S

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

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

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 Inline Memory Module (SIMM)
SIMM is a small PC circuit board that holds memory chips. A SIMM has a 32-bit memory path to the CPU. SIMM capacities are measured in bytes.

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.

Synchronous Dynamic Random Access Memory (SDRAM)
SDRAM is a type of RAM and is often referred to as DIMM. It is replacing EDO RAM because it is approximately twice as fast (up to 133 MHz).

Synchronous Graphic Random Access Memory (SGRAM)
SGRAM is a type of dynamic RAM optimized for graphics-intensive operations. Like SDRAM, SGRAM can synchronize itself with the CPU bus clock, up to speeds of 100 MHz.

System Network Architecture (SNA)
SNA is the networking architecture developed by IBM for mainframe computers and associated networks.

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.

Synchronous Optical Network (SONET)
SONET standardizes high-speed optical transmission. The SONET standard defines a signal hierarchy similar to the T-carriers, but extending to much higher bandwidths. The basic building block is the STS-1 51.84 Mbps signal, chosen to accommodate a T3 signal. The hierarchy is defined up to STS-48, that is, 48 STS-1 channels for a total of 2,488.32 Mbps, capable of carrying 32,256 voice circuits. The STS designation refers to the interface for electrical signals. The optical signal standards are correspondingly designated OC-1, OC-2, etc.