Shielded Twisted Pair. Synonymous with Shielded Foil Twisted Pair (SFTP), STP is a copper cable configuration comprising a metallic foil shield that surrounds each insulated pair, of which there may be several. An uninsulated steel or tinned copper conductor in contact with each inner shield serves as a drain wire, ensuring that the continuity of the shield remains intact in the event that the foil is broken or cracked.The core of shielded pairs is then surrounded by an overall metallic shield of metallic tape or braid, or both, which is encased in a thermoplastic cable jacket, as illustrated in Figure S-12. The outer shield typically consists of helically or longitudinally applied plastic and aluminum laminated solid tape, although it may comprise a woven mesh, and steel or copper may also be used. Each shield absorbs ambient energy and conducts it to ground through the drain wire, thereby protecting the signal transmitted through the center conductors.The shield also serves to confine the electromagnetic field associated with the transmitted Cladding Light Source Cladding Core signal within the core conductors, thereby reducing signal loss and maintaining signal strength over a longer distance. Screened twisted pair (ScTP) is a simpler version with only an outer shield. See also Cat 6, Cat 7, ScTP, and UTP.
Spanning Tree Protocol. A bridge protocol for learning bridges, as defined in IEEE 802.1D standards. Spanning tree bridges are self-learning, filtering bridges for use in connecting LANs or LAN segments on a point-to-point basis.The bridge can be programmed or can teach itself the addresses of all devices on the network; subsequently, the network tree of the bridge provides only one span connection. Some spanning tree bridges also have the capability to provide security by denying access to certain resources based on user and terminal ID. Bridges that support the spanning tree algorithm have the ability to automatically reconfigure themselves for alternate physical paths if a network segment fails, thereby improving overall reliability. Radia Perlman invented STP while working for Digital Equipment Corporation (DEC). See also algorithm, bridge, filtering bridge, LAN, path, protocol, segmentation, and self-learning bridge.
Signal Transfer Point. In the advanced intelligent network architecture (AIN) architecture, a packet switch that routes signaling and control messages between a service switching point (SSP) and a service control point (SCP), and between STPs. See also AIN, packet, SCP, signaling and control, SSP, and switch.