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Network Services

Network services can be grouped into several categories which define their basic nature. Those categories include access services, dedicated services, switched services and virtual services.

Access Services

Access services are those services which provide circuit access to the network, generally to the LEC central office. They may be analog or digital, and single channel or multichannel. Access services include residential and business lines, and PBX trunks.

Residential lines

Residential lines are local loop connections between the residential premise and the central office exchange.

Business lines

Business lines are local loop connections between the business premise and the central office exchange. Business lines provide access to single line and multiline terminal sets, as well as to Key Telephone Systems (KTSs).

PBX trunks

PBX trunks are local loop connections between PBX switches and network switches. As noted in Chapter 4, PBX trunks may be incoming only, outgoing only, or bidirectional (combination). Trunk connections may be provisioned individually, although they more typically are provisioned on a high-capacity, multichannel basis. Trunks which serve specific purposes are grouped into trunk groups.

Dedicated Transport Services

Dedicated circuits, in the traditional sense, are leased-line circuits which are dedicated to a specific use by a specific user organization. Again, they may be either analog or digital, and either single channel or multichannel. Dedicated circuits typically are provided by the LEC on an intraLATA basis, although CAPs also provide such circuits to the extent that their facilities match user requirements. InterLATA leased lines currently must be provided by an IXC, typically with the LEC or CAP providing the local loop and connection to the IXC POP, and the IXC providing the InterLATA portion to the destination POP where the circuit interfaces with the LEC serving the distant location.

Foreign EXchange (FX or FEX)

Foreign EXchange (FX or FEX) lines or trunks connect the user premise more or less directly with a foreign exchange, that is with an exchange other than the local exchange which normally would provide local dial tone. FX circuits generally are billed at a given cost per mile or kilometer, or fraction thereof, rather than on a usage-sensitive basis. A user organization can lease a FX circuit from Dallas, TX to Denton, TX to support outgoing and incoming traffic between those general areas; the circuit terminates in Dallas CPE but has a Denton local telephone number.

Tie line/trunk

Tie line/trunk circuits, as described in Chapter 4, connect KTS/PABX systems together directly and across the PSTN, although without the involvement of switching processes. Between two PBX systems, for instance, the carrier(s) provide dedicated circuits which pass through wire centers housing network switches. The circuits bypass the switches, which are unnecessary in this context, yet take advantage of amplifiers or repeaters, multiplexers, and other systems embedded in the carrier network.

Off-Premise Extension (OPX)

Off-Premise Extension (OPX) circuits are dedicated PSTN circuits that connect a PBX or KTS system to an extension terminal which is off-premise. The terminal appears exactly as would an on-premise extension, providing the user with the same level of functionality. OPXs are unusual, as both the circuit and the special purpose system interface card are expensive. Additionally, and as contemporary users are not expected to be office-bound, voice mail, cellular telephony, page, and other technologies are adequate alternatives for most situations.

Switched Transport Services

Switched services include all typical local and long distance voice traffic, whether inbound or outbound. Specific services include DDD, WATS, Virtual WATS, In-WATS, 500, and 900/976. Deregulation, divestiture, and resulting competition served for many years to reduce the costs of these services, and very significantly. During the past year or so, however, the cost has increased slightly. Long distance charges, for instance have increased about 6% since January 1, 1995 [6-13].

Message Telecommunications Service (MTS)

Also known as Direct Distance Dialing (DDD), 1+ dialing, MTS involves long distance calls which are placed by the user on a dialed basis, rather than involving the intervention of an operator. Such calls generally are billed on the basis of a combination of distance, duration, and time of day. Discounts apply to long duration and off-peak calls. DDD calls may be short-haul IntraLATA (LEC), long haul InterLATA (IXC) or international in nature. While the last manual exchange in the US was converted to dial many years ago, operators must still act on long distance calls in some developing countries, particularly in the case of International DDD (IDDD).

Wide Area Telecommunications (WATS)

Much like DDD service, WATS is billed according to a variety of discount plans for large user organizations. WATS originally required special purpose outgoing trunks which were designated as having access to specific areas of the country according to mileage bands 1 to 5, which were presented as concentric areas of coverage. Band 1, for instance, provided intrastate coverage, while Bank 5 provided full national coverage. The greater the area of coverage, of course, the higher the cost of the WATS service. Traditional WATS was provided on a fulltime or a measured basis. Fulltime WATS could be characterized as all-you-can-eat WATS as it was billed at a flat rate, with no usage monitoring or billing. Measured WATS was billed on a flat rate for the first 10 or 20 hours of usage, with overtime charges applying to traffic over the threshold. Clearly, the process of analyzing traffic patterns and configuring an optimum WATS network, with overflow to DDD, could be a fairly complex process.

Banded WATS has been abandoned in favor of 1+ WATS, also known as Virtual WATS, enabled by increased network intelligence, and encouraged by increased competitive pressure. Virtual WATS simply involves a discounted billing arrangement involving a small monthly fee and discounted usage that is sensitive to calling volume and volume commitment. The traditional requirement for special purpose circuits no longer exists, as the originating circuit and user are identified by the billing systems, with the appropriate rating algorithm being applied at the time the bill is rendered.


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