We have done our best to compile these terms from trusted sources in the telecom industry; however, when using this glossary as a guide, understand that these definitions may have alternate meanings to various service providers in different markets.
We have done our best to compile these terms from trusted sources in the telecom industry; however, when using this glossary as a guide, understand that these definitions may have alternate meanings to various service providers in different markets.
A code assigned to a customer, a project, a department, a division—whatever. Typically, a person dialing a long distance phone call must enter that code so the Call Accounting system can calculate and report on the cost of that call at the end of the month or designated time period. Many service companies, such as law offices, engineering firms and advertising agencies use account codes to track costs and bill their clients accordingly. Some account codes are very complicated. They include the client’s number and the number of the particular project. The Account Code then includes Client and Matter number. These long codes can tax many call accounting systems, even some very sophisticated ones.
A shortened name for an automated attendant, a device which answers a company’s phones, encourages you to touchtone in the extension you want, and rings that extension. If that extension doesn’t answer, it may send the call to voice mail or back to the attendant. It may also allow you to punch in digits and hear information, e.g. the company’s hours of business, addresses of local branches, etc. See also Automated Attendant.
Also known as BRA (Basic Rate Access). There are two standard interfaces in ISDN: BRI and PRI. BRI is intended for consumer,SOHO(Small Office Home Office), and small business applications. BRI supports a total signaling rate of 144 Kbps, which is divided into two B (Bearer) channels which run at 64 Kbps, and a D (Delta, or Data) channel which runs at 16 Kbps. The B channels “bear” the actual data payload, i.e. they carry the actual information that you are sending. Such information can be PCM-encoded digital voice, digital video, digital facsimile, or whatever you can squeeze into a 64 Kbps full-duplex channel. The D channel is intended primarily for signaling and control information, including call setup, call maintenance and monitoring, call teardown, Caller ID, and Name ID. As the signaling and control requirements actually are fairly modest, the D channel also will support pocket data transfer at rates up to 9.6 Kbps, by special arrangement with the servicing telephone company and at additional cost. The preferred BRI standard is the “U” interface, which uses only two wires and makes use of the 2B1Q line coding technique in theU.S.and the 4B3T technique inEurope. Another BRI standard is the “T” interface which uses four wires. See ISDN for a much fuller explanation. See also 2B1Q, 4B3T, T Interface, and U Interface.
Today’s common definition of broadband is any circuit significantly faster than a dial-up phone line. That tends to be a cable modem circuit from your friendly local cable TV provider, a DSL circuit, a T-1 or an E-1 circuit from your friendly phone company. In short, the term “broadband” can mean anything you want it to be so long as it’s “fast.” In short, broadband is now more a marketing than a technical term.
Cable TeleVision. This term originally stood for “community antenna television,” reflecting the fact that the original cable systems carried only broadcast stations received off the air; however, as cable systems began to originate their own programming, the term evolved to mean Cable Television. CATV is a broadband transmission facility. It generally uses a 75-ohm coaxial cable which simultaneously carries many frequency-divided TV channels. Each channel is separated by guard channels. Some of the industry’s first CATV pioneers were TV-set dealers who figured that cable would drive demand. See Addressable Programming and Broadband.
A 1.544 million bits per second data stream that can be configured as a single clear channel T1 interface or channelized into as many as 24 discrete DSO interfaces. Time slots are numbered from 1 through 24.
The term and concept was coined by the Telecommunications Act of 1996. Essentially the idea of the CLEC was that it would be a new local phone company that would compete with the incumbent, i.e. existing, monopoly local phone company. The idea behind the Act was that the incumbent would be forced to lease local wired loops and other bits and pieces of its phone equipment—called unbundled network elements (UNE) —to the new phone company, i.e. the CLEC. Ultimately, the theory went, the CLEC would start building its own local phone lines and installing its own equipment and the public would benefit by better, cheaper, more innovative telecom service—especially broadband service to the Internet. The idea of leasing some of the ILEC’s plan was to give the CLEC a “leg up.” This was the theory. The first problem was that the legislation was the worst-written piece of legislation ever passed by Congress. The second problem was the ILECs deeply resented the idea that they were to allow competitors to get started in business at their expense and using their equipment and their lines. So the ILECs basically did everything they could get away with to mess up the CLECs. That meant delaying CLECs’ orders, creating onerous, cumbersome, new rules for doing business with them and creating huge, new charges for new services. For example, SBC (the new Southwestern Bell) came up with something called “Unbundled Local Switching” and stated in their new tariff that “The Rate Structure for ULS will be one of 2 rate structures: Stand Alone ULS or ULS-Interim Shared Transport (ULS-IST).” SBC laid out “General Principles for Stand Alone ULS: Stand Alone Unbundled Local Switching (ULS) which included charging for a single usage sensitive component in addition to the “appropriate” non-recurring and monthly recurring rates contained in the rate table. No one, of course, new what any of this meant but it didn’t make any difference. It delayed and confused things. It was sort of like laying siege to your enemy. And when you have unlimited resources (like the ILECs) you clearly will win. The CLECs’ final problem was marketing and sales. They were basically selling a service—phone or data service—that someone (their potential customers) can’t see, feel, touch or smell. The only differentiating criterion falls on sound—the quality of which is totally indistinguishable between the CLEC and the ILEC or between the CLEC and any other phone company in the country. The lack of a market and sales differentiator made selling CLEC services very, very difficult. You couldn’t sell a better product, so you sold lower prices. But no one believes the pitch for lower telecom prices. They’ve heard that “cut price” story a thousand times since long distance was de-regulated in theU.S.in the late 1950s. One CLEC, looking for a marketing magic bullet, did some market research among its potential customers and found that virtually all believed that the local ILEC was “The devil you know” and the local CLEC was “the devil you don’t know.” As a result, virtually all CLECs formed in the U.S. after 1996 have essentially failed—gone bankrupt, about to go bankrupt, or are only surviving because some kindly soul is pouring good money after bad and hasn’t the guts to close down his disaster. This may be too harsh. There are variations on the CLEC theme that may make it, but they need to be in no way dependent on the local ILEC for anything and they need to figure in some clever way to save on their horrendously high capital expenditures and come up with some clever highly-demanded, new telecom services. Right now, the CLECs compete on a selective basis for local phone service, long distance, international, broadband Internet access, and entertainment (e.g. Cable TV and Video on Demand). CLECs include cellular/PCS providers, ISPs, IXCs, CATV providers, CAPs, LMDS operators and power utilities. See Telecommunications Act of 1996 and UNE.
Another name for the Internet. The word cloud came from the cloud symbol that you see on the computer networking charts and diagrams as representing the Internet. See cloud computing.
Cloud computing is a general term for delivering computer services over the Internet—anything from sales force management to employee expense recording, from database management to off-site data backup, from simple email to complex scientific problems whose solutions requires seriously heavy computing power. Cloud computing has many benefits (more about them in a moment) —so long as the cloud continues to work. Item: I write a daily web site—www.InSearchOfThePerfectInvestment.com. The software to create the website is in the cloud. One day I was writing my blog when my cable TV service from Time Warner crashed, thus losing most of my morning’s work. Time Warner did not repair my service for several hours. In the meantime, I had to struggle to find alternate Internet service—which turned out to be Verizon’s broadband access service. Had I not been working “in the cloud,” I would have been working on my local computer, which continued to work. I would have had a far more productive day. In the Spring of 2011, one of the industry’s biggest cloud services provider, Amazon (the book seller) had some major problems, which knocked many popular websites (i.e. Amazon’s customers) off the Internet. Amazon said a traffic shift “was executed incorrectly” and went on to explain it all in a 5,700 word postmortem report. Amazon said it will get better and hopefully the same problem won’t happen again. Suffice, the whole area of cloud computing came from the symbol of a cloud that’s often used to represent the Internet in flow charts and diagrams. Cloud computing services are broadly divided into three categories: Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS). A cloud computing service typically has three things that differ it from traditional computer hosting services. It is sold on demand, typically by the minute or the hour; it is “elastic”—a user can use as much or as little as they want and the service is managed by the provider. The customer often needs nothing more than a personal computer and Internet access. Cloud computing has two big benefits. First, a user doesn’t need to invest in his own computers and software and a place to house all the stuff. Someone else has typically done all that. That typically makes it much less expensive, especially if the user’s demand is only occasional and/or intermittent. Second, the provider keeps the system working, i.e. maintained; and often introduces upgrades and improvements, all of which cost money. Amazon and Google are key players in cloud computing. Zillions of other companies are moving in. See the following definitions.
A service provider that makes a cloud computing environment available to others. See cloud, cloud computing, external cloud, public cloud.
(See cloud, see cloud provider, see cloud computing)
A cable composed of an insulated central conducting wire wrapped in another cylindrical conducting wire. The whole thing is usually wrapped in another insulating layer and an outer protective layer. A coaxial cable has capacity to carry great quantities of information. It is typically used to carry high-speed data (as in connections of 327X terminals to computer hosts) and CATV installations.
A telecommunications facility or service which permits callers from several diverse locations to be connected together for a conference call. The conference bridge contains electronics for amplifying and balancing the conference call so everyone can hear each other and speak to each other. The conference call’s progress is monitored through the bridge in order to produce a high quality voice conference and to maintain decent quality as people enter or leave the conference.
Optical fiber through which no light is transmitted and which, therefore, no signal is being carried. Generally speaking, a dark fiber is one of many fibers contained within a bundle of fibers. Carriers commonly deploy a large number of fibers (432 is a common number) at any given time, since the incremental cost of laying a big bundle is modest compared to pulling them one at a time as the need arises. In fact, a carrier often has little choice, as the right of way may be granted once, and only once. The fibers the carrier is using immediately are “lit,” and those that currently are unused are left “dark.” The dark fiber is available for future use. Sometimes dark fiber is sold by a carrier without the accompanying transmission electronics. The customer, which may be an end user organization or another carrier, is expected to light up that strand of fiber with his own electronics. See also dark copper, dark current, dim fiber, and lit fiber.
Communications channels provided specifically for the exchange of data as compared to voice. See also IP Telephony.
A connection between a phone or phone system (like a PBX) and an IntereXchange Carrier (IXC) through a dedicated line. All calls over the line are automatically routed to a particular IXC.
A type of service often used by large companies which have a direct telephone line going directly to the long distance companies’ “Point of Presence” (POP), thereby bypassing the local telephone company and reducing the cost per minute. Often referred to as “T-1” service.
A channel leased from a common carrier by an end user used exclusively by that end user. The channel is available for use 24 hours a day, seven days a week, 52 weeks of the year, assuming it works that efficiently.
(See dedicated Channel or Circuit and see internet)
<dt style=”margin-bottom:10px;”>Line: A nondedicated communication line in which a connection is established by dialing the destination code and then broken when the call is complete.</dt>
<dt>Switch: An Internet Access Term. Category of switching equipment designed to manage the dialup connections between the PSTN and either the Internet or a corporate LAN internetwork, providing security, accounting, and service management capabilities.</dt>
Direct Inward Dialing. You can dial inside a company directly without going through the attendant. This feature used to be an exclusive feature of Centrex but it can now be provided by virtually all modern PBXs and some modern hybrids, but you must connect via specially configured DID lines from your local central office. A DID (Direct Inward Dial) trunk is a trunk from the central office which passes the last two to four digits of the Listed Directory Number to the PBX or hybrid phone system, and the digits may then be used verbatim or modified by phone system programming to be the equivalent of an internal extension. Therefore, an external caller may reach an internal extension by dialing a 7-digit central office number. Notice: DID is different from a DIL (Direct-In-Line) where a standard, both-way central office trunk is programmed to always ring a specific extension or hunt group. Traditionally, DID lines could not be used for outdial operation, since there was no dial tone offered. More recently, the individual channels in a T-1 trunk can be defined in terms of their directional nature, with some being defined as DID, some as DOD (Direct Outward Dialing), and some as combination (both incoming and outgoing). See also Combination Trunk, Direct Inward System Access, and DOD.
A generic name for a family of digital lines (also called xDSL) being provided by CLECs and local telephone companies to their local subscribers. Such services go by different names and acronyms—ADSL (Asymmetric Digital Subscriber Line), HDSL (High Bit Rate Digital Subscriber Line) and SDSL (Single Pair Symmetrical Services). Such services propose to give the subscriber up to eight million bits per second one way, downstream to the customer, and somewhat fewer bits per second upstream to the phone company. DSL lines typically operate on one pair of wires—like a normal analog phone line. See ADSL, G.990, G-Lite, HDSL, IDSL, RADSL, SDSL, Splitter, Splitterless, VDSL, xDSL, for more detailed explanations.
Another term for a naked DSL. See naked DSL.
Digital Signal, level 0. A DS-0 is a voice-grade channel of 64 Kbps (i.e. 64,000 bits per second). This channel width is the worldwide standard speed for digitizing one voice conversation using PCM (Pulse Code Modulation). The analog signal is sampled 8,000 times a second, with each sample encoded into an 8-bit byte (thus 8 x 8,000 = 64,000). There are 24 DS-0 channels in a T-1, the North American version of DS-1.
Digital Signal, level 1. It is a 1.544 Mbps (i.e. 1.544 million bits per second) in North America (T-1) and Japan (J-1), and 2.048 Mbps in Europe (E-1), i.e. 2,048,000 million bits per second. Those speeds are symmetrical. That means they’re the same in both directions. Many people ask why they are different. The first thing you have to understand is the purpose of DS-1. The reason for developing it was to increase the number of voice grade interoffice trunks that could function over a single twisted pair of wires. The Beta testing was conducted in New York’s Manhattan in 1961. When the T-1 standard was developed in North America, the engineers looked at the distribution cables then in use. What they found were cables consisting of 24 AWG wire pairs with loading coils installed every 6000 feet. Bell Labs did some experiments and found that maximum bit rate that could be achieved over each 6000 foot span was 1.544 Mbps. The loading coils were replaced with repeaters to terminate and re-generate the signals. At the same time, Ericsson was following a similar path in London. The loading coil spacing in Europe was only 4000 feet, so the maximum achievable bit rate was higher (2.048 Mpbs). Why there’s no consistency is one of those wonderful unanswered questions. T-1 is the original standard, having been developed by Bell Telephone Laboratories in the 1950s. Subsequently, the ITU-T developed the European E-1 standard, variant, which also runs at 1.544 Mbps, but it is incompatible with T-1. The T-1 standard, at 1.544 Mbps, for example, supports 24 voice conversations, each encoded at 64 Kbps. The E-1 standard, at 2.048 Mbps, supports 30 conversations, plus two signaling and control channels, for a total of 32 channels, each of 64 Kbps. See also T-1.
Digital Signal, level 2. DS-2 effectively translates to T-2 in North America, and J-2 in Japan. (There is no European equivalent.) DS-2 supports a total signaling rate of 6.312 Mbps. It is the equivalent of 4 T-1s, and supports 96 DS-0 channels of 64 Kbps, plus overhead in support of additional requirements for signaling and control functions. DS-2 is used in carrier (telco) applications, and only rarely. See DS-, DS-0, DS-1, T-1 and T-2.
Digital Signal, level 3. In North America and Japan, DS-3 translates into T-3, which is the equivalent of 28 T-1 channels, each operating at total signaling rate of 1.544 Mbps. The 28 T-1s are multiplexed through a M13 (Multiplex 1 to 3) Multiplexer, and 188 additional signaling and control bits are added to each T-3 frame. As each frame is transmitted 8,000 times a second, the total T-3 signaling rate is 44.736 Mbps. In a channelized application, T-3 supports 672 channels, each of 64 Kbps. In the European hierarchy, a DS-3 is in the form of an E-3, which runs at a total signaling rate of 34.368 Mbps, supports 480 channels, and is the equivalent of 16 E-1s. A J-3 runs at 32.064 Mbps, supports 480 channels, and is the equivalent of 20 J-1s. If you’re moving a DS-3 (or any other DS signal) across continents, the standards of the target country rule. Channels get muxed and demuxed, with signaling conventions translated, as well. Here is a question from a reader: On the U.S. side, T-1s are in multiples of 24×64 Kbps circuits and in the U.K. we have two-megabit circuits with 30×64 Kbps. If we want to interconnect to the U.S. at DS-3 level, would we receive 28 T-1s with 6 spare channels, or do they muxed and demuxed into multiples of 30 when they arrive over this side of the world? Answer: They get muxed and demuxed, along with signaling conventions translated into multiples of 30 when they arrive in the U.K.? DS-3 is also called T-3. See DS-, DS-0, DS-1, T-1, T-2 and T-3.
Digital Signal, level 4. T-4 runs at a total signaling rate of 274.176 Mbps in North America in support of 168 T-1s, yielding 4032 standard voice-grade channels. E-4 runs at 139.264 Mbps in Europe in support of 64 E-1s, yielding 1920 voice-grade channels. J-4 runs at 397.200 Mbps in Japan in support of 240 J-1s, yielding 5760 channels. See DS-0, DS-1, T-1, T-2 and T-3.
A T-1 line is 1.544 million bits per second transmission in both directions. Because these 1.544 million bites are raw bits, they can be configured in many ways—as 24 voice lines or 1.544 million bit per second line to another office or the Internet. A dynamic T-1 is not a technical term. It’s a marketing term. And what one vendor means by a dynamic T-1 may be very different from another vendor means. Essentially the idea is that this T-1 is chameleon. It changes its colors from time to time. One moment it’s 24 voice lines. The next moment it’s 1.544 million bits of data per second to the Internet. Or somewhere in between, perhaps 12 lines of voice and 772,000 bits per second of data per second to and from the Internet. In other words, it assigns bandwidth dynamically—as it’s needed. How Dynamic T-1 works depends on your vendor, how they implement the service, and how they assign priorities between voice and data. The typical approach is a black box at your office which monitors your T-1 traffic and reallocates bits to voice, to data, to a bit in between. This dynamic reallocation isn’t instantaneous and in fact, may take minutes or even hours to occur. Typically preference is given to voice, with data taking a slightly back seat. But how dynamic T-1 is implemented varies from one vendor to another. It pays to ask.
100BaseT. Ethernet at 100 Mbps, a tenfold improvement over the original Ethernet speed of 10 Mbps. Fast Ethernet is in the form of an Ethernet hub with an internal bus that runs at 100 Mbps. The interface to the hub is through a part which generally is selectable (i.e. programmable) to run at either 10 Mbps or 100 Mbps, depending on the requirement of the attached device. Connection between the hub and the attached workstation or other device is over data-grade UTP (Unshielded Twisted Pair) in the form of Cat (Category) 5, at a minimum, and over distances of up to 100 meters, at a maximum. The attached device connects to the UTP connection via a 10/100 Mbps NIC (Network Interface Card). 100BaseT hubs interconnect over fiber optic facilities, which can support 100 Mbps over relatively long distances with no loss of performance. Fast Ethernet is no longer all that fast. Gigabit Ethernet switches were standardized in 1998. See also 10BaseT, 100BaseT, Cat 5, Ethernet, Gigabit Ethernet, NIC and UTP.
A shortened way of saying “fiber optic.” Fiber is made of very pure glass. In Bill Gates’ book called “The Road Ahead,” he says that “optical fiber is so clear and pure that if you looked through a wall of it 70 miles thick, you’d be able to see a candle burning on the other side.” Digital signals, in the form of modulated light, travels on strands of fiber for long distances. The big advantage that fiber has over copper is that it can carry far, far more information over much, much longer distances. The short history of fiber optics for communications is that scientists keep discovering more and more ways of putting more and more information down the same one single strand of fiber. Based on my own personal researches, no one has any idea what the eventual capacity limit of a stand of fiber optic might be. I have personally asked many scientists (including one Nobel Physics Prize winner) and all seem to think there must be a theoretical limit. But they don’t know what it is, or when we’ll reach that limit. And they believe we have many, many years of breakthroughs in fiber still to go. As of the time of this writing, SONET OC-192 (Synchronous Optical NETwork Optical Carrier Level 192) systems are being deployed fairly routinely by a number of major long distance carriers. Each OC-192 strand supports approximately 10 Gbps. With DWDM (Dense Wavelength Division Multiplexing), as many as 32 “windows,” or wavelengths of light, can be overlaid into a single strand at OC-192, yielding a total of approximately 320 Gbps. Fiber is the American spelling. The spelling in England, Europe, Canada, Australia and New Zealand is fibre. See also the following definitions beginning with fiber.
FX. Provides local telephone service from a central office which is outside (foreign to) the subscriber’s exchange area. In its simplest form, a user picks up the phone in one city and receives a dial tone in the foreign city. He will also receive calls dialed to the phone in the foreign city. This means that people located in the foreign city can place a local call to get the user. The airlines use a lot of foreign exchange service. Many times, the seven digit local phone number for the airline you just called will be answered in another city, hundreds of miles away. See also Foreign Central Office Service and Foreign Exchange Trunk.
FT-1. Fractional T-1 refers to any data transmission rate between 56/64 Kbps (DSO rate) and 1.544 Mbps (T-1). Fractional T-1 is a four-wire (two copper pairs) digital circuit that’s not as fast as a T-1. Fractional T-1 is popular because it’s typically provided by a LEC (Local Exchange Carrier) or IXC (interexchange Carrier) at less cost than a full T-1, and in support of applications that don’t require the level of bandwidth provided by a full T-1. While FT-1 is less costly than a full T-1, it is more costly on a channel-by-channel basis, as you would expect. Users love FT-1, but carriers hate it. FT-1 costs the carriers just as much to provision as does a full T-1, they just turn down some of the channels. FT-1 is typically used for LAN interconnection, videoconferencing, high-speed mainframe connection and computer imaging.
Gigabit Ethernet (GE) uses the same framing as Ethernet and Fast Ethernet, but has a much higher clock speed (one billion bits per second). There are slower Ethernets: 10Base-T Ethernet (the kind on our desktop) runs at 10 million bits per second, while fast Ethernet runs at a clock speed of one hundred million bits per second (100BaseT) —the kind we are increasingly seeing on our desktop. The Gigabit Ethernet over fiber optic cable standard was finalized and formally approved on June 29, 1998, as IEEE 802.3z. The GE over Category 5 cable standard was ratified as IEEE 802.3ab. The IEEE 802.3ab standard uses all four pairs (8 wires) of cable in the Category 5 cable for transmission. This was a departure from previous Ethernet and Fast Ethernet copper standards which only used two pairs (4 wires) in the IEEE 802.3 and 802.3u standards. Although GE is available in both shared and switched varieties, the pricing difference between the two has become so marginal that most manufacturers are only producing the switched (and thus faster-feeling) variety. While GE is much like traditional Ethernet, differences include frame size options. The clock speed of GE is ten orders of magnitude greater than its predecessors and the previous frame size of 1,518 bytes was a bottleneck in the transmission of information. The maximum frame size has been increased from 1,518 bytes to a jumbo frame size of 9K (9,216 bytes). The larger frame size improves the frame throughput of a GE switch as each frame requires switch processing of only header information (cut-through switching). The fewer frames presented to the switch, the more data the switch can process, switch and deliver in a given period of time. Multi-mode fiber will support Gigabit Ethernet transmission at distances up to 550 meters, and single mode fiber up to 40 kilometers. The distance that really can be transmitted is dependent upon the optics used to transmit and receive the signal. In each case, there is a minimum distance of 2 meters due to issues of signal reflection (echo). GE switches adhering to the IEEE 802.3ab standard, offer auto-negotiating 10/100/1000 Mbps ports. Both half-duplex and full-duplex interfaces are supported, with full-duplex offering the advantage of the need for the CSMA/CD protocol because data collisions are impossible with a full-duplex mechanism. QoS (Quality of Service) guarantees are not currently an inherent element of GE like ATM has, but Ethernet has a prioritization mechanism revolving around the three IEEE 802.1p tagging bits written about in the IEEE 802.1q standards. Gigabit Ethernet has recently been extended to 10 gigabit speeds with the ratification of the IEEE 802.3ae. Service providers have started to adopt 10 GE as an alternative to SONET with the advent of the IEEE 802.ah Ethernet in the First Mile (EFM) standardization. See also 64b/66b, 802.3ah, 802.3ab, 802.3ae, and 10 Gigabit Ethernet.
Another name for IP Centrex. See the definition of that term.
Someone else owns my PBX and rents me space, time and telecommunications services on it. That PBX is typically away from my office. It’s joined to me by various types of phone lines, including T-1. Essentially hosted PBX is a fancy new name for what we used to call Centrex, when the phone company owned the PBX (actually it was a big central office, also called a public exchange) and rented me space, time and telephone services on it. There are advantages and disadvantages to being a customer of a hosted PBX. The arguments are similar to the age-old question: Should I buy or rent my house? See also Centrex.
See also hosted PBX. Also called virtual phone system.
Hosted VoIP (Voice Over Internet Protocol) is where the softswitch or IP PBX is on the service provider’s (SP) premises instead of the customer’s premises. The SP owns the equipment and operates and maintains it. The equipment is connected to the customer premises via fiber, DSL, T1, or even a wireless broadband link. Hosted VoIP is analogous to hosted solutions in the POTS world, such as Centrex and hosted PBX.
An xDSL variant that uses ISDN BRI (Basic Rate Interface) technology to deliver transmission speeds of 128 Kbps on copper loops as long as 18,000 feet. IDSL is symmetric, i.e. equal bandwidth is provided in both directions. IDSL is a dedicated service for data communications applications only. In that respect, IDSL differs from ISDN, which fundamentally is a circuit-switched service technology for voice, data, video and multimedia applications. IDSL terminates at the user premise on a standard ISDN TA (Terminal Adapter). At the LEC CO, the loops terminates in collocated ISP electronics in the form of either an IDSL access switch or an IDSL modem bank connected to a router. The connection is then made to the ISP POP via a high-bandwidth dedicated circuit. IDSL is used by LECs to deliver relatively low speed DSL services in geographic areas where ISDN technology is in place, but ADSL technology is not. See also xDSL, ADSL, BRI, ISDN, HDSL, RADSL, SDSL, Terminal Adapter, and VDSL.
An AT&T term for the provision of access for multiple services such as voice and data through a single system built on common principles and providing similar service features for the different classes of services.
The method by which users connect to the Internet, usually through the service of an Internet Service Provider (ISP).
The method by which users connect to the Internet, usually through the service of an Internet Service Provider (ISP).
A general term used to describe accessing the Internet using the cable TV coaxial cable for inbound Internet access (i.e. downstream) and the phone line for sending up commands and requests (i.e. upstream information). The cable TV is very fast—as much as six million bits per second. The phone is relatively slow—no more than fifty thousand bits per second. But it works because most information from the Internet flows at you, not away from you. The cable and telecom industry is working on standards to make disparate cable systems and TV set-top boxes work with each other. The industry has developed Data Over Cable Service Interface Specification (DOCSIS), which sets standards for both two-way and cable-plus-phone specifications. See DOCSIS.
Internet Protocol PBX. An IP PBX connects its phones via an Ethernet LAN and sends its voice conversations in IP packets. There are pros and cons to IP PBXs. Move and changes with the phones are easier. Wiring is easy. Voice quality and management controls vary between systems. The IP PBX is an evolving animal. See IP Telephony and TCP/IP. See also IP-enabled PBX.
Internet Protocol phone. A telephone that connects to an IP PBX or VoIP provider’s equipment via an IP connection instead of via a traditional analog phone line.
See VoIP for the best explanation. Here is Microsoft’s definition, excerpted from their white paper on TAPI 3.0: IP Telephony is an emerging set of technologies that enables voice, data, and video collaboration over existing IP-based LANs, WANs, and the Internet. Specifically, IP Telephony uses open IETF and ITU standards to move multimedia traffic over any network that uses IP (the Internet Protocol). This offers users both flexibility in physical media (for example, POTS lines, ADSL, ISDN, leased lines, coaxial cable, satellite, and twisted pair) and flexibility of a physical location. As a result, the same ubiquitous networks that carry Web, email, and data traffic can be used to connect to individuals, businesses, schools, and governments worldwide. What are the benefits of IP Telephony? IP Telephony allows organizations and individuals to lower the costs of existing services, such as voice and broadcast video, while at the same time broadening their means of communication to include modern video conferencing, application sharing, and whiteboarding tools. In the past, organizations have deployed separate networks to handle traditional voice, data, and video traffic. Each with different transport requirements, these networks were expensive to install, maintain, and reconfigure. Furthermore, since these networks were physically distinct, integration was difficult if not impossible, limiting their potential usefulness. IP Telephony blends voice, video and data by specifying a common transport, IP, for each, effectively collapsing three networks into one. The result is increased manageability, lower support costs, a new breed of collaboration tools, and increased productivity. Possible applications for IP Telephony include telecommuting, real-time document collaboration, distance learning, employee training, video conferencing, video mail, and video on demand. See the Internet, IP Telephony algorithms, TAPI, TAPI 3.0, TCP/IP, and most importantly, VoIP.
The connection between a customer’s premises and a point of presence of the Exchange Carrier.
A local phone company. See also LEC. As defined by the Telecommunications Act of 1996, a local exchange carrier means any person that is engaged in the provision of telephone exchange service or exchange access. Such term does not include a person insofar as such person is engaged in the provision of a commercial mobile service under section 332(c), except to the extent that the Commission (the Federal Communications Commission) finds that such service should be included in the definition of such term.
A telecommunications service provided by a local exchange carrier that connects a subscriber to the public switched telephone network. Examples of local exchange service are residential single-line service (also called R1 service) and business single-line service (also called B1 service).
Any telephone call to a location outside the local service area. Also called a toll call or trunk call.
MEN. Metro Ethernet Network is a way to connect buildings on the Internet like desktops within a building. Its advantages include relatively simple scalability, due to its packet-based technology. Standards compliant interfaces are available for data communication/telecommunication devices at line rates of 10/100/1000 Mbps, and the draft standard for 10 Gbps has been ratified. An Ethernet-based Metropolitan Area Network is generally terms a Metro Ethernet Network. Some European service providers have also introduced MEN-like technology for Wide Area Networks. In enterprise networks, Metro Ethernet is used primarily for two purposes: connectivity to the public Internet and connectivity between geographically separate corporate sites—an application that extends the functionality and reach ability of corporate networks. See Metropolitan Area Network.
Optical Carrier-level 12. SONET channel of 622.08 Mbps. See also Concatenation, OC-1, OC-12c, OC-N and SONET.
Optical Carrier-level 3. A SONET channel equal to three DS-3s, which is equal to 155.52 Mbps. See also Concatenation, OC-1, OC-3c, and SONET.
Optical Carrier-level 48. SONET channel of 2.488 Gbps. How you calculate OC-48 is to multiply 51.84 Mbps by 48. That gives you 2.488 thousand million bits per second, or roughly 2.5 Gbps (Gigabit per second). See also Concatenation, OC-1, OC-N and SONET.
A private circuit, conversation or teleconference in which there is one person at each end, usually connected by some dedicated transmission line. In short, a connection with only two endpoints. See also Point-to-Multipoint.
Plain Old Telephone Service. Pronounced POTS, like in pots and pans. The basic service supplying standard single line telephone, telephone lines and access to the public switched network. Nothing fancy. No added features. Just receive and place calls. Nothing like Call Waiting or Call Forwarding. They are not POTS services. All POTS lines work on loop start signaling. See also Loop Start.
An outside telephone number separate from the PBX, can be set up to appear on one of the buttons of a key telephone. Also called an Auxiliary Line. See also Private Line.
Symmetrical Digital Subscriber Line, also sometimes referred to as Single-line DSL. SDSL is a proprietary version of symmetric DSL versions such as HDSL and HDSL2. SDSL technology offers digital bandwidth of up to 2.3 Mbps both ways (that’s why it’s called symmetrical) over a single twisted-pair copper phone line, over distances up to about 10,000 feet on an unrepeated basis. SDSL is aimed at the corporate and SOHO markets that require high upstream and downstream traffic rates. SDSL uses the same 2B1Q modulation scheme used in ISDN BRI. In February 2001, the ITU-T standardized on G.shdsl, which largely obsoleted SDSL. See also xDSL, ADSL, G.shdsl, HDSL, HDSL2, IDSL, RADSL, SHDSL, and VDSL.
Session Initiation Protocol trunk. A virtual circuit set up on an Internet access line, and over which VoIP calls travel from the customer’s IP PBX to the outside world via the customer’s VoIP provider, which uses peering arrangements with other VoIP operators and/or interconnections with the PSTN to send the call to the destination network. Calls into the customer’s IP PBX from the outside world use the same interconnections, in the reverse direction. See SIP.
A telecommunications service for which the subscriber is given a toll-free number that others can call without incurring toll charges because the subscriber pays for calls to the number.
A VoIP-enabled service whereby a secondary number is established that is only able to receive incoming calls, and when such a call comes, the call is automatically forwarded over an IP network to the customer’s primary phone number. When a virtual phone number is established for another area code, it enables long-distance charges to be avoided for calls to the virtual phone number that originates in that area code. Similarly, when a virtual phone number is established for another country code, it means avoiding international charges.
Same as hosted phone system. See also hosted PBX. The phone company owns the equipment, typically located in their offices. You get to rent (or buy) the phones sitting on your organization’s desks.
A service performed by Internet Service Providers (ISPs) and Internet Access Providers (IAPs) who encourage outside companies to put their websites on computers owned by the ISPs. These computers are attached to communications links to the Internet—often high-speed links. For this Web hosting service, the ISPs typically charge their clients by equipment and transmission capacity used. See also Server Colocation and Web Host.
Wireless Fidelity. Wi-Fi is now the most common way people access the Internet. Whether at their homes, in coffee shops, in Internet cafes, in hotels, in airports, or in their offices, people open their laptops, turn on their wireless access and attach to a nearby Wi-Fi service. Wi-Fi is a low power wireless system with a range of no more than 300 feet from the transmitter. Hence the closer you are to a transmitter, the more change you have of connecting and the faster your Wi-Fi transmit/receive will be. You can improve your connection chances and “extend” the distance with a device called a range extender or signal booster. In my house, I have one installed 50 feet from my main Wi-Fi transmitter/receiver. It allows me to move farther from my main transmitter and still get a stronger signal. I use it for surfing the Internet in bed—an activity my wife tolerates. Wi-Fi is defined in the IEEE’s standard 802.11b. That standard specifies a simple low power (tops 1 WATT), unlicensed radio frequency service which actually operates on the same frequency as some cordless phones, garage door openers, walkie-talkies, etc. An 802.11b Wi-Fi base station is typically attached to a local area network, which is then attached to the Internet and/or the corporate network through a cable modem, a DSL router, or T-1 line. 802.11b defines both the Physical (PHY) and Medium Access Control (MAC) protocols. Specifically, the PHY spec includes three transmission options—one Ir (Infrared), and two RF (Radio Frequency). Most Wi-Fi systems work in the 2.4 GHz range (2.4-2.483 GHz).