Glossary S, T, U

sFlow - A technology present in some HP switches for monitoring network devices traffic levels. 

SFP (Small Form-factor Pluggable) - A hot-swappable input/output device that plugs into a SFP slot on a switch and provides copper or fibre connectivity. In Ethernet systems the speed can be 100Mbp/s and Gigabit.

SFP+ - As SFP but capable of data rate of 10Gbit/s. 

SFP28 - As SFP/SFP+ but supporting 25Gbit/s.  Typically used to break out from a 100GbE port.

Shielded Twisted Pair (STP) - A type of cable that includes one or more sets of cable pair moulded together by insulating materials and covered with a braided shielding conductor offering better noise protection than Unshielded Twisted Pair. 

Single Mode Fibre - An optical fibre that carries only one ray of light (a mode) through it. 

SNMP - A protocol for managing devices on an IP network for conditions that require administrative attention. 

Spanning Tree Protocol (STP) - Sometimes referred to as STP, this is a data link layer protocol that ensures a loop free layout for an Ethernet LAN with the aim of preventing broadcast radiation.  See also RPST.

Stranded - In the context of Ethernet cable, the conductors each consist of multiple strands of copper cable.

Subnet mask A number that specifies what part of an IP address represents the network number and what part represents the host address.

SWA Steel Wire Armour - A cable that is armoured providing the highest level of crush resistance and rodent protection meaning that it is suitable for rugged external installations. Compared to CSTA the cable is more flexible but heavier. 

SWDM4 A proprietary wavelength division multiplexing (WDM) technology that operates at four wavelengths: 850nm, 880nm, 910nm and 940nm.  Transceivers are designed to use two OM3, OM4 or OM5 fibres.

Tactical Fibre - Extremely strong and lightweight fibre cable that offers exceptional cut, abrasion and chemical resistance. 

Tight Buffered Fibre - A type of fibre cable with includes a polymer coating component used to tightly encapsulate the optical fibres to provide increased protection suitable for both internal and external use. 

Trunking Using two or more cables to connect switches supporting the IEEE802.3ad Link Aggregation functionality; allowing the use of two or more connections to act as a single higher capacity or redundant connection.

Twisted Pair A cable with two insulated copper wires twisted together with the twists varied in length to reduce potential signal interference between the pairs. 

Unicast The 802.3 Ethernet standard, allowing information to be sent to only one specific device on a network. Since the transmitted packets only use up bandwidth on the ports and cables on the route from transmitter to sender, the network can support more connections compared to Multicast.

Uniter - Another name for an adapter which has two female fibre sockets and is used to interconnect two terminated fibre cables.

Unmanaged Switch - A plug and play switch which is desktop or rack mounted, these types of switches have no configuration interfaces or options. 

UPS Uninterruptible Power Supply - An electrical apparatus that provides emergency power when the primary power source fails, this switchover is instantaneous and provides protection against business disruption and data loss. 

Unshielded Twisted Pair (UTP) - A cable with insulated copper twisted pairs but without any shielding.

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