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Scanner

A device that reads printed text or illustrations and translates the information into a form that a computer can use, i.e. a scanner "digitizes" printed information. A small handheld scanner can be rolled across the printed medium, while a larger flatbed scanner works rather like a photocopying machine in that users place the item to be scanned onto the glass as would be done for a photocopier, close the lid and scan. A scanner's resolution is measured in dpi (dots per inch), which refers to the number of dots in a one-inch line—the more dots per inch, the higher the resolution and the sharper the image.

Secure Sockets Layer (SSL)

A protocol designed by Netscape to enable users to transmit private documents via the Internet. The SSL protocol provides connection security via three basic properties. (1) The connection is private since encryption is used after an initial handshake to define a secret key and symmetric cryptography is used for data encryption (e.g. DES, RC4, etc.). (2) The peer's identity can be authenticated using asymmetric, or public key, cryptography (e.g. RSA, DSS, etc.). (3) The connection is reliable since message transport includes a message integrity check using keyed MAC and secure hash functions (e.g. SHA, MD5, etc.) for MAC computations. The programming for keeping a message confidential is composed of two layers. At the lowest level is the SSL Record Protocol, which is layered on top of some reliable transport protocol, typically TCP/IP. The SSL Record Protocol is used for encapsulation of various higher level protocols. One such encapsulated protocol, the SSL Handshake Protocol, allows the server and client to authenticate each other and to negotiate an encryption algorithm and cryptographic keys before the application protocol transmits or receives its first byte of data. One advantage of SSL is that it is application protocol independent. A higher level protocol can layer on top of the SSL Protocol transparently.

Service Set Identifier (SSID)

An identifier attached to packets sent over the wireless LAN that functions as a "password" for joining a particular radio network such as a basic service set (BSS). All radios and access points within the same BSS must use the same SSID, or their packets will be ignored.

Session Initiation Protocol (SIP)

An Internet Engineering Task Force (IETF) standard protocol for initiating an interactive user session that involves multimedia elements such as video, voice, chat, gaming, and virtual reality. Like HTTP or SMTP, SIP works in the Application Layer of the OSI Model. Since the Application Layer is the level responsible for ensuring that communication is possible, SIP can establish multimedia sessions or Internet telephony calls, and modify, or terminate them.

Short Text Messaging

Better known as Short Message Service or SMS.

See also Short Message Service (SMS).

Short Message Service (SMS)

A messaging service that is similar to paging. SMS sends messages consisting of no more than 160 characters (224 characters if using a 5-bit mode) to mobile phones that use Global System for Mobile (GSM) communication. However, unlike paging, SMS messages do not require the receiving device to be active and within range since the SMS message can be held (for a specific time period) until the phone is active and within range.

SID

See System Identification Code (SID).

Silicon

The second most abundant element on Earth is silicon (oxygen ranks higher). Silicon, a component of common sand, is the raw material that is commonly used for making computer chips.

SIM Card

Also known as a "Smart Card."

See also Subscriber Identification Module (SIM).

Simple Management Transfer Protocol (SMTP)

A member of the TCP/IP protocol suite and as such it is used to send and receive email messages. However, since SMTP is limited in its ability to queue messages at the receiving end, it's usually used with either POP3 or Internet Message Access Protocol (IMAP), either of which allow the end-user to save messages in a server mailbox and download them periodically from the server.

See also Internet Message Access Protocol (IMAP).

See also Post Office Protocol (POP).

Simple Network Management Protocol (SNMP)

A protocol that reads and sets both standard and manufacturer variables in network equipment. SNMP enables a management station to configure and monitor network devices. Furthermore, an SNMP agent can generate a "TRAP" (message) to an SNMP manager to send back information related to one or more variables for which thresholds have been associated

SIP

See Session Initiation Protocol (SIP).

Smart Card

Also known as a "SIM Card."

See also Subscriber Identification Module (SIM).

Soft Client

As used in this book, the term "soft client" refers to software that runs on a computing device to provide voice services over an IP network, typically using the computing device's built-in microphone/speaker components and sound card.

SOHO (Small Office/Home Office)

An acronym used to distinguish small businesses from mid-sized and large businesses. However, many SOHOs are home-based businesses, which is where the "home office" in Small Office Home Office comes from. Still, the term SOHO has a broad sweep—including everyone who works in a small office environment, whether as employer or employee.

SQL

Acronym of Structured Query Language, and pronounced as "sequel." The pronunciation came about because SQL was developed as a result of an IBM project called "Structured English Query Language." The SQL acronym is typically used instead of its progenitor.

See also Structured Query Language (SQL).

Spanning Tree Protocol

An IEEE protocol designed to prevent a condition known as a "bridge loop," which can occur when a network uses two bridges to interconnect the same two computer network segments. The Spanning Tree Protocol and the Spanning Tree Algorithm enable the bridges to exchange information so that only one of them will handle a given message sent between two computers within the network.

Spam

A term used to refer to an email message sent to a large number of people without consent. Also known as Unsolicited Commercial Email (UCE) or junk email. Spam is usually sent to promote a product or service. It is also found in newsgroups, where people post identical and irrelevant messages to many different newsgroups that have nothing to do with the content of the posting.

Spectrum

A conceptual tool used to organize and map a set of physical properties to delineate electromagnetic waves that are produced by electric and magnetic fields, and which move through space at different frequencies.

See also Electromagnetic Waves.

See also Radio Frequency (RF).

Spectrum Allocation

This term refers to the governmental function of apportioning bands to services such as radio, TV, and WLANs. Although various governments have declared their control over all spectrum and set up laws and rules to govern the use of such spectrum, realistically speaking, no one can really "own" spectrum.

Spread Spectrum

This term refers to a type of wireless signal modulation that scatters data transmissions across the available frequency band in a pseudo-random pattern. This results in a much greater bandwidth than the signal would have if its frequency were not varied and spread. Spreading the data across a frequency spectrum makes the signal resistant to noise and to interference.

Structured Query Language (SQL)

A type of programming language that is commonly used to construct database queries and perform updates and other maintenance of relational databases. Despite its name, SQL is not a full-fledged language, in that it cannot create standalone applications. However, it is strong enough to create interactive routines in other database programs.

SSID

See Service Set Identifier (SSID).

Statement of Work (SOW)

A document primarily used to specify the work requirements for a project or program. A SOW typically is used in conjunction with specifications and standards as a basis for a contract and often is used to determine whether the contractor met stated performance requirements once the contract is completed.

Stream Control Transmission Protocol (SCTP)

Also known as next-generation TCP or TCPng, SCTP is designed to make it easier to support a telephone connection over the Internet (and specifically to support the telephone system's Signaling System 7, commonly known as SS7, over an Internet connection). SCTP is invaluable when transmitting simultaneous multiple streams of data between two end points with an established connection in a network.

Subnet

A contiguous string of IP addresses. The first IP address in a subnet is used to identify the subnet, the last IP address in the subnet is used as the broadcast address, thus anything sent to the last address is sent to every host on the subnet.

See also IP Address.

Subscriber Identification Module (SIM)

Commonly referred to as a "SIM Card" or "Smart Card"; a SIM is a small printed circuit board, which is commonly found in GSM phones and other devices. For instance, when used in GSM phones, the SIM identifies the user via information, stored on the card. A typical SIM includes subscriber details, security information and the personal directory of numbers. The module or card holds a microchip that stores information and encrypts voice and data transmissions, making it close to impossible to listen in on calls. Without the SIM, the mobile phone cannot operate.

Switch

A network device that selects a path or circuit for sending a data packet to its next destination is called a "switch." However, a switch can also function as a router (a device or program that can determine the route and specifically to what adjacent network point data should be sent). In general, a switch is a simpler and faster mechanism than a router, since a router requires knowledge about the network and how to determine the route. A switch is not always required in a network since many local area networks are organized as rings or buses in which all destinations inspect each message, but read only those intended for that destination.

System Identification Code (SID)

A 5-digit number assigned to each cellular carrier by the FCC. The SID is programmed into the cell phone when a service plan is subscribed to and is part of the activation process.

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