S

Scope
A collection of IP configuration information specifying the IP parameters used by all DHCP clients on a given subnet. Each subnet may have one scope, which is comprised of a single contiguous range of IP addresses.

Scope Creep
Scope creep is the process of gradually adding requirements to a project during its life cycle.

Scripts
Scripts are interpreted programs that are both human readable and executable, in contrast to compiled programs which are converted into machine-readable code that humans cannot understand. Common interpreted scripting languages include Perl, UNIX Shells, JavaScript, and VBScript.

Secure Electronic Transaction(SET)
SET is a standard, based on digital signatures, that allows merchants to verify the identity of buyers over the Internet.

Secure Sockets Layer (SSL)
SSL is an application of both public-key and single-key encryption, that secures an Internet connection between browser and server. Web pages that use SSL carry the URL " https://" .

Sed
Sed is a UNIX utility for editing large streams of text that may be generated by another processing step.

Sell-Side
Sell-side refers to e-commerce Web technology that takes orders from corporate customers.

Segment
A segment is a physical portion of a network. A network must be made up of one or more physical segments.

Semaphore
A semaphore is a flag (bit) set to indicate use of a shared system resource, such as a file. For example, if a semaphore is set to 1, the file is in use and cannot be accessed by another user.

Serial Line Internet Protocol (SLIP)
SLIP is a very simple communications protocol originally developed for use over dedicated circuits or leased lines; it does not include provisions for establishing a connection over the telephone network. SLIP is a de facto standard included in many implementations of TCP/IP.

Server
A server is a device attached to a network that provides one or more services to users of the network.

Server-Side Script
A server-side script is a program that runs on the server side of a client/server process. For example, server-side Web programs (such as CGI programs, and server-side scripts embedded in Web pages) run on Web servers.

Server Farm
A server farm is a collection of departmental servers located in a data center, where they can be provided with consolidated backup, an uninterrupted power supply, and a proper operating environment.

Server Message Block (SMB)
SMB is the IBM personal computer (PC) LAN Presentation Layer protocol used to communicate with devices located on a LAN. It uses NetBIOS at the Session Layer to communicate across a LAN. Functions requiring LAN support, such as retrieving files from a file server, are translated into SMB commands before they are sent to a remote device.

Shared-Media Protocol
This is a media access protocol in which multiple stations share the same physical transmission medium. A station cannot transmit data until it has a token (FDDI and Token Ring), or until other stations are not transmitting (Ethernet).

Shockwave
Shockwave is a popular multimedia animation format from Macromedia. A browser must have the Shockwave plug-in installed before it can play a Shockwave animation file.

Simple Network Management Protocol (SNMP)
SNMP is a network management protocol based on the manager/agent model, in which a complex central manager directs simple device-based agents to supply information or change configurations. The original version of SNMP was derived from the SGMP, and published in 1988.

Simple Mail Transfer Protocol (SMTP)
SMTP is a protocol and set of processes that use the protocol to transfer e-mail messages between user mailboxes.

Single-Key (Symmetric) Encryption
Single-key encryption is a cryptographic system that uses the same key to both encrypt and decrypt a message. Single-key encryption systems require both the sender and receiver of a message to share the same key before using it to communicate.

Smart Hub
A smart hub is a hub enhanced with additional hardware that can support multiple media types and media access methods (Data Link protocols), such as Ethernet, Token Ring, and FDDI. Smart hubs can provide additional internetworking functionality through plug-in bridge and router modules and network management.

Spanning Tree
A spanning tree is a set of device-to-device paths through a bridged network that ensures there is one, and only one, path between any two devices.

Stakeholders
All parties who have a vested interest in the success of a Web site or computing system are referred to as stakeholders. Stakeholders include the system owners, users, designers, and builders.

State
State is a term describing the collective values of all of an object's properties. Whenever one property changes the object's state is said to change. If an object has only methods and no properties, it is said to be "stateless."

Static Routing
The practice of having a network administrator manually build and maintain routing tables is referred to as static routing.

Strategic Alliance
A strategic alliance is a cooperative relationship between related, but noncompeting businesses, which offers consumers a wider range of products or services. Strategically allied Web-based businesses hyperlink their sites to each other, so that customers of one site are more likely to visit the other sites.

Statistical Time-Division Multiplexing (STDM)
STDM is a multiplexing technology in which each port competes for access to the bus based on need. Bandwidth is not wasted on unused time slots, as sometimes happens in TDM. STDM is good for bursty traffic.

Structured Wiring Plan
A structured wiring plan consists of specifications to create the physical topology of a network. Structured wiring plans may include voice, data, and image transmission over a single wiring system. Many vendors offer proprietary and/or standards-based structured wiring plans. In the United States, EIA/TIA has ratified the EIA/TIA-568 standards that provide users and vendors precise guidelines for premises wiring, including topology, cabling types for a given network speed, connector types for a given cabling type, and minimum performance specifications for cables and connectors.

Subnet
A subnet is a "subdivision of a network." It is a section of a network in which users are grouped logically based on their network address.

Subnetwork
Networks can be classified according to the area over which they extend. A LAN can consist of a few nodes up to several hundred, but will typically be confined to a few buildings within a few thousand meters of one another. It can consist of subnetworks linked together in certain ways to form a larger, but still local, network.

Supernetted Address
These are groups of contiguous Class C addresses allocated to an ISP, such as UUNET or AOL, to provide large pools of IP addresses for temporary dial-up connections.

Switch
A device that operates at the Data Link Layer of the OSI Model. A switch can LANs or segments of the same media access type. A switch dedicates its entire bandwidth to each frame it switches.

Switching Hub
See "switch."

Synchronous Optical Network (SONET)
SONET is an optical transmission standard that defines a signal hierarchy. The basic building block is the STS-1 51.84-Mbps signal, chosen to accommodate a T3 signal. The STS designation refers to the interface for electrical signals. The optical signal standards are correspondingly designated OC-1, OC-2, etc.

Systems Development Life Cycle (SDLC)
SDLC is the process of creating a new system, or changing an existing system, from concept to completion.

System Network Architecture (SNA)
SNA is IBM's architecture for computer networking. SNA was designed for transaction processing in mission-critical applications, often involving services provided to customers. SNA networks usually involve a large number of terminals communicating with a mainframe. Typical transactions perform inquiries and update information in a database. For example, a commercial bank might have a number of 3270-type display units and printers in each of hundreds of branch offices which are used to access a central database in the home office.

Synchronous Data Link Control (SDLC)
SDLC is a Data Link Layer protocol used for transmission across a physical link. It is often found in IBM SNA networks.