Glossary
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Cisco uBR10012 Universal Broadband Router Hardware Installation Guide
78-11450-03 Rev.B0
S
SAR Segmentation and reassembly. One of the two sublayers of the AAL common part convergence
sublayer, responsible for dividing (at the source) and reassembling (at the destination) the protocol data
units (PDUs) passed from the convergence sublayer. The SAR sublayer takes the PDUs processed by
the convergence sublayer and, after dividing them into 48-byte pieces of payload data, passes them to
the ATM layer for further processing. See also AAL.
SFP small formfactor pluggable (module) as in GBIC
Short reach See SR.
Simple Network
Management
Protocol
See SNMP.
Single-mode fiber See SMF.
SMF Single-mode fiber. Fiber-optic cabling with a narrow core that allows light to enter only at a single
angle. Such cabling has higher bandwidth than multimode fiber, but requires a light source with a
narrow spectral width (for example, a laser). Also called monomode fiber. See also Multimode fiber.
SNMP Simple Network Management Protocol. Network management protocol used almost exclusively in
TCP/IP networks. SNMP provides a means to monitor and control network devices, and to manage
configurations, statistics collection, performance, and security. See also SNMP2.
SNMP2 SNMP Version 2. Version 2 of the network management protocol. SNMP2 supports centralized as well
as distributed network management strategies, and includes improvements in the SMI, protocol
operations, management architecture, and security. See also SNMP.
SONET Synchronous Optical Network. High-speed synchronous network specification developed by Bellcore
and designed to run on optical fiber. STS-1 is the basic building block of SONET. It was approved as
an international standard in 1988.
SR Short reach. SONET/SDH specification for transmit power and receive sensitivity that achieves a
1.2-mile (2 km) reach.
SRAM A type of RAM that retains its contents for as long as power is supplied. SRAM does not require
constant refreshing, like DRAM. Compare with DRAM.
Subrate DS3 A generic term to describe a process in which the bandwidth of a clear channel DS3 is limited to a lower
rate. Several proprietary formats exist.
Synchronous
Optical Network
See SONET.
T
T1 Digital WAN carrier facility. T1 transmits DS1-formatted data at 1.544 Mbps through the telephone
switching network.