Term
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Definition
Asymmetric DSL
A variation of DSL that offers more throughput when data travel downstream, downloading from a local carrier's switching facility to the customer, than when data travel upstream, uploading from the customer to the local carrier's switching facility. |
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Term
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Definition
| The characteristic of a transmission technology that affords greater bandwidth in one direction (either from the customer to the carrier, or vice versa) than in the other direction. |
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Term
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Definition
| A transmission method in which data being transmitted and received by nodes dod not have to conform to any timing scheme. In asynchronous communications, a node can transmit at any time and the destination node must accept the transmission as it comes. |
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Term
| ATM(Asynchronous Transfer Mode) |
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Definition
| A data link layer technology originally conceived in the early 1980's at bell labs and standardized by the ITU in the mid-1990's. ATM relies on fixed packets, called cells, that each consist of 48 bytes of data plus a 5 byte header. ATM relies on virtual circuits and establishes a connection before sending data. the reliable connection ensured by ATM allows network managers to specify QoS levels for certain types of traffic. |
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Term
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Definition
| In ISDN, the bearer channel, so named because it bears traffic from point to point. |
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Term
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Definition
| The process of combining more than one bearer channel of an ISDN line to increase throughput. For example, BRI's two 64 Kbps B channels are bonded to create an effective throughput of 128Kbps. |
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Term
BPL
Broadband over Powerline |
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Definition
| High-speed internet access delivered over the electrical grid. |
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Term
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Definition
| A variety of ISDN that uses two 64Kbps bearer channels and one 16Kbps data channel, as summarized by the notation 2B+D. BRI is the most common form of ISDN employed by home users. |
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Term
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Definition
| A method of connecting to the internet over a cable network. in broadband cable, computers are connected to a cable modem that modulates and demodulates signals to and from the cable company's head-end. |
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Term
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Definition
| A WAN in which each location is connected to no more than two other locations in a serial fashion. |
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Term
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Definition
| The fiber-optic or coaxial cable that connects a neighborhood cable node to a customer's house. |
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Term
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Definition
| A device that modulates and demodulates signals for transmission and reception via cable wiring. |
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Term
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Definition
| A packet of a fixed size, In ATM technology a cell consists of 48 bytes of data plus a 5 byte header. |
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Term
CIR
Committed Information Rate |
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Definition
| The guaranteed minimum amount of bandwidth selected when leasing a frame relay circuit. Frame relay costs are partially based on CIR. |
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Term
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Definition
| The location where a local or long distance telephone service provider terminates and interconnects customer lines. |
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Term
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Definition
| A device used with T-carrier technology that provides termination for the digital signal and ensures connection integrity through error correction and line monitoring. Typically, a CSU is combined with a DSU in a single device. |
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Term
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Definition
| A combination of a CSU and a DSU that serves as the connection point for a T1 line at the customer's line. Most modern CSU/DSU also contain a multiplexer. ACSU/DSU may be a separate device or an expansion card in another device, such as a router. |
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Term
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Definition
| In ISDN, the data channel is used to carry information about the call, such as session initiation and termination signals, caller identity, call forwarding, and conference calling signals. |
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Term
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Definition
| A continuously available link or service that is leased through another carrier, examples of dedicated lines include ADSL, T1, and T3. |
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Term
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Definition
| A type of connection in which a user connects to a distant network from a computer and stays connected for a finite period of time. Most of the time, the term, dial-up refers to a connection that uses a PSTN line. |
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Term
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Definition
| A term used to describe data traffic that flows from a carrier's facility to the customer. In asymmetrical communications, downstream throughput is usually much higher than upstream throughput. In symmetrical communications, downstream and upstream throuhputs are equal. |
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Term
DS0
Digital Signal Level 0 |
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Definition
| The equivalent of one data or voice channel in T-Carrier technology as defined by ANSI physical layer standards. All other signal levels are multiples of DS0 |
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Term
DSL
Digital Subscriber Line |
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Definition
| A dedicated WAN technology that uses advanced data modulation techniques at the physical layer to achieve extraordinary throughput over regular phone lines. DSL comes in several different varieties, the most common of which is ASYMMETRIC DSL (ADSL) |
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Term
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Definition
| A device that demodulates an incoming DSL signal, extracting the information and passing it to the data equipment (such as telephone lines and computers) and modulates an outgoing DSL signal. |
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Term
DSLAM
DSL Access Multiplexer |
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Definition
| A connectivity device located at a telecommunications carrier office that aggregates multiple DSL subscriber lines and connects them to a larger carrier or to the internet backbone. |
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Term
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Definition
| A device used in T-Carrier technology that converts the digital signal used by bridges, routers, and multiplexers into the digital signal used on cabling. Typically a DSU is combined with a CSU in a single device, a CSU/DSU. |
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Term
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Definition
| A digital carrier standard used in Europe that offers 30 channels and a maximum of 2.048Mbps throughput. |
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Term
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Definition
| A digital carrier standard used in Europe that offers 480 channels and a maximum of 34.368Mbps throughput |
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Term
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Definition
| An arrangement that allows a customer to lease only some of the channels on a T1 line. |
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Term
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Definition
| A digital packet switched WAN technology whose protocols operate at the Data Link Layer, The name is derived from the fact that data is separated into frames, which are then relayed from one node to another without any verification or processing. Frame Relay offers throughput between 64Kpbs and 45Mbps. A frame relay customer chooses the amount of bandwidth he requires and pays for only that amount. |
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Term
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Definition
| A service in which a residential customer is connected to his carrier's network using fiber-optic cable. |
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Term
FTTP
Fiber to the Premises |
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Definition
| A service in which a residential or business customer is connected to his carrier's network using fiber-optic cable. |
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Term
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Definition
| A version of the mesh topology WAN in which every site is directly connected to every other site. Full-mesh WAN's are the most fault tolerant type of WAN. |
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Term
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Definition
| A cable company's central office, which connects cable wiring to many nodes before it reaches customer's sites. |
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Term
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Definition
| A link that consists of fiber cable connecting the cable company's offices to a node location near the customer and coaxial cable connecting the node tot he customer's house. HFC upgrades to existing cable wiring required before current TV cable systems can provide Internet Access. |
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Term
ISDN
Integrated Services Digital Network |
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Definition
| An international standard that uses PSTN lines to carry digital signals. it specifies protocols at the physical, data link, and tranpsort layers of the OSI Model. ISDN lines may carry voice and data signals simutaneously. two types of ISDN connections are used in North America: BRI (Basic Rate Interface) and PRI( Primary Rate Interface). Both use a combination of bearer channels (B Channels) and data (D Channels). |
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Term
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Definition
| A method for transporting token ring or Ethernet frames over ATM networks. LANE encapsulates incoming Ethernet or token ring frames, then converts them into ATM cells for transmission over an ATM network. |
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Term
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Definition
| The part of a phone system that connects a customer site with a telecommunications carrier's switching facility. |
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Term
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Definition
| A type of WAN in which several sites are directly interconnected. mesh WAN's are highly fault tolerant because they provide multiple routes for data to follow between any two points. |
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Term
NIU
Network Interface unit |
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Definition
| The point at which PSTN owned lines terminate at a customers premises. The NIU is usually located at the demarc. |
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Term
NSP
Network Service Provider |
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Definition
| A carrier that provides long-distance (often global)connectivity between major data switching centers across the internet. AT&T, Verizon, and Sprint are all examples of network service providers in the United States. Customers including IPS's can lease dedicated private or public internet connections from an NSP. |
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Term
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Definition
| A device used on ISDN networks that connects the incoming twisted pair wiring with the customer;s ISDN's terminal equipment. |
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Term
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Definition
| AN additonal connection device required on PRI to handle the multiple ISDN lines between the customers network termination connection and the local phone company's wires. |
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Term
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Definition
| AN internationally recognized rating that indicates throughput rates for SONET connections. |
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Term
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Definition
| A device located at the carrier's endpoint of a passive optical network. An OLT contains multiple optical ports, or PON interfaces and a splitter that subdivides the capacity of each port into up to 32 logical channels, one per subscriber. |
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Term
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Definition
| In a passive optical network, the device the customer premises that terminates a carrier's fiber optic cable connection and distributes signals to multiple endpoints via fiber optic cable, in the case of FTTP, or via copper or coax cable. |
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Term
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Definition
| A version of a mesh topology WAN in which only critical sites are directly interconnected and secondary sites are connected through start or ring topologies. Partial mesh WAN's are less expensive to implement than full mesh WAN's. |
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Term
PON
Passive Optical Network |
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Definition
| A network in which a carrier uses fiber-optic cabling to connect with multiple end-points-for example, many businesses on a city block. the word passive applies because PON no repeaters or other connectivity devices intervene between a carrier and its customer. |
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Term
PRI
Primary Interface Rate |
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Definition
| A type of ISDN that uses 23 bearer channels and one 64Kpbs data channel represented by the notation 23B+D. PRI is less commonly used by individual subscribers than BRI, but it may be used by business and other organizations needing more throughput. |
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Term
PSTN
Public Switched Telephone Network |
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Definition
| The network of lines and carrier equipment that provides telephone service to most homes and businesses. Now, except for the local loop, nearly all of the PSTN uses digital transmission. Its traffic is carried by fiber-optic or copper twisted pair cable, microwave, and satellite connections. |
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Term
PVC
Permanent Virtual Circuit |
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Definition
| A point-to-point connection over which data may follow any number f different paths, as opposed to a dedicated line that follows predefined path X, 25, frame relay, and some forms of ATM use PVC's. |
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Term
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Definition
| A type of WAN in which each site is connected to two other sites so the entire WAN forms a ring pattern. |
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Term
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Definition
| A standard for terminating wires in an eight pin connector. RJ-48 is the preferred connector type for the T1 connections that rely on twisted pair wiring. |
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Term
SDH
Synchronous Digital Hierarchy |
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Definition
| The international equivalent of SONET |
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Term
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Definition
| A characteristic of dual ring topologies that allows them to automatically reroute traffic along the backup ring if the primary ring becomes severed. |
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Term
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Definition
| An ANSI standard for T-carrier technology that refers to its physical layer electrical signaling characteristics. DS0 is the equivalent of one data or vice channel. All other signal levels are multiples of DS0. |
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Term
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Definition
| A termination for T-carrier wire pairs that is located at the customer demark and which functions as a connection protection and monitoring point. |
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Term
SONET
Synchronous Optical Network |
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Definition
| A high-bandwidth WAN signaling technique that specifies framing and multiplexing techniques at the physical layer of the OSI model. it can integrate many other WAN technologies (for example, T carriers, ISDN, and ATM technology)and allows for simple link additions and removals. SONET's topology includes a double ring of fiber optic cable, which results in very high fault tolerance. |
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Term
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Definition
| A type of WAN in which a single site acts as the central connection point for several other points. This arrangement provides separate routes for data between any tow sites; however, if the central connection point fails, the entire WAN fails. |
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Term
SVC
Switched Virtual circuit |
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Definition
| A logical point-to-point connection that relies on switches to determine the optimal path between sender and receiver. The ATM technology uses SVC's. |
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Term
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Definition
| A characteristic of transmission technology that provides equal throughput for data traveling both upstream and downstream and is suited to users who upload and download significant amounts of data. |
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Term
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Definition
| A variation of DSL that provides equal throughput both upstream and downstream between the customer and the carrier. |
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Term
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Definition
| A transmission method in which data being transmitted and received by nodes must conform to a timing scheme. |
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Term
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Definition
| A digital carrier standard used in North America and most of Asia that provides 1.544Mbps throughput and 24 channel for voice, data, video, or audio signals. T1's rely on time division multiplexing and may use shielded or unshielded twisted pair, coaxial cable, fiber optics, or microwave links. |
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Term
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Definition
| A digital carrier standard used in North America and most of Asia that can carry the equivalent of 672 channels for voice, data, or audio, with a maximum data throughput of 44.736 Mpbs (typically rounded up to 45Mpbs for purposes of discussion). T3's rely on time division multiplexing and require either fiber optic or microwave transmission media. |
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Term
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Definition
| The term for any kind of leased line that follows the standards for T1's, fractional T1's, T1C, T2's, T3's, or T4's. |
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Term
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Definition
| A device used to convert digital signals into analog signals for use with ISDN phones and other analog devices. TA's are sometimes called ISDN modems. |
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Term
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Definition
| The end nodes (such as computers and printers) served by the same connection (such as an ISDN, DSL, or T1 Link). |
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Term
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Definition
| A type of WAN in which sites that are connected in star or ring formations are interconnected at different levels, with the interconnection points being organized into layers to form hierarchical groupings. |
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Term
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Definition
| A term used to describe data traffic that flows from a customer's site to a carrier's facility. In asymmetrical communications, upstream throughput is usually much lower than downstream throughput. In symmetrical communications, upstream and downstream throughputs are equal. |
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Term
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Definition
| A connection between network nodes that, although based on potentially disparate physical links, logically appears to be a direct, dedicated link between those nodes. |
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Term
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Definition
| A point-to-point connection between tow nodes on a WAN. |
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Term
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Definition
| AN analog, packet switched WAN technology optimized for reliable, long distance data transmission and standardized by the ITU in the mid-1970's. The X.25 standard specifies protocols at the physical, data link, and the network layers of the OSI model. It provides excellent flow control and ensures data relaibility over long distances by verifying the transmission at every node. the X.25 can support a maximum of only 2 Mbps throughput. |
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Term
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Definition
| The term used to refer to all varieties of DSL. |
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