Carriers are required to satisfy all ESP requests for services that meet the FCC's criteria of demand, utility, technical feasibility, and costing feasibility. Each ONA plan describes a set of Basic Service Elements (BSEs), Basic Serving Arrangements (BSAs) and Complementary Network Services (CNSs) supplied by the service provider and based on a set of requests for services placed by the ESPs. Basic Service Elements are optional unbundled features, such as calling number identification, that ESPs may require in providing an enhanced service. Basic Serving Arrangements are fundamental switching and transport services. ESPs obtain access to various Basic Service Elements through Basic Serving Arrangements. An example of a Basic Serving Arrangements is the physical connection to the telephone network. Complementary Network Services are optional unbundled basic service features that an end user may obtain from a carrier in order to use an enhanced service. Call forwarding is an example of a Complementary Network Service. Basic Serving Arrangements, Basic Service Elements, and Complementary Network Services cannot be ordered until appropriate tariffs are effective. The carriers are required to satisfy all ESP requests that meet the FCC's criteria of demand, utility, technical feasibility and costing feasibility.
BOC ONA Special Report Number 1, Issue 2 (October 1987) listed 118 ONA services requested by ESPs prior to the filing of initial ONA plans. A few ONA services are no longer offered and many new services have been added. Currently, there are over 150 services. Amendments to an ONA plan must be filed before a carrier is allowed to offer a new service. An example of a representative set of services can be found in ``ONA Services: Names, Descriptions, Cross References'' [9]. This document is also known as the ``ONA Services User Guide.''
It should be noted that the initial standardization efforts involved in the provision of the ONA plans by the carriers related primarily to the nature of the services offered, and not to the interactions between the different services or the nature of such interactions. This is because, in the large majority of cases, the services that were to become the Basic Service Elements and Basic Serving Arrangements were already in existence prior to the ONA mandate, and as such so were the communications protocols used between the the service elements. The ONA mandate does not address how Basic Service Elements/Basic Serving Arrangements should interact, merely that they should be available on an individual basis to the ESPs and be nondiscriminatory.
In various orders, the FCC addressed two types of uniformity: availability of services and technical uniformity. After reviewing initial ONA plans, the FCC noted significant differences in ONA services offered by the carriers. Of the 118 services requested by ESPs, in the original ONA plans, the carriers offered 29 common services with an average of 54 services offered by each carrier. In an attempt to increase the uniformity of services offered among the carriers, the FCC required each carrier to review other carriers' plans and to try to increase the number of ONA services offered by each carrier's ONA plan [22]. The amended plans indicated that 37 services were offered on a nationwide basis and that each carrier proposed to offer an average of 70 services [24].
Today, the number of services offered by the carriers has increased, but there is still considerable difference in the number of services offered by the individual carriers. The Services Descriptions section of ``The ONA Services User Guide'' [9] represents an agreement on the part of the carriers for uniform names and technical descriptions of the Basic Serving Arrangements, Basic Service Elements, and Complementary Network Services. For each ONA service, a table is provided that lists the generic name of the ONA service or Basic Serving Arrangements, which carrier plans to offer the service, the individual carrier's product name, and whether the carrier classifies the service as Basic Serving Arrangements, Basic Service Elements, or Complementary Network Service. The ``ONA Services User Guide'' directs the reader to refer to the individual BOC ONA plans and amendments for information on BOC availability and deployment plans for ONA services.
Although the FCC noted that technical uniformity in the initial offerings would be difficult to achieve because of the differences in embedded technology and uncertainties in market demand, the FCC directed the carriers to continue working through the IILC to develop procedures for achieving uniformity in key services areas. In the BOC ONA Amendment Order, AT& expressed concern about the carriers' use of different technical means of providing similar ONA services.