Developing the Integrated Rapid Public Transport Network ...
The Public Network
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Transcript of The Public Network
Objectives
In this chapter, you will learn to: Explain, in general terms, the structure of the public telephone
network Describe the types of carriers who currently participate in the public
telephone network Recognize the elements of outside plant and describe their
purposes Recognize the elements of inside plant and describe their purposes Describe the hierarchy of central offices that participate in the public
telephone network Explain issues related to interconnection and billing between
common carriers Describe the current telephone numbering plan and explain how it
has evolved
An Overview of the Public Network
Public Switched Telephone Network (PSTN) - consists of all the facilities and connections maintained by all local and long distance providers.
In telecommunications, line is used frequently to refer to one of two things: the physical connection between a subscriber and the
telephone company’s facilities a single communications channel between a
subscriber and the central office
An Overview of the Public Network
Termination - the place where a wire is connected to another part of the public telephone network (for example, a switch or a customer’s home).
Point of presence (POP) - refers to a carrier’s facilities that allow it or its customers access to the public network.
Common Carriers
Common carriers - entities directly involved in supplying regulated telecommunications services to the public.
Reseller - a common carrier, or a company that leases another company’s facilities, and then sells services over those facilities under its own name.
Local Exchange Carriers (LECs)
Currently, two types of common carriers provide local phone service: Incumbent local exchange carriers (ILECs): companies that
have been providing local phone service since before competition was allowed for intraLATA traffic
Competitive local exchange carriers (CLECs): companies that began offering local phone service after the Telecommunications Act of 1996 introduced competition.
Facilities-based - CLECs that build their own facilities in addition to leasing and using ILEC facilities to provide service under their name.
Local Loop
The portion of a business or residential telephone network that connects the demarcation point to the local phone company’s nearest central office is called the local loop.
Local loop (last mile) portion of a connection is the most expensive for a carrier to provide because separate lines must be installed for each individual subscriber.
The local loop is the part of a connection most likely to have the lowest throughput and, further, be the most susceptible to damage or noise.
Serving Area Concepts (SAC)
Drop wire - the cable that runs from a subscriber’s demarcation point to a telephone pole or underground conduit. The drop wire connects the subscriber’s home or business line to a
distribution cable, which gathers multiple drop wires from a neighborhood.
Conduit - the thick tube (usually made of PVC plastic) that surrounds a distribution cable. The conduit protects the wires within the cable from environmental
damage.
Distributing Frames
Main distributing frame (MDF) - a piece of equipment where incoming wires terminate and their circuits are connected to another set of wires that lead to central office equipment.
Punch-down block - a row of metallic clips (or receptors) that accept a wire termination.
Jumper wires - used to connect incoming lines’ punch-down blocks with the outgoing lines’ punch downblocks.
Cross-connect - wires terminating at two sets of punch-down blocks are interconnected.
Switching Equipment
Major functions of switching equipment at a central office:
• Dial tone • Customer and phone number identification• Call setup• Call routing• Call supervision• Line testing and maintenance
Central Office Hierarchy
Serving area (of a local office) - the geographical boundary that includes all its subscribers. It extends roughly three miles in all directions from the central office (CO).
Trunk - a transmission route between switches that typically has a great deal more capacity than a feeder.
Regional offices - Class 1 central offices.
Billing Between Carriers
The fees charged by ILECs are based on the leasing carrier’s: Grade of service received Number of trunks used Amount of traffic transmitted Placement of equipment in ILEC’s facility, also called
collocation Facilities and circuit installation Maintenance and support agreement
North American Numbering Plan
A scheme for assigning unique phone numbers to every line in the country.
For numbering purposes, North America is divided into several smaller geographic regions called Numbering Plan Areas (NPAs), more commonly known as area codes.
North American Numbering Plan
NPAs reserved for special purposes include:
Easily Recognizable Codes (ERCs) - When the second and third digit of the NPA are identical (for example, the numbers 888 or 411), the NPA is known as an Easily Recognizable Code (ERC).
N9b - these 80 NPA codes have been reserved for use when the current NANP numbering scheme undergoes further expansion.
37b and 96b - these 20 NPA codes have been reserved in case a previously unanticipated need for blocks of 10 contiguous NPAs arises.
Summary
The Public Switched Telephone Network (PSTN) is defined as the collection of local and long distance providers’ facilities and connections that are available for public voice (and more recently, data) communications.
Common carriers are entities directly involved in supplying regulated telecommunications services to the public.
The local loop, or "last mile," is the connection between a subscriber and the nearest central office.