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SECTION I BACKGROUND, SUMMARY, AND CONCLUSIONS BACKGROUND The "Carterphone Decision" was widely recognized as potentially leading to a fundamental change in communications carrier/user relation- ships. By this decision, the FCC ordered EheAIl'leiicari Teleph6neand Telegraph Company to delete general prohibitions against interconnection and customer attachments from its interstate message toll tariffs. In compliance, the AT&T, after consultation with representatives of the independent telephone companies, filed the following revised tariffs: lF259 - "Wide Area Telecommunications Service"; lF260 - "Private Line Service"; lF263 - "Long Distance Message Telecommunications Service." These revised tariffs specify and define certain key limiting signal characteristics and" access arrangements" believed necessary by AT&T to protect telephone service and the telephone system, as well as those who come in contact with the system as employees or users. l The FCC allowed these proposed tariffs to go into effect and requested comments from interested parties. It received a considerable number and range of responses. The technical portions of these responses ranged from complete acceptance, through challenges as to the basis of determination of the protection requirements, to complete rejection. The FCC decided that a study should be made of the technical factors involving interconnection and user-provided attachments. The National Academy of Sciences, through its Computer Science and Engineering Board, agreed to undertake such a study. The objective was to evaluate and report on the issues of "harm," and protection of the telephone network from "harm," under conditions of user-interconnection. The approach involved the following considerations: (a) Susceptibility of the network of "harm" in terms of hazards to personnel and equipment, network performance, and degradation of service to other users (b) Evaluation of the tariff criteria limiting signal amplitude, waveform, and frequency distribution of interconnected lines ISection 3
-2- (c) Evaluation of the effectiveness of several methods of protecting the network (d) Evaluation of the impact of interconnection on innovation by carriers and user-manufacturers. The charter of the Panel and the urgency of the problems of voice-band interconnection required that this report concentrate on the technical aspects of those problems, to the exclusion of other significant considerations involved in interconnection, such as: (a) Distribution of costs of interconnection among carriers, the general non-interconnected user, and the interconnected user (b) Reliability or adequacy of service obtained by a user from his own interconnected equipment (c) Effect on service when one party has carrier- provided equipment and the other party has his own interconnected equipment (d) Validity of the criteria for acoustic or inductive coupling Final judgment by the FCC as to courses of action must, of course, include, in addition to the technical factors, such matters as rates, costs, legal implications, and basic economic policy. In this connection, it should be noted that future changes in costs or rates by the carriers for interconnection devices could have a signi- ficant impact on the interconnection situation. 2 This factor was not evaluated by the Panel. The principles that underlie the conclusions in this report may be applicable to other types and circumstances of interconnection. Principal Conclusions The principal conclusions arrived at by the Panel follow. Further detailed conclusions are included in the body of this section. (a) Uncontrolled interconnection can cause harm to personnel, network performance, and property.3 2Se ction 6 3Sections 3, 4, and 8
- 3- (b) The signal criteria in tariffs 260 and 263 relating to signal amplitude, waveform, and spectrum are technically based and valid and, if exceeded, can cause harm by interfering with service to other users. (c) Present tariff criteria together with carrier- provided connecting arrangements are an acceptable basis for assuring protection. 4 Present tariff criteria together with a properly (d) authorized and: enforced program of standards development, equipment certification, and controlled installation and maintenance are an acceptable basis for achieving direct user interconnection. S Innovation by carriers need not be significantly ( e) impeded by a certification program. Opportunities for innovation by users would be increased. 6 Mechanisms are needed to promote the exchange of (f) information among carriers, users, and suppliers. 7 STUDY PLAN Organization An initial analysis indicated that a broad range of experience should be represented in the membership of the Panel. The technical coverage included the following subjects: SWitching Systems Transmission Systems Standards - Development and Use Equipment Manufacturing Privately Owned and Operated Communications Systems Communications-Oriented Computer Systems 4Section 5 SSections 3, 4, and 5 6Section 7 7S ec ti on 9
-4- Procedures The Panel first reviewed the FCC files concerning interconnection and determined what additional data were necessary. Facts and opinions were accumulated from those who expressed their interest to the FCC and directly to the NAS Panel as a result of announcements, publicity, and direct solicitations. Organizations and individuals with knowledge of and experience in subjects of particular interest to the Panel were also contacted directly.8 Among the organizations providing data were: Communication Common Carriers Telephone Equipment Manufacturers Computer Manufacturers Terminal Equipment Manufacturers Organizations with Private Communications Networks Regulatory Agencies u. S. Government Agencies Standards Agencies Foreign Communications Agencies Testing Laboratories Computer Service Organizations Installation and Service Organizations Trade Associations In all, over fifty written technical communications were submitted, and over twenty-five organizational representatives, by Panel invitation, made supplemental oral presentations and responded to --..> intensive questioning at closed panel sessions. This study makes clear the need for improved communications between the carriers, users, manufacturers, and other members of the community in this field. On a number of occasions what were considered to be significant problems raised were apparently a matter of lack of, or poor, information. EFFECTS OF INTERCONNECTION ON THE PERFORMANCE OF THE NETWORK The objective of the Panel has been to determine how 8Section 8
-5- qe achieved without impairment of service to users interconnection can of the network, generally, and hazards to employees of the carriers. In its approach to this objective, the Panel has analyzed the appropriate portions of the carrier network to determine how harm can be caused and has then considered how this harm can be prevented. Harmful Effects Harm may arise through the introduction into the network of (a) voltages dangerous to human life, (b) signals of excessive amplitude or impro~er spectruiri, (c) improper line balance,or (([) improper control signals. INCREASED EXPOSURE TO HAZARDOUS VOLTAGES CAN RESULT FROM UNCONTROLLED INTERCONNECTIONlO , Uncontrolled installation of user-owned terminal devices involving the use of 115 v AC and other hazardous voltages can introduce risks to telephone company installation and maintenance personnel. For maintenance and expansion of telephone service to be carried on without interruption of existing service, it is standard and efficient practice for cable and exchange plant workers to work bare-handed on pairs and junctions in the immediate proximity of hundreds of other pairs in normal use. To avoid increasing the hazard, it is mandatory that stringent measures be taken to ensure that hazardous voltages will not be applied at points of interconnection. SIGNALS THAT VIOLATE THE CRITERIA RELATING TO SIGNAL AMPLITUDE, WAVEFORM, AND SPECTRUM IN TARIFFS 260 AND 263 CAN CAUSE HARM BY INTER- FERING WITH SERVICE TO OTHER USERS ll 9Sec tion 2 lOSection 3 llSection 3
-6- The non-linear characteristics of transmission components, which are widely used in the telephone plant, require that inband signal power be limited to avoid deterioration of service to others due to cross-talk or overload. The signal-limiting characteristics of voice- frequency and carrier-transmission systems do not provide the required restraints on signal power. The signal powers specified in the tariffs represent reasonably optimized values for voice and data usage; The limits on the inband signal-power spectrum are specified to avoid the possibility of interference with internal network signaling. The out-of-band power limits are based upon limitations of local cable plant and requirements for minimum interference with present and expected greater-than-voice-band services. The telephone plant does not supply this protection. Signal criteria specified in the tariff must be observed for both voice and data services. Data services present the more serious problem, since, when transmitting data, the user has an incentive to exceed the signal-power criteria in order to reduce his error rate with possible degradation of service to others. LINE BALANCE IS IMPORTANT TO NETWORK PERFORMANCE12 Imbalance in line terminations will render ineffective the careful electrical balance built into the pairs in the cables connecting users and the telephone company central offices. The resultant imbalances can cause loss of privacy and increased interference, not only to the unbalanced pair, but to other pairs in the cable as well. Terminal imbalance can occur due to poorly built equipment, improper installation, or inadequate maintenance. IMPROPER NETWORK-CONTROL SIGNALING CAN IMPAIR TELE- PHONE SERVICE AND INCREASE COSTS13 l2S e ctions 1 and 3 l3Sections 1 and 4
-7- Network-control signaling must be properly performed for correct system operation and message accounting. For example, in a telephone set, these signals are produced by the switchhook and the rotary dial or the touch-tone pad. Mechanisms for producing these signals, if not carefully designed, manufactured, installed, and maintained, can, in conjunction with the varying characteristics of the telephone loops, cause improper signals to be received at the central offices. Central offices vary in their tolerance to distorted control signals and in their ability to correct such signals before re-transmission into the network. In particular, dial-pulse signaling of poor quality can cause significant harm by the generation of wrong numbers, causing annoyance to others, wasteful use of cent.rn.I office . equipment ··and transmission fad 1 ities,andimp:t"9pe:t"billing. On the other hand, improper signals generated by touch-tone pads are inherently less harmful since, if a signal is out of tolerance, the central office equipment will not complete the call. Network-control signaling on multiparty lines is particularly difficult to define because of different practices with respect to ringing and line identification. Protecting the Network Several approaches for protecting the public telephone network were considered. Two which the Panel considers acceptable are: (a) Operation under present tariffs that call for common-carrier ownership, installation, and maintenance of connecting arrangements and adherence to tariff-specified signal criteria. (b) A program of enforced certification of equipment and personnel, with appropriate standards for safety and network protection. This approach would allow user ownership, installation, and maintenance of protective coupling units or complete terminal equipment. PRESENT TARIFF CRITERIA AND CARRIER-PROVIDED CONNECTING ARRANGEMENTS ARE AN ACCEPT- ABLE WAY OF ASSURING NETWORK PROTECTION14 The present tariffs specify signal criteria for electrical, acoustic, and inductive coupling, and specify that the carrier provide 14S ec tions 3 and 5
.--- ~ 8- connecting arrangements and network-control signaling. The signal criteria limit the signal inputs to the network to those considered to be harmless. The carriers, under the tariffs, assume responsibility for installation and maintenance of the connecting arrangements and for protection of carrier personnel and of the network itself, Technically, the Panel considers this to be an acceptable approach. Carrier-provided connecting arrangements involve addition by the carrier of components between the user's terminal and the carrier's facilities. In some situations, these may duplicate components of the users' equipment; this redundancy in components and functions may, in principle, cause some·loss in performance and some reduction in reliability. However, the Panel's analysis indicates that the added components, if well designed, should not significantly affect overall reliability or performance. Concerning the need for some of the protective features, analyses of the presently available connecting arrangements indicate that they provide a degree of protection of voice-signal limiting that, in some cases, is unnecessary. Present carrier~provided coupling units are, in some instances, complicated and marginally effective and may degrade performance,lS particularly in net-control signaling. According to AT&T, the problems relating to present protective equipment can be attributed to the rapid introduction of the connecting arrangements and lack of experience on which to base judgments. Further development should produce more effective units. Additionally, the sudden demand for interconnection and the need for time to determine the features required by a large number of users is a cause for present delays. Desired connecting arrangements are not yet available according to some 'Users. THE ESTABLIS}IMENT OF STAND- ARDS AND ENFORCED CERTIFICATION OF USER-SUPPLIED EQUIPMENT AND PERSONNEL CONSTITUTE AN ACCEPTABLE WAY OF ASSURING NETWORK PROTECTION16 It is important to note that the standards to be established cover only network-protection considerations such as personnel safety, signal levels, transmission, and network-control signaling, and do not include standards for user-equipment performance. lSSection S 16Section 16
-9- Despite some variability from installation to installation, there has been enough experience with the telephone network to provide a basis for standards for network protection. A standards-development program requires the resources of a qualified standards organization. The purpose here is to provide coordination, structural guidance, and staff services to those preparing the standards. Such organizations exist in both the private sector and government. Standards can be prepared by qualified representatives of the carriers, suppliers, and users. A definition of the interface between the user-owned equipment and the network, so far as protection is concerned, is part of the basis for standardization. Finally, although general standards can be written to cover interconnection with various types of central offices and loops, each individual installation will be, to some extent, customized due to varying loop characteristics and other factors. Therefore, interconnected equipment should be provided with proper adjustment features to deal with individual case-by-case variations. Necessary adjustments can be worked out cooperatively at the time of installation between carrier and user. Cooperative guideline procedures should be formalized. Type certification of equipment could be accomplished by government or by independent testing laboratories. It must include evaluating and monitoring each manufacturer and his specific products. Government and independent test laboratories exist which are capable of performing these functions in related fields. They could expand their resources to qualify for the program envisaged here. With a significant volume of work, costs of this program should not be prohibitive. Certification can be applied to couplers, to protective sections of larger equipment, or to the protective characteristics of entire units of equipment. Equipment-type certification alone is not sufficient to protect the telephone network. The equipment must be installed and maintained by certified technicians. In addition, standards must make provisions for assurance that the network protection is maintained by documented periodic inspection. Certification of the installation and maintenance of interconnected equipment will require a program of personnel training, development of tests and test equipment, and licensing of installation and maintenance personnel. On the last point, the Panel believes that a nucleus of support personnel exists in the servicemen and organizations who now install and service communications and computer equipment. They can be certified (or licensed) by examination, following procedures included in the overall certification program. Each certification (or license) would be endorsed as applicable to equipment of one or more classes.
- 10 - ~ Requirements for an Enforced Certification Program AUTHORITY FOR A NATION- ,.- WIDE CERTIFICATION PRO- ~. GRAM MUST RESIDE WITH \. i''''' THE FEDERAL AGENCY I: RESPONSIBLE FOR THE TARIFFS 17 To be effective, a certification program must be recognized in the tariffs and the federal agency that approves these tariffs must assume responsibility for authorizing implementation of the overall certification program. This agency should develop and publish rules and procedures and propose timetables and sequence of applications. Plans should be developed under control of the federal agency for the selection of the organization or organizations that will coordinate the preparation of standards, the procedures for the qualification of technicians, and the organizations to be given the authority to certify equipment. Uniformity in standards and certification procedures for equipment and in personnel qualifications throughout the country is desirable, since installation and maintenance may be supervised and inspected locally. Therefore, coordination by federal and state agencies in necessary to establish policies which will permit the nationwide use of certified equipment and procedures for the certification of technicians. 18 ENFORCED CERTIFICATION PROCEDURES MUST BE TAKEN AS A WHOLE The Panel emphasizes that the development of standards and a program of certification requires a complete system of control, which will not be effective unless all elements of the system, as described in this report, are adopted. For example, the development of standards alone is inadequate. Certification of equipment without certification of installation, testing, and maintenance will be ineffective in protecting personnel, facilities, services, etc. l7Section 6 l8 Sec tion 6
- 11 - A CAREFULLY PLANNED STEP-BY-STEP EFFORT IS NECESSARY TO ENSURE THE SUCCESSFUL IMPLEMENTATION OF A CERTIFICATION PROGRAMl9 Experience with interconnection is limited and has, for the most part, been with users with extensive experience and resources. 20 There is little applicable experience involving smaller, less sophisticated users or with large-scale public interconnection. A certification program is new to the telephone industry and to many of the major user industries. Existing laboratories are not equipped to test and certify communications equipment in the quantities envisioned. The personnel needed by all parties for this kind of operation are in short supply. There is much to be learned. If a start is made promptly, and if all concerned assign the task a high priority, the necessary certifi- cation programs and guidelines for qualifying personnel should be produced in reasonable time. The same effort should produce both standards for equipment and guidelines for qualifying personnel. Thereafter, when the personnel program has started to function, the certification of interface devices and equipment will permit their installation and operation by users according to the new standards. The Panel believes that the certification program should be undertaken on an incremental basis in order to develop a meaningful base of knowledge and experience. The first implementation should be in an area with high probability of success and sufficient complexity to test the validity of the certification program. The first application should be to equipment with limited distribution and for which a knowledgeable technical base for manufacture, installation, and maintenance now exists (such as PBX). Application of the standards to one service can proceed while standards are set for others. Since the standards program is an iterative process, requiring procedures for continuous reconsideration and renegotiation of specifications, it is important that an organizational mechanism be set up to gather data and evaluate the progress of the program. SELF-CERTIFICATION BY MANUFACTURERS OR USERS WILL NOT ENSURE AN ACCEPT- ABLE DEGREE OF NETWORK PROTECTION21 19Section 6 2lS e ction 6 20Section 8
- 12 - A self-certification program allows the manufacturer or user to test and approve his own equipment, installation, and maintenance, On the other hand, an enforced certitication program separates the responsibility for certification from the organizations having direct financial involve~ ment in the production or use of interconnected equipment. Self-certification requires the user to procure and use equipment considered harmless and to operate in accordance with the tariffs. In the absence of some control system, it is inevitable that marginal equipment will make its way to the market and that there will be usage outside of the rules .. WE FIND NO PERSUASIVE ARGU- MENTS FAVORING THE EXEMPTION OF WHOLE CLASSES OF USERS The Panel endeavored to classify users, including utilities, right-of-way companies, agencies of the federal government, etc" in an effort to show that one or more classes might be permitted unrestricted interconnection without risk of impairment to the operation of the network. An analysis of information in the Applicable Experience section 22 and other information presented to the Panel led to a firm conclusion that this was not possible. In a certification program that enables any user to qualify on reasonable terms, there is no reasonable basis, in the opinion of the Panel, for any class or group of users to be exempted from conforming, EFFECTS OF INTERCONNECTION ON INNOVATION THE PROPOSED CERTIFI- CATION PROGRAM SHOULD NOT SIGNIFICANTLY IM- PEDE INNOVATION BY THE CARRIERS AND MAY PRO- MOTE INNOVATION BY USERS Several opinions have been expressed to the Panel regarding the potential impact of interconnection on innovation. 22Section 8
- 13 - The carriers have said that widespread interconnection will tend to impede innovation in the network, because, among other things, users will tend to oppose changes by the carriers that make the users' equipment obsolete or require it to be -mod i f ied , They have also said that direct interconnection without carrier-owned interconnecting arrangement will :i;urther impede their innovation because it removes the carrier-cont'rolled buffer with known characteristics between the network and the interconnected equipment. Some users, especially the large ones and those in rapidly developing fields such as computer time-sharing, have expressed the opinion that,' with the necessarily deliberate rate. of innovation expected in the network, there will be no ~ajor problems in keeping up with the network innovation. They do not agree with the carriers' concerns regarding the need for a carrier-controlled buffer. Some suppliers of equipment and services have expressed the that the presence of the carrier-owned interconnecting arrange- op~n~on ment will impede innovation on the user side of the interface where the goal is to optimize the users' system or use of equipment. Further, and perhaps more importantly, they question the ability of the carrier to respond rapidly enough to new situations in which new interconnection arrangements are required~ While data on which to base conclusions are limited, it is the opinion of the Panel that: (a) The advent of widespread interconnection itself, regardless of how it is implemented and controlled, will indeed have some effect on the rate of innovation by car-r Ler s , supp Li.e'r s , and uaer s , In some cases~ it may impede innovation in the net- work; in others, it could conceivably promote innovation because of competition and the pressures of demand from users. It will certainly tend to increase the rate of innovation by suppliers and users. (b) The introduction of a certification program permitting direct interconnection should not significantly restrict carrier innovation if there is effective information exchange between carriers, suppliers, and users. On the other hand, the suppliers and users will have more freedom to innovate. (c) On balance, under the certification program, innovation in the overall system of carriers and users of interconnected equipment is likely to increase.
14 ~ ~ INFORMATION INTERCHANGE THE PANEL BELrEVES THA,T MECHANISMS SHOULD BE ESTABLrSHED TO PROMOTE THE EXCHA,NGEO;F I.NFOR~ MATrON AMONG CARIU:ER~1. USERS, AND SUPl'LIERSLl As stated earlier, the l'ane1 was continnally reminded of the need for improved exchange 6f information among the parties concerned, There were instances of incorrect interpretations of conditions of use of the network by user and marmfac tur er s , causing unnecessary confusion at both the technical. and administrative levels. The carriers expressed strongly the need for more direct information exchange and a mOTe compre- hensive picture of user reqUirements. With the aniticipated acceleration in innovation affecting data systems and telecommunications, the require- ment for this improved exchange is even more pronounced. At present, no mechanism exists that adequately serves this function; such a mechanism should be established,· 23Section 9
