Glossary- S
A Data Communication Historical Series
By Bob Pollard

HOME                        INDEX

SA:  

1) Service Affecting: Category of conditions that interrupt payload traffic.

2) Security Association: Instance of security policy and keying material applied to a data flow.

SABRE:

See Semi Automated Business Research Environment

SAC:

FDDI or CDDI concentrator that connects to the network by being cascaded from the master port of another FDDI or CDDI concentrator.

See Single Attachment Concentrator

SAIC:

Science Applications International Corporation - An employee-owned research and engineering company

SAL:

See Special Access Line

SA&P:

System Analysis and Programming: A Western Union software (programming) group.

SAMPLING RATE:

Rate at which samples of a particular signal or waveform amplitude are taken

SAN: 

Storage Area Networking: A data communications platform that interconnects servers and storage at Giga-baud speeds. By combining LAN networking models with the core building blocks of server performance and mass storage capacity, SAN eliminates the bandwidth bottlenecks and limitations imposed by previous SCSI bus-based architectures.

SAP:

1) Service Access Point: Field defined by the IEEE 802.2 specifications that is part of an address specification. The destination plus the DSAP define the recipient of a packet. The same applies to the SSAP.

2) Service Advertising Protocol: IPX protocol that provides a means of informing network clients, via routers and servers, of available network resources and services.

See Service Access Point

SAPI:

See Service Access Point Identifier

SAR: 

Segmentation and Reassembly: One of the two sub-layers of the AAL CPCS, responsible for dividing, at the source, and reassembling, at the destination, the PDU(s) passed from the CS. The SAR sub-layer takes the PDU(s) processed by the CS and, after dividing them into 48-byte pieces of payload data, passes them to the ATM layer for further processing.

SARAH:Standard Automated Remote-to-AUTODIN Host

SARTS:

See Switched Access Remote Test System

SAS:

1) Single Attachment Station: Device attached only to the primary ring of a FDDI ring; also known as a Class B station.

2) Statically Assigned Socket: Socket that is permanently reserved for use by a designated process. In an AppleTalk network, SAS(s) are numbered 1 to 127; they are reserved for use by specific socket clients and for low-level built-in network services.

See Single Attachment Station

SAT:

Standard AUTODIN Terminal

SATCOM:

Satellite Communication: See Satellite Communications narrative

SATELLITE COMMUNICATIONS:

  Satellite communications, initiated in 1958, has progressed from the experimental stage to a reliable media for data communications, television, telephone and other communications requirements. Any form of communication can be sent to and received from any point on the earth at the speed of light (186,000 miles per second) via a Satellite.

  Satellite operation can be viewed in much the same manner as microwave communications. Both are very efficient methods of transferring information over long distances. Although satellites eliminate one of the major problems of microwave transmission, the requirement to maintain line-of-sight between microwave relay towers (repeaters)

  There are basically two types of satellite operation relative to the earth's rotation. One is the asynchronous satellite and the other is the synchronous satellite. The asynchronous satellite is not stationary and orbits the earth. It does not maintain a stationary location over a particular area of the earth. The synchronous satellite is positioned above the earth at approximately 22,500 miles and is set in a synchronous orbit with the earth's rotation, maintaining a set position. Set in a position over the United States it can provide a direct communications link between the East and West Coast, and other areas in between. Transmission between a satellite and ground station is by line-of-sight microwave transmission.

SATELLITE COMPUTER:

A processor connected locally or remotely to a larger central processor, and performing certain assigned processing tasks, sometimes independent or subordinate to the central processor.

SATELLITE RELAY:

A repeater, in geosynchronous orbit around the Earth that amplifies the signals it receives before transmitting the signals back to earth.

SATURATION:

1) The point at which a traffic handling system will refuse to accept and complete additional requests for connections or input: An electrical condition where electronic devices will permit no more additional electrical signal to pass. 2) In color management: The purity of a colors hue, moving from gray to the pure color.

SATURATION TESTING:

A program-testing technique that uses a large volume of messages to expose errors that occur infrequently, but can be triggered by high volume saturation of the system, or may be caused by two different messages arriving at the same time.

SB:

Another designation for Universal Serial Bus (USB): Refers to a high-speed (12Mbps) serial port for PCs. USB can support up to 127 devices.

SBU:

Sensitive but Unclassified

SBUS:

Bus technology used in Sun SPARC-based workstations and servers: The SBus specification was adopted by the IEEE as a new bus standard.

SC:

See Systems Console, Signaling Converter or Switching Center

SCA: 

Subordinate Certification Authority: CA whose public-key certificate is issued by another (superior) CA

S.C. INTERLOCKS:

Switch Controls for switching an ADU or other devices depending on where switches are used.

SCALABILITY:

The capacity of hardware, software and networks to change size according to the number of users they accommodate: Most often, scalability refers to the capacity to expand rather than shrink.

SCAN:

1) To scan stored information for a specific purpose, for content or arrangement.

2) To examine the status of communication lines or input/output channels.

3) To determine the status of terminal requests to send or if available to receive messages.

4) To check for abnormal conditions internally or externally

5) A non-intrusive analysis technique that identifies the open ports found on each live network device and collects the associated port banners found as each port is scanned. Each port banner is compared against a table of rules to identify the network device, its operating system, and all potential vulnerabilities.

SCAN LINE FIX UP:

Mechanism used for non-ECM calls to eliminate fax failures caused by an excessive number of received page errors because of data loss. If data loss is detected, the data of the current scan line is discarded and replaced with the previous line or white space.

SCANNER:

A virus detection program that searches for viruses

SCATTERING:

The signal loss that occurs in fiber-optic transmission when light waves strike molecules and imperfections in the fiber core.

SCCA / SCCB:

System Console: DEC station 3100 running Ultrix (Unix)

SCCP: 

Signaling Connection Control Part: Trillium software that supports routing, translation and management functions and data transfer without logical signaling connections.

SCENARIO (Use Case):

A documented set of typical interaction dialogs between the users of a system and a proposed system. Scenarios are developed during the analysis phase of system development to assist in understanding business events, objects and interactions. Use case scenarios facilitate communication between the people who request a system, analysts, developers and testers. They are used to validate understanding, and to identify normal and special use situations. Scenarios clarify an evolving agreement between requesters and development teams. Similar to the Request For Proposal (RFP) documents.

SCHEMATIC:

A diagram that specifies the design features for the electrical connections and components of a circuit or system.

SCI:

Special Compartmental Information

SCMP:

Systems Console Monitor Printer: (Flexowriter was the original AUTODIN printer)

See FREIDEN PRINTER.

SCOOP:

Status Control Of Orders Program

SCP:

Service Control Point: An element of a SS7-based Intelligent Network that performs various service functions, such as number translation, call setup and teardown, etc.

See Service Control Point

SCPC:

See Single Channel Per Carrier

SCR: 

Sustainable Cell Rate: Parameter defined by the ATM Forum for ATM traffic management. For VBR connections, SCR determines the long-term average cell rate that can be transmitted.

SCRAMBLER:

A device that deliberately distorts transmitted signals to make them unreadable. It is necessary for the receiving media to have a de-scrambling device installed.

SCRAP:

A file that is created when a user drags part of a document to the desktop

SCREEN FONTS:

A typeface designed for display on a computer monitor screen. Screen fonts often have accompanying PostScript fonts for printing to PostScript-compatible printers.

SCREEN RESOLUTION:

A setting that determines the amount of information that appears on the monitor screen, measured in pixels. Low resolution, such as 640 x 480, makes items on the screen appear large, although the screen area is small. High resolution, such as 1024 x 768, makes the overall screen area large, although individual items appear small.

SCREEN SAVER:  

Desktop Pattern: A design that appears across the desktop screen. You can create your own pattern or select a pattern provided by the operating system (Windows).

SCREENING (Shielding):

1) The process of wrapping (housing) electrical conductors with a grounded metallic foil or braid to insulate the conductors from interference1) Script is a type of programming language that can be used to fetch and display Web pages. They can be used to create all or part of a page, and communicate with search-able databases. Forms (boxes) and many interactive links, which respond differently, depending on what is entered, all require some kind of script language. When a question mark (?) is present in the URL of a page, some kind of script command was used in generating and/or delivering that page.

2) A set of instructions to an application or tool program: A script usually expresses instructions by using the applications or tools rules and syntax, combined with simple control structures such as loops and if/then expressions. ‘Batch program’ is often used interchangeably with ‘script’ in the Windows environment.

SCRIPT FILE:

A script file contains scripting commands, parameters, and expressions that provide information to and from the too be connected remote computer. This information includes your user name and password, port information, carriage returns, line feeds, and pauses.

SCSA:

Signal Computing System Architecture: An industry standard architecture from Dialogic Corp. SCSA integrates multiple technologies through an open, non-proprietary, specification for developing Integrated Voice Response (IVR) systems.

SCSI:

Small Computer System Interface: The standard set of protocols for host computers communicating with attached peripherals. SCSI allows connection to as many as six peripherals including printers, scanners, hard drives, zip drives, and CD-ROM drives. See Small Computer System Interface

SCSI-2:

Small Computer System Interface-2: An enhanced ANSI standard for the SCSI standard for SCSI buses. It offers increased data width, increased speed, or both.

SCSI BUS:

A parallel bus that carries data and control signals from SCSI (Small Computer System Interface) devices to an SCSI controller.

SCTC:

Systems Console Transfer Channel

SCTE: 

Serial Clock Transmit External: Timing signal that DTE echoes to DCE to maintain clocking. SCTE is designed to compensate for clock phase shift on long cables. When the DCE device uses SCTE instead of its internal clock to sample data from the DTE, it is better able to sample the data without error even if there is a phase shift.

SCVT:

System Console Video Terminal

SDH:

Synchronous Digital Hierarchy: European standard that defines a set of rate and format standards that are transmitted using optical signals over fiber. SDH is similar to SONET, with a basic SDH rate of 155.52 Mbps, designated at STM-1.

See Synchronous Digital Hierarchy

SDLC:

Synchronous Data Link Control: SNA data link layer communications protocol. SDLC is a bit-oriented, full-duplex serial protocol that has spawned numerous similar protocols, including HDLC and LAPB. See Synchronous Data Link Control

SDLC BROADCAST:

Feature that allows a Cisco router that receives an all stations broadcast on a virtual multi-drop line to propagate the broadcast to each SDLC line that is a member of the virtual multi-drop line.

SDLC TRANSPORT:

A Cisco router feature that allows disparate environments to be integrated into a single, high-speed, enterprise-wide network: Native SDLC traffic can be passed through point-to-point serial links with other protocol traffic multiplexed over the same links. Cisco routers can also encapsulate SDLC frames inside IP data-grams for transport over arbitrary (non-SDLC) networks.

SDLLC:

SDLC Logical Link Control: Cisco IOS feature that performs translation between SDLC and IEEE 802.2 type 2

SDM:

Space Division Multiplexing: The transmission of signals over discrete voice lines.

SDN:

Software Defined Network

SDP:

1) Session Definition Protocol: An IETF protocol for the definition of Multimedia Services. SDP messages can be part of SGCP and MGCP messages.

2) Session Data Protocol: SDP is intended for describing multimedia sessions concerning session announcement, session invitation, and other forms of multimedia session initiation.

SDR:

Special Drawing Right

SDSL:

1) Symmetric Digital Subscriber Line: As its name implies, is a symmetric service that can deliver variable data communications speeds up to 2.3 Mbps. SDSL can be packaged in a range of bandwidth configurations that include 160 Kbps, 192 Kbps, 384 Kbps, 416 Kbps, 768 Kbps, 1.1 Mbps, 1.5 Mbps and 2.3 Mbps depending on the DSL provider. Both the downstream and upstream speeds can be, and often are, the same speed.

2) Single-line Digital Subscriber Line: One of four DSL technologies. SDSL delivers 1.544 Mbps both downstream and upstream over a single copper twisted pair. The use of a single twisted pair limits the operating range of SDSL to 10,000 feet (3048.8 meters).

SDSU:

SMDS Data Service Unit: DSU for access to SMDS via HSSI(s) and other serial interfaces.

SDTM:

Statistical Time Division Multiplexer

SDU:

Service Data Unit: Unit of information from an upper-layer protocol that defines a service request to a lower-layer protocol.

See Service Data Unit

SEAL:

Simple and Efficient AAL: Scheme used by AAL5 in which the SAR sub-layer, segments CS PDU(s), without adding additional fields.

SEAMLESS INTEGRATION:

Refers to a situation in which a caller/user does not experience any difficulties or interruptions when their call involves an interconnection between different networks or systems.

SEARCH ENGINE:

A method or service that provides the necessary tools for locating information and/or Web sites, by topic, on the Internet.

SEARCH TOOLS – WWW:

Search Engines (tools) - Are computer systems for finding information on the WWW. These tools allow you to search the Web in the following manner: by subject, by key word, and by surfing.

SECAM:

See Sequential and Memory Color Television

SECAM FORMAT:

625 lines of resolution at 25 frames per second

SECONDARY CHANNEL:

A portion of a channel having a lower transmission rate than the primary channel in a system where two channels (services) share one facility (interface).

SECONDARY RS-449 SIGNALS AND CONNECTORS:

See RS-449 (secondary) signals and connectors

SECONDARY RING:

One of the two rings making up a FDDI or CDDI ring: The secondary ring usually is reserved for use in the event of a failure of the primary ring.

SECONDARY / SECONDARY STATION:

In bit-synchronous data link layer protocols, such as HDLC, a station that responds to commands from a primary station: Sometimes referred to simply as a secondary.

A station on a network that has been selected to receive a transmission originally directed to the primary station. The assignment of secondary status is controlled by the primary station.

SECONDARY STORAGE:

Associated computer device(s) providing additional information storage space: This storage media may be composed of additional solid state memory, disc or other devices.

SECTION:

The smallest unit of a SONET service: It is the span between regenerators and other section terminating equipment.

Portion of a transmission facility (circuit / line): Includes terminating points between a terminal NE and a regenerator or two regenerators. A terminating point is the point after signal regeneration at which performance is monitored or can be monitored.

SECTION DATA COMMUNICATIONS CHANNEL:

A SONET-embedded operations channel that is processed by each STE node in a network: It provides many data channels for maintenance and operations functions, such as order-wire, performance monitoring, and craft/OS data communication channel (DCN) extension.

SECTION DCC:

Section Data Communications Channel: In OSS (Operations Support System), a 192-kbps data communications channel embedded in the section overhead for OAM&P traffic between two SONET network elements.

SECTOR VIRUSES:

See: Boot Sector Infector or Master Boot SectorVirus

SECURE / MULTIPURPOSE INTERNET MAIL EXTENSIONS (S/MIME):

An extension of MIME to support secure mail: It enables message originators to digitally sign e-mail messages to provide proof of message origin and data integrity. It also enables messages to be transmitted in encrypted format to provide confidential communications.

SECURE SHELL PROTOCOL:  

Protocol that provides a secure remote connection to a router through a Transmission Control Protocol (TCP) application

SECURE SOCKETS LAYER (SSL):

A proposed open standard for establishing a secure communications channel to prevent interception of critical information: Such as credit card numbers. Primarily, it enables secure electronic financial transactions on the World Wide Web, although it is designed to work on other Internet services as well.

SECURE STATE:

System condition in which no subject / person can access any object in an unauthorized manner

SECURITY:

See System Security

SECURITY ASSOCIATION (SA):

An instance of security policy and keying material applied to a data flow. Both IKE and IP-Sec use SA(s), although SA(s) are independent of one another,

SECURITY CERTIFICATE:

Information (often stored as a text file) that is used by the SSL (Secure Socket Layer) protocol to establish a secure connection

SECURITY GROUP:

A group that can be listed in Discretionary Access Control Lists (DACL) used to define permissions on resources and objects. A security group can also be used as an e-mail entity. Sending an e-mail message to the group sends the message to all the members of the group.

SECURITY HOST:

An authentication device, supplemental to standard Windows and remote access server security, that verifies whether a caller from a remote client is authorized to connect to the remote access server.

SECURITY ID (SID):

A data structure of variable length that identifies user, group, and computer accounts. Every account on a network is issued a unique SID when the account is first created. Internal processes in Windows refer to an accounts SID rather than the accounts user or group name.

SECURITY MANAGEMENT:

One of five categories of network management defined by ISO for the management of OSI networks: Security management subsystems are responsible for controlling access to network resources.

SECURITY PARAMETER INDEX (SPI):

This is a number that, together with a destination IP address and a security protocol, uniquely identifies a particular security association. When using IKE to establish the security associations, the SPI for each security association is a pseudo-randomly derived number. Without IKE, the SPI is specified manually for each security association.

SECURITY PRINCIPAL:

An account holder that is automatically assigned a security identifier for access to resources. A security principal can be a user, group, service, or computer.

SECURITY PRINCIPAL NAME:

A name that uniquely identifies a user, group, or computer within a single domain: This name is not guaranteed to be unique across domains.

SEED ROUTER:

Router in an AppleTalk network that has the network number or cable range built in to its port descriptor. The seed router defines the network number or cable range for other routers in the network segment, and responds to configuration queries from non-seed routers on its connected AppleTalk network, allowing those routers to confirm or modify their configurations accordingly. Each AppleTalk network must have at least one seed router.

SEFS:

Severely Errored Framing Second: A PM parameter that counts out-of-frame seconds.

SEGMENT:

1) Section of a network that is bounded by bridges, routers, or switches.

2) In a LAN using a bus topology, a segment is a continuous electrical circuit that often is connected to other such segments with repeaters.

3) Term used in the TCP specification to describe a single transport layer unit of information. The terms datagram, frame, message and packet also are used to describe logical information groupings at various layers of the OSI reference model and in various technology circles.

SELECT:

To specify (identify) a block of data or text on the monitor screen by highlighting or marking it: Usually followed by performing some operation on it.

SELECT FREQUENCY:

RS-449 signal from the DTE (Data Terminal Equipment) to the DCE (Data Communication Equipment) indicating which analog carrier frequency should be used.

SELECT STANDBY:

RS-449 (Pin 32): A signal from the Data Terminal Equipment (DTE) to the Data Communication Equipment (DCE) indicating a switch between a normal or standby status.

SELECTION:

Refers to the addressing of a terminal or a component on a selective calling basis

SELECTIVE CALLING:

The ability of a transmitting station to specify, through the use of assigned codes, which of the receiving stations will receive the message

SELECTOR:

Identifier (octet string) used by an OSI entity to distinguish among multiple SAP(s), where it provides services to the layer above.

SELECTOR CHANNEL:

A data channel designed to operate with only one input/output peripheral device at a time, at a rate of only one byte at a time, until the complete record is transferred. Contrast with block multiplexer channel and multiplexer channel.

SELECTOR LIGHTPEN:

An input device in the form of a "pen" attached to the display station (CRT) as an extra feature. The light-pen may be pointed at an item on the screen and then activated, thereby selecting the item for subsequent processing.

SELF-CHECKING CODE:

An error checking code where one or more errors in a code expression produces a forbidden combination. A parity check makes use of a self-checking code employing binary digits in which the total number of 1s (or 0s) in each permissible code expression is always odd or always even (odd or even character bits). A redundancy check scheme employs a self-checking code, which makes use of redundant digits called check digits.

SELF-CHECKING NUMBERS:

Any numbers containing redundant information to enable error detection

SELF DIAGNOSTICS:

An automatic feature: Allows a system or network to monitor itself and detect intermittent system failures.

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 Self-garbling Virus, Encrypted 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 VIRUSES:

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.

SELF LEARNING BRIDGE:

See Smart Bridge

SELF ROUTING:

See Spanning Tree algorithm (STA)

SEMI AUTOMATIC BUSINESS RESEARCH ENVIRONMENT (SABRE):

An online flight reservation network system:. SABRE provides ticket information and purchasing outlets for airlines, hotels, and rental-car services worldwide.

SEMIAUTOMATIC TAPE:

A method of communication switching where messages are received and retransmitted in teletypewriter tape form, vial manual intervention in transfer of the tape from the receiving re-perforator to the transmitter. See Plan 51 for example.

SEMICONDUCTOR:

A class or group of material that allows electrical current to flow through them under certain conditions: Semiconductors are used to create common electronic components, such as diodes and transistors.

SEND COMMON:

RS-449 (Pin 37): Return signal for transmitter circuit reference.

SEND DATA (Transmitted Data):

RS-449 (Pin 4A & 22B) DTE (Data Terminal Equipment) send circuit to DCE (Data Communication Equipment).

SEND TIMING:

RS-449 (Pin 5A & 23B): Timing signal from the DCE (Data Communication Equipment) to the DTE (Data Terminal Equipment).

SENDER:

Equipment that sends out the routing digits along with the called terminal (station) number

SEO:

Search Engine Optimization: The practice of designing web pages so that they rank as high as possible in search results from Search Engines. This involves making the web page clearly describe its subject, making sure it contains useful information, including accurate information in Meta Tags, and arranging for other web sites to make links to the page.

SEQUENTIAL AND MEMORY COLOR TELEVISION (SECAM):

The television system used in France and most of Eastern Europe and the Middle Eastern countries: Also known as Systeme Electronique Couleur Avec Memoire (French)

SEQUENCED PACKET EXCHANGE (SPX):

Novell Xerox Networking System (XNS): Provides the protocol for guaranteed delivery services.

SEQUENCING:

Refers to the division of a data message into discrete units for transmission; each unit is sequentially numbered in order to facilitate re-assembly of the message.

SEQUENTIAL ACCESS:

The method for gaining entry to data through a serial ordered sequence: Contrast with random access

SEQUENTIAL DATA SET:

Refers to data that is assembled on the basis of its successive physical position

SERIAL:

The processing of successive items (jobs) on a single facility or connecting devices in series on one cable.

SERIAL INTERFACE:

A data transmission mechanism: Converts a parallel data arrangement to a serial form or applies to the connection of devices in series on one cable.

SERIAL-KEY DEVICE:

A device that enables a user to attach an alternate input device (augmentative communication device) to the computers serial port: This feature is designed for individuals who are unable to use the computers standard keyboard and mouse.

SERIAL LINE INTERNET PROTOCOL (SLIP):

An Internet protocol (IP) for connections over telephone lines, RS-232 cables, or other serial lines. Point-to-point protocol (PPP) is replacing/replaced SLIP. See SLIP

SERIAL PORT:

An interface on the computer that allows asynchronous transmission of data characters one bit at a time: Also called a communication or COM port.

SERIAL TRANSMISSION:

Transmitting data characters or bytes one bit at a time, in sequence. Contrast with Parallel Transmission.

SERIAL TUNNEL:

Router feature allowing two SDLC- or HDLC-compliant devices to connect to one another through a multi-protocol topology (Cisco routers) rather than through a direct serial link

SERVER:

A combination of hardware and software capable of recognizing and responding to client requests for services, such as shared access to a file system, a printer, a electronic mail system, or for local area network (LAN) users or clients. A single server machine can (and often does) have several different server software packages running on it, thus providing many different servers to clients on the network.

SERVER MESSAGE BLOCK (SMB):

A Microsoft originated distributed system which enables network access to another computer's files and peripherals. The function appears to be a local operation.

SERVICE:

A program, routine, or process that performs a specific system function to support other programs, particularly at a low (close to hardware) level: When services are provided over a network, they can be published in Active Directory, facilitating service administration and usage. Example: Security Accounts Manager Service, File Replication service, and Routing and Remote Access service.

SERVICE ACCESS POINT (SAP):

The logical address: The specific service entity to which data must be delivered.

SERVICE ACCESS POINT IDENTIFIER (SAPI):

Part of the layer 2 (LAPD) Address: Identifies transmitted frames to and/or from a particular service.

SERVICE AREA:

Refers to a specific geographic area served by a telecommunications provider.

SERVICE BUREAU:

A data processing Center that does work or provides services for clients, such as: timesharing.

SERVICE CLASS:

Collection of service types required for a specific service offered. Each service class includes the attributes and values that define the type or quality of service associated with a given class. For example, data connectivity is a service class that may be defined and it would include the service type data-bandwidth.

SERVICE CONTROL POINT (SCP):

A computer system that enables carriers to offer enhanced services, such as: Acting on the format, content, code, protocol or similar aspects of transmitted information. Allow subscriber interaction with stored data, such as translating 800 numbers to a Plain Old Telephone Service (POTS) number or a trunk group.

SERVICE DATA UNIT (SDU):

The unit-of-data-transfer measurement between a service user and a service provider

SERVICE LEVEL:

Various levels and quality of services defined for each service type. For example, the service type called quality of sound might have service levels defined for telephone, broadcast, and digital CD.

SERVICE MANAGEMENT SYSTEM (SMS):

1) An IBM interactive Information Management System (IMS) that coordinates all national 800 numbers for U.S. telephone companies and carriers.

2) A system outside of a network that provides a support interface through which customer in Service Control Points (SCP) can be added to or managed.

SERVICE ORDER (SO and S/O):

A request to provide communications service(s).

SERVICE PACKAGE:  

Quality of service that a cable provider offers subscribers: For example, Basic Student, Family Plus, and Internet are possible service packages. Subscribers may choose one or more service packages. A service class is selected for each service package, defining which service types make up the service package.

SERVICE POINT:

An IBM network management term for a system that allows non-SNA equipment and network components to be incorporated into an SNA management structure.

Interface between non-SNA devices and Net-View that sends alerts from equipment unknown to the SNA environment.

SERVICE PROFILE IDENTIFIER (SPID):

An 8 to 14 digit number that identifies the services ordered for each B-channel. For example: when ordering Primary Rate ISDN two phone numbers and two SPID identifiers are provided by the ISDN provider. Typical ISDN adapters cannot operate without configuring SPID(s).

SERVICE SWITCHING POINT:

A central office switching system that recognizes a variety of triggers (flags) within the customer’s data and based on the trigger generates queries to a Service Control Point (SCP). Then they use the information from the SCP to process calls.

SERVICE TERMINAL:

Refers to equipment required to terminate a channel and connect to the telephone equipment or customer terminal.

SERVICE TYPE:

A component of a service that cable providers offer subscribers: For example, devices-supported might be a service type defined for the home networking service, indicating the number of computers the subscriber can connect to the cable network from home. One or more service levels are defined for each service type.

SERVING AREA:

A telephone company geographic service area, usually the same as a LATA (Local Access and Transport Area)

SERVING TRANSLATION SCHEME:

Refers to a method used in translating an 800 number to a Plain Old Telephone Service (POTS) number or trunk group.

SERVING WIRE:

Refers to a telephone number related connection or Plain Old Telephone Service (POTS) related connection number.

SERVLET:

A small computer program designed to add capabilities to a larger program (software) running on a server. For example: Java servlets, which are small programs written in the java language, which are added to web server software. Typically a web server that uses Java servlets will have many of them, each one designed to handle a very specific situation, for example one servlet will handle adding items to a "’hopping cart’, while another servlet will handle deleting items from the ‘shopping cart’.

 SES:

Severely Errored Second: Examples: DS1: A second which has an equivalent error ratio greater than 1-in-1, 000. In SF, a second with one or more frame sync losses, six or more framing bit errors, or 1,544 or more BPV. In ESF, a second with one or more frame sync losses, 320 or more CRC-6 errors, or 1,544 or more BPV.

SESSION (SESS):

1) A connection between two devices or stations that permits them to communicate.

2) The time interval during which a terminal user can communicate with a distant point.

3) A logical network connection between two workstations for the exchange of data. It is possible to have more than one session active between two devices simultaneously.

4) In SNA, a logical connection enabling two NAUs to communicate.

SESSION GROUP:

Logically ordered list of sessions based on priority of the sessions. All the sessions in the session group should be configured to connect the same physical machines.

SESSION LAYER:

The fifth layer (Layer 5) in the Open Systems Interconnection (OSI) responsible for binding and unbinding logical links between users: It manages, maintains, and controls the dialogue between the users of the service.

SESSION MANAGER:

Manages all the sessions in a specific client

SESSION SET:

Collection of session groups

SET:

Secure Electronic Transactions. SET specification developed to allow for secure credit card and off-line debit card (check card) transactions over the World Wide Web.

SET-BY-CALLER CALLBACK:

In Network Connections, a form of callback in which the user supplies the telephone number that the remote access server uses for callback. This setting may spare the user of any long-distance telephone charges.

SF:

Super frame: Common framing type used on T1 circuits. SF consists of 12 frames of 192 bits each, with the 193rd bit providing error checking and other functions. SF was superseded by ESF but is still widely used; also called D4 framing.

SF (Signaling):

See Single Frequency Signaling

S-FRAME:

Supervisory Frame: One of three SDLC frame formats.

SFS: See Single Frequency Signaling

SG:

Signaling Gateway: Gateway that supports only signaling traffic (no bearer traffic.) For example, a gateway that terminates SS7 A-links is a signaling gateway.

Also see Super group

SGCP:

Simple Gateway Control Protocol: Controls Voice over IP gateways by an external call control element (call-agent). This allows SGCP to control switch ATM Circuit Emulation Service circuits (endpoints). The resulting system (call-agents and gateways) allows for the call-agent to engage in Common Channel Signaling (CCS) over a 64-kbps CES circuit.

SGML:

Standardized Generalized (Graphics) Markup Language: International standard for the definition of system independent and device-independent methods of representing text in electronic form

SGMP:

Simple Gateway Monitoring Protocol: Network management protocol that was considered for Internet standardization and later evolved into SNMP; documented in RFC 1028.

See Simple Gateway Monitoring Protocol

SGNT:

See Special Grade Network Trunk

SHA-1:

Secure Hash Algorithm 1: Algorithm that takes a message of less than 264 bits in length and produces a 160-bit message digest. The large message digest provides security against brute-force collision and inversion attacks. SHA-1 (NIS94c) is a revision to SHA that was published in 1994.

SHADOWING:

Form of replication in which well-defined units of information are copied to several DSA(s)

SHANNON EQUATION:

A formula: Uses signal-to-noise ratio and bandwidth for determining the maximum rate of transmission that can be handled by a facility.

SHARE:

To make resources, such as folders and printers, available to others

SHARED ACCESS:

A term used in a LAN (Local Area Network) environment to describe an access method that allows many terminals to share a transmission medium, as opposed to discrete access. Examples of shared access methods would be explicit access and contended access

SHARED CABLE MODEM:

Single cable MODEM servicing multiple CPE(s): Normally associated with multiple subscriber/accounts and is administered in the User Registrar Admin UI through a neighborhood.

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.

SHARED FOLDER:

A folder on another computer on the network that is accessible for use by other individuals.

SHARED FOLDER PERMISSIONS:

Permissions that restrict shared resources availability over the network to only certain users.

SHARED PRINTER:

A printer that receives input from more than one computer: For example: A printer attached to another computer on the network can be utilized by other users. Shared printer is also called a network printer.

SHARED RESOURCE:

Any device, data, or program that is used by another device or program: For Windows, shared resources refer to any resource that is made available to network users, such as folders, files, printers, and named pipes. A shared resource can also refer to a resource on a server that is available to network users.

SHARING:

Refers to the use of telecommunications services by two or more persons, via jointly leased or purchased facilities from a telecommunications carrier.

SHAREWARE:

Software distributed for evaluation without cost, but that requires payment to the author for full rights. After trying the software and the user does not intend to continue using it, the software should be deleted. Using unregistered shareware beyond the evaluation period is considered pirating.

SHEATH:

The outer cable jacket surrounding copper and fiber conductors: Creates a waterproof environment for the covered conductor.

SHELL / SHELL ACCOUNT:

An Internet account, usually unix based, that provides the Internet software for a user. In contrast, SLIP, PPP, and Ethernet accounts give the user a connection where the user runs their own Internet software, such as browsers, gopher, telnet, e-mail, and so on. Shell accounts run these for the user, and usually only provide text modes without graphics. A shell account can be based in VMS, as well, such as Delphi Internet Service's older text-side access.

SHF:

See Super High Frequency

SHIELD GROUND: RS-449 (Pin 1): Chassis ground or protective ground

SHIELDED CABLE:

Cable that has a layer of shielded insulation (metal) to reduce EMI (Electromagnetic Interference)

SHIELDED TWISTED PAIR (STP):

Twisted-pair cabling covered with a grounded protective metallic foil / mesh to help prevent data transmission errors caused by electro-magnetic interference.

SHIELDING:

The protective grounded coating or shield used on data communications medium, such as coaxial cable.

SHIPS IN THE NIGHT MODE:

Capability to support both MPLS functions and ATM Forum protocols on the same physical interface: or on the same router or switch platform. In this mode, the two protocol stacks operate independently.

SHIFT:

See figures shift or letters shift.

SHIFT IN:

See SI

SHIFT OUT (SO):

An ASCII Control Character indicating that the code combinations that follow should be interpreted as outside of the character set of the standard code table (non-printable) until a Shift In character is detected.

SHORT HAUL:

Basically refers to circuits designed for use over distances of 10-200 miles.

SHORT HAUL MODEM (SHM):

See Line Driver.

SHORT HAUL FACILITIES:

Refers to facilities contained within the digital serving area. Normally provides for intrastate or interstate services with distances typically less than 50 miles.

SHORTCUT:

A link to any item accessible on the computer or on a network, such as a program, file, folder, disk drive, Web page, printer, or another computer: A user can put shortcuts in various areas, such as on the desktop, on the Start menu, or in specific folders.

SHORTEST PATH ROUTING:

Routing that minimizes distance or path cost through the application of an algorithm.

SHOW-SOUNDS:

A feature that instruct programs, that usually convey information only by sound, to also provide all information visually, such as by displaying text captions or informative icons.

S.I.:

1) ICCDP System Interface: Equivalent to a Drum (disk) Transfer Channel.

2) Shift in: An ASCII control character indicating that the code combinations which follow should be interpreted according to the standard code table (set).

SID:

Service ID: A number at the MAC sub-layer that defines a particular mapping between a cable MODEM (CM) and the CMTS. The SID is used for the purpose of upstream bandwidth allocation and class-of-service management.

SIDEBAND:

The resultant added signals above and below a carrier frequency resulting from the modulation process on the carrier. Since the process produces two identical side-bands, telephony has in most systems for years filtered one out to save transmission space in AM analog systems, resulting in single side-band transmission. See Single side band

SIDESTREAM NETWORK MANAGEMENT:

A method of controlling and diagnosing networks that rely on a MODEM or multiplexer to monitor components in the analog portion of the network; some can also check the digital facilities.

SIGN-ON CHARACTER:

The first character transmitted on an auto-baud circuit to determine the appropriate data rate.

 SIGNAL, SIGNALS or SIGNALING:

A term used for digital and analog data transmission, voice or other analog information, fax, and any other type of information being transmitted over lines, circuits, channels or facilities. This would include characters and bits.

SIGNAL ATTENUATION:

The reduction in strength (amplitude) or deterioration of an electrical signal

SIGNAL CONVERTER:

A device designed to accept input signals in one form and transmit output signals in a different form, such as a MODEM.

SIGNAL ELEMENT:

Each part (bits) of a digital signal, distinguished from others by its duration, position, and/or reference. A signal element (bit) could be a start, information, or stop element.

SIGNAL GROUND:

RS-449 (Pin 19): a ground reference between the DTE (Data Terminal Equipment) and the DCE (Data Communication equipment), value of 0 volts.

SIGNAL PATH:

Route of a signal channel that carries signaling data.

SIGNAL QUALITY ERROR (TEST) (SQE’T’);

A transceiver function initiated immediately after the connected computer has transmitted to the LAN. The transceiver sends a simple test signal over the AUI back to the computer confirming the connection is functioning properly.

SIGNAL STATUS:

The absence or presence of a signal

SIGNAL TO NOISE (RATIO):

Ratio of the signal power to the noise power in a specified bandwidth usually expressed in decibels: The smaller the ratio, the poorer the channel. Generally speaking a ratio of 20 db or more would be considered excellent for telephony. A 1200 bps modem can function with only 12 db. As the data speed increases a higher ratio is required.

S/N (also SNR): The difference in amplitude between a base-band signal and the noise in a portion of the spectrum.

SIGNAL UNIT ERROR RATE MONITOR:

SS7 MTP 2 function that provides monitoring of signal unit events

SIGNALING CONVERTER (SC):

A device that transforms electrical signals to allow connections between different types of systems without changing the signal information: Signal converters are used at the terminal to convert the signals to the media used on the trunk. For example, ring-down signals are converted to Super Frame (SF) or E&M are converted to SF.

SIGNALING TRANSFER POINT (STP): A packet switch optimized for SS7 message handling.

SIGNATURE:

Virus Signatures: 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.

SIM:

1) Subscriber Identity Module: Component of an MS in a GSM network that contains all the subscriber information.

2) Set Initialization Mode

SINR:

Signal to Noise Ratio: The ratio of the received strength of the desired signal to the received strength of undesired signals (noise and interference).

SIP:

1) SMDS Interface Protocol: Used in communications between CPE and SMDS network equipment. Allows the CPE to use SMDS service for high-speed WAN internetworking

2) Serial Interface Processor:

3) Session Initiation Protocol: Protocol developed by the IETF MMUSIC Working Group as an alternative to H.323. SIP features are compliant with IETF RFC 2543, published in March 1999. SIP equips platforms to signal the setup of voice and multimedia calls over IP networks.

SLAC:

Stanford Linear Accelerator Center

SLAM / SLAMMING:

Slamming is the practice of telephone companies shifting you to their long distance service without your permission or obtaining your permission deceptively.

SLC:

Signaling Link Code: Code that identifies a link-set

SLOW INFECTOR:

Slow infectors are active in memory and only infect new or modified files.

SM FIBER:

Single-Mode Fiber: Fiber with a relatively low (narrow) diameter through which only one mode can propagate.

SMAC:

Source MAC: MAC address specified in the Source Address field of a packet.

SMATV:

Satellite Master Antenna Television: Transmission of television programming to a Satellite Master Antenna installed on top of an apartment building, a hotel, or at another central location from where it serves a private group of viewers. The transmission usually is done in C-band; 1.5 or 2 meter dishes.

SMF:

Single-Mode Fiber

SMI:

Structure of Management Information: Document (RFC 1155) specifying rules used to define managed objects in the MIB.

SMO:

State Machine Object

SIMPLE TCP/IP SERVICES:

Four TCP/IP (Transmission Control Protocol/Internet protocol) services: Character Generator, Daytime Discard, Echo and Quote of the Day.

SIMPLE VOLUME:

A dynamic volume made up of disk space from a single dynamic disk. A simple volume can consist of a single region on a disk or multiple regions of the same disk that are linked together. A user can extend a simple volume within the same disk or onto additional disks. If a user extends a simple volume across multiple disks, it becomes a spanned volume. A user can create simple volumes only on dynamic disks. Simple volumes are not fault tolerant, but a user can mirror them to create mirrored volumes.

SIMPLEX (SX):

A channel (line/terminal) capable of transmitting in one direction only and cannot operate in a reverse direction. Broadcast television is an example of a simplex technology.

In the early days a Simplex circuit referred to a DC telegraph circuit tapped into a telephone line through a coil matrix, which allowed simultaneous telegraph (DC) and telephone (AC) usage of the line.

SIMPLEX MODE:

See Simplex

SIMULATION:

Refers to the simulation of an existing program or the running of a computation process to implement a model of some dynamic system or phenomenon; A number of digital simulation programming languages are available for both mainframe and personal computers.

SIMULATORS:

Simulators are used for debugging during system development to verify beforehand the expected operations of the final system. Simulators differ from emulators, which are used to act like a given system. Emulators can perform actual operational and functional tasks.

SIMULTANEOUS VOICE AND DATA TRANSMISSION:

Refers to the capability of a telephone set to simultaneously transmit voice and data signals.

SINE WAVE:

A continuously variable and repeating analog signal: A sine wave signal is often used as the carrier in an analog modulation process. Sine waves can be generated by electronic oscillators and electromechanical generators.

SINGING:

A continued whistle or howl in an amplified telephone circuit: It occurs when the sum of the repeater gains exceeds the sum of the circuit losses, a reason why loss (amplification reduced) is often deliberately put into transmission channels.

SINGLE ATTACHMENT CONCENTRATOR (SAC):

A concentrator that offers one slave port for attachment to the Fiber Distributed Data Interface (FDDI) network and multiple master ports for the attachment of stations or other concentrators

SINGLE ATTACHED STATION (SAS):

A Fiber Distributed Data Interface (FDDI) Station: Offers one slave port for connecting to the FDDI network. The SAS is connected to the FDDI ring through a concentrator.

SINGLE CHANNEL PER CARRIER (SCPC):

A high-speed satellite data communications system using digital encoding and Phase-Shift Keying (PSK): SCPC can handle larger data volumes in narrower bandwidths than FM transmissions.

SINGLE ENDED TESTING:

A test equipment configuration used for testing between test units at two points on the circuit.

SINGLE FREQUENCY SIGNALING (SF/SFS):

A method of conveying dial-pulse and supervision signals from one end of a trunk or line to the other. This method uses the presence or absence of a single specified frequency (usually 2600 Hz).

SINGLE-MODE:

A process of using only one light ray or mode on a fiber optic medium having a core diameter only a few times greater than the wavelength of the transmitted light; The advantage of single mode propagation is to avoid the interference between light rays propagated under a different process known as multimode fiber.

Fiber-optic cabling with a narrow core that allows light to enter only at a single angle: Such cabling has higher bandwidth than multimode fiber, but requires a light source with a narrow spectral width (example: laser).

SINGLE SIDEBAND (SSB):

A form of radio signal modulation in which only one of the two side bands is transmitted. Either of the two side bands may be transmitted, and the carrier may be transmitted, reduced or suppressed. See Side band.

SINGLE SIGN-ON:

A process that allows a user with a domain account to log on to a network once, using a password or smart card, and to gain access to any computer in the domain.

SINGLE SWITCH DEVICE:

An assistive computer technology for individuals with mobility impairments: A single switch device allows users to interact with a computer by using slight body movements.

SINK

The portion of a communications system that receives or accepts information from a transmission device

SIR:

See Speaker Independent (Voice) Recognition

SITE or WEB-SITE:

This term is sometimes used to identify a ‘web page’, but a web page is a single entity, one URL (Uniform Resource Locator), one file that will be found at a Web site. A Web site is a location where many web pages are stored and linked, which are accessible through a URL address for each page

Group of closely related configuration data: It can be the name of a physical location or it can be a name given to one segment of the overall system.

SITREP:

Situation Report – Messages transmitted to interested agencies reporting unusual communications outages.

SKEWING:

The time delay between two data signals.

SKIP CODE:

A function code, which directs a machine to omit certain data parts in the information that follows.

SKYNET:

An AT&T communication product offering digital transmission service featuring on-site earth station facilities for wideband satellite transmission using Accunet Reserved 1.5 circuits.

SLAVE STATION:

Within a data communications network a slave station is the station that is selected and controlled by a master station. The slave station can usually only call or be called by the master station.

SLCC:

See Subscriber Line Carrier Circuit

SLEEVE:

A tubular covering, of lead, plastic, bronze, or copper, used over splices, cables or outer contacts of switchboard plugs.

SLICING LEVEL:

The voltage threshold determining where a one or a zero bit signal can be distinguished.

SLIP:

Serial Line Internet Protocol: A standard for using a regular telephone line, dial-up connection, and a MODEM to connect a computer representing an Internet site. SLIP has largely been replaced by PPP (Point-to-Point Protocol).

SLOT:

A time unit (slot) used in TDM (Time Division Multiplexing): Where a sub-channel character or bit is inserted and transmitted to the other end of the circuit, along with other bits or characters, and extracted by the receiving TDM unit.

SLOTTED RING:

A LAN feature, which circulates a constant number of fixed length slots (packets) continuously around the Ring, A full/empty indicator within the slot header indicates when a station can place information into the slot.

SLOTTING:

The process of assigning a network circuit, during the circuit design process, within the available channel capacity,

SLOW INFECTOR:

Slow infectors are active in memory and only infect new or modified files.

SLOW RELEASE RELAY:

An electromechanical relay with a copper sleeve over one end of its core, causing it to release slowly after the energizing current is removed.

SMALL COMPUTER SYSTEM INTERFACE (SCSI):

A standard high-speed parallel interface defined by the American National Standards Institute (ANSI). A SCSI interface is used for connecting microcomputers to peripheral devices such as hard disks and printers, and to other computers and Local Area Networks (LAN).

SMART BRIDGE:

A bridge that reads the source address of received packets and develops routing tables from those addresses.

SMART CARD:

A credit card-sized device that is used with an access code to enable certificate-based authentication and single network sign-on: Smart cards securely store certificates, public and private keys, passwords, and other types of personal information. A smart card reader in or attached to the computer reads the smart card.

SMART CARD READER:

A device installed in or connected to computers to enable the use of smart cards for enhanced security features.

SMART HUB:

A twisted-pair concentrator used in Ethernet or ARCnet networks. The smart hub has built in network management facilities that allow a network manager to control and monitor the network performance and to plan the network configuration.

SMART WIRING HUB:

A network concentrator: Allows multiple media (criteria) to be supported and managed from a central location. When supporting structured wiring systems, smart hubs provide port management.

SMARTEST:

A REACT option: Allows maintenance to schedule automatic and unattended testing.

SMARTJACK:

An interface connector that provides T1 loop backs at the network interface.

SMART TERMINAL:

A data terminal with the capability to operate in either a conversational or block mode: The terminal usually provides a full set of local editing capabilities without reliance on a controlling external computer.

SMAS:

See Switched Maintenance Access System

SM&R:

System Management and Reports or System Management and Review; See R&A

SMB:

Server Message Block: File-system protocol used in LAN manager and similar NOS(s) to package data and exchange information with other systems.

See Server Message Block

SMC:

Systems Management Center: A small Computer Center located on the 1st floor at McLean that processed all the Systems Statistics from the Status Reports generated by the ASC. SMC took all the information from those reports and compiled charts and statistics, and reviewed the overall efficiency of the system.

SMDS:

Switched Multi-megabit Data Services:

1) A broadband communications standard for the public network that does not require pre-definition of a specific path.

2) A fast packet-switching service using uniform-sized cells to transmit information, operating at speeds of 1.544 Mbps to 45 Mbps.

3) High-speed, packet-switched, datagram-based WAN networking technology offered by the telephone companies.

SMG:

Wireless-Special Mobile Group: A standards body within ETSI that develops specifications related to mobile networking technologies, such as GSM and GPRS.

Also see super master group

SM&R:

System Management and Reports or System Management and Review; See R&A

SMRP:

Simple Multicast Routing Protocol: Specialized multicast network protocol for routing multimedia data streams on enterprise networks. SMRP works in conjunction with multicast extensions to the AppleTalk protocol.

SMRT:

Single Message-unit Rate Timing: A message unit system tariff used by telephone companies to measure and time calls in increments of 5 minutes or less, applying a single message unit charge to each increment.

SMS:

1) Short Messaging System: A feature of PCS (Personal Communication Service) phones, primarily Global Standard for Mobil (GSM) that allows users to receive and sometimes transmit short text messages using their wireless telephone.

2) See Service Management System

SMT:

Station Management: ANSI FDDI specification that defines how ring stations are managed

See Station Management

SMTP:

Simple Mail Transfer Protocol: A protocol dictating how e-mail messages are exchanged over the Internet. Send side server for a LAN or Internet Service Provider

S/N:

See signal-to-noise ratio.

SNA:

See Systems Network Architecture

SNA DISTRIBUTION SERVICES (SNADS):

Asynchronous Distribution Service Architecture: Provides for the transmission of files or jobs through an IBM SNA network.

SNA NETWORK INTERCONNECT (SNI):

Defines the manner in which autonomous SNA (IBM) networks can be connected together; allowing independent management of each individual network.

SNADS:

SNA Distribution Services: Consists of a set of SNA transaction programs that interconnect and cooperate to provide asynchronous distribution of information between end users; one of three SNA transaction services.

See SNA Distribution Services

SNAIL MAIL:

United States Post Office mail service

SNAP:

Sub-network Access Protocol: Internet protocol that operates between a network entity in the sub-network and a network entity in the end system. SNAP specifies a standard method of encapsulating IP data-grams and ARP messages on IEEE networks. The SNAP entity in the end system makes use of the services of the sub-network and performs three key functions: data transfer, connection management, and QoS selection.

SNAP-IN:

A type of tool that can be added to a console supported by Microsoft Management Console (MMC): A stand-alone snap-in can be added by itself; an extension snap-in can only be added to extend the function of another snap-in.

SNI:

1) Subscriber Network Interface: Interface for SMDS-based networks that connect CPE and a SMDS switch.

2) SNA Network Interconnection: IBM gateway connecting multiple SNA networks

3) See Subscriber Network Interface (SNI) or SNA Network Interconnect (SNI)

SNIFFER:

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

SNMP:

Simple Network Management Protocol: A set of standards for communication with devices connected to a TCP/IP (Transmission Control Protocol / Internet Protocol) network. For example: routers, hubs, and switches. SNMP provides a means to monitor and control network devices, and to manage configurations, statistics collection, performance, and security.

SNMP COMMUNITIES:

Authentication scheme that enables an intelligent network device to validate SNMP requests

SNMP2:

SNMP Version 2: Version 2 of the popular network management protocol. SNMP2 supports centralized as well as distributed network management strategies, and includes improvements in the SMI, protocol operations, management architecture, and security.

SNP:

Sequence Number Protection

SNPA:

Sub-network Point of Attachment: Data link layer address, such as an Ethernet address, X.25 address, or Frame Relay DLCI address. SNPA addresses are used to configure a CLNS route for an interface.

See Sub-network Point of Attachment

SNR:

Signal-to-Noise Ratio: SNR is the ratio of the usable signal being transmitted compared to the undesired signal (noise). It is a measurement of transmission quality. The ratio of good data (signal) to bad (noise) on a line, expressed in decibels (dB).

See Signal-to-Noise Ratio

SNRM:

Set Normal Response

SNRME:

Set Normal Response Mode Exchange

SO or S/O:

See Service Order, or Switching Office, or Shift Out

SOA:

Start of Address: Usually contained in the ‘Header’ of a message and will identify that the following characters contain the destination address.

SOAP:

Simple Object Access Protocol: A protocol for client-server communication that sends and receives information ‘on top of’ HTTP (Hypertext Transfer Protocol). The data sent and received is in a particular XML (Extensible Markup Language) format specifically designed for use with SOAP. SOAP is similar to the XMLRPC (XML Remote Procedure Call) protocol except that SOAP provides for more sophisticated handling of complex data being sent between a client and a server. SOAP actually grew from the work that created XMLRPC. Microsoft's ‘.NET’ system is largely based on SOAP.

SOCIAL ENGINEERING:

Refers to a cracker term for tricking users of a system to reveal passwords so that the cracker can gain entry to the system: A common technique is to contact users via chat room or e-mail, pretend that they are employees of the system performing security checks, and insist that the users give their password to prove who they are or their account will be closed. Such requests are never legitimate! Social engineering schemes can be quite ingenious and convincing and more subtle than the simple technique above.

SOCIETY FOR WORLDWIDE INTERBANK FINANCIAL TELECOMMUNICATIONS (SWIFT):

A worldwide communications network: Connecting most of the banks and financial institutions.

SOCKET:

1) A set of subroutines: Provides access to transmission control protocol/ Internet protocol (TCP/IP) on most systems. Also could be a connection point or holder where a unit is plugged in.

2) Software structure operating as a communications end point within a network device.

3) Addressable entity within a node connected to an AppleTalk network: Sockets are owned by software processes known as socket clients. AppleTalk sockets are divided into two groups: SASs, which are reserved for such clients as AppleTalk core protocols, and DAS(s), which are assigned dynamically by DDP upon request from clients in the node. An AppleTalk socket is similar in concept to a TCP/IP port.

SOCKET NUMBER:

8-bit number that identifies a socket: A maximum of 254 different socket numbers can be assigned in an AppleTalk node.

SOFT COPY:

A term used to describe a video display image or CRT display offering no provision for a permanent record, such as a printed hardcopy of the display.

SOFTWARE:

A set of program codes, instructions, or groups of programs that cause the computer to perform processing functions.

SOFTWARE RAID:

Uses the server processor to perform RAID (Redundant Array of Independent Disks) calculations; the Host CPU cycles that read and write data from and to disk are taken away from applications. Software RAID is less costly than dedicated hardware RAID storage processors, but its data protection is less efficient and reliable.

SOH:

Start Of Header: Usually, immediately follows the “Start of Message” symbol(s) and identifies that the message priority, address(s) and other pertinent handling information follows.

SOHO:

Small Office Home Office: A type of DSL connection possessing qualities better than ADSL. Designed especially for smaller business Networking solutions and access technologies for offices that are not directly connected to large corporate networks

SOLB:

Start Of Line Block: A control character identifying the start of a block of data.

SOLID STATE:

Semiconductors: Transistors, Printed Circuits, Chips, not electromechanical relays and electron tubes.

SOM:

Start Of Message: A control character or a group of alpha/numeric characters.

SOMH:

Start Of Message High: A control character designating high priority message.

SONET:

Synchronous Optical Network: A standard format for transporting a wide range of digital telecommunications services over optical fiber. SONET is characterized by standard line rates, optical interfaces, and signal formats.

High-speed, up to 2.5 Gbps, synchronous network specification developed by Bellcore and designed to run on optical fiber. STS-1 is the basic building block of SONET. Also see Synchronous Optical Network

SONET MULTIPLEXING:

SONET multiplexing byte interlaces the lower-rate payloads, which creates a high-rate synchronous signal.

SOUND CARD:

Accessory expansion board for personal computers that permits recording and playing back sound.

SOUND FILE:

1) Refers to a World Wide Web (WWW) sound file; a computer file containing digitized sound that can be retrieved by a Web browser; 2) a file containing information that Windows uses to play sounds on the computer. Sound files have the file name extension .wav.

SOUND-SENTRY:

A Windows feature that produces a visual cue whenever the computer plays a system sound, such as a screen flash or a blinking title bar

SOURCE:

The data originator or the transmission of information in a data communications network or link

SOURCE ADDRESS:

Address of a network device that is sending data

The part of a message, usually a group of characters or bits that defines the origination, or source, of the message

SOURCE-ADDRESS FILTERING:

A bridge feature that always forwards or always rejects messages from designated source addresses.

SOURCE CODE:

A computer program written in a language one or more steps removed from the ‘machine code (language)’ of a particular computer. Machine code consists of a very explicit set of digital instructions capable of direct execution by the computer hardware. Writing (coding) programs in machine code would be very tedious, therefore, other languages have been developed to make it easier for a programmer to express their desires, and these programs are known as source programs or source code. These source code programs are processed by a program compiler that converts them to machine code.

SOURCE DOCUMENT:

The document where a linked or embedded object was originally created: Could also refer to programming code.

SOURCE PROGRAMS:

Programs written and coded by the programmer: Require translation to machine code in order to operate the computer.

SOURCE ROUTING:

A feature used by a bridge for moving data between two networks. Source routing relies on information contained within the token to route the packet between the two networks.

SOURCE ROUTING TRANSPARENT (SRT):

A Token Ring bridging standard jointly sponsored by the Institute of Electrical and Electronic Engineers (IEEE) and IBM: It combines IBM Source Routing and Transparent Bridging under IEEE 802.1 in the same unit.

SP:

1) Signaling Processor; Signaling Point.

2) Switch Processor: Cisco 7000-series processor module that acts as the administrator for all CxBus activities; sometimes called Cisco-Bus controller.

3) Space: Normally a non-printing graphic character used to separate words. It is also a format affecter which controls the movement of the printing (CRT display) position, with one space being equal to one print (display) position. See Space

SPA:

Security Posture Assessment: Comprehensive security analysis of large-scale, distributed client networks conducted by Cisco Systems engineers.

SPACE:

The communications signal state corresponding to binary zero; represented by a no current, no hole-in-a-paper-tape or a negative (usually) voltage condition. A very ‘long space’ is used in telegraphy as a circuit failure alarm and a disconnect signal for Telex lines.

SPACE-DIVISION SWITCHING:

A switching method that uses a separate physical path through the switch for each connection supported.

SPACE HOLD:

The transmission of a steady space signal to indicate a line condition with no traffic

SPACE-TO-MARK TRANSITION:

The action of switching from a spacing signal to a marking signal

SPACING:

A term used to indicate an open circuit, no current flow.

SPAG:

Standards Promotion and Application Group: A group of European OSI manufacturers that chooses option subsets and publishes these in the Guide to the Use of Standards (GUS).

SPAM:

Spam Mail: The act of sending multiple, sometimes millions, of unwelcome messages to individuals, businesses or news group promoting various activities or products.

SPAN:

Normally refers to a full-duplex digital transmission line between two digital facilities

SPANNED VOLUME:

A dynamic volume consisting of disk space on more than one physical disk: A user can increase the size of a spanned volume by extending it onto additional dynamic disks. A user can create spanned volumes only on dynamic disks. Spanned volumes are not fault tolerant and cannot be mirrored.

SPANNING TREE:

A method of creating a loop-free logical topology on an extended local area network (LAN); Formation of a spanning tree topology for transmission of messages across bridges is based on the spanning tree algorithm defined in the Institute of Electrical and Electronic Engineers (IEEE) 802.1 specification.

SPANNING TREE ALGORITHM (STA):

The Institute of Electrical and Electronic Engineers (IEEE) 802.1 standard for bridge-to-bridge communications: This standard makes it possible to automatically update routes as an organization adds or deletes bridges from a network. STA allows bridge products from different vendors to communicate.

SPARSE INFECTOR:

A sparse infector viruses use 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 these conditions to infect less often and therefore avoid detection.

SPC:

Service Platform Card: Provides call processing services, such as tone receivers and conference ports, within the Cisco VCO/4K switch. Available resources include DTMF detection, call progress analysis, MF reception, MFCR2 reception and transmission, tone generation, DTMF and MF out-pulsing, and call conferencing.

SPE:

1) Synchronous Payload Envelope: The payload carrying portion of the STS signal in SONET. The SPE is used to transport a tributary signal across the synchronous network. In most cases, this signal is assembled at the point of entry to the synchronous network and is disassembled at the point of exit from the synchronous network. Within the synchronous network, the SPE is passed intact between NE(s) on its route through the network.

2) System Processing Engine: A card that acts as a single-board computer and runs system software applications, such as Cisco ICS 7750 System Manager and Cisco Call-Manager.

SPEAKER INDEPENDENT (VOICE) RECOGNITION (SIR):

The developed technologies for the automated conversion of speech to accurate and meaningful textual information: typically ASCII.

SPECIAL ACCESS LINE (SAL):

A class of Local Exchange Carrier (LEC) service that provides the link from the customer's premises to an Inter-Exchange Carrier (IEC): This would include: Point of Presence (POP) for non-switched, dedicated circuits; private line local access, private line entrance facilities, and other LEC-provided private line services.

SPECIAL ACCESS PERMISSIONS:

On NTFS (New Technology File System), a custom set of permissions. A user can customize permissions on files and directories by selecting the individual components of the standard sets of permissions.

SPECIAL CHARACTER:

A non-alpha-numeric printable character: Control character

SPECIAL GRADE NETWORK TRUNK (SGNT):

A trunk conditioned by providing amplitude and delay equalization for the purpose of handling special services such as medium-speed data in the range of 600 to 2400 BPS.

SPECIALIZED COMMON CARRIER (SCC):

Common carriers specializing in one type of technology or service: Examples: Mobile radio common carriers, microwave radio common carriers, radio-paging common carriers.

SPECTRUM / FREQUENCY SPECTRUM:

1) A specified group or the entire range of electromagnetic (radio) frequencies

2) The continuous range of frequencies beginning with audible sounds in the 20 Hz range to cosmic rays occurring above 1000 gHz . Voice grade telephone channel usable frequency spectrum exists between 300 and 3300 Hz.

SPEED CALLING / SPEED DIALING / SPEED NUMBER:

A telephone feature that allows the subscriber to use short sequences of digits to represent frequently called numbers.

SPEED CONVERSION:

The process of changing transmission speeds so that two devices having different transmission speeds can communicate with each other. A Front End Processor (FEP) function

SPEED PLUS:

Refers to a technique used to combine voice and data on the same line by assigning the top part of the normal voice bandwidth to data.

SPF:

Shortest Path First algorithm: Routing algorithm that iterates on length of path to determine a shortest-path spanning tree. Commonly used in link-state routing algorithms

SPI:

Security Parameter Index: This is a number that, together with a destination IP address and security protocol, uniquely identifies a particular security association. When using IKE to establish the security associations, the SPI for each security association is a pseudo-randomly derived number. Without IKE, the SPI is manually specified for each security association.

SPID:

Service Profile Identifier: Number that some service providers use to define the services to which an ISDN device subscribes. The ISDN device uses the SPID when accessing the switch that initializes the connection to a service provider.

SPIDERS:

Computer robot programs, which may be referred to by other names, such as: ‘crawlers’, ‘knowledge-bots’ or ‘knowbots’. Search engines that roam the World Wide Web via the Internet accessing web sites and databases in order to keep the search engine database of web pages up to date use spiders. They obtain new pages, update known pages, and delete obsolete ones. Their findings are then integrated into the search engine database.

SPIM:

Spam sent by instant messaging

 SPIRAL PARITY:

An error checking system where the check character is developed by making diagonal rows; either odd or even.

SPLITTER:

A device that separates the ADSL signal into the voice and data components; A device that separates signal components based on their frequency content; A filter, which separates high frequency (ADSL) and low frequency (POTS) signals at both the end user and central office end.

SPNNI CONNECTION:

Frame Relay connection between two VNS(s) in different areas or domains. The SPNNI connection gets its name from the proprietary Network-to-Network Interface protocol that operates over this connection.

SPO:

Systems Programming Office

SPOOFING:

1) Scheme used by routers to cause a host to treat an interface as if it were up and supporting a session. The router spoofs replies to keep-alive messages from the host in order to convince that host that the session still exists. Spoofing is useful in routing environments, such as DDR, in which a circuit-switched link is taken down when there is no traffic to be sent across it in order to save toll charges.

2) The act of a packet illegally claiming to be from an address from which it was not actually sent. Spoofing is designed to foil network security mechanisms, such as filters and access lists.

SPOOLING:

A process on a server in which print documents are stored on a disk until a printer is ready to process them. A spooler accepts each document from each client, stores it, and then sends it to a printer when the printer is ready.

SPOT BEAM:

A term used in the satellite transmission environment to describe a narrow and focused down-link to an earth station.

SPP:

Sequenced Packet Protocol: Provides reliable, connection-based, flow-controlled packet transmission on behalf of client processes. Part of the XNS protocol suite.

SPREAD SPECTRUM:

A communications technology where a signal is transmitted over a broad range of frequencies and then re-assembled when received.

SPX:

Sequenced Packet Exchange: Reliable, connection-oriented protocol that supplements the datagram service provided by network Layer 3 protocols. Novell derived this commonly used NetWare transport protocol from the SPP of the XNS protocol suite.

See Sequenced Packet Exchange, or Simplex

SPYWARE:

A term generally referring to software that is secretly installed on a user’s computer, which then monitors the computer in some way without the user’s knowledge or consent. Spy-ware is usually installed without a user’s knowledge during the installation of other software, especially music sharing software obtained via download.

Most Spy-ware attempts to get the user to view advertising and/or particular web pages. Some Spy-ware also sends information about the user to another machine over the Internet.
SQE:

Signal Quality Error: Transmission sent by a transceiver back to the controller to let the controller know whether the collision circuitry is functional.

See Signal Quality Error (Test)

SQL:

Structured Query Language: A specialized language for sending queries to databases; most industrial and many smaller database applications can be addressed using SQL. Each specific application will have its own slightly different version of SQL implementing features unique to that application, but all SQL capable databases support a common subset of SQL

SR:

Short Reach: The distance specification for optical systems that operate effectively up to 3 km (1.8 mi).

SRAM

Static Random Access Memory: A volatile read/write memory device that, in contrast with DRAM Dynamic Random Access Memory), does not need to be refreshed.

SRB:

Source-Route Bridging: Method of bridging originated by IBM and popular in Token Ring networks. In a SRB network, the entire route to a destination is predetermined, in real time, prior to the sending of data to the destination.

SRC:

Spiral Redundancy Checking: An error checking (block parity) method for transmitted data blocks where the receiving terminal would accumulate redundant error checking information in a spiral bit position fashion.

SRCP:

Simple Resource Control Protocol: Set of extensions to MGCP to allow the VSC to poll the gateway about its current configuration.

SRDM:

Sub-Rate Data Multiplexer: A multiplexer that would combine several data streams below a basic rate into a single, higher rate Time Division Multiplexer (TDM) signal.

SRP:

Spatial Reuse Protocol

SRT:

Source-Route Transparent bridging: IBM bridging scheme that merges the two most prevalent bridging strategies: SRB and transparent bridging. SRT employs both technologies in one device to satisfy the needs of all EN(s). No translation between bridging protocols is necessary.

See Source Routing Transparent

SR/TLB:

Source-Route Translational Bridging: Method of bridging where source-route stations can communicate with transparent bridge stations with the help of an intermediate bridge that translates between the two bridge protocols.

SRTP:

Sequenced Routing Update Protocol: Protocol that assists VINES servers in finding neighboring clients, servers, and routers

SRVTAB:

Password that a network service shares with the KDC: The network service authenticates an encrypted service credential by using the SRVTAB to decrypt it. Also known as a KEYTAB

SS:

Start of Special Sequence: An ASCII control character used to indicate the start of a variable length sequence of characters which have special significance or which should receive special handling.

SSAP:

Source Service Access Point: SAP of the network node designated in the Source field of a packet.

SSCOP:

Service Specific Connection Oriented Protocol: Data link protocol that guarantees the delivery of ATM signaling packets.

SSCP:

System Services Control Points: Focal points within a SNA network for managing network configuration, coordinating network operator and problem determination requests, and providing directory services and other session services for network end users.

SSCP-PU SESSION:

System Services Control Points - Physical Unit Session: Used by SNA to allow an SSCP to manage the resources of a node through the PU. SSCP(s) can send requests to, and receive replies from, individual nodes in order to control the network configuration.

SSCS:

Service Specific Convergence Sub-layer: One of the two sub-layers of any AAL. SSCS, which is service dependent, offers assured data transmission

SSD SERVER:

Service Selection Dashboard server: Customizable Web-based application that works with the Cisco SSG to allow end customers to login to and disconnect from proxy and pass-through services, through a standard Web browser. After the customer logs in to the network of the service provider, an HTML Dashboard is populated with the services authorized for that user.

SSG:

Service Selection Gateway: Gateway that offers service providers a means for menu-based service selection. End users can select services from the Dashboard menu, and the Cisco SSG can set up and tear down proxy and pass-through network connections based on a selection of a user. The Cisco SSG accounts for the services selected so that service providers can bill for individual services.

SSO:

System Security Officer: Person responsible for enforcement or administration of the security policy that applies to the system.

SSRP:

Simple Server Redundancy Protocol: The LANE simple server redundancy feature creates fault-tolerance using standard LANE protocols and mechanisms

SS7:

Signaling System 7: Standard CCS system used with BISDN and ISDN

See Signaling System 7

SSB:

Single Side Band

SSCP:

See Systems Services Control Point

SSI:

Small Scale Integration: A term used to describe a silicon chip containing 10 electronic circuits or less.

SSI (commands):

Server-Side Include: A type of HTML (Hypertext Markup Language) instruction telling a computer that services Web pages to dynamically generate data, usually by inserting certain variable contents into a fixed template or boilerplate Web page. Used especially in database searches.

SSID:

Service Set Identifier: A 32-character unique identifier attached to the header of packets sent over a WLAN (Wireless Local Area Network) that acts as a password when a mobile device tries to connect to the BSS (Basic Service Set). The SSID (Service Set Identifier) differentiates one WLAN from another, so all access points and all devices attempting to connect to a specific WLAN must use the same SSID. A device will not be permitted to join the BSS (Basic Service Set) unless it can provide the unique SSID. Because a SSID can be sniffed (detected) in plain text from a packet it does not supply any security to the network.

A SSID is also referred to as a network name because essentially it is a name that identifies a wireless network.

SSL:

Secure Socket Layer: A protocol designed by Netscape Communications to enable encrypted communications across the Internet. Encryption technology for the Web used to provide secure transactions, such as the transmission of credit card numbers for e-commerce.

SSM:

1) Solid State Memory (replaced rotating discs)

2) Source Specific Multicast: A datagram delivery model that best supports one-to-many applications; also known as broadcast applications. SSM is the core networking technology for the Cisco implementation of the IP Multicast Lite suite of solutions, targeted for audio and video broadcast application environments.

SSN:

Subsystem Number: See Switched Service Network

SSP:

1) System Switch Processor: A card that acts as an Ethernet switch and passes data between all system cards and to any other switches connected to the system.

2) Service Switching Point: Element of an SS7-based Intelligent Network that performs call origination, termination, or tandem switching.

3) Switch-to-Switch Protocol: Protocol specified in the DLSw standard that routers use to establish DLSw connections, locate resources, forward data, and handle flow control and error recovery.

4) Silicon Switch Processor: High-performance silicon switch for Cisco 7000 series routers that provides distributed processing and control for interface processors. The SSP leverages the high-speed switching and routing capabilities of the SSE to increase aggregate router performance and minimize performance bottlenecks at the interface points between the router and a high-speed backbone. See Service Switching Point

ST CONNECTOR:

A type of connector used for terminating optical fiber cables

STA:

Spanning Tree Algorithm

STANDBY INDICATOR:

RS-449 (Pin 36): A signal to the DCE (Data Communication Equipment) indicating the use of the normal or standby channel.

STANDARD-BASED ARCHITECTURE:

Defines interfaces, standards, and the framework in which computers (networks) operate. The purpose is to promote portability, interoperability, and scalability.

STANDBY:

A state in which the computer consumes less power when it is idle, but remains available for immediate use: While your computer is on standby, information in computer memory is not saved on the hard disk. If there is an interruption in power, the information in memory is lost.

STAR:

A network in which each station connects only to a central station (hub) through a point-to-point link: Communicates with all other stations through the central station. In a local area network (LAN), the hub may be a workstation; and in a larger network, the hub may be a multiplexer or a computer.

STAR-LAN:

CSMA/CD LAN, based on IEEE 802.3, developed by AT&T

STAR NETWORK:

See Star or Star Topology

STAR TOPOLOGY:

A network interconnection method: One central node (hub) has links to all the other nodes and the individual nodes (stations) communicate through the Central Node.

STARLAN:

AT&T local area network: Transmits data at l Mbps (mega bits per second) over unshielded twisted-pair wires.

START BIT:

The first bit (space) of a character in an asynchronous serial transmission. The start bit triggers the necessary mechanism to cause the decoding of the following character bits. Baudot and ASCII use a start bit in asynchronous operation.

START ELEMENT:

See Start Bit

START OF ADDRESS:

See SOA

START OF HEADER:

See SOH

START of TEXT:

See STX

START-STOP SYSTEM / TRANSMUISSION:

A system that uses both a character start bit and stop bit. See asynchronous.

START/STOP TRANSMISSION:

In asynchronous transmission each byte or character is preceded by a start signal (‘space’ bit) and followed by a stop signal (‘mark’ bit).

STARTUP ENVIRONMENT:

In dual-boot or multiple-boot systems, the configuration settings that specify which system to start and how each system should be started.

STATIC DIALOG BOX:

A scripted dialog box between the client computer and an intermediary device: This type of dialog box requires no response from the user.

STATIC IP ADDRESSING:

An assigned Internet Protocol (IP) address used to connect to the Internet. The IP address is assigned to the customer's computer.

STATIC ROUTING:

Refers to a routing procedure in which the network manager permanently configures the routing table; the paths on the network are considered fixed and do not change.

STATION:

Any terminal equipment located on a network capable of sending or receiving messages or calls.

STATION ADDRESS:

A group of alphanumeric characters that uniquely identifies a station on a network /system: The destination address is used for data transmitted to a station, while the source address identifies a message transmitted from a station.

STATION CONTROLLER:

A device with processing capabilities, designed to control data communications between terminals and host systems, usually providing error handling functions. Refer to DTE.

STATION MANAGEMENT (SMT):

Fiber Distributed Data Interface (FDDI) Hardware and Software specifications that provide control at the station level to ensure that the station works efficiently on a network.

STATION MESSAGE DETAIL RECORDING (SMDR):

A computer generated report showing internal usage on a telephone system. Usually includes extension number, trunk number, phone number dialed, time of call, duration and operator involvement.

STATION MESSAGE REGISTERS:

A centrally located counting device that records each connected stations outgoing calls

STATISTICAL MULTIPLEXING:

A method of adding dynamic buffering and time slot assignment to time division multiplexing, such that time slots are allocated only to active ports; effectively increases data volume and throughput.

STATUS AREA:

See Notification Area

STC:

Service Test Center: A term used to describe a DDS (Data-phone Digital Service) test location that maintains and controls circuit layout records.

STD:

1) Sub-series of RFC(s) that specify Internet standards; STD 1: Official list of Internet standards.

2) Subscriber Trunk Dialing; the international equivalent of Direct Distance Dialing (DDD)

STDM

Statistical Time-Division Multiplexer: A device that combines a multiple of varying speed bit streams into a single bit stream for transmission.

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.

STEMMING:

In keyword searching, word endings are automatically ignored; searches are performed on the stem + common endings; for example ‘line’ or ‘lines’ will retrieve line, lines, line’s, lines’, lining or lined. This can usually be avoided by placing a term in "quotes”.

STEP INDEX:

A fiber optic type facility preferred for long-distance, single-mode operation.

STICKY-KEYS:

A keyboard feature that enables a user to press a modifier key (CTRL, ALT, or SHIFT), or the Windows logo key, and have it remain active until a non-modifier key is pressed. This is useful for individuals who have difficulty pressing two keys simultaneously.

STM-1:

Synchronous Transport Module level 1: One of a number of SDH formats that specifies the frame structure for 155.52-Mbps lines used to carry ATM cells

STOP BIT:

The last mark bit (element) of a character in an asynchronous serial transmission, it is used to lock up the device mechanism and to ensure recognition of the next start bit. The stop bit may be longer than one character bit time, as in the Baudot teletypewriter operation it is 1.42 bits (mark).

STOP CODE:

A Control Character(s) – In the case of a Teletype would turn off (stop) the paper tape reader; in card reading device may stop the card reader or punch; or control the stop function of a device.

STOP ELEMENT:

See Stop Bit

STOPWORD:

Commonly used words that are normally excluded from automated searches: Examples: a, an, the, for, to, in, on, and, etc.

STORE AND FORWARD:

Transmission technique where messages / packets / data received are stored and then forwarded to the next location as addressed. Normally messages are processed on a first in – first out (FIFO) basis, except where priority routing is used. In this case high priority messages would be processed first.

STORAGE:

A device to enter, hold and retrieve information such as data and programs. Several types of computer storage exist. Typically, storage can be categorized as ‘main’ (primary) storage, usually consisting of semi-conductor circuits or ‘secondary’ (auxiliary) storage, drum and tape. Main storage, known as RAM and sometimes as ROM in personal computers, is implemented using fast but relatively expensive components, while secondary storage as a rule is slower and less expensive. A typical system will have more secondary storage than main storage. Main storage is also known as main memory or just ‘memory’.

STORED PROGRAM CONTROL (SPC):

A system of stored program instructions of a common control switching computer for processing message formats and protocols and provides for trouble analysis functions.

STP:

1) Shielded Twisted-Pair: Two-pair wiring medium used in a variety of network implementations. STP cabling has a layer of shielded insulation to reduce EMI.

2) Spanning-Tree Protocol: Bridge protocol that uses the spanning-tree algorithm, enabling a learning bridge to dynamically work around loops in a network topology by creating a spanning tree. Bridges exchange BPDU messages with other bridges to detect loops, and then remove the loops by shutting down selected bridge interfaces. Refers to both the IEEE 802.1 Spanning-Tree Protocol standard and the earlier Digital Equipment Corporation Spanning-Tree Protocol upon which it is based. The IEEE version supports bridge domains and allows the bridge to construct a loop-free topology across an extended LAN. The IEEE version generally is preferred over the Digital version.

3) Signal Transfer Point: Element of an SS7-based Intelligent Network that performs routing of the SS7 signaling.

4) See Shielded Twisted Pair or Signaling Transfer Point

STRAIGHT AWAY TEST:

Maintenance tests in which the transmitter and receiver are connected to physically different points (areas) on a circuit under test: The transmitter originates the tests on the circuit, and the receiver displays the results. This differs from loop back testing where the transmitter and the receiver are usually located in the same area.

STREAM PROTOCOL 2 (ST-II):

A protocol built on top of IP for audio-visual and reserved resource applications and services.

STREAMING:

Nonstop transmission of signals (bits/characters) on a data communication line from a defective piece of equipment, such as a MODEM or transmitter; Streaming equipment will tie up a multipoint circuit with false signals and prevent other equipment from using the circuit.

STREAMING AUDIO / STREAMING VIDEO:

Technologies which permit listening and watching continuously as the signal is transferred to your system from a remote web site. It requires a high degree of compression to transfer audio or video at low speeds, such as 28.8 Kbps or 14.4 Kbps, and still retain quality music and non-jerky video. These technologies continue to improve, but faster connection speeds are needed to really improve quality. The systems generally use a few seconds buffering, but signal slowdowns or interruptions longer than that break the flow.

STREET-TALK:

The VINES naming system that identifies every user and component of a network: A Street-Talk name consists of three parts, each separated by an @ sign. The three parts are: Item Name, Group Name, and Organization Name.

STRESS TEST:

Refers to a data test pattern used to determine a circuit's ability to accurately carry digital signals with a minimum ones (mark) density."

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.

STS:

1) Serving Translation Scheme.

2) Synchronous Transport Signal.

3) An ASCII Control Character used to identify the start of text portion of a message. See STX

STS-1:

Synchronous Transport Signal level 1: Basic building block signal of SONET, operating at 51.84 Mbps. Faster SONET rates are defined as STS-n, where n is a multiple of 51.84 Mbps.

STS-3c:

Synchronous Transport Signal level 3, concatenated: SONET format that specifies the frame structure for 155.52-Mbps lines used to carry ATM cells.

ST-II:

See Stream Protocol 2

STUCK BEACON:

A condition in token-passing networks where a station is locked up and is sending continuous beacon frames

STUN:

Serial Tunnel: Router feature allowing two SDLC or HDLC compliant devices to connect to one another through an arbitrary multi-protocol topology rather than through a direct serial link.

STUNT BOX:

A device used to control the non-printing protocol functions (handshaking) of a teletypewriter terminal.

STX (STS):

Start of Text – A control character(s) that indicates the end of Header (Priority/Address) section and the beginning of the text portion of the message. In the ASCII code set the STS Control Character is used for this purpose.

STYLE SHEET:

See Cascading Style Sheets

SU:

1) Signaling Unit: Another name for the Trans-Path product.

2) Service Unit or Signaling Unit

SUB-AREA:

Portion of an SNA network that consists of a sub-area node and any attached links and peripheral nodes

SUB AREA NETWORK:

Refers to the original hierarchical approach used in the construction of IBM SNA backbone networks, where the structure of a Sub-Area Network is predefined.  The relationship between the components of the network and the links is incorporated into the software in the host system. The network can, however, be modified without having to re-build the definition of the entire network.

SUBCHANNELS:

The subdivision of a communications channel into narrower specific bandwidth sub-channels, with each sub-channel separated to avoid interference.

SUBKEY:

A key within a key: In the registry structure, sub-keys are subordinate to sub-trees and keys. Keys and sub-keys are similar to the section header in .ini files; however, sub-keys can carry out functions.

SUBNET:

The portion of a network partitioned by a router

SUBNET ADDRESS:

An extension of an Internet protocol (IP) address: Allows a network to be autonomous and still be a subsection of a larger user network.

SUBNET MASK:

A 32-bit value that enables the recipient of IP (Internet Protocol) packets to distinguish between the network ID and host ID portions of the IP address. Typically, subnet masks use the format 255.x.x.x.

SUB-NETWORK:

1) In IP networks, a network sharing a particular subnet address. Sub-networks are networks arbitrarily segmented by a network administrator in order to provide a multilevel, hierarchical routing structure while shielding the sub-network from the addressing complexity of attached networks; sometimes called a subnet.

2) In OSI networks, a collection of ES(s) and IS(s) under the control of a single administrative domain and using a single network access protocol.

SUB-NETWORK POINT OF ATTACHMENT (SNPA):

Refers to the address used by the Sub-network to route data units through the network and deliver the data units to the addressed DTE.

SUB-RATE:

A term used in the DDS (Data-phone Digital Service) environment to describe a transmission speed that is either 2400 bps, 4800 bps or 9600 bps

 SUBRATE DIGITAL MULTIPLEXER:

A unit located in a hub office that combines several low bps data streams into a single 64-kbps (DS0B) signal.

SUBRATE FRAM SLIP:

Refers to a slip that occurs when a Sub-rate framing bit is lost or duplicated, but the integrity of the framing pattern maintained.

SUBRATE FRAMING ERRORS:

Reception of incorrect framing bits from the DS0B signal under test.

SUBSCRIBER LINE:

The telephone line that connects a local telephone company to the subscriber's telephone system or medium and it may be used for data.

SUBSCRIBER LINE CARRIER CIRCUIT (SLCC):A system design feature that allows one pair of copper wires to carry multiple conversations: SLCC is used between central offices and areas that have outgrown the original cable serving the area.

SUBSCRIBER LOOP:

A circuit, usually a pair of wires that links a central office (CO) to a demarcation point on a customer's property. See Subscriber Line.

SUBSCRIBER NETWORK INTERFACE (SNI):

User-to-Network Interface (UNI) for SMDS; based on the Institute of Electrical and Electronic Engineers (IEEE) 802.6 access protocol.

SUBSYSTEM:

A secondary system that is able to work independently or asynchronously with the primary system.

SUBVOICE GRADE CHANNEL:

A channel of narrow bandwidth used for low speed data communications and Teletype; not a voice grade channel

SUPER FRAME (SF):

A data transmission format comprised of 12 frames of 192 bits each. A single 193rd bit is used for link control and error checking.

SUPER HIGH FREQUENCY (SHF):

Frequencies between 3 GHz to 30 GHz

SUPERGROUP (SG):

Normally, 60 voice grade lines processed as a unit in a carrier system, occupying adjacent individual frequency bands in the spectrum, for simultaneous modulation or demodulation.

SUPERMASTERGROUP (SMG):

A facility with sufficient bandwidth to allow 600 voice grade lines (channels) to be processed as a unit, example: a microwave system.

SUPPRESSED CARRIER TRANSMISSION:

A method used in data communication where the carrier frequency is suppressed (removed) in order to transmit on one or both of the sidebands.

SURF / SURFING:

To explore the internet without any specific purpose other than to see what is out there.

SVC:

Switched Virtual Circuit: A virtual circuit that is dynamically established on demand and is torn down when transmission is complete: SVC(s) are used in situations where data transmission is sporadic; called a switched virtual connection in ATM terminology.

See Switched Virtual Call, Switched Virtual Circuit or Switched Virtual Connection

SVG:

Scalable Vector Graphics: A proposed format by the World Wide Web Consortium (W3C) for web page graphics based on vectors, rather than bitmap formats. These files will normally be smaller than bitmap files and will scale to different size screens.

SWIFT:

See Society for Worldwide Inter-bank Financial Telecommunications (SWIFT)

SWITCH:

1) A controlled device that can connect two circuits together.

2) A device, similar to a DMS-250 or a Private Branch Exchange (PBX) that responds to originator signals and dynamically routes, and places or forwards a call, or performs other connection functions.

3) A packet / message switching system: In a packet-switched environment, the ‘switch’ is installed on the packet networks backbone, at one of the nodes and serves to direct packets, also known as a switching processor.

5) Network device that filters, forwards, and floods frames based on the destination address of each frame. The switch operates at the data link layer of the OSI model.

6) General term applied to an electronic or mechanical device that allows a connection to be established as necessary and terminated when there is no longer a session to support.

7) In telephony, a general term for any device, such as a PBX, that connects individual phones to phone lines.

SWITCH HOOK:

Plunger or switch where a telephone handset sits when the telephone is on hook (hung up). When the handset is lifted, the switch hook goes up and the telephone is off hook. Also called hook switch.

SWITCH OVER:

The manual or automatic activation of an alternate (back-up) system when an equipment failure occurs, such as a file unit, a communications line, or a computer,

SWITCH SITE:

A location that supports dynamic Circuit (path) routing, circuit switching, or message routing.

SWITCH TYPE:

The type of interface to which the ISDN device is being attached: Switch type is also called switch.

SWITCHED 56Kbps:

Dial up Digital Data Service (DDS).

SWITCHED ACCESS REMOTE TEST SYSTEM (SARTS):

AT&T operations support system: Permits remote testing of end offices through the public data packet network.

SWITCHED CIRCUIT:

A communication path (circuit): Allows the call originator to specify a desired destination (connection) for each call.

SWITCHED LINE:

Refers to a communications link (connection) where the physical path may vary with each use, for example, the dial-up telephone network.

SWITCHED MAINTENANCE ACCESS SYSTEM (SMAS):

An AT&T system that provides remote circuit test capability for intermediate and end offices: It allows a tester to access and test a circuit without assistance from the distant office.

SWITCHED MATRIX:

A term used in the LAN (Local Area Network) environment to describe the electronic switching counterpart to a crossbar switch.

SWITCHED MESSAGE NETWORK:

A network service: Telex or TWX, providing interconnection of message devices, such as teletypewriters.

SWITCHED MULTI-MEGABIT DATA SERVICES (SMDS): See SMDS

SWITCHED NETWORK:

The telecommunication components, including lines, central offices and related switching equipment, trunk facilities and other integrated network components designed to provide voice/ data communication.

SWITCHED NETWORK BACKUP:

The function of using a public switched line as an alternate line to a failed leased facility.

SWITCHED PUBLIC NETWORK: See Switched Network

SWITCHED SERVICE NETWORK (SSN):

A private-line Network: Uses polling scan or common control switching.

SWITCHED VIRTUAL CALL (SVC):

A call or connection established only for the duration of one session.

SWITCHED VIRTUAL CIRCUIT (SVC):

A logical connection across a packet switched network.  A SVC is established on an as-needed basis and can provide a connection to any other switched user in the network.

SWITCHED VIRTUAL CONNECTION (SVC):

A virtual connection established for a short period-of-time, using signaling techniques to generate, capture, and accommodate the connection and provisioning request.

SWITCHING:

The operations involved in interconnecting circuits in order to establish communications or another term for a switching center

SWITCHING CENTER (SC):

1) A location at which telephone traffic, either local or toll, is switched or connected from one circuit or line to another. A SC is usually a part of a Central Office (CO).

2) Data Computers that provide the digital communications functions of store and forward, routing, priority processing, code and speed conversion, and transmission, in addition to other functions.

SWITCHING ENTITY:

Basically any switching device: See Switching or Switching Center

SWITCHING HUB:

A central network device (multiport hub) that forwards packets to specific ports rather than broadcasting every packet to every port: This allows the connections between ports to utilize the full bandwidth available.

SWITCHING MATRIX:

Refers to a space division exchange; a group of cross points that operates as a traffic switch.

SWITCHING OFFICE (SO):

A telephone company office: Contains a communications routing switch.

SWITCHING PROCESSOR:

See Switching or Switching Center

SWITCHING UNIT:

See Switching Entity

SYMBOL:

1) Flag(s), Control Character(s), Protocol character(s), etc.

2) The smallest signaling element used by the Media Access Control (MAC) sub layer.  The symbol set consists of 16 data symbols and 16 non-data symbols.  Each symbol corresponds to a specific sequence of code bits to be transmitted by the physical layer.

SYMBOLIC NAME:

A method of identification for computer devices such as terminals, computers or Front End Processor (FEP) ports, etc.

SYMMETIC ENCRYPTION:

An encryption algorithm that requires the same secret key to be used for both encryption and decryption: Because of its speed, symmetric encryption is typically used when a message sender needs to encrypt large amounts of data. Symmetric encryption is also called secret key encryption.

SYMMETRIC DSL (SDSL):

Like HDSL, receives and sends data at the same speed. SDSL also requires a separate line from your phone, it uses only a single line instead of the two used by HDSL. See SDSL

SYN / SYNC / SYNCHRONOUS IDLE:

1) A control character used to maintain bit or character synchronization during the transmission of data in a synchronous transmission mode (Mode 1).

2) A control character used to maintain timing or synchronize timing in a TDM (Time Division Multiplexing) environment.

3) By sequencing two SYN characters in succession, synchronization is maintained following each line turnaround. See Synchronous

SYNC CHARACTER (FLAG):

A character transmitted to establish character synchronization in synchronous communication and periodically inserted in the data stream to maintain synchronization. See synchronous.

SYNCHRONIZATION:

See Synchronous

SYNCHRONIZATION LOST SECONDS:

A term used for the number of seconds of lost DS1 synchronization.

SYNCHRONIZE:

To reconcile the differences between files stored on one computer and versions of the same files on another computer. Once the differences are determined, both sets of files are updated. Synchronize can also refer to a synchronizing process between two devices for communication purposes.

SYNCHRONOUS:

Events occurring at the same time or a continuous flow of data without start/stop bits: The bit sampling rate at the receiving station must be precisely the same as the bit transmission rate at the transmitting station, and the point at which one character ends and the next character begins must be recognized. This synchronization is accomplished and maintained through the periodic transmission of a sync character or sync bit.

SYNCHRONOUS COMMUNICATIONS:

See Synchronous

SYNCHRONOUS DATA LINK CONTROL (SDLC):

IBM communications protocol for data transfer between stations in a point-to-point, multipoint, or loop arrangement, using synchronous data transmission techniques.

SYNCHRONOUS DATA SWITCHING:

A facility for transmitting synchronous data using a synchronous data adapter and the transmitter and receiver function in a synchronized bit timing mode.

SYNCHRONOUS DIGITAL HIERARCHY (SDH):

The Consultative Committee on International Telephone and Telegraph (CCITT) standard for the Synchronous Optical Network (SONET) functions.

SYNCHRONOUS ERROR MEASUREMENT:

A measurement taken for a second in time, and after an error occurs measures any further errors in that synchronous second. After one second from the original event, the second is marked as containing a synchronous error, and a new measurement begins.

SYNCHRONOUS MODEM:

A type of MODEM designed to provide a clocking signal to perform bit synchronization.

SYNCHRONOUS NETWORK:

A network in which all transmissions are synchronized with a shared clock: See Synchronous

SYNCHRONOUS OPTICAL NETWORK (SONET):

An American National Standards Institute (ANSI) specified standard, developed by the Exchange Carriers Standards Association (ECSA), for optical fiber transmission on the public network. The transmission speed is 52Mbps to 13.22Gbps. Available for Integrated Services Digital Network (ISDN) services, including Asynchronous Transfer Mode (ATM).

SYNCHRONOUS SATELLITE ORBIT:

See Satellite Communications

SYNCHRONOUS TRANSPORT:

See Synchronous

SYNCHRONOUS TRANSPORT SIGNAL (STS):

The signal carried over a SONET OC unit of capacity. STS-1 corresponds to OC-1 at 51.84 Mbps; STS-24 corresponds to OC-24, etc.

SYNDROME:

A code transmitted along with data to enable correction of transmission-induced errors in the received data; see Forward Error Correction or Checksum.

SYSOP:

Systems Operator: Usually the person who is in charge of a BBS (Bulletin Board System) or other systems; a person responsible for the physical operations of a computer system or network resource.

SYSTEM:

1) An organization of equipment, personnel, and facilities, designed to perform a set of functions governed by a set of procedures.

2) The equipment connected to a fiber pair to enable it to transmit, regenerate, and receive signals. For example, a cable with three pairs of fiber in service would be said to have three systems in place. A system is usually designated by its speed in Mbps or Gbps.

SYSTEM ACCESS CONTROL LIST (SACL):

The part of an objects security descriptor that specifies which events are to be audited per user or group. Examples of auditing events: file access, logon attempts, and system shutdowns.

SYSTEM BOOT RECORD:

See: Boot Record

SYSTEM CONTROLLER NODE:

The location of the REACT system controller equipment and the system console: The system console node provides the means to perform maintenance of the REACT software. Maintenance tasks include installing, updating, modifying, and backing up the REACT software and circuit databases.

SYSTEM DISK:

A disk that contains the MS-DOS system files necessary to start MS-DOS. System Disk could also be a manufacturer version for configuration purposes.

SYSTEM INTEGRATOR:

A network vendor: Offers design, connection, implementation and management services.

SYSTEM NETWORK ARCHITECTURE DLU:

Dependent LU: LU that depends on the SSCP to provide services for establishing sessions with other LU(s)

SYSTEM PARTITION:

The partition that contains the hardware-specific files needed to load Windows (example: Ntldr, Osloader, Boot.ini, Ntdetect.com). The system partition can be, but does not have to be, the same as the boot partition.

SYSTEM QUEUE:

For Message Queuing, a queue that stores various types of administrative or text messages: Message Queuing uses up to five system queues, all of which are private queues. System queues cannot be deleted.

SYSTEM RELIABILITY:

Usually a statement of equipment quality and a probability failure percentage level for the equipment performance under normal and abnormal operational conditions.

SYSTEM RESTORE:

A tool that tracks changes to the computer and creates a restore point when it detects the beginning of a change. An individual can use the System Restore Wizard to select a restore point, which will restore the computer to an earlier state following an abnormal condition.

SYSTEM SECURITY:

Example: AUTODIN security was on two levels, internal and external. Internal security was guarded primarily by the fact that the switching centers did not have any form of conventional operating system, nor were they ever connected to a public network, like the Internet. This made ‘hacking’ or ‘penetration’ from outside totally impossible. In addition, on-line encryption devices encrypted all circuits extending outside the secure area. One security feature of AUTODIN was that all lines transmitted all the time, sending ‘SYNC’ characters when there was no data on the line. This meant that the encryption equipment always had something to encrypt. Later encryption devices also transmitted ‘garbage’ even when the switching Center itself failed or the device was being reset at the specified interval.

SYSTEM SELECTION SWITCH:

A feature of some cellular phones that allows switching between 'A' and 'B' cellular carriers. This feature is often used during roaming functions.

SYSTEM SERVICES CONTROL POINT (SSCP):

A function of a network based on the IBM System Network Architecture that provides overall network control. The SSCP is usually a mainframe (computer).

SYSTEM VOLUME:

The volume that contains the hardware-specific files that are needed to load Windows on x86-based computers with BIOS (Basic Input/Output System): The system volume can be, but does not have to be, the same volume as the boot volume.

SYSTEMS MANAGEMENT CENTER (SMC):

Refer to SMC.

SYSTEMS NETWORK ARCHITECTURE (SNA):

The proprietary architecture developed by IBM for mini and mainframe computers. SNA can be viewed as three distinct entities: a specification, a plan for constructing a network, and a set of products. SNA provides a structure that allows users to establish and manage their networks and, in response to new requirements and technologies, to change or expand them.

SYSTEMROOT:

The path and folder name where the Windows system files are located. Typically, this is C:\Windows, although a user can designate a different drive or folder when Windows is installed. An individual can use the value %systemroot% to replace the actual location of the folder that contains the Window system files. Example: To identify the systemroot folder, click Start, click Run, type %systemroot%, and then click OK.