In May, 1986, in its Third Computer Inquiry, also known as the Computer III Decision [1], the Federal Communications Commission (FCC) introduced the concept of an Open Network Architecture (ONA), which represents an attempt to create free market conditions within the telecommunications industry through regulation.
ONA is a regulatory framework imposed on the Regional Bell Operating Companies (RBOCs) and AT& by the Federal Communications Commission (FCC) for the provision of enhanced communications services. ONA requirements were imposed on GTE in early 1994. Subsequent FCC orders have substantially reduced the applicability of unbundling and other aspects of ONA on AT&. Currently, AT& is not directly subject to ONA requirements, but is subject to Comparatively Efficient Interconnection (CEI) requirements.
Before initial ONA plans were filed, the RBOCs and AT& were subject to Comparatively Efficient Interconnection requirements. Under Comparatively Efficient Interconnection requirements, the carrier is required to provide comparably efficient interconnection for each enhanced service that is offered, such that any Enhanced Service Provider (ESP) can access the elements of the basic telephone network in a manner that is completely equivalent to the method that carrier's enhanced services access the basic network. Comparatively Efficient Interconnection was initially used for determining interim approval of any specific enhanced service of a carrier prior to the implementation of ONA plans. For the purposes of this paper, the term carrier will be used to refer to those carriers subject to ONA or Comparatively Efficient Interconnection requirements.
Under Comparatively Efficient Interconnection, the set of
basic service functions that a carrier uses
in an enhanced service offering should be available to
ESPs under tariff as a Basic Service Element (BSE) or a set of
Basic Service Elements.
For example, if a carrier's enhanced service utilizes
digital transmission, calling number identification, and specific signaling
capabilities, then the Comparatively Efficient Interconnection
for that service must include these basic
services as a set of Basic Service Elements unbundled from other
basic service offerings.
ONA mandates that the carriers should provide independent ESPs access to basic communications services on an equal basis and at an equal cost to those enjoyed by the carriers' own Enhanced Service operations. This so-called unbundling of services forces the carriers to relinquish their local monopolies on telecommunications services, creating an open market, and allowing various service providers to compete on an equal basis. The carriers are required to satisfy all ESP requests that meet the FCC's criteria of demand, utility, technical feasibility, and cost feasibility, regardless of whether the carrier plans to offer the enhanced service.
Basic services are limited to ``the common carrier offering of transmission capacity for the movement of information'' [21]. Enhanced Services consist of the combination of transmission and basic switching services with other services, such as services provided by computer application programs, to produce additional or restructured information, and/or involve subscriber interaction with stored information. Current examples are in the form of enhanced telephone services, such as call forwarding, voice mail, caller ID, and last number redial. In order to provide enhanced services, an ESP requires access to basic communications functions from the common carrier. Under ONA, these basic functions are unbundled from one another into tariffed basic building blocks known as Basic Service Elements (BSEs). ESPs are free to purchase these basic services individually in a way that best matches their requirements for the provision of a particular enhanced service. Rutkowski [2] offers the following distillation of the ONA framework sketched out by the FCC in its Computer III Decision:
ONA is the overall design of a carrier's basic network facilities and services to permit all users of the basic network, including the enhanced service operations of the carrier and its competitors, to interconnect to specific basic network functions and interfaces on an unbundled and equal access basis.
The FCC declined to provide a specific standard for
ONA [page 1067]computer-iii.
Rather, it placed the burden for the development of
Open Network Architectures on the carriers. Initial ONA plans were
filed with the FCC by February 1, 1988.
ONA plans for each carrier are continually being amended to reflect
changes in services offered and to comply with
additional requirements of the FCC.
Appendix 
provides additional information on FCC
Orders directing the development and evolution of ONA plans.