The Network Hierarchy (Post 1984)

After 1984, the telephone network went thru a dramatic change with the breakup of the AT&T monopoly. The BOCs were classified as separate telephone companies. They are also called Local Exchange Carriers (LECs) and now Incumbent Local Exchange Carriers (ILECs). Seven spin off companies formed from the divesture becoming Regional Bell Holding Companies (RBHCs), which had regulated divisions called Regional Bell Operating Companies (RBOCs). Each RBOC had its own geographical market. Additionally, each RBHC also had an unregulated side of business that could enter new business markets such as equipment sales, finance, real estate, and etc.

            Equal access was given to every interexchange carrier to connect to the BOC for long-distance service. Before if customers chose a competitor of AT&T for long distance service they would have to go thru a long and complicated process to complete their call. Most people chose not to use alternative long-distance companies because of the time and frustration in completing calls.  

The Public-Switched Network

The U.S. public-switched network has been the best and largest in the world. Primary calling capacity in the U.S. is handled via the public-switched network. This was the environment that AT&T had built and some people still refer to it as the Bell System.

            Public network allows access to the end office, connects through the long-distance network, and delivers to the end point. The goal of the network hierarchies is to complete the call in the shortest amount of time and the shortest route possible. The network is dynamic enough to pass the call along longer routes to complete the call wherever possible.

The North American Numbering Plan

The network numbering plan was designed to enable quick and discreet connection to any phone in the country. The North American number plan (NANP) works on a series of ten numbers.

The Area Code and Exchange Code

The first three digits is the area code or numbering plan assignment (NPA). The second set of three digits called the exchange code is also referred to as NAA. We are facing a worldwide number shortage with the use of pagers, cellular phones, and additional lines using up all the numbering sequences.

Local Access and Transport Areas (LATAs)

Local access and transport areas (LATAs) is a term introduced with the divesture of AT&T. One of the problems was dealing with the long-distance versus local calling areas in the court decisions. AT&T demanded some form of revenue sharing so a single LEC wouldn’t have the option of handling all calls and cutting out the IECs.

            To solve this problem, it was agreed that the LECs would handle all the local calling and the long-distance calls would be carried out by the IECs. The country was broken down into 195 separate areas for local calling based on population. To complicate things even more, four types of calling are under the LATA concept:

Intrastate-Intra-LATA belongs to the LECs

Intrastate-Inter-LATA belongs to the IECs

Interstate-Inter-LATA belongs to the IECs

Interstate-Intra-LATA can be either/or, but originally given to the LEC

The results of this are a confused consumer and confusing tariffs. After the Telecommunications Act of 1996, this LATA boundary began to erode quickly. The local telephone companies and CLECs are all extending their reach in the local area and many of the IECs are registered as CLECs now.