Technical Glossary T - X

TCP/IP - Transmission Control Protocol/Internet Protocol. The dominant protocol suite in the worldwide Internet, TCP is Layer 4, the transport layer. IP is Layer 3, the network layer.

TDM - Time Division Multiplexer. A device that enables the simultaneous transmission of multiple independent data streams into a single high-speed data stream. Or Time Division Multiplexing - A means of dividing a digital circuit into several channels by creating a separate Time Slot for each. Channels are essentially groups of bits separated by time and reassembled at the destination.

TDM Tributary - A DSU or modem that is, for diagnostic purposes, at a logically subsidiary level in an hierarchical network. Tributary DSUs or modems in a network receive control data from the control DSU or modem, as well as from any network management system present in the network.

Telnet - Virtual terminal protocol in the Internet suite of protocols. Allows the user of one host computer to log into a remote host computer.

TIMS - Transmission Impairment Measurement Set.

UAWG - Universal ADSL Working Group.

UNI - User to Network Interface.

Upstream - Typically refers to the transmission speed from the customer premises toward the telephone network.

URL - Uniform Resource Locator. An Internet standard addressing protocol for location and access of resources.

UTP - Unshielded Twisted Pair. See CAT5.

VC - Virtual Circuit. A logical connection or packetswitching mechanism established between two devices at the beginning of a transmission.

VDSL - Very-high-bit-rate DSL. Generally refers to a data transmission speed from 25 to 50+ Mbps over very short distances.

V.Fast Class - A unofficial standard for 28,800 bps transmission. Came before the V.34 standard was approved.

VLAN - Virtual LAN. Workstations on different LANs can be connected using VLAN tagging.

VLSI - Very Large Scale Integration.

VOD - Video On Demand. A service allowing many users to request the same video at the sarne time.

Voice Frequency (VF) - The part of the audio frequency range used to transmit voice sound (usually 300 Hz to 3,400 Hz).

VoiceSpanTM - A paradyne proprietary technology that provides simultaneous voice and data over a single telephone line.

VPN - Virtual Private Network. Software-defined private network.

V.xx - Format for standards governing the transmission of data over analog transmission facilities. While most V.xx standards were developed by the International

Telecommunications Union (Telecommunications Standards Sector (ITU-TSS, formerly CCITT), some (such as V.32terbo) were developed by vendors and became de facto standards. These standards include:

V.17	14.4 Kbps	Fax transmission over dial lines
V.21	300 bps	Dial line modulation
V.22	1.2 Kbps	Dial line modulation
V.22bis	2.4 Kbps	Dial line modulation
V.27bis	4.8 Kbps	Four-wire-leased-line modulation
V.27ter	4.8 Kbps	Fax transmission over dial lines
V.29	9.6 Kbps	Four-wire leased-line modulation (data and fax)
V.32	9.6 Kbps	Dial and two-wire leased-line modulation
V.32bis	14.4 Kbps	Dial and two-wire leased-line modulation
V.32terbo	19.2 Kbps	Dial and two-wire leased-line modulation
V.33	14.4 Kbps	Four-wire leased-line modulation
V.34	28.8 Kbps	Dial and two-wire leased-line modulation
V.34+	33.6 Kbps	Dial and two-wire leased-line modulation
V.35	48 Kbps	Discontinued modem. Interface still in use.
V.42	N/A	E ror control procedures on an analog circui
V.42bis	N/A	Data compression on an analog circuit

WAN - Wide Area Network. A network that spans a large geographic area.

WIPO - World Intellectual Property Organization.

XDSL - Refers to all DSL-based services.