STS u Synchronous Transport SignalSTS1 u Synchronous Transport Signal level 1 Basic building block signal of SONET, operating at 51.84 Mbps. Faster SONET rates are defined as STS-n, where n is a multiple of 51.84 Mbps.
SVC u Switched Virtual Circuit Virtual circuit that is dynamically established on demand and is torn down when transmission is complete. SVCs are used in situations where data transmission is sporadic. Called a switched virtual connection in ATM terminology.
T1 u T1 transmits DS1-formatted data at 1.544 Mbps through the telephone-switching network, using AMI or B8ZS coding.
T3 u Digital WAN carrier facility. T3 transmits DS3-formatted data at 44.736 Mbps through the telephone switching network.
TCP u Transmission Control Protocol Connection-oriented transport layer protocol that provides reliable full-duplex data transmission. TCP is part of the TCP/IP protocol stack.
TCP/IP u Transmission Control Protocol/Internet Protocol Common name for the suite of protocols developed by the U.S. DoD in the 1970s to support the construction of worldwide internetworks. TCP and IP are the two best-known protocols in the suite.
TFTP u Trivial File Transfer Protocol Simplified version of FTP that allows files to be transferred from one computer to another over a network.
Token Ring u Token-passing LAN developed and supported by IBM. Token Ring runs at 4 or 16 Mbps over a ring topology. Similar to IEEE 802.5.
TTY u Teletypewriter General term for an input device.
Tx u Transmit or TransmitterUSRBUF u A driver structure describing the use of a specific buffer containing payload data to be transferred using ATM. They can be linked together to allow non-contiguous areas of memory to be sent as one unit.
X.25 u ITU-Tstandard that defines how connections between DTE and DCE are maintained for remote terminal access and computer communications in PDNs. X.25 specifies LAPB, a data link layer protocol, and PLP, a network layer protocol. Frame Relay has to some degree superseded X.25.
VBR u Variable Bit Rate QoS class defined by the ATM Forum for ATM networks. VBR is subdivided into a Real Time (RT) class and Non-Real Time (NRT) class. VBR (RT) is used for connections in which there is a fixed timing relationship between samples. VBR (NRT) is used for connections in which there is no fixed timing relationship between samples, but that still need a guaranteed QoS.
VCC u Virtual Channel Connection Can be a Permanent Virtual Connection (PVC) or a Switched Virtual Connection (SVC). Any ATM connection between two nodes.
VCI u Virtual Channel Identifier16-bit field in the header of an ATM cell. The VCI, together with the VPI, is used to identify the next destination of a cell as it passes through a series of ATM switches on its way to its destination. ATM switches use the VPI/VCI fields to identify the next network VCL that a cell needs to transit on its way to its final destination. The function of the VCI is similar to that of the DLCI in Frame Relay.
VCL u Virtual Channel Link Connection between two ATM devices. A VCC is made up of one or more VCLs.
VPI u Virtual Path Identifier 8-bit field in the header of an ATM cell. The VPI, together with the VCI, is used to identify the next destination of a cell as it passes through a series of ATM switches on its way to its destination. ATM switches use the VPI/VCI fields to identify the next VCL that a cell needs to transit on its way to its final destination. The function of the VPI is similar to that of the DLCI in Frame Relay.
WAN u Wide-Area Network Data communications network that serves users across a broad geographic area and often uses transmission devices provided by common carriers. Frame Relay, SMDS, and X.25 are examples of WANs.
