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A Technical Analysis of the Common Carrier/User Interconnections Area (1970)

Chapter: Section 8-- Applicable Experience

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Suggested Citation:"Section 8-- Applicable Experience." National Academy of Sciences. 1970. A Technical Analysis of the Common Carrier/User Interconnections Area. Washington, DC: The National Academies Press. doi: 10.17226/13320.
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Suggested Citation:"Section 8-- Applicable Experience." National Academy of Sciences. 1970. A Technical Analysis of the Common Carrier/User Interconnections Area. Washington, DC: The National Academies Press. doi: 10.17226/13320.
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Suggested Citation:"Section 8-- Applicable Experience." National Academy of Sciences. 1970. A Technical Analysis of the Common Carrier/User Interconnections Area. Washington, DC: The National Academies Press. doi: 10.17226/13320.
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Suggested Citation:"Section 8-- Applicable Experience." National Academy of Sciences. 1970. A Technical Analysis of the Common Carrier/User Interconnections Area. Washington, DC: The National Academies Press. doi: 10.17226/13320.
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Suggested Citation:"Section 8-- Applicable Experience." National Academy of Sciences. 1970. A Technical Analysis of the Common Carrier/User Interconnections Area. Washington, DC: The National Academies Press. doi: 10.17226/13320.
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Suggested Citation:"Section 8-- Applicable Experience." National Academy of Sciences. 1970. A Technical Analysis of the Common Carrier/User Interconnections Area. Washington, DC: The National Academies Press. doi: 10.17226/13320.
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Suggested Citation:"Section 8-- Applicable Experience." National Academy of Sciences. 1970. A Technical Analysis of the Common Carrier/User Interconnections Area. Washington, DC: The National Academies Press. doi: 10.17226/13320.
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Suggested Citation:"Section 8-- Applicable Experience." National Academy of Sciences. 1970. A Technical Analysis of the Common Carrier/User Interconnections Area. Washington, DC: The National Academies Press. doi: 10.17226/13320.
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Suggested Citation:"Section 8-- Applicable Experience." National Academy of Sciences. 1970. A Technical Analysis of the Common Carrier/User Interconnections Area. Washington, DC: The National Academies Press. doi: 10.17226/13320.
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Suggested Citation:"Section 8-- Applicable Experience." National Academy of Sciences. 1970. A Technical Analysis of the Common Carrier/User Interconnections Area. Washington, DC: The National Academies Press. doi: 10.17226/13320.
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SECTION 8 ·ArrLICABLE EXrERIENCE COMMON-CARRIER ArrLICABLEEXrERIENCE The common carrters havehadextenstve expertence with inter- connect ton between carrter·systemsand wi.th non-carrter user-owned and user-maintained equipment and systems. Interconnecting with Each·Other Communtcations carrters are extensively interconnected with each other. There are app'roxfmat edy 1,900 independent treLephone systems connected wi.th the Bell System. TheWestem Unton Telegral?h Company is interconnected with the Bell. System and many of the independent telephone coml?anies. The tntemationalcommuntcattons carriers, including COMSAT, are interconnected wtth the ~ell System~ The Bell System; the international carriers, and COMSAT are tnterconnectedwith foreign carriers. These interconnections are all arranged on a contractual basis with standardized interface arrangements developed by extensive inter-· carrier committees and consultative groups. The Federal Communications Commtsston and forty-nine state regulatory commissions act as referees, or courts of al?l?eal, tf dtfficulties arise over the interconnection interface. However, the fifty or more years of experience the telephone industry has had in arranging interconnections from simple interfaces involving manual l?lug and jack telephone switchboard to the complex automatic systems providing for nationwide (and now international) Direct Distance Dtaling (DDD) have resulted in a surprisingly small number of al?peals to these commtssions. Design procedures and the authority for tnterconnection have been.formalizedbetween the carriers and the regulatory commissions, such that these practices are well established and thoroughly understood throughout the telecommunications industry. Equipment standards and practices are based on voluminous docu- mentation prepared by joint tndustry committees. Equipments and practices develol?ed by the Western Electric Company are widely used "standards" of reference throughout the industry and many manufacturers substantially dUl?licate this equipment for use by the tndependent telephone companies. Standards for maintenance and repair and standard practices for installation and preventive maintenance have been ehablished by the industry through experience with extenstve analysts of equipment failures and faults. Techntcal equipment and system innovation promoted by both the carriers and the manufacturers of communications equipment is pursued on an industry-wide basis, with ext ens tve consultation through the many joint .... 65--

- 66 - connnittees between the Bell System and the independent carriers. New services, when requiring new technical equipment, system practices, transmission standards, etc" are developed jointly between.the.AT&T and the independent companies. After new serVices have been tested , experimentally, standard operating procedures, inter~company tari~~ I agreements, and revenue-sharing arrangements are established. ( The assignment o~ cost burdens between the several carriers is established on the basis o~ the current separations formulas, or through negotiation and action with the responsible regulatory commissions. The experience o~ inter~carrier interconnection arrangements has applicability to the present study to the extent that two organizations operating on the opposite side of an interconnection inter~ace can perform successfully when both operate to compatible or the same standards and are technically and operationally quali~ied, and when both are similarly motivated to provide e~ficient, economical service with minimum disrup- tion due to interconnection dif~iculties. Connnon regulatory authority assures a degree of connnon motivation Of all telephone carriers. Non-Carrier Interconnections There has been experience with a very considerable number of non-carrier interconnection arrangements. The largest o~ these users are the United States Government agencies, particularly the Department of Defense, which, for many years, has made extensive use of common- carrier systems, of ten providing its own terminal equipment, including PBX's. Another class o~ users has been the so-called right-o~-way organizations (railroads, pipelines, electric utilities) who have operated their own communications systems with varying degrees of interconnection with the telephone carriers. Aeronautical Radio Incorporated (ARINC), serving the air-transport industry, has operated an extensive network and many localized interconnection arrangements. Most o~ these are on an allocated circuit (leased-line) basis, but there has been some use of interconnection with the switched network, theoretically only on an emergency basis. User systems are designed, in most cases, with extensive consul- tation with the carrier involved and often with installation of test equipment and practices to protect the network. In many cases in the past, the equipment employed has been Western Electric-manufactured or manufactured by other concerns on the baSis o~ Western Electric's speci~ications and designs. Currently, equipment is being manu~actured in accordance with accepted national or international standards by competent manufacturers and many satisfactory . interface arrangements have resulted. In most cases, the organizations concerned are adequately competent technically and motivated to maintain equipment to high standards of performance, and interconnection problems have been manageable.

- 67 - There is applicability to the present study in these non-carrier interconnection arrangements, both-from-the standpoint-that several have been highly successful and trouble-free,while others have resUlted in troubles,-Both of these cases will be discussed in greater detail later in this section, Experience-Qf-Right;;'of"'-Way:C6mpatiies-With-Cartier-Ititerc6titiections Theright-of-waycompanies~to which might be added ARINC, have had extensive experience using carrier circuits as part of their systems. In many cases, these right-of-way companies own and operate private communications systems (microwave relays being the most important, but other- systems are also included) which serve their principal operational locations, These locations include railroad sWitchyards and terminals, pipeline pumping stations and control centers, utility generating and distribution systems, substations, and other installations. In the case of ARINC, circuits are used to interconnect transmitter and receiver or transceiver sites with communications and control centers. Much of the equipment used by the right-of-way and similar utility companies has been developed and procured in accordance with specifications or practices developed by carriers or manufacturers who are skilled in providing equipment for the telephone utilities. Interface problems have developed from time to time, but these are generally worked out amicably between the user and the carrier with satisfactory settlement of areas of responsibility. One submission by such a user summarizes its experience with inter- connection. It has nearly 500 unattended stations controlled over Bell System circuits by operating centers sometimes located several hundred miles away. The user also has an Electronic SWitching System interconnected with over 800 Bell System circuits. This user had no reports of dangerous voltages or currents having been introduced into the carrier system through its operations, and, from the user's standpoint, service has been entirely satisfactory without the necessity of interface devices between the user and the carrier facilities. The user has extensive procedures and facilities for monitoring the nature of the signals introduced by it into the carrier network. It has also established rigorous preventive maintenance procedures with about sixty maintenance men and thirty fully-equipped maintenance trucks constantly visiting and checking facilities throughout the United States. EXperience of Forei$nC6mmutiicati6tis-Carriers Foreign communications carriers have been concerned with the problem-of interconnection of non-carrier equipment in varying degrees. The extent of the problem depends upon the policies of the carrier, the extent to which the carrier is able to meet urgent demands for switched telephone services, and the nature of its organization.

- 68 - The. applicability of the experience of foreign carriers to the specific problems facing.the·FCC.andthe·U.S. carriers varies~,bothbecause of the widely differing circumstances· under which different foreign carriers operate and.the1ag in the· development of pressures for the.use ·of the carrier networks for manynon~te1ephone purposes, In general, the carriers in the developed industrial countries have a monopoly of telecommunications services, This is achieved by the carriers, either being a ministry of government -- as in the case of the Bundespost and the PIT's in various countries ~- or a chosen instrument government- chartered corporation, such as the Nippon Telephone and Telegraph Public Corporation or the British Post Office Corporation. The ~tent of the monopoly varies but, in general, it is quite complete and to challenge it is, in effect, to challenge the government. Most of these foreign carriers are responsible for the total ·0£ domestic (and,in many cases, foreign) telecommunications . services. This includes message telephone service, telegraph services including. TELEX, the provision of leased lines for all services from narrow-band telegraph to television program relay. There are exceptions to the provision of television program distribution, such as the separate network of EUROVISION in Europe, but such exceptions are limited. In the case of the communications systems operated by government ministries, the ministry is, in effect, the FCC, the AT&T, the independent telephone companies, Western Union, private microwave services, etc., all incorporated in one organization. In general, the policies of such an organization can be challenged only through the national parliament. In the case of the recently established British Post Office Corporation, one .•.. of the objectives was to remove the carrier from detailed political surveillance by parliament and permit it to concentrate on the technical, operational, and business-management aspects of a major service business. In this case, to provide for customer or public influence or guidance in the operations of the carrier, several Country Councils and a National Council have been established. In many countries, the primary orientation has been almost exclusively toward public message telephone and telegraph services and financial and plant resources have been inadequate to fulfill the demands for these services; hence, the carriers have been slow in permitting any extensive use of their facilities for other services. This has been particularly true of certain countries of Western Europe that have been loath to commit transmission facilities to private-line services when they are sorely needed for public message telephone service. An advantage a government ministry or chosen instrument corpora- tion has is the, ability to rank order subscribers or using agencies giving preference to those adequately qualified. These include other government departments and agencies, the railroads or other right-of-way companies, and large technically qualified industries. The government department, OT government-backed corporation, is in a strong position to

.. - 69 - discontinue service if established specifications, practices', or standards are not adhered to. These ''monopoly'' carriers can, and do, establish and enforce rules ensuring adherence to hf.gbvst andarde in the pr-ocurement; of customer equip- ment. They can establish specifications, 'require type approval of all equipment -- even to the extent of testing it in their own laboratories before manufacturers are permitted to sell to prospective users for inter- connection. The British Post Office, for example, has long avoided the investment in large PBX's by requiring the user to procure his own, but it has type-approved only a few models produced by manufacturers who supply equipment to the Post Office and manufacture in accordance with Post Office specifications, practices, and standards. The PBX is then installed in accordance with the Post Office-established specifications and then maintained by Post Office personnel. The Post Office permits in:ter- connection of automatic dialers and other devices for fire, burglary, high water, and other alarm services. However, these must be connected in parallel with a standard telephone installation, the device must pass a Post Office qualification test, and be maintained in accordance with established standards. The ministry of telecomm~lications or a national telecommunications corporation can make'any necessary decisions as to the placement of economic burden for provision of non-standard services for any interconnection arrangements or for other costs occasioned by user-provided ,equipment. The British Post Office requirement that the user provide large PBX's is a good example of this. Experience with Extra~LegalInterconnections Prior experience with unauthorized interconnection has given some indication of problems that might develop with formal arrangements for inter- connection of user-provided equipment Without some protective interface between customer-owned and customer~maintained equipment and the carrier facilities. Amateur radio operators have long used "phone patches" for connecting amateur radio telephone stations to the switched network in order to permit their friends to communicate with distant parties through amateur radio. Most of the telephone companies have countenanced this "illegal" use of the system as a service to the amateurs and the public and relatively few cases of trouble have been experienced. In general, an amateur operator is a competent technician and the amateur's carrier- provided telephone is used to perform the signaling functions, and the,phone patch is only connected while the call is in progress. There is a body of experience of difficulties with user-installed extension telephones that usually shows up only when the telephone is defective or the mismatch between the characteristics of the "foreign"

- 70 - telephone andvthe requirements:,o.t" the loop are such as to result in a report o.t" poor service or a JailuJ:'e,o.t" service, A survey of state'regtilatoJ:'Y commissions indicates a limited accumulation of knowledge ,conceJ;ning ,troubles frOm interconnection of user~owned equipment, althoUgh a consideJ:'able number of eXalllples were cited in which such equipment had been\interconnected with telephone company facilities'resulting'in service calls and difficulties in clearing the trouble, One connnission cited fifty-four trouble reports during a ' recent, ,but unspecified, period in which user-owned equipment was involved, of which forty-five were found to be faults in the user equipment. A second'connnission cited' an example of computer time-sharing terlllinals connected through a local central office, which contributed to a serious overload condition,. In this case, the holding time per call on the ",:e'erminals Was approximately ten times the holding time on regular business telephone lines. A number of other specific examples were cited by this connnission. The experience here is applicable to the present study to the extent that it indicates that a customer with inadequate technical and operational competence may create difficulties in the connnon-carrier network, Experience in Other 'Areas There is experience in other technical and service enterprises in which interconnections between systems or system components may be pertinent to the study of interconnection with telephone systems. Computers (MainFrames and Peripheral Equipment) A good example is the interconnection of peripheral equipment of one or several manufacturers with a computer main frame of another manufacturer. The computing industry had to face the interconnection issue years ago. The large computer main-frame manufacturer maintained a strong sense of overall systems responsibility very similar to the connnon carrier's position, which has been altered by the Carter phone decision. The manufac- turers maintained that they could not be responsible for the perforlllance of the system if the customer uses other than the manufacturer's equipment and supplies. The issues are comparable in certain respects to those posed in the ca.mmon-carrier interconnection case. Who is responsible for mainten- ance and installation? Will the attachment harm the system? The attach- ment may have gJ:'eater capability, lower cost, etc. The first departure from the entrenched position of the main-frame manufacturers in the computer field occurred over ten years ago in the

- 71 - magnetic tape area. Computer manufacturers sold their approved magnetic tape, but the users started' buying from other independent suppliers. In general, the tape worked quite well and it represented an appreciable cost saving to the user. Customers were warned, however, that they had now transferred the responsibility. for tape-handler performance to themselves. When there was doubt as to whether the tape handler or the tape was at fault, the manufac tur er l s serviceman used a "good standard" tape to prove the case one way or the other, Even though the responsibility for tape performance was rhirs assumed by the user, he was willing to take this responsibility judging by. the amount of magnetic tape being purchased from independent manufactureJ;'s today, Within the past few years and with the fantastic growth of the computer indllst.:rY, many independent peripheral device businesses have b een ..... spawned. More are being born each day. There are now a large number of .. organizations providing peripheral devices like punchedccard readers and punches, high-speed printers, tape handlers, and disc handlers to customers in competition with computer main-frallle lIlanufacturers. Interconnection of these attachments raised grave concerns among the' computer main-frame manufacturers. The complexity of the inter- face between the peripheral device and the control unit or computer is such as to make the telephone interconnection interface seem much simpler in comparison. Signal frequencies are in the megacycles rather than cycles, levels are in the milli or microvolts, cross-talk. problems are fierce, and timing-control sequences are much more complex and precise than the dial pulses or tones used in the telephone network-control system. Yet, users have decided of their own volition to risk the interface problem and incur the division of responsibility to accrue cost savings. To the Panel's knowledge, the use of such attachments, especially disc and tape units, has been successful despite the complexities of the interface. The user will undoubtedly ~perience greater difficulty and delay in resolving a lIlalfunction, but he apparently feels it is worth the cost differential. In the event of malfunction, the user will, in most cases, have to call the computer main-frallle maintenance man to diagnose whether the problem is in the peripheral or in the system. If the problem is in the peripheral, he then has to call the peripheral service company, thus paying a double.maintenance charge and incurring extra delay. If the problems are obViously in the peripheral, he need call only the one company. The Sallle lIlaintenance philosophy can apply to the interconnection of foreign attachments to the telephone lines. It appears that foreign attachments will be a way of life for the computer industry. The weakness of the analogy pointed to above is that only the user may be harmed in the case of the computer attachment while many, who aJ;'e generally unknown, may be harmed with a bad telephone attachment, although, With the advent of computer time-sharing, this may become less

t rue, but here again, it is the,user or provider of the particular computer time-sharing, service who'accepts . the,degradation in seririceto reduce costs. Further,there is no comparable problem of hazard to personneL or property of other than the user of the compute.r, Broadcast 'Interconnection 'Arrangement There is considerable experience of some relevance in' the broadcasting industry (sound as well as television) in the interconnection of user-owned equipment with the carrier facilities, These are almost exclusively leased~line situations with full-period or temporarily 'allocated circuits in use for broadcast purposes. These systems are operated without additional complex interface devices between the user and the carrier facilities, Experience with Government 'Networks and Equipment The largest single class of interconnected communications systems and terminals in the United States are those of U.S. Government agencies -- the largest being the Department of Defense. Defense Communications systems There is a long complex history of a partnership between the Department of Defense and the U.S. domestic and international common carriers. In this connection, a wide latitude of interconnection of government-owned equipment and systems has been permitted by the common carriers as exceptions to_normal tariff arrangements. Last year, the 'government obtained approximately one-half billion dollars of telecommunica- tions services and facilities from these carriers. The largest singleaggre- gat ion of such facilities is the Defense Communications System (DCS),which is being evolved from the systems of the three military services. When put together with systems of the other principal departments and agencies of the government, the Whole becomes the National Communications System. Leased carrier facilities (particularly in the continental forty-eight states) comprise the bulk of the National Communications System (NCS). Major components of the NCS are: The CONUS AUTOVON system, a leased telephone 1, network provided by AT&T and the independent telephone companies. AUTOVON provides the backbone voice network for national security' command-control communications. 2, A companion to AUTOVON is CONUS AUTODIN, a leased'system provided by the Western Union

- 73 ;.., Telegraph Company, providing record c6mmunications, for. the'. Department of Defense and certain other associated activities~ DCSSpecifications The Defense Connnunications Agency, with the advice and assistance of other agencies, has developed'DCS and NCS specifications (in many cases, s~b­ stantia1ly equivalent to those descriptive of the public telephone network) to guide the evolution of the Defense Communications System and the National Connnunications System. These specificatious include interface specifications for interconnection of the government-owned equipment with carrier facilities. Gove:rrtlIlent Systems Other Than Those Operated byDefEinse There are a number of 'government systems other than those operated by Defense. Principal among these are: 1. The FTS (Federal Teleconnnunications System), a CCSA voice network administered by the General Services Administration and providing service to all government agencies, but primarily service to agencies other than DoD. 2. The ARS (Advanced Record System), a GSA- administered record-connnunications system leased from Western Union, provides these services for government agencies other than the DoD. PrefEirEintial'TreatmEintb~'CommonCarrier Because of the nature of government requirements, particularly those associated with national security activities, the space program, and other critical government activities, the carriers have afforded the government special treatment in regard to interconnection, such as the use of customer-provided equipment and the provision of special teleconnnunications arrangements to meet unique requirements. As was demonstrated to the Panel, these arrangements have not been without cost and difficulty. Although the DoD is probably the largest technical organization in the world with extensive capabilities for procurement, installation, and operation of teleconnnunications-type equipment, many problems have developed as a result •

- 74 - of interconnection arrangements without interface devices to shield the common carriernetwotk from failure;·malfunct~on, or delibetate·misuse of user facilities. It has been shown. that DoD interconnection of user-owned and maintained equipment with the Bell System accounts for a disproportionate share of the troubles in te:rillinal eqiIipments and transmission arising through interconnection. Conclusions The teview of the practices of certain foreign carriers and the experience of U.S.·carriers with interconnections provides many lessons germane to therecilmmendations of the study Panel. The most comprehensive experience is that derived from interconnections of government-owned equipments and systems (primarily those of the U.S. Department of Defense) with systems of the common carriers. There is also a large background of experience with interconnection of systems and equipments operated by the right-of-way companies, including the railroads, pipelines, electric utilities~ etc., and with communications- service organizations such as ARINC. There is also some applicable experience with the connection of user-owned telephones and other terminal devices to carrier networks. There is, however, no experience applicable to large-scale interconnection of small, individual users, and the Panel concludes that it must be approached with great care. The Panel also concludes that: 1. Interconnection without special interface devices is possible without service impairment or hazard to carrier personnel only under favorable conditions; 2. Such interconnections without restrictions could cause substantial service impairment, 3. Favorable conditions are necessarily associated with incentive, ability, responSibility, and user resources.

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A Technical Analysis of the Common Carrier/User Interconnections Area assesses the technical factors affecting the common carrier/user interconnection area of public communications. This book develops technical and background information that might be useful to common carriers, users, and equipment manufacturers in reaching and implementing solutions to immediate problems. This includes a technical evaluation of various contending points fo view regarding the common carrier/user interaction area, the various problems to which these views relate, and the various technical and policy alternatives for responding to these problems in the near future.

A Technical Analysis of the Common Carrier/User Interconnections Area addresses questions of the propriety of the telephone company-provided network control signaling requirements and various alternatives to the provision thereof by the telephone company; the necessity and characteristics of telephone company-provided connecting arrangements and various alternatives to the provision thereof by the telephone company; and basic standards and specifications for interconnection and the appropriate method to administer them.

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