone companies and assigned by administrators to a BRI port. SPIDs are used to determine subscription services of a device connected via ISDN. ISDN devices use SPID when accessing the telephone company switch that initializes the link to a service provider.

Service Provider

A MAPI program that provides messaging-oriented services to a client. There are three main types of service providers: address book, message store, and message transport.

Service Record (SRV)

Links the location of a service such as a domain controller with information about how to contact the service. It provides seven items of information: service name, a transport protocol, the domain name for which the service is offered, the priority, the weight, port number on which the service is offered, and the DNS name of the server which offers the service.

Services for Macintosh

Service available through NT Server that allows Macintosh users to take advantage of NT file and print services. See also Macintosh.

Session

In the context of Terminal Services, a connection between a Terminal Services client and a Terminal Services server. Users log on through any client on the network and can see only their individual session. See also Terminal Services, Terminal Services Client, and Terminal Services Server.

Session Layer

Layer 5 of the OSI reference model, responsible for creating, managing, and terminating sessions between applications and overseeing data exchange between Presentation layer entities. See also Application Layer, Data Link Layer, Network Layer, Physical Layer, Presentation Layer, and Transport Layer.

SET

Displays, sets, or removes MS-DOS environment variables.

Set-Based

Set-based routers and switches use the set command to configure devices. Cisco is moving away from set-based commands and is using the Command-Line Interface (CLI) on all new devices.

Setup Manager (SETUPMGR)

A Windows utility used to create automated installation scripts or unattended answer files. See also Answer File.

SETUPMGR

See Setup Manager.

Setup Mode

Mode that a router will enter if no configuration is found in nonvolatile RAM when the router boots. Allows the administrator to configure a router step-by-step. Not as robust or flexible as the Command-Line Interface.

SETVER

Sets the version number that MS-DOS reports to a program.

Severity Level

For a system error, a component of the error message that provides information about the error. Levels from 0 to 10 are informational, 11 to 16 are user errors, 17 and 18 are resource problems, and 19 to 25 are fatal errors.

SF

See Super Frame.

Shadow Postoffice

A postoffice without mailboxes. The Exchange MS Mail Connector Postoffice is referred to as a shadow postoffice because it does not contain user mailboxes and only temporarily stores incoming and outgoing MS Mail messages.

SHARE

Installs file-sharing and locking capabilities on your hard disk.

Share

A resource (e.g., a directory or a printer) shared by a server or a peer on a network. See also Resource, Server, and Peer.

Shared Drive

A disk drive available to other computers on the network. Shared drives use the Universal Naming Convention to differentiate themselves from other drives. See also Mapped Drive and Universal Naming Convention.

Shared Folder Object

An Active Directory object that specifies the name and location of specific shared resources that are available to users of the Active Directory.

Share-Level Security

Security applied to resources such as directories and printers that have been shared on the network.

Share Permissions

Permissions used to control access to shared folders. Share permissions can only be applied to folders, as opposed to NTFS permissions, which are more complex and can be applied to folders and files. See also NTFS Permissions.

Shared Folder

A folder on a Windows computer that network users can access.

Shared Folders

A Windows utility for managing shared folders on the computer.

Shareware

Software distributed for evaluation without cost, but that requires payment to the author for full rights. If, after trying the software, you do not intend to use it, you simply delete it. Using unregistered software beyond the evaluation period is pirating.

Sharing

Only by specifying that you want to grant others access to a resource – be it a directory, a CD-ROM drive, or a printer – do you make the resource available for use from remote computers and devices. A shared resource is simply a resource whose owner has leveraged networking to make it available for use by others.

Shell

The user interface of an operating system; the shell launches applications and manages file systems.

Shielded Twisted-Pair Cable (STP)

A form of twisted-pair cabling that has EMI shielding.

Shortcut

A quick link to an item that is accessible from a computer or network, such as a file, program, folder, printer, or computer. Shortcuts can exist in various locations including the Desktop, the Start menu, or within folders. See also Desktop and Start Menu.

Shortest Path First Algorithm (SPF)

A routing algorithm used to decide on the shortest-path spanning tree. Sometimes called Dijkstra’s algorithm and frequently used in link-state routing algorithms. See also Link-State Routing Algorithm.

SID

See Security Identifiers.

Signaling

The process of sending information over media.

Signaling Packet

An informational packet created by an ATM-connected mechanism that wants to establish connection with another such mechanism. The packet contains the QoS parameters needed for connection and the ATM NSAP address of the endpoint. The endpoint responds with a message of acceptance if it is able to support the desired QoS, and the connection is established. See also Quality of Service.

Signal Quality Error (SQE)

In an Ethernet network, a message sent from a transceiver to an attached machine that the collision-detection circuitry is working.

Signal-Regenerating Repeaters

A type of repeater that eliminates noise by creating an exact duplicate of incoming data, identifying it amidst the noise, reconstructing it, and retransmitting only the desired information.

Signature

A search pattern, often a simple string of characters or bytes, expected to be found in every instance of a particular virus. Usually, different viruses have different signatures. Anti-virus scanners use signatures to locate specific viruses. Also known as Virus Signatures.

Signing

The process of placing a digital signature on a message.

Silicon Switching

A type of high-speed switching used in Cisco 7000 series routers, based on the use of a separate processor (the Silicon Switch Processor, or SSP). See also Silicon Switching Engine.

Silicon Switching Engine (SSE)

The software component of Cisco’s silicon switching technology, hard-coded into the Silicon Switch Processor (SSP). Silicon switching is available only on the Cisco 7000 with an SSP. Silicon-switched packets are compared to the silicon-switching acahe on the SSE. The SSP is a dedicated switch processor that offloads the switching process from the route processor, providing a fast-switching solution, but packets must still traverse the backplane of the router to get to the SSP and then back to the exit interface.

Simple Authentication and Security Layer (SASL)

A protocol that provides authentication of SMTP client connections to an SMTP server.

Simple Mail Transport Protocol (SMTP)

A major standards-based protocol that allows for the transfer of messages between different messaging servers. SMTP is defined under RFC821 and uses simple command verbs to facilitate message transport over TCP/IP port 25. See also Internet.

Simple Network Management Protocol (SNMP)

An Internet protocol used to manage heterogeneous computers, operating systems, and applications. Because of its wide acceptance and applicability, SNMP is well suited for enterprise-wide management. See also Internet Protocol.

Simple Volume

A dynamic disk volume that contains space from a single disk. The space from the single drive can be contiguous or noncontiguous. Simple volumes are used when the computer has enough disk space on a single drive to hold an entire volume. See also Dynamic Disk.

Simplex

The mode at which data or a digital signal is transmitted. Simplex is a way of transmitting in only one direction. Half duplex transmits in two directions but only one direction at a time. Full duplex transmits both directions simultaneously.

Single-Instance Storage (SIS)

Storing only one copy. A message that is sent to multiple recipients homed on the same server has only one copy (i.e., instance) stored on that server. Each recipient is given a pointer to that copy of the message.

Single-Master Environment

An environment in which multiple servers hold replicas of the same database (or portions thereof) and in which only one of these servers can accept changes to the data and replicate those changes to the other servers.

Single Master Operations

Specific functions that must be managed within an Active Directory environment but are only handled by specific domain controllers. Some Single Master Operations are unique to each domain, and some are unique to the entire Active Directory forest.

Single-Seat Administration

The ability to manage a number of sites, servers, etc., from a single application on a single computer.

Sink

See Event Sink.

SIS

See Single Instance Storage (SIS).

Site

1. A related collection of HTML documents at the same Internet address, usually oriented toward some specific information or purpose. See also Hypertext Markup Language and Internet.
2. A collection of IP subnets. All computers that are in the same site have high-speed connectivity – local area network (LAN) speeds – with one another. Unlike an Exchange site, an Active Directory site does not include a unit of namespace; for example, multiple sites may exist within a single domain, and conversely, a single site may span multiple domains.

Site Consistency Checker (SCC)

The updated version of the Exchange Server Knowledge Consistency Checker (KCC) that works in conjunction with (and is part of) the Exchange Site Replication Service to ensure that knowledge consistency of sites, administration groups and Active Directory domains is maintained when interoperating between Exchange 2000 and Exchange 5.5. When changes are detected in either environment, the SCC may create new Connection Agreements (disabled) for the ADC.

Site Link

The connection between sites. A site link is usually a representation of the wide area connection between two locations, although it can also represent a backbone that connects multiple locations.

Site Link Bridge

A connection between two or more Active Directory site links. A site link bridge can be used to create a transitive relationship for replication between sites. See also Site Link.

Site Replication Service (SRS)

A directory service implemented in Exchange to allow the integration with downstream older version Exchange sites using both RPC and mail-based replication. The SRS works in conjunction with the Active Directory Connector to provide replication services from Active Directory to the Exchange 5.x Directory Service.

Site Services Account

The Windows user account that Exchange Server components within a site use to communicate with each other.

Sliding Window

The method of flow control used by TCP, as well as several Data Link layer protocols. This method places a buffer between the receiving application and the network data flow. The “window” available for accepting data is the size of the buffer minus the amount of data already there. This window increases in size as the application reads data from it and decreases as new data is sent. The receiver sends the transmitter announcements of the current window size, and it may stop accepting data until the window increases above a certain threshold.

SLIP

See Serial Line Internet Protocol.

Slipstream Technology

A Windows technology for service packs. With slipstream technology, service packs are applied once, and they are not overwritten as new services are added to the computer. See also Service Pack.

Slow Infector

Slow infector viruses are active in memory and only infect new or modified files. See also Fast Infector.

Small Computer Systems Interface (SCSI)

A high-speed, parallel-bus interface that connects hard disk drives, CD-ROM drives, tape drives, and many other peripherals to a computer. SCSI is the mass storage connection standard among all computers except IBM compatibles, which use either SCSI or IDE.

SMDS

See Switched Multimegabit Data Service.

S/MIME

Secure MIME is an Internet protocol that enables mail messages to be digitally signed, encrypted, and decrypted.

SMTP

See Simple Mail Transport Protocol.

SNA

See System Network Architecture.

SNAP

See Subnetwork Access Protocol.

Snap-In

An administrative tool developed by Microsoft or a third-party vendor that can be added to the Microsoft Management Console (MMC) in Windows. See also Microsoft Management Console.

Sniffer

A software program that monitors network traffic. Hackers user sniffers to capture data transmitted via a network.

SNMP

See Simple Network Management Protocol.

Socket

1. A software structure that operates within a network device as a destination point for communications.
2. In AppleTalk networks, an entity at a specific location within a node; AppleTalk sockets are conceptually similar to TCP/IP ports.

Soft Costs

Costs that are incurred during a project and cannot be easily quantified, such as lost productivity due to unfamiliarity with new tools, employee turnover, or downtime due to server problems.

Software

The program and instructions that control your PCs functionality. See also Program, Application, and Process.

Software Package

A software package contains all of the files necessary to install an application along with a description of all system changes needed (Registry changes, file locations, etc.).

Software Publishing

One of the services that can be offered through GPOs. Software publishing allows an administrator to assign an application to a user, group, or computer. (The application can appear either as an icon that will install the program when accessed or as an additional option in the Add/Remove Programs applet.)

SONET

See Synchronous Optical Network.

SORT

Sorts input.

Sort Order

In SQL Server, an option that determines how the system will collate, store, and present data. The sort-order options available depend on the character set chosen. The most important sort-order descriptions include dictionary order, binary order, case-sensitive, and case-insensitive.

Source Extractors

Software programs that can copy messaging resources, such as mailboxes and messages, from a foreign mail system and put the information in a format that can be imported into Exchange.

Source-Route Bridging (SRB)

Created by IBM, the bridging method used in Token Ring networks. The source determines the entire route to a destination before sending the data and includes that information in route information fields (RIF) within each packet. See also Transparent Bridging.

Source-Route Translational Bridging (SR/TLB)

A bridging method that allows source-route stations to communicate with transparent bridge stations aided by an intermediate bridge that translates between the two bridge protocols. Used for bridging between Token Ring and Ethernet. See also Source-Route Transparent Bridging.

Source-Route Transparent Bridging (SRT)

A bridging scheme developed by IBM, merging source-route and transparent bridging. SRT takes advantage of both technologies in one device, fulfilling the needs of all end nodes. Translation between bridging protocols is not necessary. See also Source-Route Translational Bridging.

Source-Routing Bridge

Created by IBM, the bridging method used in Token-Ring networks. The source determines the entire route to a destination before sending the data and includes that information in route information fields (RIF) within each packet.

Source Service Access Point (SSAP)

The SAP of the network node identified in the Source field of the packet. See also Destination Service Access Point and Service Access Point.

SP

See Switch Processor.

Span

A full-duplex digital transmission line connecting two facilities.

SPAN

See Switched Port Analyzer.

Spanned Volume

A dynamic disk volume that consists of disk space on 2 to 32 dynamic drives. Spanned volume sets are used to dynamically increase the size of a dynamic volume. With spanned volumes, the data is written sequentially, filling space on one physical drive before writing to space on the next physical drive in the spanned volume set. See also Dynamic Disk.

Spanning Explorer Packet

Sometimes called limited-route or single-route explorer packet, it pursues a statically configured spanning tree when searching for paths in a source-route bridging network. See also All-Routes Explorer Packet, Explorer Packet and Local Explorer Packet.

Spanning Tree

A subset of a network topology, within which no loops exist. When bridges are interconnected into a loop, the bridge, or switch, cannot identify a frame that has been forwarded previously, so there is no mechanism for removing a frame as it passes the interface numerous times. Without a method of removing these frames, the bridges continuously forward them – consuming bandwidth and adding overhead to the network. Spanning trees prune the network to provide only one path for any packet. See also Spanning -Tree Protocol and Spanning Tree Algorithm.

Spanning Tree Algorithm (STA)

Enables complex Ethernet networks to use bridges while redundant routes exist. The algorithm enables the bridges to communicate and construct a logical network without redundant paths. The logical network is reconfigured if one of the paths fails. See also Spanning Tree and Spanning-Tree Protocol.

Spanning-Tree Protocol (STP)

The bridge protocol (IEEE 802.1d) that enables a learning bridge to dynamically avoid loops in the network topology by creating a spanning tree using the spanning-tree algorithm. Spanning-tree frames called bridge protocol data units (BPDUs) are sent and received by all switches in the network at regular intervals. The switches participating in the spanning tree do not forward the frames; instead, they are processed to determine the spanning-tree topology itself. Cisco Catalyst series switches use STP 802.1d to perform this function. See also Bridge Protocol Data Unit, Learning Bridge, MAC Address, Spanning Tree, and Spanning-Tree Algorithm.

Sparse Infector

A sparse infector virus uses conditions before infecting files. Examples include files infected only on the 10th execution or files that have a maximum size of 128kb. These viruses use the conditions to infect less often and therefore avoid detection. Also known as Sparse Virus.

Special Group

A group used by the system, in which membership is automatic if certain criteria are met. Administrators cannot manage special groups.

Special Ports Tab

Lists the port mappings you have in effect; you can add, edit, and remove them using buttons at the bottom of the tab.

SPF

See Shortest Path First Algorithm.

spid (Server Process ID)

In SQL Server, the number that identifies a connection currently accessing the SQL Server machine. It is most often found in the Enterprise Manager in the Activity window, or by running the sp_who stored procedure.

SPID

See Service Profile Identifier.

Spike

See Transient.

Split-Horizon

Useful for preventing routing loops, a type of distance-vector routing rule where information about routes is prevented from leaving the router interface through which that information was received.

Spoofing

1. In dial-on-demand routing (DDR), where a circuit-switched link is taken down to save toll charges when there is no traffic to be sent, spoofing is a scheme used by routers that causes a host to treat an interface as if it were functioning and supporting a session. The router pretends to send “spoof” replies to keepalive messages from the host in an effort to convince the host that the session is up and running. See also Dial-on-Demand Routing.
2. The illegal act of sending a packet labeled with a false address, in order to deceive network security mechanisms such as filters and access lists.

Spooler

A management application that processes requests submitted to it for execution in a sequential fashion from a queue. A good example is a print spooler.

Spread-Spectrum Radio

Spread-spectrum radio transmission is a technique originally developed by the military to solve several communications problems. Spread-spectrum involves reliability, reduces sensitivity to interference and jamming, and is less vulnerable to eavesdropping than single-frequency radio.

SPX

See Sequenced Packet Exchange.

SQE

See Signal Quality Error.

SQL-DMO (SQL Server Distributed Management Objects)

An interface that exposes COM-based objects that other programs can take advantage of to manipulate the SQL Server Engine and the SQLServerAgent utilities.

SQL Enterprise Manager

The main SQL Server administration program provided with SQL Server 7 and 2000. Multiple servers can be monitored and maintained by SQL Enterprise Manager. The Enterprise Manager works with SQL Server through the SQL-DMO.

SQL Login

See Login.

SQLMaint

A SQL Server utility that can be used to create tasks that will take care of day-to-day administration of SQL Server. This includes automating backups, updating statistics, and rebuilding indexes. SQLMaint is configured by the Database Maintenance Plan Wizard.

SQL Profiler

A SQL Server utility that can be used to create trace files. Trace files can track all connections to SQL Server and what those connections are doing. These are often used for security and for optimization.

SQL Server Administrator

The individual usually responsible for the day-to-day administration of SQL Server databases. The administrator takes over where the programmer stops.

SQLServerAgent

A SQL Server service that can take care of automating tasks on your server. The service includes managers that can handle alert processing, tasking, event processing, and replication. It works for local automation with the local system account, but for many activities that occur over the network, it will need to be assigned a separate logon account that has administrative rights to the computer, as well as the Log on as a Service right.

SQL Server Books Online

All the books that normally ship with Microsoft SQL Server, in an electronic form.

SQL Server Developer

The individual responsible for designing, programming, and populating SQL Server databases.

SQL Server Engine

The core service (MSSQLServer) that performs all query-related activities of SQL Server as well as the data storage and management.

SQL Server Web Assistant

A SQL Server 7 utility that facilitates the creation of push Web pages. It can use the SQL Executive service to schedule the creation of the static Web pages in order to keep them more current.

SQL Trace

A SQL Server file created by the SQL Profiler utility used to monitor who is running what on a SQL Server machine. It is used primarily to audit security in SQL Server and for optimization purposes.

SRB

See Source-Route Bridging.

SRT

See Source-Route Tranparent Bridging.

SR/TLB

See Source-Route Translational Bridging.

SRV

See Service Record.

SRV Resource Records

DNS records that provide the IP address of a service rather than a device.

SSAP

See Source Service Access Point.

SSE

See Silicon Switching Engine.

STA

See Spanning-Tree Algorithm.

Stand-Alone Dfs Root

In the Distributed file system (Dfs), a type of Dfs root that does not use the Active Directory or support automatic replication. See also Distributed File System and Active Directory.

Stand-Alone Environment

Computers operating without connection to a network.

Standard IP Access List

IP access list that uses only the source IP addresses to filter a network.

Standard IPX Access List

IPX access list that uses only the source and destination IPX address to filter a network.

Standby Monitor

A device on a Token Ring network that monitors the network status and may become the active monitor in the case of failure of the active monitor.

Standby Server

A server configured to be used in place of another server. If a server goes down because of a failure or is taken down for maintenance, a standby server can be brought online to provide continued service to users. See also Recovery Server.

Star

A network topology in which all the cables run from the computers to a central location, where they are connected by a hub.

Start Bit

A bit that is sent as part of a serial communication stream to signal the beginning of a byte or packet.

Start Menu

A Windows Desktop item, located on the Taskbar. The Start menu contains a list of options and programs that can be run. See also Taskbar.

Star Topology

A LAN physical topology with endpoints on the network converging at a common central switch (known as a hub) using point-to-point links. A logical ring topology can be configured as a physical star topology using a unidirectional closed-loop star rather than point-to-point links. That is, connections within the hub are arranged in an internal ring. See also Bus Topology and Ring Topology.

Startup Range

If an AppleTalk node does not have a number saved from the last time it was booted, then the node selects from the range of values from 65280 to 65534.

Statement Permissions

SQL Server permissions that allow database users and groups to perform tasks that are not specific to objects. These permissions are generally related to the creation of certain database objects.

State Transitions

Digital signaling scheme that reads the “state” of the digital signal in the middle of the bit cell. If it is five volts, the cell is read as a one. If the state of the digital signal is zero volts, the bit cell is read as a zero.

State Transmission

State transmission relies on the change of the state of a network signal to represent a new transmission of data.

Static Route

A route whose information is purposefully entered into the routing table and takes priority over those chosen by dynamic routing protocols.

Static Router

A router that must have a manually programmed routing table.

Static Route Selection

A type of routing in which the data path is determined in advance rather than on the fly by the router.

Static Routing

Doesn’t make any attempt to discover other routers or systems on the networks.

Static VLANs

Static VLANs are manually configured port-by-port. This is the method typically used in production networks.

Statistical Multiplexing

Multiplexing in general is a technique that allows data from multiple logical channels to be sent across a single physical channel. Statistical multiplexing dynamically assigns bandwidth only to input channels that are active, optimizing available bandwidth so that more devices can be connected than with other multiplexing techniques. Also known as statistical time-division multiplexing or stat mux.

Stealth Virus

Stealth viruses attempt to conceal their presence from anti-virus software. Many stealth viruses intercept disk-access requests, so when an anti-virus application tries to read files or boot sectors to find the virus, the virus feeds the program a “clean” image of the requested item. Other viruses hide the actual size of an infected file and display the size of the file before infection. Stealth viruses must be running to exhibit their stealth qualities. Also known as Interrupt Interceptors.

STM-1

See Synchronous Transport Module Level 1.

Stop Bit

A bit that is sent as part of a serial communication stream to signal the end of a byte or packet.

Storage Group

A collection of Exchange databases on an Exchange server that share the same ESE instance and transaction log. Individual databases within a storage group can be mounted and dismounted. Each Exchange server can architecturally host up to 16 storage groups, although only 4 can be defined through the Exchange System Manager.

Store

The generic name given to the storage subsystem on an Exchange server. This term is used interchangeably to describe the Store.exe process and Exchange databases.

Store-and-Forward

A delivery method that does not require the sender and the recipient to have simultaneous interaction. Instead, when a message is sent, it is transferred to the next appropriate location in the network, which temporarily stores it, makes a routing decision, and forwards the message to the next appropriate location. This process occurs until the message is ultimately delivered to the intended recipient, or an error condition causes the message to be returned to the sender.

Store-and-Forward Packet Switching

A technique in which the switch first copies each packet into its buffer and performs a cyclical redundancy check (CRC). If the packet is error-free, the switch then looks up the destination address in its filter table, determines the appropriate exit port, and sends the packet.

Stored Procedure

In SQL Server, a set of Transact-SQL statements combined together to perform a single task or set of tasks. This object is like a macro, in that SQL code can be written and stored under a name. Invoking the name actually runs the code. Because stored procedures are precompiled, they run much more quickly and efficiently than regular queries do. There are three types of stored procedures: system, user-defined, and extended. System stored procedures are shipped with SQL Server and are denoted with an sp_ prefix. These are typically found in the Master database. User-defined stored procedures can be registered with a system by the SA. Extended stored procedures work outside the context of SQL Server and generally have an xp_ prefix. These are actually calls to DLLs.

STP

See Shielded Twisted Pair and Spanning-Tree Protocol.

String

A consecutive series of letters, numbers, and other characters. "afsH(*&@~” is a string; so is “The Mad Hatter”. Anti-virus applications often use specific strings, called virus signatures, to detect viruses. See also Signature.

Stripe Set

A single volume created across multiple hard disks and accessed in parallel for the purpose of optimizing disk access time. NTFS can create stripe sets. See also New Technology File System, Volume, and File System.

Striped Volume

A dynamic disk volume that stores data in equal stripes between 2 to 32 dynamic drives. Typically, administrators use striped volumes when they want to combine the space of several physical drives into a single logical volume and increase disk performance. See also Dynamic Disk.

Stub Area

An OSPF area carrying a default route, intra-area routes, and interarea routes, but no external routes. Configuration of virtual links cannot be achieved across a stub area, and stub areas are not allowed to contain an ASBR. See also Non-Stub Area, Autonomous System Boundary Router, and Open Shortest Path First.

Stub Network

A network having only one connection to a router.

Stub Zone

Functions like dynamic delegation. The stub zone server will periodically query the target name servers for updates. This is used to keep the DNS server that hosts the parent zone aware of its child zone for more efficient name resolution. The DNS server that hosts both the parent zone and the stub zone maintains a current list of authoritative DNS servers for the child zone by regularly updating the stub zone. Stub zones keep delegated zone information current, as well as simplify DNS administration. See also Delegation Resource Record.

STUN

See Serial Tunnel.

Subarea

A portion of an SNA network made up of a subarea node and its attached links and peripheral nodes.

Subarea Node

An SNA communications host or controller that handles entire network addresses.

Subchannel

A frequency-based subdivision that creates a separate broadband communications channel.

Subdirectory

When a disk is formatted, a root directory is created. Any number of directories (called subdirectories) can be created within the root directory, to organize data in a logical way. A subdirectory can have it’s own subdirectories. See also Directories.

Subdomain

Branches of a network.

Subinterface

One of many virtual interfaces available on a single physical interface.

Subnet (Subnetwork)

1. Any network that is part of a larger IP network and is identified by a subnet address. A network administrator segments a network into subnetworks in order to provide a hierarchical, multilevel routing structure, and at the same time protect the subnetwork from the addressing complexity of networks that are attached. See also IP Address, Subnet Mask, and Subnet Address.
2. In OSI networks, the term specifically refers to a collection of ESs and ISs controlled by only one administrative domain, using a solitary network connection protocol.

Subnet Address

The portion of an IP address that is specifically identified by the subnet mask as the subnetwork. See also IP Address, Subnet, and Subnet Mask.

Subnet Mask

Also simply known as mask, a 32-bit address mask used in IP to identify the bits of an IP address that are used for the subnet address. Using a mask, the router does not need to examine all 32 bits, only those selected by the mask. See also Address Mask and IP Address.

Subnetwork Access Protocol (SNAP)

SNAP is a frame used in Ethernet, Token Ring, and FDDI LANs. Data transfer, connection management, and QoS selection are three primary functions executed by the SNAP frame.

Subscribing Server

In SQL Server replication, the server that gets data originating on the publishing server and updates one or more tables with both new and changed data.

Subsidiary Office

Sites that are part of the overall business but are not controlled by the company.

SUBST

Associates a path with a drive letter.

Subsystem

A software component that, when loaded, extends the operating system by providing additional services. The MAPI program, MAPI32.DLL, is an example of a subsystem. MAPI32.DLL loads on top of the Windows operating system and provides messaging services.

Success Audit Event

An Event Viewer event that indicates the occurrence of an event that has been audited for success, such as a successful logon. See also Event Viewer.

Super Frame (SF)

A super frame (also called a D4 frame) consists of 12 frames with 192 bits each, and the 193rd bit providing other functions including error checking. SF is frequently used on T1 circuits. A newer version of the technology is Extended Super Frame (ESF), which uses 24 frames. See also Extended Super Frame.

Superscope

Allows you to group two or more scopes together even though they are actually separate.

Super Server

A hardware solution offered by several different hardware manufacturers. The idea behind a Super Server is that almost any piece of equipment can be changed on the Super Server without needing to shut down the server.

Surf

To browse the Web randomly looking for interesting information. See also World Wide Web.

Suspect Database

A database that SQL Server believes to be corrupt or otherwise unavailable. A database can be marked suspect for a number of reasons, such as when a database device is offline or has been removed or renamed.

Sustainable Cell Rate (SCR)

In Asynchronous Transfer Mode (ATM), the maximum average cell rate that can be maintained over a virtual connection. See also Asynchronous Transfer Mode, Available Cell Rate, Minimum Cell Rate, and Peak Cell Rate.

SVC

See Switched Virtual Circuit.

SVGA

Super Video Graphics Array: it has all the VGA modes but with 256 colors.

Swap File

The virtual memory file on a hard disk containing the memory pages that have been moved out to disk to increase available RAM. See also Virtual Memory.

Switch

1. In networking, a device responsible for multiple functions such as filtering, flooding, and sending frames. It works using the destination address of individual frames. Switches operate at the Data Link layer of the OSI model.
2. Broadly, any electronic/mechanical device allowing connections to be established as needed and terminated if no longer necessary.

Switch Fabric

Term used to identify a layer-2 switched internetwork with many switches.

Switched 56

A dial-up version of the 56 Kbps DDS. With Switched 56, users can dial other Switched 56 sites and pay only for the connect time.

Switched LAN

Any LAN implemented using LAN switches. See also LAN Switch.

Switched Line

A communications link for which the physical path may vary with each usage, such as the public telephone network.

Switched Multimegabit Data Service (SMDS)

Developed by Bell Communications Research in 1991, SMDS technology is related to ATM in that it transports data in 53-byte cells. SMDS is a connectionless Data Link layer service that supports cell switching at data rates of 1.544 to 45 Mbps.

Switched Port Analyzer (SPAN)

A feature of the Catalyst 5000 switch, offering freedom to manipulate within a switched Ethernet environment by extending the monitoring ability of the existing network analyzers into the environment. At one switched segment, the SPAN monitors traffic onto a predetermined SPAN port, while a network analyzer connected to the SPAN port is able to monitor traffic from any other Catalyst switched port.

Switched Virtual Circuit (SVC)

SVC is created for a specific communication session and then disappears after the session. The next time the computers communicate, a different virtual circuit might be used.

Switching

In a LAN environment, switching provides each network transmission with an independent path through the network free of collisions with other network transmissions.

Switch Processor (SP)

Also known as a ciscoBus controller, it is a Cisco 7000 series processor module acting as governing agent for all CxBus activities.

Symmetrical Multiprocessing

A multiprocessing methodology that assigns processes to processors on a fair-share basis. This method balances the processing load among processors and ensures that no processor will become a bottleneck. Symmetrical multiprocessing is more difficult to implement than asymmetrical multiprocessing, as processors must share certain hardware functions. See also Asymmetrical Multiprocessing and Multiprocessing.

Synchronization

Directory synchronization occurs between dissimilar implementations of a directory service. For example, because both Active Directory services and Novell Directory Services follow an industry-standard method of access, it is possible for each environment to update the other with information from its own database.

Synchronous

Pertaining to two or more processes that depend upon the occurrence of a specific event, such as a common timing signal.

Synchronous Data Link Control (SDLC)

A protocol used in SNA Data-Link layer communications. SDLC is a bit-oriented, full-duplex serial protocol that is the basis for several similar protocols, including HDLC and LAPB. See also High-Level Data Link Control and Link Accessed Procedure, Balanced.

Synchronous Modems

A simple, inexpensive technology ideally suited for transmitting small frames at irregular intervals by using start, stop, and parity bits added to each character being transmitted. Overhead for asynchronous transmission is high, often in the neighborhood of nearly 20 to 30 percent.

Synchronous Optical Network (SONET)

Bell Communications Research developed SONET, which has been accepted as an ANSI standard. As the “optical” in the name implies, SONET is a standard for communication over fiber-optic networks. Data rates for SONET are organized in a hierarchy based on the Optical Carrier (OC) speed and the corresponding Synchronous Transport Signals (STS) employed. The basic OC and STS data rate is 51.84 Mbps, but higher data rates are provided in multiples of the basic rate.

Synchronous Transmission

Signals transmitted digitally with precision clocking. These signals have identical frequencies and contain individual characters encapsulated in control bits (called start/stop bits) that designate the beginning and ending of each character. See also Asynchronous Transmission and Isochronous Transmission.

Synchronous Transport Module Level 1 (STM-1)

In the European SDH standard, one of many formats identifying the frame structure for the 155.52Mbps lines that are used to carry ATM cells.

SYS

Copies MS-DOS system files and command interpreter to a disk you specify.

Sysprep

See System Preparation Tool.

System

Short for computer system, implying a specific collection of hardware and software.

System Attendant

One of the core Exchange services that performs miscellaneous functions (usually related to directory information) such as generation of address lists, offline Address Books, and directory lookup facilities.

System Boot Record

See Boot Record.

System Disk

A disk containing DOS’ three main files and other utilities.

System Group

A Windows special group that contains system processes that access specific functions as a user. See also Special Group.

System Information

A Windows utility used to collect and display information about the computer’s current configuration.

System Log

A log that tracks events that relate to the Windows operating system. The System log can be viewed through the Event Viewer utility. See also Event Viewer.

System Monitor

A program that collects information on a Windows machine in real time. System Monitor collects information on different categories of items on the system.

System Network Architecture (SNA)

A complex, feature-rich, network architecture similar to the OSI reference model but with several variations; created by IBM in the 1970s and essentially composed of seven layers.

System Partition

The system partition is the active partition on an Intel-based computer that contains the hardware-specific files used to load the operating system. See also Partition and Boot Partition.

System Policy

A policy used to control what a user can do and the users environment. System policies can be applied to a specific user, group, a computer, or all users. System policies work by overwriting current settings in the Registry with the system policy settings. System policies are created through the System Policy Editor. See also Registry and System Policy Editor.

System Policy Editor

A utility found within the Administrative Tools group used to create system policies. See also System Policy.

System Preparation Tool (Sysprep)

A Windows utility used to prepare a disk image for disk duplication. See also Disk Image.

System Prompt

The prompt displayed on the screen, such as A:\> or C:\> indicating that DOS is ready to accept commands when not working with DOSSHELL.

Systems Network Architecture Distribution Services (SNADS)

An International Business Machines (IBM) store-and-forward protocol for the transmission of data. SNADS enables the sender and recipient to not have to be synchronized.

System State

Information used to manage the configuration of a Windows operating system. For Windows domain controllers, the System State information includes a copy of the Active Directory data store. The Windows Backup utility can be used to back up and restore the System State.

System Stored Procedure

See Stored Procedure.

System Table

Tables in relational databases that are used for administrative purposes by SQL Server. For example, in the Master database, the sysxlogins table, which holds SQL logins and passwords, is a system table. The Master database has two sets of system tables. The first set, known as the system catalog, tracks information about the configuration of SQL Server as a whole. Every database also has a database catalog made up of system tables that track configuration information about that particular database. This could include the objects in the database as well as the permissions granted on those objects. System tables generally begin with the “sys” prefix.

System Tools

A Computer Management utility grouping that provides access to utilities for managing common system functions. The System Tools utility includes the Event Viewer, System Information, Performance Logs and Alerts, Shared Folders, Device Manager, and Local Users and Groups utilities. See also Event Viewer, System Information, Performance Logs and Alerts, Shared Folders, Device Manager, and Local Users and Groups.