Shadow
eCorridors - enhancing communities with the speed of light
Virginia Tech
Glossary of Terms
The part of a communications network that connects to the commodity internet and handles the major traffic. It employs the highest-speed transmission paths and typically covers the greatest distance for a regional network. Smaller networks are connected to the backbone via short-haul fiber lines and/or a variety of "last mile" technologies.
The smallest unit of information on a computer network; a binary digit. Data is transmitted in bits per second.
The wires and connectors used to tie a network together.
A building that houses a telecommunications switching or tracking system such as a local telephone company-switching center. There are two types. The first is called an "end office" (EO) or "local exchange" (LE) and connects directly to the outside plant, which is the feeder and distribution system to homes and offices. The second type is the tandem office (also toll office or tandem/toll office), which is a central office that does not connect directly to the customer. Toll call record generation and accounting used to be handled in the tandem offices.
Placing equipment owned by a customer or competitor in an organization's own facility. Telephone companies often allow co-location in order to provide the best interconnection between devices.
(Digital Signal) A classification of digital circuits. The DS technically refers to the rate and format of the signal, while the T designation refers to the equipment providing the signals. In practice, "DS" and "T" are used synonymously; for example, DS1 and T1, DS3 and T3.
The most widely-used local area network (LAN) access method, defined by the IEEE as the 802.3 standard. Ethernet has become so popular that a specification for "LAN connection "or" network card" generally implies Ethernet without saying so. Twisted pair Ethernet (10BaseT) uses economical telephone wiring and standard RJ-45 connectors, often taking advantage of installed wires in a building. It is wired in a star configuration and requires a hub. Fast Ethernet (100BaseT) is similar, but uses two different twisted pair configurations (see 100BaseT). 10BaseT and 100BaseT are the most popular versions of Ethernet. "see also Gigabit Ethernet, below")
Communications systems that use optical fibers for transmission. Fiber-optic transmission became widely used in the 1980s when the long-distance carriers created nationwide systems for carrying voice conversations digitally over optical fibers.

Eventually, all transmission systems may become fiber optic-based. Also, in time, the internals of computers may be partially or even fully made of light circuits rather than electrical circuits.
A high-speed packet switching protocol used in wide area networks (WANs). Providing a granular service of up to DS3 speed (45 Mbps), it has become very popular for LAN to LAN connections across remote distances. Many of the major carriers offer frame relay services.
An Ethernet technology that raises transmission speed to 1 Gigabit per second (Gbps). It is used primarily for backbones.
Internet service provider. An organization that provides connectivity to the Internet. Many also offer related services such as web page hosting, on-call support, training, etc. Small internet service providers (ISPs) provide "dial-up" service via modem and ISDN while the larger ones also offer dedicated ethernet (ethernet service is offered with a wide range of transmission speeds and other added features depending on the level of sophistication of the ISP and the market demand)
An organization that provides interstate (long distance) communications services within the U.S. Examples are: AT&T, MCI WorldCom, Sprint and more than 700 others.
A communications network that serves users within a confined geographic area. It consists of servers, workstations, a network operating system and a communications link.
An optical fiber with a core diameter of from 50 to 100 microns. It is the most commonly-used optical fiber for short distances such as LANs. Light can enter the core at different angles, making it easier to connect the light source to broader light sources such as LEDs.
An in-house telephone switching system that interconnects telephone extensions with the outside telephone network. It may include functions such as least cost routing for outside calls, call forwarding, conference calling and call accounting. Modern PBXs use all-digital methods for switching and may support both digital terminals and telephones along with analog telephones
The point at which a line from a long distance carrier (IXC) connects to the line of the local telephone company or to the user if the local company is not involved. For online services and Internet providers, the POP is the local exchange users dial into via modem.
DS0 1 64 Kbps
DS1 24 1.544 Mbps (T1)
DS1C 48 3.152 Mbps (T1C)
DS2 96 6.312 Mbps (T2)
DS3 672 44.736 Mbps (T3)
DS4 4032 274.176 Mbps (T4)
OC-1 STS-1 51.84 Mbps (28 DS1s or 1 DS3)
OC-1 STS-1 51.84 Mbps (28 DS1s or 1 DS3)
OC-3 STS-3 155.52 Mbps (3 STS-1s)
OC-3c STS-3c 155.52 Mbps (concatenated)
OC-12 STS-12 622.08 Mbps (12 STS-1, 4 STS-3)
OC-12c STS-12c 622.08 Mbps (12 STS-1, 4 STS-3c)
OC-48 STS-48 2488.32 Mbps (48 STS-1, 16 STS-3)
OC-192 STS-192 9953.28 Mbps (192 STS-1, 64 STS-3)
OC-768 STS-768 39813,12 Mbps (768 STS-1, 256 STS-3)
An optical fiber with a core diameter of less than 10 microns. Used for high-speed transmission over long distances, it provides greater bandwidth than multimode, but its smaller core makes it more difficult to couple the light source. Increasingly, singlemode fiber is used for shorter distances.
A fiber-optic transmission system for high-speed digital traffic. Employed by telephone companies and common carriers, SONET speeds range from 51 megabits to multiple gigabits per second. SONET is an intelligent system that provides advanced network management and a standard optical interface.
Another name for a PBX or central office (see above definitions)
An Ethernet network that runs through a high-speed switch. Changing to switched Ethernet means replacing the Ethernet hub with a switch. Instead of sharing 10 Mbps for Ethernet or 100 Mbps for Fast Ethernet among all users on the network segment, the full bandwidth is made available to each sender and receiver pair.
A 1.544 Mbps point-to-point dedicated, digital circuit provided by the telephone companies (is it only ever provided by phone co's?). The monthly cost is typically based on distance. T1 lines are widely used for private networks as well as interconnections between an organization's PBX or LAN and the telco. A T1 is the typical connection used in campus and office building networks. T1 carries both voice and data.
A 44.736 Mbps point-to-point dedicated line provided by the telephone companies. A T3 line provides 672 64-Kbps voice or data channels. Telecommunications infrastructure An advanced, seamless web of public and private communications networks, interactive services, interoperable hardware and software, computers, databases, and consumer electronics to put vast amounts of information at users' fingertips. A telecommunications infrastructure includes more than just the physical facilities used to transmit, store, process, and display voice, data, and images; it encompasses a wide range of interactive functions, user-tailored services, and multimedia databases that are interconnected in a technology-neutral manner that will favor no one industry over any other (where did this come from? this last phrase is interesting, is that an opinion or fact?)
A company that provides telephone services. It may refer only to local telephone companies or to both local and long distance carriers if referring to the telephone industry in general.
A communications network that covers a wide geographic area, such as state or country. A LAN (local area network) is contained within a building or complex, and a MAN (metropolitan area network) generally covers a city or suburb. Following is a bandwidth comparison between major LAN and WAN technologies.
Shadow