T1 - A digital transmission link with a capacity of 1.544 Mbps used in North America. Typically channelized into 24 DS0s, each capable of carrying a single voice conversation or data stream. Uses two pairs of twisted pair wires.
T1 MLPPP (Multilink Point-to-Point Protocol) - Combining (bonding) multiple PPP (Point-to-Point Protocol) links between two systems into one logical data pipe. MLPPP is a standard IETF protocol.
T3 - A digital transmission link with a capacity of 45 Mbps, or 28 T1 lines.
TCP/IP (Transmission Control Protocol/Internet Protocol) - A protocol platform, known also as the Internet protocol suite, that combines both TCP and IP. Widely used applications, such as Telnet, FTP and SMTP, interface to TCP/IP.
TDM (Time Division Multiplexer) - A device which divides the time available on its composite link among its channels, usually interleaving bits (Bit TDM) or characters (Character TDM) of data from each terminal.
TDMoIP® - TDM over IP is a standards-based transport technology that extends voice, video or data circuits across packet-switched networks simply, transparently and economically. Acting as a pseudowire, TDMoIP is unique in that it supports the multiple signaling standards, OAM mechanisms and clock recovery features demanded by TDM networks for carrying voice-grade telephony channels. A simple alternative to VoIP, TDMoIP enables using legacy TDM equipment while facilitating a smooth migration to newer IP, Ethernet and MPLS networks. TDMoIP technology was developed and patented by RAD, and is found in RAD’s IPmux, Vmux and Megaplex products.
Telnet - The virtual terminal protocol in the Internet suite of protocols. It lets users on one host access another host and work as terminal users of that remote host. Instead of dialing into the computer, the user connects to it over the Internet using Telnet. When issuing a Telnet session, it connects to the Telnet host and logs in. The connection enables the user to work with the remote machine as though it were a terminal connected to it.
TETRA (Terrestrial Trunked Radio) - A wireless communications standard for Professional Mobile Radio (PMR) and Private Access Mobile Radio (PAMR) applications. It is a digital format, i.e. speech is transmitted as binary data, which makes it far more difficult to monitor or eavesdrop.
Throughput - The amount of information transferred through the network between two users in a given period, usually measured in the number of packets per second (pps).
Timeslot - A portion of a serial multiplex of timeslot information dedicated to a single channel. In T1 and E1, one timeslot typically represents one 64 kbps channel.
Timing over Packet Standards - Various methods and standards developed to ensure that accurate time and frequency is distributed in packet-based networks.
ToS (Type of Service) Field - In a QoS scheme, an eight-bit field that lets values from 0 to 15 be assigned to request special handling of traffic (for example, minimize delay, maximize throughput). The ToS field is being phased out in favor of DSCP.
Traffic Contract - An agreement between the user and the network management agent regarding the expected QoS provided by the network and the user’s compliance with the pre-determined traffic parameters (i.e. PCR, MBS, burstiness, average cell rate).
Traffic Policing - Mechanism whereby any traffic which violates the traffic contract agreed to at connection setup, is detected and discarded.
Traffic Shaping - A method for smoothing the bursty traffic rate that might arrive on an access virtual circuit so as to present a more uniform traffic rate on the network.
Transparent LAN Service (TLS) - A high speed data service which allows for the interconnection of different LANs across an extended campus, metropolitan area or national network. Using VLANs and native LAN interfaces (such as 10/100 Mbps Ethernet), TLS provides a much simpler solution to the customer for connection of dispersed sites, than other forms of WAN, such as ATM or Frame Relay.
Trunk - A single circuit between two points, both of which are switching centers or individual distribution points. A trunk usually handles many channels simultaneously.
U
UNI (User Network Interface) - The interface, defined as a set of protocols and traffic characteristics, between the CPE and the ATM network.
V
VCAT (Virtual Concatenation) - An inverse multiplexing technique used to split SDH/SONET bandwidth into logical groups, which may be transported or routed independently.
VLAN (Virtual LAN) - A network architecture which allows geographically distributed users to communicate as if they were on a single physical LAN by sharing a single broadcast and multicast domain.
VLAN-Aware - A device that is doing the Layer 2 bridging according to the VLAN tag in addition to the standard bridging parameters. A VLAN-aware device will not strip or add any VLAN header.
VLAN Stacking - A mechanism specified in IEEE standard 802.1ad (“Provider Bridges”) to extend the IEEE VLAN tagging standard (802.1Q). Also known as double VLAN tagging or Q-in-Q, VLAN stacking allows service providers to assign service VLAN tags (S-VLAN) to Ethernet frames that are already marked with customer VLAN tags (C-VLAN), resulting in hierarchical or “stacked” VLAN tags.
VLAN Stripping - Removal of VLAN tags from a network frame.
VoIP (Voice over IP) - Set of facilities for managing the delivery of voice information using the Internet Protocol (IP). Voice information is sent in digital form in discrete packets over the Internet instead of in analog form over the public switched telephone network (PSTN). A major advantage of VoIP is that it avoids the tolls charged by ordinary telephone service.
VPLS (Virtual Private LAN Service) - An IETF (Internet Engineering Task Force) proposal for providing Layer 2 VPNs that can support the connection of multiple sites in a single bridged domain over a managed IP/MPLS network. Edge routers, inter-connected by a full mesh of MPLS label switched path (LSP) “tunnels” through which run multiple pseudowires, enable any-to-any connectivity on a per-VPLS basis.
To the customer, all services in a VPLS appear to be on the same Ethernet LAN, regardless of actual geographic location. This removes complexity from enterprise networks, and lets carriers scale the networks.
VPN (Virtual Private Network) - A restricted network that uses public wires to connect nodes. A VPN provides a way to encapsulate, or “tunnel,” private data cheaply, reliably, and securely through a public network, usually the Internet.
W
WAN (Wide Area Network) - A network that typically spans nationwide distances and usually utilizes public telephone networks.
WDM (Wave Division Multiplexing) - Optical transmission technique in which two or more wavelengths (each carrying its own information) are combined for transmission over a single optical fiber. At the receiving end, the wavelengths are separated and directed to separate receivers. Increases the capacity of data transmission over fiber optics. Also used to connect two fiber optic devices over a single strand of fiber.
Glossary
