Viop phone - Voice Over IP

Prior to 1984, AT&T owned most of the network through its local Bell operating telephone companies. A layered hierarchy of office connections was designed around a five−level architecture. Each of these layers was designed around the concept of call completion. The offices were connected together with wires of various types called trunks. These trunks can be twisted pairs of wire, coaxial cables (like the CATV wire), radio (such as microwave), or fiber optics. As the convergence of voice and data networks continues, we see a revisitation to the older technologies as well as the new ones. Fiber is still the preferred medium from a carrier’s perspective. However, microwave radio is making a comeback in our telecommunications systems, linking door−to−door private−line services. Carrying voice, data, video, and high−speed Internet access is a given for a microwave system. Light−based systems, however, are limited in their use by telephone companies. It has been user demand that has brought infrared light and now Synchronous Optical Network−based (SONET) infrared systems in place. Recently, the introduction of an unguided light introduced by Lucent Technologies operates at speeds up to 2.4 Gbps to 10 Gbps. This offers the connectivity to almost anyone who can afford the system, because the right of way is no longer an issue.

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A network is a series of interconnections that form a cohesive and ubiquitous connectivity arrangement when all tied together. That sounds rather vague, so let’s look at the components of what constitutes the telecommunications network. The telecommunications network referred to here is the one that was built around voice communications but has been undergoing a metamorphosis for the past two decades. The convergence of voice and data is nothing new; we have been trying to run data over a voice network since the 1970s. However, to run data over the voice network, we had to make the data look like voice. This caused significant problems for the data because the voice network was noisy and error−prone. Reliability was a dream and integrity was unattainable, no matter what the price.
Generally speaking, a network is a series of interconnection points. The telephone companies over the years have been developing the connections throughout the world so that a level of cost−effective services can be achieved and their return on investment (ROI) can be met. As a matter of due course, whenever a customer wants a particular form of service, the traditional carriers offer two answers:

• It cannot be done technically.
• The tariff will not allow us to do that!

Regardless what the question happened to be, the telephone carriers were constantly the delay and the limiting factor in meeting the needs and demands for data and voice communications. In order to facilitate our interconnections, the telephone companies installed wires to the customer’s door. The wiring was selected as the most economical way to satisfy the need and the ROI equation. Consequently, the telephone companies installed the least expensive wiring possible.

Because they were primarily satisfying the demand for voice communications, they installed a thin wire (26−gauge) to most customers whose locations were within a mile or two from the central office. At the demarcation point, they installed the least expensive termination device (RJ−11), satisfying the standard two−wire unshielded twisted pair communications infrastructure. The position of the demarcation point depended on the legal issues involved. In the early days of the telephone network, the telephone companies owned everything, so they ran the wires to an interface point and then connected their telephone equipment to the wires at the customer’s end. The point here is that the telephone sets were essentially commodity−priced items requiring little special effect or treatment. When the data communications industry began during the late 1950s, the telephone companies began to charge an inordinate amount of money to accommodate this different service. Functionally, they were in the voice business and not the data business. As a matter of fact, to this day, most telephone companies do not know how to spell the word data! They profess that they understand this technology, but when faced with tough decisions or generic questions, few of their people can even talk about the services. How sad, they will be left behind if they do not change quickly. New regulations in the United States, in effect since the divestiture agreement, changed this demarcation point to the entrance of the customer’s building. From there, the customer hooked up whatever equipment was desired. Few people remember that in early 1980, a 2400 bps modem cost $10,000. The items that customers purchase from myriad other sources include all the pieces
we see during the convergence process. In the rest of the world today, where full divestiture or privatization has not yet taken place, the
telephone companies (or Post, Telephone, and Telegraph [PTTs]) still own the equipment. Other areas of the world have a hybrid system under which customers might or might not own their equipment. The combinations of this arrangement are almost limitless, depending on the degree of privatization and deregulation. However, the one characteristic that is common in most of the world to date is that the local provider owns the wires from the outside world to the entrance of the customer’s building. This local loop is now under constant attack from the wireless providers offering satellite service, local multipoint distribution services (LMDS), and multichannel multipoint distribution services (MMDS). Moreover, the CATV companies have installed coaxial cable or fiber, if new wiring has been installed, and they offer the interconnection to business and residential consumers alike. The Competitive Local Exchange Carriers (CLECs) who survived the bloodbath and fallout of 2000 and 2001 still remain as formidable foes to the local providers. They are installing fiber to many corporate clients (or buildings) with less expense and long−term write−off issues. The CLECs are literally walking away from the telephone companies’ local loop and using their own infrastructure. Add the x−Type Digital Subscriber Line (xDSL) family of products to this equation and the telephone companies are running out of options. The Community Antenna Television (CATV) companies are still outpacing the installation of Internet cable modems compared to the use of DSL services by the Regional Bell Operating Company (RBOC) and the CLECs. The numbers will probably change over time, but the current rate of installation is in the favor of the cable companies. This is where the CATV companies see the convergence occurring.

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In the local loop, the topological layout of the wires has traditionally been a single−wire pair or multiple pairs of wires strung to the customer’s location. Just how many pairs of wires are needed for the connection of a single line set to a telecommunications system and network? The answer (one pair) is obvious. However, other types of services, such as digital circuits and connections, require two pairs. The use of a single or dual pair of wires has been the norm. More recently, the local providers have been installing a four−pair (eight wires) connection to the customer location. The end user is now using separate voice lines, separate fax lines, and separate data communications hookups. Each of these requires a two−wire interface from the LEC. However, if a CATV provider has the technology installed, they can get a single coax (or fiber) to satisfy the voice, fax, data, and high−speed Internet access on a single interface, proving the convergence is rapidly occurring at the local loop. It is far less expensive to install a coax running all services (TV, voice, and data) than multiple pairs of wire, so the topology is a dedicated local connection of one or more pairs from the telephone provider to the customer location or a shared coax from the CATV supplier. This is called a star and/or shared star−bus configuration. The telephone company connection to the customer originates from a centralized point called a central office (CO). The provider at this point might be using a different topology. Either a star configuration to a hierarchy of other locations in the network layout or a ring can be used. The ring is becoming a far more prevalent method of connection for the local Telcos. Although we might also show the ring as a triangle, it is still a functional and logical ring. These star/ring or star/bus combinations constitute the bulk of the networking topologies today. Remember one fundamental fact: the telephone network was designed to carry analog electrical signals across a pair of wires to recreate a voice conversation at both ends. This network has been built to carry voice and does a reasonable job of doing so. Only recently have we been transmitting other forms of communication, such as fax, data, and video. The telephone switch (such as DMS−100 or #a5ESS) makes routing decisions based on some parameter, such as the digits dialed by the customer. These decisions are made very quickly and a cross−connection is made in logic. This means that the switch sets up a logical connection to another set of wires. Throughout this network, more or fewer connections are installed, depending on the anticipated calling patterns of the user population. Sometimes there are many connections among many offices  At other times, it can be simple with single connections. The telephone companies have begun to see a shift in their traffic over the past few years. More data traffic is being generated across the networks than ever before. As a matter of fact, 1996 marked the first year that as much data was carried on the network as voice. Since that time, data has continued its escalated growth pattern upwards of 30 percent, whereas voice has been stable at around a 4−percent growth.

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