Summary

Small Computer System Interface 25segment A portion of a computer network in whichevery device communicates using the physical layerof the OSI reference model. Hubs and repeatersextend and become part of a network segment,whereas switches and routers define and separatenetwork segments.semiconductor Material used to make computerchips that can be either a conductor or an insulator,depending on the control signals applied to it. Themost common semiconductor materials are siliconand germanium. These materials then have othermaterials added to them to increase conductivity.serial advanced technology attachment A computerbus primarily designed to transfer data betweena computer and storage devices.serial cable An external cable that connects theserial port on the computer to a peripheral device.serial data transfer The movement of single bitsof information in a single cycle.serial port A socket that is used to connect adevice such as a mouse or trackball.serial transmission A method of data transmissionin which the bits of a data character are transmittedsequentially over a single channel.server A repository for files, or other resources,that can be accessed and shared across a network bymany users.service level agreement (SLA) A contract thatdefines expectations between an organization and theservice vendor to provide an agreed-upon level ofsupport.session layer Layer 5 of the Open SystemsInterconnection (OSI) reference model. This layerestablishes, manages, and terminates sessionsbetween applications and manages data exchangebetween presentation layer entities. The OSI referencemodel includes the application layer, presentationlayer, session layer, transport layer, networklayer, data link layer, and physical layer.shielded twisted pair (STP) A two-pair wiringmedium used primarily with Token Ring networks.STP cabling has a layer of shielded insulation toreduce electromagnetic interference (EMI). Comparewith UTP.A key combination that activates a com-shortcutmand.Simple Mail Transfer Protocol (SMTP) An e-mail protocol servers use to send ASCII text messages.When augmented by the MIME protocol,SMTP can carry e-mail with pictures and documents.E-mail clients sometimes use SMTP to retrieve messagesfrom an e-mail server. However, because of thelimited capability to queue messages at the receivingend, other protocols such as POP or IMAP typicallyare used to receive e-mail.simplex The capability for data transmission inonly one direction between a sending station and areceiving station.single-mode A fiber cable that has a very thincore. Uses a high-energy laser as a light source. Cantransmit signals over longer distances than multimodefiber-optic cable.site survey Physically inspecting a building to helpdetermine a basic network topology.Small Computer System Interface (SCSI) A parallelinterface standard that supports multiple deviceson the same cable and achieves faster data transmissionrates than standard buses.