S

S!P

Supr!se Productions

S-REGISTERS

RAM in your modem that is used to store the current configuration profile (operating characteristics) of your modem.

S-VIDEO

Type of video signal used in Hi8, S-VHS and some laserdisc formats. It transmits luminance and color portions separately, using multiple wires. S-Video avoids composite video encoding, such as NTSC, and the resulting loss of picture quality. Also known as Y-C Video.

S/T INTERFACE

A 4-wire ISDN circuit. The more common ISDN circuit is the U interface.

SA BUTTON

See System Access Button.

SAA

See Systems Application Architecture.

SABME

Set Asynchronous Balanced Mode Extended

SAG

Short term decreases in voltage levels. This is the most common power problem, accounting for 87% of all power disturbances according to a study by Bell Labs. Also called a brownout.

SAG

SQL Access Group

SAI

See Serial adapter interface.

SALAMI VIRUS

A program that slices away tiny pieces of data. For example, it can change the decimal point position in a spreadsheet or shave pennies from an account. These errors are likely to go undetected; you might attribute them to a computer glitch or error-rounding in arithmetic calculations.

SAMPLING

The first step in the process of converting an analog signal into a digital representation. This is accomplished by measuring the value of the analog signal at regular intervals called samples. These values are then encoded to provide a digital representation of the analog signal.

SANS SERIF FONTS

Any typeface without Serifs. Frequently used in electronic presentations because they project well even at lower resolutions.

SAP

See Service Access Point. See Service Advertising Protocol.

SAT-EXPAK

Satnet and Backroom EXPAK

SAT-MON

SATNET Monitoring

SATELLITE COMMUNICATION

Often used for global communications, satellite offers fast throughput, but suffers from comparatively long propagation times due to uplink and downlink delays. Borders on being very expensive.

SATURATED COLORS

Strong, bright colors (particularly reds and oranges) which do not reproduce well on video; they tend to saturate the screen with color or bleed around the edges, producing a garish, unclear image.

SATURATION

The amount of pigment. See HSB Model.

SBGA (T)

See Super Ball Grid Array.

SCADA

Supervisory Control and Data Acquisition

SCALABILITY

The ability of a computing element such as a process, processor, or structure to grow seamlessly. The ability to vary the information content of a program by changing the amount of data that is stored, transmitted or displayed. In a video image, this translates into creating larger or smaller windows of video on screens (shrinking effect).

SCALABLE VIDEO

With respect to Indeo™ video technology, it is a playback format that can determine the playback capabilities of the computer on which it is playing. Using this information, it allows video playback to take advantage of high-performance computer capabilities while retaining the ability to play on a lower performance computer.

SCALING

Process of uniformly changing the size of characters or graphics.

SCANNING

Dialing a large number of telephone numbers in the hope of finding interesting carriers (computers) or tones.

SCB

See System Command Block.

SCC

See Serial Communications Controller.

SCS

System Communication Services

SCSI

See Small Computer System Interface.

SCSI-2

See Small Computer System Interface-2.

SDF

Standard Delay Format (Logic simulation acronym)

SDI

See Single Document Interface.

SDK

The Windows Software Development Kit.

SDLC

See Synchronous Data Link Control. See Synchronous Date Link Control.

SDMA

Spatial Division Multiple Access

SDMA CHANNEL

See Serial Direct Memory Access.

SE

IC part number prefix indicating Signetics Corp.

SECAM

"SEquential Couleur A Memoire" (sequential color with memory). Video format having 625 lines of resolution at 25 frames per second used in France, Eastern Europe, F.S.U, and other countries.

SECONDARY STATION

In an SDLC configuration, a station that is governed by a primary station. When using the SNA Gateway, the workstations are secondary stations.

SECURE LAN DISTANCE WORKSTATION

A LAN Distance workstation on which LAN Distance security is enabled. LAN Distance security helps to prevent unauthorized users from accessing the LAN Distance workstation. See also security policy.

SECURITY ADMINISTRATOR

See LAN Distance security administrator.

SECURITY POLICY

The set of rules that can be customized to enable the security requirements of a particular user environment. Examples of configurable items include maximum allowed logon attempts and passphrase durations.

SEGMENT

An electrically isolated cabling section. LAN segments are connected with repeaters. A single Ethernet LAN can have as many as 1024 segments, but no more than four repeaters can be used in series. The term 'segment' is sometimes used by Novell and industry writers to describe a LAN. See Segmentation and Repeater.

SEGMENTATION

A term used to describe separation of a LAN into multiple LANs using a bridge or a router. The term often is used in the industry in this manner. This term is used more accurately to mean splitting a single LAN segment into multiple LAN segments for the purpose of isolating electrical problems on a cable segment to provide improved cabling reliability. This is the primary function of a wiring concentrator. When reading industry literature, determine whether this term is meant to convey the first meaning or second meaning.

SELECTOR

The identifier used by an OSI entity to distinguish among multiple SAPs at which it provides services to the layer above. See port.

SELF CLOCKING

See Manchester Encoding

SELF-MODIFYING PROGRAM

Software that deliberately changes its own program file, often to protect against viruses or illegal copying, and is therefore difficult to validate in conventional ways.

SEMANTIC KNOWLEDGE

Taught through concepts, relationships, and analogies. Semantic knowledge is task based and, once learned, is not easily forgotten. It is often conveyed through pictures. An example is how certain GUIs use a picture of a file cabinet for their file managers. See GUI.

SEP

Sequential Exchange Protocol

SEQUENCED PACKET EXCHANGE

(SPX) A NetWare connection-oriented protocol and packet format that provides transport layer functions for NetWare communications. SPX calculates a checksum of each IPX packet at the sending end, and again at the receiving end where the checksum is compared for accuracy. If the IPX packet is received with no checksum error, an SPX positive acknowledgment is sent. If a checksum error is detected, a negative acknowledgment is sent. If no acknowledgment is sent, IPX resends the packet again. SPX fulfills the standard functions of OSI layer 3, the transport layer. By default, SPX is used only by NetWare's Print Server and Remote Console utilities. Unless an application specifically calls for the use of SPX through an API, it is not used. Instead, NCP acknowledges the receipt of NCP packets without calculating a checksum or verifying accuracy. SPX uses the Internetwork Packet Exchange (IPX) protocol to deliver the messages.

SEQUENTIAL COLOR WITH MEMORY

See SECAM.

SEQUENTIAL COULEUR A MEMOIRE

See SECAM.

SERIAL ADAPTER INTERFACE

A device for the dual Ethernet interface card that interfaces the 82596CA coprocessor to the 10BASE5 AUI connector.

SERIAL COMMUNICATIONS CONTROLLER

A full-duplex controller that supports two channels and high-level/synchronous data link control (HDLC/SDLC), universal asynchronous receiver transmitter (UART), binary synchronous communication (BISYNC), and synchronous/asynchronous digital data communications message protocol (DDCMP).

SERIAL DIRECT MEMORY ACCESS CHANNEL

(SDMA) A channel that manages the flow of data for the receive or transmit operations of an SCC for the serial interface card. Two SDMA channels are associated with each SCC.

SERIAL LINE IP

(SLIP) A simple scheme designed to do transmission of IP datagrams over serial lines. SLIP provides a simple framing scheme for transmitting IP packets over modems. Its main shortcoming is that it only supports IP protocol. It also provides no error detection scheme. Added to these deficencies is the fact that any parameter change within the SLIP configuration requires the SLIP driver to be recompiled. Finally, due to the numerous deficencies of SLIP, vendors generally come up with proprietary enhancements, thus making interoperability between different versions of SLIP a dicey proposition.

SERIAL PORT

The circuits and connector that let your computer communicate with serial devices such as printers, modems, plotters, mice, and custom laboratory equipment. Also called a COM or Communications Port.

SERIF FONTS

Any typeface tha has fine cross strokes at the top and bottom. Serifs are designed to draw the eye from one character to the next across a line of text. On screen the fine lines sometimes run together, making the text hard to read.

SERV SERIES TECHNOLOGY

Uses a powerful microcontroller that enables one workstation to control multiple CPUs, as well as multiple monitors, keyboards, and mice. By typing simple commands on the controlling keyboard, multiple Serv Series products provide total control of up to 256 connected CPUs. Useful if every controlled CPU doesn't need a keyboard, monitor, and mouse.

SERVER

A node that provides services to other nodes on the network. A server can be a print server and provide print spooling and printer access for other nodes on the network. On a local area network, the computer that runs the administrative software to control access to the network. The server makes network resources available to the workstations. See also File Server and Print Server. A computer (or application) that is primarily used to provide shared resources. Provides services to other applications or computers.

SERVER APPLICATION

1. On a network, a process or program that runs on a server, typically as a network resource. For example, a communications program that organizes and allocates network communications resources. More sophisticated server programs, known as client/server applications, run interactively with an application resident on network nodes. See also Client/Server Computing. 2. In a compound document, any Windows application that allows you to edit an object when Windows informs it that you selected the object in an OLE client application.

SERVICE ACCESS POINT

(SAP) As used by IEEE: The SAP is the interface between two layers of protocol. Each layer of protocol must communicate with the layer above it and beneath it. SAPs are also connection points between parallel layers of protocol in an internetwork. Each bridge is either a Destination SAP (DSAP) or Source SAP (SSAP) for bridged LAN communications.

SERVICE ADVERTISING PROTOCOL

(SAP) (As used by Novell) A NetWare proprietary protocol and packet format that provides notification between servers of their existence, service type and network address location. Each server broadcasts SAP packets to inform all file servers and routers of its existence. Each SAP packet can contain up to seven server names, service type, and routing information. SAP packets are broadcast every 60 seconds. When a SAP packet is received by a file server, an object is created in its bindery, which makes the server available for user requests. A logical protocol identifier that allows a system to route data between a remote device and the appropriate communications support. For example, the SAP value for NetBIOS is hex FO.

SERVICE ORDER NUMBER

The number used by the Local Exchange Carrier (LEC) to track your ISDN order.

SERVICE PROFILE IDENTIFIER

(SPID) This number is issued by the telephone company and is used to identify your ISDN line to the Central Office switch.

SESSION

A logical connection between two nodes in a network that allows them to exchange messages.

SESSION LAYER

The fifth layer of the ISO OSI Model, providing administrative jobs for the network, such as security. The OSI layer that provides means for dialogue control between end systems.

SESSION SUPPORT UTILITY

(SSU) A DEC-proprietary protocol that allows multiple sessions to run simultaneously over a single serial cable. SSU is used to allow terminals to provide two session "windows" that can display session output simultaneously.

SESSIONID

(For a Telephony Services Driver Interface) The sessionID is used to properly route messages to the appropriate client application. The PBX Driver will obtain this ID when it receives a message corresponding to an acsOpenStream() request from a client application, and this sessionID must be included in the Driver Control block for each message passed on the stream. The driver must populate this field of the DC with the appropriate sessionID of the client whenever a confirmation report or unsolicited event for a client is sent via the tdiSendToTserver() routine.

SFTP

Simple File Transfer Protocol

SGMP

See Simple Gateway Monitoring Protocol

SHADOW ROM

A process used in many 386 machines to map ROM BIOS activities into faster 32-bit RAM memory. Shadow memory must be loaded with BIOS routines each time the computer boots.

SHADOWING

The act of one variable being accessed in preference to a second variable. For example, when two variables have the same name but different scopes, the more local variable always shadows the less local variable.

SHARED RESOURCE

A printer, file, or serial computer communications device made available through the LAN to multiple computers not physically attached to the resource.

SHAREWARE

Shareware is a distribution method, NOT a type of software. Copyrighted software which is distributed by authors through bulletin boards, on-line services, disk vendors, and copies passed among friends. It is commercial software which you are allowed to use and evaluate before paying for it. The primary difference between shareware and retail software is that with shareware you know if it's good or bad BEFORE you pay for it.

SHELL

The workstation software that connects a DOS workstation with the file server and provides a DOS interface with the server operating system. The NETX.COM software (or its equivalent) provides this function. NetWare 4.0 now uses a NETX.VLM (Virtual Loading Module) and terms this same functionality a DOS requester. See OS/2 Requester.

SHOULDER SURFER

Person who steals PINs for credic cards, etc. by actually looking over someone's shoulder.

SHUTTERING

Does not necessarily refer to a mechanical device; images electronically "shuttered" by collecting or scanning out portion of charge accumulated over one field time.

SHUTTLE

The LAN Distance feature that allows a workstation to switch between a standalone LAN Distance Remote workstation and a Non-LAN Distance LAN-attached workstation. It is associated with physically moving the workstation on and off the LAN.

SIB

See System Integration Block.

SIC

Standard Industrial Classification

SIF

See System Interface.

SIGNATURE

A short piece of text appended to a posting or electronic mail message typically describing the author and his/her interests and affiliation. It's considered bad form for the signature to be more than four lines. Also called Sig.

SIGNIFICANT DATA

A digit that contributes to the precision of a value. The number of significant digits begins with the one contributing the most value (called the most significant digit) and ends with the digit contributing the least value (called the least significant digit).

SIMM

See Single In-line Memory Module.

SIMPLE GATEWAY MANAGEMENT PROTOCOL

(SGMP) Simple Gateway Management Protocol. The predecessor to SNMP. See SNMP.

SIMPLE MAIL TRANSFER PROTOCOL

(SMTP) The standard protocol for sending and receiving electronic mail on the Internet. SMTP provides specifications for mail system interaction and control message formats. SMTP is defined in RFCRFC-821.

SIMPLE NETWORK MANAGEMENT PROTOCOL

SNMP is the most popular network management protocol in the TCP/IP protocol suite. SNMP lets TCP/IP sites exchange information about the configuration and status of a node's TCP/IP protocol stack.

SIMPLEX FIBER OPTIC CABLE

Tight buffered cable with 1 fiber

SINGCARS

Single Channel Airborne Radio System

SINGLE DOCUMENT INTERFACE

An application that supports only a single document window.

SINGLE IN-LINE MEMORY MODULE

(SIMM) A small memory module built with all pins in a single line; to be plugged into a mother board.

SINGLE-ENDED CIRCUIT

Unbalanced, as when one side is grounded.

SIP

SMDS Interface Protocol

SITD

Still in the dark.

SKEWING

Refers to time-delay offset between any two signals in relation to each other.

SL

National Semiconductor part prefix that indicates the device is in device family: Special Linear

SLIP

See Serial Line IP.

SLOPE

The difference between path attenuation at the highest frequency and at the lowest frequency in a cable system. Alco called Spectrum Tilt.

SM

Standby Monitor

SMA CONNECTOR

Fiber optic connctor similar to an ST connector, but screws on to equipment. See ST Connector.

SMALL COMPUTER SYSTEM INTERFACE-2

(SCSI-2) An ANSI standard that improves on SCSI-1 standards for disk and other device interfaces. SCSI-2 bandwidth is 10 Mbytes/sec, whereas SCSI-1 is 5 Mbytes/sec. SCSI-2 also permits command-tag queuing, which enables up to 256 requests to be queued without waiting for completion of the first request. Another feature of SCSI-2 is the bus's capability to communicate with more than one type of device at the same time, where a single SCSI-1 host adapter could only support one type of device (that is, a disk drive or CD-ROM) to communicate on the bus. See SCSI.

SMALL COMPUTER SYSTEM INTERFACE

(SCSI) An ANSI standard bus design. SCSI host adapters are used to adapt an ISA, EISA, or MCA bus to a SCSI bus so that SCSI devices (such as disk drives) can be interfaced. A SCSI bus can accommodate up to eight devices, however the bus adapter is labeled as one device, thereby enabling only seven usable devices to be interfaced on each SCSI adapter. SCSI devices are intelligent devices. SCSI disk drives have embedded controllers and are interfaced to a SCSI bus adapter. A SCSI interface card is therefore a 'bus adapter,' not a 'controller.' See SCSI-2.

SMART VIDEO RECORDER

Intel's PC Video single-step compression, real-time video capture card that uses Indeo™ technology and an Intel I750® processor.

SMB

Server Message Block

SMDR

Station Message Detail Reporting

SMDS

See Switched Multimegabit Data Service

SMFA

Specific Management Functional Area

SMI

See Structure of Management Information.

SMP

See Symmetrical Multiple Processing

SMPS

Switch Mode Power Supply

SMPTE

The Society of Motion Picture and Television Engineers.

SMPTE TIME CODE

An 80-bit standardized edit time code adopted by SMPTE, the Society of Motion Picture and Television Engineers. See also Time Code.

SMR

Specialized Mobile Radio

SMT

See Station Management Task.

SMTP

See Simple Mail Transfer Protocol.

SNA

See Systems Network Architecture.

SNA MODEL

The seven-layer model for network operations that is part of the Systems Network Architecture. Compare OSI model.

SNADS

Systems Network Architecture Distribution Services

SNAP

Sub-Network Access Protocol

SNI

Subscriber Network Interface

SNMP

See Simple Network Management Protocol.

SNPA

Subnetwork Point of Attachment. An OSI reference to the access point to a subnetwork topology.

SOCKET

An abstraction that allows application programs to access communication protocols by serving as an endpoint of a communication path within/between operating systems.

SOCKET ADDRESS

An extension to the ultimate source and destination in an IPX combined address. The socket identifies the type of request and therefore where the request should be forwarded in a server operating system. Separate socket addresses are assigned to NCP, routing, printing, and other types of requests.

SOCKET SERVICES

The software interface that manipulates the PC Cards, sockets, and adapters. See also PC Cards, sockets, adapters.

SOFTWARE

Starts out full of bugs, but the older it gets, more and more of them get fixed. See Hardware.

SOFTWARE FLOW CONTROL

See XON/XOFF.

SOFTWARE WRITERS

Programmers who write programs at home for commercial release. They wear T-shirts and John Lennon glasses and have long hair and beer bellies (men and women alike). They spend all their money on beer and floppy disks. They love their jobs. See Programmers.

SOH

Start of Header

SOLDER BALLS

BGA contact point or lead. Typically 30-mil preformed tin/lead/silver solder balls reflowed onto the BGA bottom side solder pads. See BGA.

SON

See Service Order Number.

SONET

See Synchronous Optical Network.

SOURCE CODE

Programs in an uncompile or unassembled form. A set of programming language instructions that must be translated to machine instructions before the program can run.

SOURCE SERVICE ACCESS POINT

(SSAP) The entry point bridge in an LLC-bridge that uses 802.2 protocol. See Bridges, DSAP.

SOURCE-ROUTING BRIDGE/PROTOCOL

A type of LLC bridge and protocol generally used with Token Rings that use IEEE 802.2 source-routing protocol and frame header fields to identify the path a frame should take through a system of bridges. The protocol is termed 'source-routing' because the source of the communications (the workstation) determines the path to be taken by a discovery process. The protocol and frame header fields identify SSAPs and DSAPs (entry and exit points) in the series of bridges. See Bridges, DSAP, and SSAP.

SPAG

See Standards Promotion and Application Group.

SPAM

A Usenet posting, often commercial in nature, that has been loaded onto lots of inappropriate newsgroups, one at a time.

SPANNED VOLUME

A volume that spans across more than one logical partition, and therefore more than one disk drive.

SPANNING TREE

An algorithm used by bridges to create a local topology that connects all network segments, and ensures that only one path exists between any two stations.

SPANNING-TREE BRIDGE/PROTOCOL

A type of LLC bridge and protocol, generally used with Ethernet, that provides service for more complex configurations of multiple bridges using one of IEEE's 802.2 spanning-tree protocols. When multiple bridges are employed, the possibility of frame traffic entering infinite loops exists, and complications develop, such as determining the most efficient path. This protocol designates bridges as SSAPs and DSAPs (entry and exit points) in the series of bridges. See Bridges, DSAP, and SSAP.

SPE

Synchronous Payload Envelope. See Synchronous Optical Network.

SPECTRUM TILT

See Slope.

SPGA

System-Programmable Gate Array

SPID

See Service Profile IDentifier.

SPIKE

An instantaneous, dramatic increase in voltage. Akin to the force of a tidal wave, a spike can enter electronic equipment through AC, network serial or phone lines and damage or completely destroy components. Also called an impulse.

SPOILER

Material people might not want to read by accident but is not really offensive, such as giving away the ending of a movie.

SPOOF

A program that tricks a user into giving away privileges. A spoof is usually implemented by a Trojan horse. Prime targets for spoof programs are the network log-in or authentication mechanism. The spoof goes through the entire log-in sequence only to steal the user's password. It is possible to play back the log-in sequence to the NetWare server from another workstation and obtain unauthorized access. NetWare uses some undocumented methods to protect itself from playback attacks. See Cryptology.

SPOOLER

A program that intercepts the data going to a device driver and writes it to the disk. The data is later printed or plotted when the required device is available. A spooler prevents the intermixing of output from different sources.

SPP

Sequenced Packet Protocol

SPX

See Sequenced Packet Exchange.

SQE

Ethernet-defined signal quality test function, frequently called "heartbeat".

SQL

See Structured Query Language

SQLSRV

SQL Service

SQUELCH

Voice-controlled audio gating

SR

Source Routing

SRAM

See Static Random Access Memory.

SRF

Specifically Routed Frame

SRI

Stanford Research Institute

SRT

Source Routing Transparent

SS

Special Service

SSAP

See Source Service Access Point.

SSB

See System Status Block.

SSSI

Solaris Server Suite Installation

SSU

See Session Support Utility.

ST

Stream Protocol

ST CONNECTOR

A metal connector with a "straight tip" (ST) to join the ends of optical fibers so their fine light-conducting cores meet exactly, ensuring precise optical alignment. Each end carries the same type of single-element plug and cylindrical sleeve. These attach to either side of a common housing, called a lightwave coupling, that holds the cables together. Closes like a BNC connector - push the cable on and turn to secure.

STANDALONE WORKSTATION

A workstation that runs application programs independently of another system, and is not LAN-attached.

STANDARD ETHERNET CABLE

Half-inch coax for Ethernet networks.

STANDARD RADIO MODEM

A standard radio modem is an assembly that contains both a radio and a modem, which transmits data without any special handling. Data error checking is the responsibility of the receiving station (DTE).

STANDARDS PROMOTION AND APPLICATION GROUP

(SPAG) A group of European OSI manufacturers which chooses option subsets and publishes these in a "Guide to the Use of Standards" (GUS).

STAR NETWORKS

Star networks usually employ a polling technique much like IBM's SNA. The poll is used to determine which nodes are still active and to maintain the network. However, no special access methods are required on a Star network, since every node is connected directly to a master node. Each node simply sends a request to the master node. If the master node does not respond to the sending node, the sending node resends its message. Star networks are contentionless and the effective bandwidth of the Star network increases every time a new node is added. There are no set standards, such as IEEE, FIPS, or ISO for Star-connected networks. Star networks are very susceptible to major catastrophe should the master node becomes inoperable, as a backup master node does not usually exist. If there were a backup master node, it would have either a set of connections physically separate from the primary master node or it would share the same connections, perhaps through dual communication controllers at each non-master node.

STAR-BUS

A bus network topology configured into a star by introducing a wiring concentrator. See Multiport Repeater.

STAR-RING

See Star-Wired Ring.

STAR-WIRED RING

A network topology in which connections are strung along a cable that is configured as a ring, and wired into a star. The ring is contained within a Multistation Access Unit (MAU) or Control Access Unit (CAU), with two pairs of wires extending to each connection. MAUs/CAUs can be connected together to form a larger ring. This topology is the preferred method for configuring Token Ring LANs, because a break in a cable can be detected and corrected without losing the ring configuration and disabling the LAN.

START/STOP BITS

The bits at the beginning and end of a data block when using asynchronous data transmission. See Asynchronous.

STATIC RANDOM ACCESS MEMORY

A type of random-access memory that holds its contents without constant refreshing from the CPU.

STATION

A PLC controller, EI module, or other intelligent device communicating across a link. Allen-Bradley term for node. See Node.

STATION MANAGEMENT TASK

A protocol function for the FDDI interface card that controls and monitors overall station activity including initialization, activation, maintenance, and error control within each station.

STATISTICAL MULTIPLEXING

A multiplexing technique: Bandwidth is dynamically allocated on the basis of need.

STATSRV

Statistics Service

STATUS WORK

One of the frame types sent from the gateway server to the host in response to a poll command, indicating the status of the gateway server.

STC

System Timing Controller

STE

Spanning Tree Explorer

STEALTH VIRUSES

Viruses which have features intended to hide their presence in memory or on disk. If a virus is to succeed in spreading, it must first escape detection.

STONED

During boot, might display a message similar to "Your PC is now stoned." Overwrites root directory entries on 1.2 MB floppy disks.

STORE AND FORWARD

Technique for examining incoming packets whereby an Ethernet switch or bridge looks at the whole packet packet before forwarding or filtering it. This process is slightly slower than Cut-Through, but it does not allow bad packets to get through. See Cut-Through.

STP

Shielded Twisted Pair

STREAM

A stream is a full-duplex connection between a user's task and a device. It can include an encapsulated processing module. The TCP/IP stream service does not support structured data streams.

STREAM MODE

See MNP Class 2.

STREAM SOCKET

Stream sockets imply a data stream is passed on the socket. When used, a stream socket is connected with another stream socket to form a two-way pipe across the network. See Socket.

STREAMING-DATA MODE

A function of MCA and EISA bus architectures in which four bytes are transferred at a time with only one address byte, instead of the normal one address byte per data byte. Devices that access this mode can increase data transfer rates up to fourfold for short bursts of data through the computer bus. This technique is used with 32-bit bus mastering devices.

STRIPING

Blocks, sectors, or bytes of data that are recorded to separate disk drives can be striped across the drives. Striping can produce better performance by writing or reading data from or to multiple drives at the same time. If NetWare volumes are spanned, NetWare automatically stripes sectors of blocks (of newly recorded data) across the drives, splitting seeks as it does, and reducing access time.

STRUCTURE OF MANAGEMENT INFORMATION

(SMI) The rules used to define the objects that can be accessed via a network management protocol. See MIB.

STRUCTURED QUERY LANGUAGE

(SQL) A standard database query and programming sublanguage. SQL (commonly pronounced "sequel" and originally developed for IBM mainframe computers) is an established set of statements used to add, delete, or update information in a table, or request information from one or more tables in the form of a report. There is now an ANSI-standard SQL definition for all computer systems.

STX

(Start of Text) A control character used to indicate the beginning of a message; it immediately follows the header in transmission blocks.

SU

Temporarily switch effective user ID (UNIX command)

SU-MIT-TG

SU/MIT Telnet Gateway Protocol

SUA

Stored Upstream Address

SUBNET

In IP, a distinct network within a network. In OSI, subnet is the connection from the IS to the subnetwork.

SUBNET ADDRESS

An extension of the IP addressing scheme that allows a site to use a single IP address for multiple physical networks.

SUBNET MASK

A 32-bit long mask that selects the bits from the network portion and one or more bits from the local portion of the IP address to designate subnet addressing.

SUBNETWORK

An OSI reference to a group of ESs connected to the same media (thicknet, UTP fiber) through similar MAUs (Media Access Units). This allows the ESs and ISs to conform with physical and data link layer requirements.

SUBSAMPLING

Bandwidth reduction techniques which reduce the amount of digital data used to represent an image. Part of a compression process.

SUBSCRIBER VERIFICATION NUMBER

The number used by the Inter eXchange Carrier (IXC) to track your ISDN order.

SUBSTRATE

The body or leadframe of a BGA. Typically composed of bismaleimide triazine (BT) epoxy/glass laminate.

SUN-RPC

SUN Remote Procedure Call

SUNDAY VIRUS

When activated on any Sunday, displays the message "Today is Sunday! Why do you work so hard? All work and no play make you a dull boy! Come on! Let's go out and have some fun!"

SUNTOOLS

The SunView window environment (UNIX command)

SUPDUP

SUPDUP Protocol

SUPER BALL GRID ARRAY

(SBGA (T)) A multilayer cavity-down version developed by AMKOR for higher-power and higher-performance applications.

SUPER TWIST NEMANIC LCD COLOR DISPLAY

Displays use a filtering scheme to generate colors. As a passive display technology, it does not respond as quickly as a TFT display, nor does it cost as much. Typically capable of 256 colors.

SUPER-USER

System Administrator

SUR-MEAS

Survey Measurement

SURGE

A short term increase in voltage, typically lasting at least 1/120 of a second.

SVC

See Switched Virtual Circuit

SVN

See Subscriber Verification Number.

SWIFT-RVF

Remote Virtual File Protocol

SWITCHED LINE

Within a network, a line that is switched to establish a continuous pathway between the sender and the receiver. In telecommunications, a line in which the connection is established by dialing. Contrast with nonswitched line. This terms applies to both PSTN and ISDN connections.

SWITCHED LINK

A wide area connection between workstations.

SWITCHED MULTI-MEGABIT DATA SERVICE

(SMDS), developed by Bellcore, interfaces with WAN/LAN by using a three-layer approach. The top layer, the SMDS Interface Protocol level 3 (SIP 3), provides a datagram service of up to 9188 bytes. At level 2 (SIP 2), this datagram is broken down to 53-byte ATM cells. The ATM cells are transported over the MAN network, discussed earlier in this chapter. SMDS is compatible with B-ISDN in its use of ATM. ATM cells in turn use the MAN standard, which is the subject of standardization by IEEE (IEEE 802.6). The router to the 10BASE5 LAN serves the role of Customer Premise Equipment (CPE) and Channel Service Unit (CSU). The OSI stack shown next to this router provides translation between Ethernet protocols and SMDS protocols. Since SMDS in its current version uses MAN, the router uses the DQDB to communicate with the Metropolitan Switching System (MSS). This link is the Subscriber Network Interface (SNI) used to connect the LAN subscriber to the MSS. The MSS switches are provided to the subscriber by the telephone company or other commercial organization.

SWITCHED VITRUAL CIRCUIT

See Frame Relay.

SYMMETRICAL COMPRESSION

A compression system which requires equal processing capability for compression and decompression of an image. This form of compression is used in applications where both compression and decompression will be utilized frequently. Examples include: still-image databasing, still-image transmission (color fax), video production, video mail, videophones, and videoconferencing.

SYMMETRICAL MULTIPLE PROCESSING

SMP Personal computers designed to accept multiple Pentium Pro processors, but requiring only one processor to operate. As the computing power of the machine is used up by applications, additional processor can be added.

SYNCHRONOUS

A data transmission mode that synchronizes entire blocks of data. In synchronous communications, blocks of data are encapsulated into a data frame. The frame includes a starting delimiter, an ending delimiter, and a checksum (or cyclic redundancy check) preceding the ending delimiter for error control. Synchronous transmissions have less overhead, and they more fully utilize available bandwidth of transmission media. They also have better error control than asynchronous transmissions. Synchronous transmission is used in both analog and digital communications.

SYNCHRONOUS DATA LINK CONTROL

(SDLC) A protocol used to transfer data in SNA environments. A method of controlling the transfer of data between stations in a point-to-point, multi-point, or loop arrangement in which synchronous data transmission techniques are used. IBM's development of SDLC is based on HDLC. SDLC is a subset of HDLC and is 100-percent compatible with HDLC. The reverse is not true, however, because SDLC does not use some of the advanced functions of HDLC. IBM uses SDLC in WAN terminal-to-mainframe connections.

SYNCHRONOUS OPTICAL NETWORK

(SONET) was first proposed as a standard by Bellcore for a family of interfaces to be used in optical networks. The lack of standards for high-speed digital transport to be used for single-mode fiber led to a number of proprietary standards. SONET is now an international standard accepted by ANSI and CCITT. The SONET standard provides a point-to-point link over fiber optic media. It provides the physical layer connection for B-ISDN and is defined in terms of a hierarchy of data rates. This hierarchy is defined in terms of the Optical Carrier (OC) speeds and the corresponding electrical signals used to interface with electrical components. OC Hierarchy/STS Hierarchy/Data rate OC-1/STS-1/51.84 OC-3/STS-3/155.52 OC-9/STS-9/466.56 OC-12/STS-12/622.08 OC-18/STS-18/933.12 OC-24/STS-24/1244.16 OC-36/STS-36/1866.24 OC-48/STS-48/2488.32 The OC and STS rates are multiples of 51.84 Mbps. The basic building block is the 51.84 Mbps line rate. Thus OC-8 is 48 x 51.84 Mbps = 2488.32 Mbps. The standard defines up to OC-240; that is, 240 x 51.48 = 12.4416 Gbps rate. STS-1 rates are roughly equivalent to the T3 (45 Mbps) data rates that are available today. Design goals of SONET included providing a way to accommodate T3 data rates and resolving the incompatibility between the North American and European digital hierarchies, as expressed in the T1, T2, and T3 signals. The North American standard is based on a T1 rate of 1.544 Mbps, whereas the European standard is based on 2.048 Mbps. As a result of this incompatibility, T1-based routers for NetWare LANs operate differently in North America than they do in Europe. STS data streams can be combined to yield higher STS rates. Three STS-1 rates multiplexed together, therefore, can yield a data rate of STS-3. The STS-1 frame is 810 bytes and is made up of a 90 column-by-9-row matrix with each cell of this matrix being one byte long. This data matrix is transmitted in one STS-1 frame. The first three bytes of each row contain overhead information. The first three rows contain nine bytes of section overhead, and the remaining six rows contain 18 bytes of line overhead. The combined section and line overhead of each frame is 27 bytes. The remaining 87 columns contain the payload or data. This frame payload is called the synchronous payload envelope (SPE) and works out to be 783 bytes (9 x 87). Not all of the SPE contains data; the first nine bytes contain path information. The STS-1 frame is sent once every 125 microseconds or at the rate of 8000 frames every second. Because each byte in the frame is eight bits, the data for each byte of data in a frame corresponds to an 8000 x 8 = 64,000 bps channel. You can use this data rate to transport digitized speech or data. Of the 783 bytes that make up the SPE nine bytes are used for transport overhead for every row. This transport overhead contains a pointer to the location in the SPE that the actual data begins, thus allowing data to float.

SYNCHRONOUS PAYLOAD ENVELOPE

See Synchronous Optical Network.

SYNTACTIC KNOWLEDGE

Short term and based on device-dependent details of a system. It is often learned by rote and is frequently void of relationships to a system. An example of syntactic knowledge is the popular use of meta or combination keys such as "Ctrl-A" or "Alt-B". Msny DOS based word processors use these key combinations as part of their menu systems. It fades quickly from memory unless used on a regular basis.

SYNTAX

Rules governing the structure of a language.

SYS5

The version of the DOMAIN/IX system that implements UNIX System V, Release 2, from AT&T Bell Laboratories.

SYSTEM 75

AT&T digital PBX - voice/data - small to medium offices

SYSTEM 85

AT&T digital PBX - voice/data - medium to large offices

SYSTEM ACCESS BUTTON

(SA Button) Three buttons you press to make inside and outside calls with the AT&T Merlin Legend system.

SYSTEM ADMINISTRATOR

The person responsible for planning computer or network installation and for ensuring the successful installation and use of the system by other users.

SYSTEM COMMAND BLOCK

A 6-byte buffer for the token-ring interface. The SCB holds the commands that the interface card executes.

SYSTEM ERRORS

Errors that can prevent Scan from completing its job successfully. System error conditions include disk format errors (such as unformatted disks), media errors (bad sectors), file system errors (unreadable files), network errors (unable to log in), file access errors (access permission denied), device access errors (printer out of paper), and report failures.

SYSTEM ID

The portion of the OSI NSAP address that identifies a specific system within an area.

SYSTEM INTEGRATION BLOCK

A system building block that integrates the microprocessor core with the serial ports and system peripherals for the MC68302 integrated multiprotocol processor (IMP).

SYSTEM INTERFACE

A register function within the TMS38030 chipset for the token-ring interface card that provides slave and bus master interfaces to the CNX 500 I/O bus.

SYSTEM MANAGEMENT SERVICES

The IBM PC LAN Program Extended Services function that allows the system administrator to maintain the information held by the system concerning users, applications, and machines.

SYSTEM OPERATOR

A co-worker who answers incoming calls and transfers the calls or takes messages.

SYSTEM SERVICE CONTROL POINT

SNA software component that manages the network or a portion of it.

SYSTEM STATUS BLOCK

An eight-byte buffer that holds status codes for the token-ring interface card.

SYSTEMS APPLICATION ARCHITECTURE

(SAA) IBM's blueprint, or framework, for developing applications.

SYSTEMS NETWORK ARCHITECTURE

A set of protocols, message formats, and other specifications developed by IBM that unites several generations of computers, operating systems, peripheral devices, and telecommunications systems. SNA specifies how computer equipment connects and communicates. IBM's blueprint, or framework, for networking computing systems and end-user devices. (See network architecture.)