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Glossary of broadband terminology: S

SDSL: SDSL - symmetrical digital subscriber line
I believe SDSL, which only requires a single copper pair, will only deliver T1 speeds of 1.544 Mbps.
Semiconductor: Usually made from either silicon or germanium, semiconductors make it possible to miniaturize electronic components, such as transistors, which require less space and are faster and more energy-efficient.
Serial Line Internet Protocol: An older layer two protocol used for Internet traffic; much less sophisticated than PPP.
Service Level Agreement: Outlines minimum acceptable performance parameters (such as delay, throughput, percent availability, etc.) for public data services such as frame relay, VPNs, DSL access, and Interne taccess.
Service User: The end user at the customer premises.
Serving Central Office: The central office in the local communications network that is directly connected to the end user location in question.See Central Office.
Set Top Box: A transmission/reception device that acts as an interface typically to a television or other video output display device. In addition to ADSL, SDSL, HDSL, and VDSL interfaces, set top units are increasingly modular, and other interfaces can include Ethernet, MMDS,coaxial cable, V.34 modem, and ISDN, among others.
SHDSL: Single-pair High-speed Digital Subscriber Line was developed as a meltdown of several symmetric DSL technologies (HDSL, SDSL, HDSL-2) producing as a result one single internationally recognized industry standard
Signaling: The process of sending a transmission over a physical medium for purposes of communication.
Simple Network Management Protocol: The network management protocol used with TCP/IP-based Internets.
SLC: Subscriber Line Carrier - AT&T/Lucent's name for DLC (Digital Loop Carrier).
SMDS Interface Protocol: Formal name given to each layer of the SMDS network interface.
Splitter: Filters which separate high frequency (DSL) and low frequency (POTS) signals at both the end user and central office end points.
Splitter-less modem: .
STS-1: An ATM physical layer implementation supporting 51 Mbps.
STS-3: An ATM physical layer implementation supporting 155 Mbps.
Subscriber Line Carrier: AT&T/Lucent's name for DLC (Digital Loop Carrier).
Subscriber Network Interface: SMDS term describing generic access to a SMDS network over a dedicated circuit which can be DS-0, DS-1, or DS-3.
Switched Multimegabit Data Service: A connectionless data service based on global addressing that enables communications between sites typically at speeds between 1.5 Mbps and 34 Mbps.
Switched Virtual Circuit: A term found in frame relay and ATM networking in which a virtual connection, with variable endpoints, is established through an ATM network at the time the call is begun; the SVC is de-established at the conclusion of the call. See also Permanent Virtual Circuit.
Symmetrical Digital Subscriber Line: A DSL connection that provides equivalent upstream and downstream transmission rates.
Synchronous Digital Hierarchy: The international standard for transmitting digital information over optical networks. Term used by ITU to refer to SONET.
Synchronous Optical Network: Standards for transmitting digital information over optical networks. Fiber optic transmission rates range from 51.84 Mbps to 13.22 Gbps. It defines a physical interface, optical line rates known as Optical Carrier (OC) signals, frame formats, and an OAM&P (Operations, Administration, Maintenance, and Provisioning) protocol.The base rate is known as OC-1 and runs at 51.84 Mbps. Higher rates are a multiple of this such that OC-12 is equal to 622 Mbps (12 times 51.84 Mbps).
Synchronous Transmission: Data transmission using synchronization bytes, instead of star/stop bits, to control the transmission. In xDSL, videostreams are considered to be synchronous in nature. See AsynchronousTransmission.
Synchronous Transport Module-1: SDH standard for transmission over OC-3 optical fiber at 155.52 Mbps.
Synchronous Transport Signal-1: SONET standard for transmission over OC-1optical fiber at 51.84 Mbps.
Systems Network Architecture: IBM's vendor-specific, connection-oriented virtual circuit network architecture for terminal/host communication.