Telenet Communications Corp

The user's role in connecting to a value added network

Early next year data will start flowing at 56,000 bits a second over the circuits of a unique nationwide common carrier service Richard B. Hovey called a value added network. This new approach Telenet Communications Corp. to data communications combines old and new Washington, D.C. transmission facilities and adds to them a form of intelligence to improve the performance. The value added network (VAN) is different from present data transmission services and from private data networks in both the enhanced and extensive offerings to users and the sophisticated technology it employs. The technology, called packet switching, makes it possible for the value added carrier—the implementer and operator of the VAN—to provide any user, large or small, with the kind of fast-response, error-free, low-cost-per- transaction data transmissions now available only to companies that have invested in their own large private networks. In essence, the value added carrier (VAC) takes advantage of the substantial economies of scale resulting from one very large network— fully utilizing such expensive resources as transmission lines and concentration equipment by sharing the network among the VAN'S subscribers. The VAC passes on a portion of the consequent savings to the individual user-subscribers through a tariff charge based mainly on traffic volume. Beyond the simple economics, leasing existing communications facilities allows the carrier to obtain just as much transmission capacity for each location as is required by the traffic load. This provides the flexibility to adapt quickly to subscriber traffic and geographical demands, and permits the incorporation of new transmission offerings—such as satellites and AT&T'S Dataphone Digital Service- as they become available. Conceptually and technologically, VAN'S have their origin in the Arpanet, a nationwide consor- tium of computers at numerous research centers tied together over a packet swtching network. How- ever, the Arpanet is operated in behalf of the gov- ernment to support research activities of various Once a user opts to buy Federal agencies, not as a common carrier facility. services from a value added This lack of availability of VANS to individual network, it's necessary for user-companies in commerce and industry was re- medied in 1973 when the Federal Communi- him to do some initial work, cations Commission approved the concept of value mostly some reprograming added networks, determined that VACs should be PACKET SWITCHING NETWORK

TO SAN FRANCISCO TO SATELLITE CENTRAL OFFICE | EARTH STATION

TO DALLAS CENTRALOFFICE

WIDEBAND TERRESTRIAL CHANNEL IMP INTERFACE MESSAGE PROCESSOR

MULTIACCESS SATELLITE CHANNEL TIP TERMINAL INTERFACE PROCESSOR

LOCAL LINE TO SUBSCRIBER TERMINAL BACKUP AND REDUNDANT LOCAL LINE TO SUBSCRIBER HOST COMPUTER PROCESSORSNOTSHOWN

1. Wideband terrestrial and satellite links permit different packets of bits in a subscriber's message to take alternative paths from source central office to destination central office.

regulated as common carriers, and declared an A value added carrier such as Telenet, however, open entry (non-monopoly) policy permitting po- will not supply data processing services nor will it tential public network operators to propose a value provide hybrid data processing involving both data added network so long as they applied for FCC ap- processing and data communications services. proval. Thus, VACs will be regulated, but will oper- What a VAC will do is simply permit data transfer ate in a somewhat entrepreneurial and competitive between any two or more dynamically selected environment. Telenet Communications Corp. re- user stations, where a station is defined as a data ceived FCC authorization as a VAC on April 16, terminal or host computer. To accomplish this, the 1974. Telenet's start up is slated for next January, VAC leases long-haul wideband lines and invests in with the network eventually having central switch- computerized interface and switching equipment, ing offices in over 60 cities. high-speed modems, diagnostic facilities, and the In addition to FCC's advocacy, the viability of the like to construct a network. The VAC programs the VAC concept was enhanced when AT&T amended computerized interfaces to provide such services its FCC tariff 260, for private voice-grade and wide- for customers as code conversion, speed conver- band lines, to permit VAC'S to "resell" the trans- sion, and error detection and control. In addition, mission channels they leased from AT&T to VAN the computers at the VAC's monitoring centers user-subscribers. More recently, AT&T specifically gather data for user traffic statistics and billings and included provision for lease of dedicated lines to provide other network related services. VACs for resale in its new FCC tariff 267 for Data- Typical tariffs phone Digital Service. Furthermore, specialized and satellite carriers have agreed to provide wide- In return, the user pays a tariffed charge. Telenet, band transmission facilities to VAC'S. for example, is proposing a basic $1.25 charge for a The FCC has authorized a VAC to provide the data kilopackct, 1,000 packets of up to 1,024 bits each. communications network required to connect a This charge is independent of mileage between sta- user's terminals and computers. Specifically, con- tions. In addition, there is a monthly charge for nections can be made from terminal to computer, connecting the access line from the user's station computer to terminal, and computer to computer. to a port at the VAC's nearest central office. As an Transmission will be available to users at all com- example, Telenet's port charge for a dedicated ac- mon speeds, ranging from that for the slowest tele- cess line is $50 a month for up to 9,600 b/s service. printers up to 56,000 bits per second (b/s) for high- And the charge for a dial-up port is, for example, speed data transfer between two computers. $1.00 an hour for asynchronous service and $2.00 an hour for 2,400 b/s synchronous service, with This redundant access to a central office serves such charges decreasing proportionately for shorter several useful purposes. For one thing, multiple calls. In general, lower speed service is less and lines permit traffic to be simultaneously routed higher speed service more. The toll charge, if any, over parallel channels between source and destina- for dial-up calls is borne by the user-subscriber. tion central offices. For another, multiple access The access lines and modems, leased by Telenet lines permit traffic to immediately reach its desti- but paid for by the user, are under operational con- nation via an alternate route in the network trol of Telenet personnel to permit continuous net- should one of the lines become degraded with ex- work diagnostics and to relieve the customer of cessive noise or go out altogether. having to deal with more than one vendor in case of difficulty. Packet switching nodes A prospective user of a VAN service must con- But most intriguing from a technical and oper- sider two areas: the technical and operational tasks ational viewpoint is that different packets compris- and responsibilities which are the factors discussed ing one message may be delivered along different here; and the possible impact of new communi- routes. For example, suppose a user-subscriber locations services on the user's operating and organi- cated in a suburb of Seattle wants to transmit an zation structure. For although immediate cost sav- 8,000-bit message to Houston. The message is deliv- ings may be achieved, of greater long-run ered to the VAC'S central office in Seattle over a significance is the new flexibility users will have dial-up or leased-line, and is formatted into eight for accommodating growth in existing systems and 1,000-bit packets in high-speed core memory by a for implementing new remote and multi-comput- special processor there. ing applications based on overall communications The first packet is released from buffer and, for needs and not on present technical and economic example, travels to and through the central offices constraints. in San Francisco, Los Angeles, Dallas, and on to As mentioned, the user must make a certain Houston—being error-checked over each hop of the technical and operational effort to be able to match journey and buffered at Houston to await the ar- up with a VAN. The amount of effort is quite small rival of the other seven packets. if the user just wants to connect a popular termi- The second packet, however, might have to take nal,- more effort, mainly some reprograming, may a different route if the line to San Francisco is busy be required to connect a host computer. That is, at that moment. In such a case, the packet could while the VAC operates the network, for the sub- take the route from Seattle to Houston, via Min- scriber to employ the network properly is, at least neapolis, Milwaukee, Chicago, St. Louis, and Dal- during startup, a joint project involving both the las. And so on for the other packets in the message. VAC and the user. These points will be detailed fol- Once a message is accepted by the network, the lowing this description of how the packet-switched VAC assumes responsibility for error-free trans- VAN itself goes about providing data communi- mission. Therefore, at the sending office the buffer cations transmission services to a multitude of di- for a packet is not released until the next receiving verse users. office acknowledges correct receipt. If received in In time, several VANS may be in operation, so error, the buffered packet can be retransmitted. users will have some choices in selecting competi- When all packets have arrived without error at the tive and alternative services. It appears likely that buffer in Dallas, the message is released from the all VANS will use packet-switching technology and central office to the recipient terminal or com- all will be configured in substantially the same puter. The recipient gets the packets in the same way—but each, certainly, with some technical and order they were sent. tariff differences. The Telenet network should Although the original message may have started serve, then, as representative of what will be avail- out, say, at a 4,800 b/s message rate, once it enters able in the next few years (Fig. 1). An 18-city net- the network it is transmitted at 50,000 or 56,000 work is expected to be on-line by the end of 1975 b/s. Even including electrical propagation, although a 7-city subnetwork will be operational queuing, and acknowledgement delays, a packet early in the year. Telenet has leased-medium- and will proceed from any source office to any destina- high-speed lines from transmission carriers to carry tion office in, on average, one-third of a second. data traffic among host computers and terminals. In addition, transmission capacity will be leased Central office interfaces from domestic satellite carriers to serve both as pri- The inset in Figure 1 shows the two major pieces of mary wideband channels and secondary back-up equipment in a Telenet central office, the terminal circuits to the terrestrial lines. interface processor (Til1) and the interface message One or more central offices are to be located in processor (IMP). Each TIP has hardware/software each of the cities functioning as nodes in the net- ports to accept data from a user's terminal or host work. Note that each node city has two or more computer. Terminal data can be a character, a (full duplex) lines connected to it. block of characters, or some segment of a long, con- LOCAL DISTRIBUTION

SUBSCRIBER

VALUE-ADDED VIA CARRIER MULTIPOINT KEYBOARD LEASED LINES TERMINAL CRT/KEYBOARD TERMINAL REMOTE BATCH TERMINAL

HOST COMPUTER

TERMINAL CONTROLLER REMOTE CONCENTRATING DEVICES MULTIPLEXER

HOST ON-SITE TERMINAL HOST CONNECTIONS INTERFACE PROCESSORS

2. Any kind of terminal and concentration de- vice can have access to a value added network's central office over dial-up lines and point-to-point and multipoint private lines. tinuous message. Even though data from the sev- spread traffic evenly throughout the network, and eral terminals may be in different lengths, codes, increase reliability. At each TIP and IMP along a and speeds, the TIP formats the output data stream route, packets are checked for errors and, if neces- into the standard packets used for internal network sary, retransmitted. Flow-control techniques within transmission. the network (invisible to users, as are the packets At the user's option, all data entered from a char- themselves) ensure that the fast-access core memo- acter-oriented terminal attached to the Telenet net- ries of the processors do not become overloaded work can be translated into a single, well-defined while maintaining high channel utilization. There- 'virtual terminal' format by the TIP. Conversely, fore a packet cannot get lost for lack of buffer ca- data sent from the host computer in 'virtual termi- pacity at any node. nal' format is translated back into a form compat- Each interface message processor and terminal ible with the terminal. This mechanism can re- interface processor periodically reports observa- move much of the burden of code conversion and tions about itself and its environment to network terminal support from the host computer, which monitoring center processors. These computers supervises the single 'virtual terminal' type to com- watch the instantaneous state of the network- municate with the diverse terminal models con- warning of network components whose capacity nected to the network. may need to be increased and initiating remote The number of TIPS actually located in each cen- diagnostics and repair activity when necessary. tral office depends on the expected number of ter- The system is designed such that the failure of an minals and host computers being serviced. How- individual component can be immediately de- ever, each central office will have at least two TIPS, tected and its tasks simultaneously absorbed by each handling a share of subscribers even though one of its functionally redundant counterparts neither one may be fully loaded under normal flow without interrupting service. conditions. If a TIP should go out of service, either Interface message processors and terminal inter- on a planned or emergency basis, all its connec- face processors are stored program processors. Be- tions to users can be instantly switched to back-up cause they employ software, not hardwired logic, interface equipment. new programs can be readily added to permit the The terminal interface processor arc multiply processors to interface with new types of terminals connected to IMPS which route the standardized and host computers and provide new terminal sup- packets of data over the optimal long-haul links. port functions. In fact, new or modified programs The technique of dynamically routing packets in- can be sent over the network itself from a central dividually along one of several alternate paths is location to all, or selected, IMPS and TIPS to make a used to minimize end-to-end transmission delay, new service immediately available to all subscribers without having to halt the network. mission parameter or mode. For example, it is User terminals can reach the central office in a feasible for the operator to change the speed at number of ways, including dial-up lines, mul- which an asynchronous terminal sends and re- tipoint, and point-to-point leased-lines, and using ceives data, assuming, of course, that the terminal such concentrating devices as multiplexers, remote and the associated modem can support the selected data concentrators, and terminal controllers. In transmission speed. some instances, VAC-owned TIPS may be installed at In addition, a VAN quite efficiently provides a the user site (Fig. 2). The lines and devices in color number of simple functions beyond pure data represent items supplied by the subscriber and transfer. For example, local editing is available for those in black designate those supplied and/or un- unbuffered typewriter-oriented terminals and dis- der control of the VAC. plays. Data entered on these terminals is normally Terminal access accumulated by the TIP prior to being forwarded to the destination host computer for processing. Be- The criteria for choosing either a dial-up line or a fore the buffered data leaves the TIP, it may be dedicated line to access the central office are sub- edited by the operator on a character or line basis, stantially the same as those employed in configur- typically to correct keyboard input errors. Again, ing private data communications networks. In this editing facility can be preset or the user can is- short, such factors as transmission speed, accept- sue short commands that define characters which able busy-signal incidence, response time, volume when typed will delete the last preceding character of traffic, length of individual transmissions or from the data just entered or all the data in the cur- transactions, and whether line use is substantially rent line of input. continuous or mostly occasional, must be consid- These and other functions are strictly optional; ered. Because these lines extend only to a local cen- their ultimate utility may depend on the nature of tral office, cost is less of a determining factor than the user's particular application. In short, some ter- in an extensive private network. minal users will want to become familiar with a In addition to establishing a physical connection limited repertory of commands and facilities. For over a line to the VAN'S nearest central office, the others, the network interface can be pre-initializcd terminal must also establish a logical connection to exactly those parameters and facilities required, through the network to some destination com- eliminating the need for any commands during puter. For data terminals, the logical connection routine usage. In either case, the user can adapt the can be established in either of two ways depending network to his needs with ease and little training. whether the terminal has a dedicated or dialed Normally, the VAC will build a software module connection to the central office. into each TIP'S program for each class of terminal. When a terminal on a dedicated line is merely For popular terminals this software is part of the required to converse with one particular computer VAN service. Therefore, at the outset about the on the network, that terminal's TIP port may be pre- only concern a user may have is to make sure the initialized to the desired transmission parameters VAN can handle his type of terminals. But, if the and host computer address. When the terminal is terminal is very special, or brand new on the mar- switched on-line it will be automatically connected ket, the user may have to help defray the cost of to the preselected computer in less than one sec- unique software development. ond and the computer may respond by printing out its own name, such as MH COMP, on the termi- Computer access nal's display. Then the terminal-computer-terminal Since a host computer converses simultaneously dialog can proceed just as if there were a direct with many terminals or other hosts through the physical circuit between the two station sites. network the physical connection to a VAN'S central For a dial-up terminal, the process is similar, ex- office will usually be via a dedicated local point-to- cept that the operator may first have to provide a point access line operating at up to 56,000 b/s. (A short command identifying his terminal model second access line, perhaps of a lower speed, may and a second command specifying the host com- be installed for reliability or increased throughput puter with which it is to be connected. capacity.) There is little a subscriber has to do to Simple commands obtain a physical connection to the network. But the user must get involved in planning for logical In the majority of cases, the terminal operator will connections of host computers as the VAN takes on be concerned with, at most, the command that de- more and more of a subscriber's load. fines his terminal model and the commands re- Format, signaling, and error control protocols en- quired to establish and break the connections to able a subscriber's computer to send and receive host computers. From time-to-time, however, some data over the carrier's system. These protocols users may wish to communicate other instructions must be incorporated in the user's system in the directly to the TIP. This is accomplished by issuing form of software routines. The protocol software additional commands, most of which set a trans- may reside in either the host computer, when the ADDING TO A VAN

CENTRAL ,» OFFICE ,'

REMOTE TERMINAL DEVICES LINE \T FRONT-END INTERFACES PROCESSOR COMPUTER

3. By connecting to the nearest central office, users can convert point-to-point and multipoint links into less costly local access links. interface between the communications lines and However, VAN utilization can grow to the stage the host computer is a hardwired transmission con- shown at the bottom of Figure 3. Here, all terminals trol unit, or in a programable processor that front- connected to the multipoint line and all dedicated ends the host computer. To minimize the effort re- line terminals, except the two closest to the host quired to connect a host computer to a VAN, the in- computer, are connected to nearest central offices. terfaces have been designed to emulate standard Thus, using the value added network has elimi- communications devices on a conventional data nated several point-to-point lines and one mul- control links—something the host "already knows tipoint line with minor impact on user programing. about." Thus, the changes required because of the The subscriber also needs fewer line terminations use of VAN links may involve no more than repara- at his central office. meterizing the communications macros in present If the subscriber also opts to convert from hard- vendor-supplied packages. wire transmission control unit to a true program- Consider the system configuration at the top of able front-end processor he can remove consider- Figure 3. Here, several point-to-point lines and one able inefficiencies from the host computer, but at multipoint line go to a hardwired transmission the initial cost of programing the front-end proces- control unit. The top left most terminals were pre- sor. (Such programing costs are not attributable to viously accessed via an expensive, transcontinental going on a VAN.) If this change is made at the same line. As a means of initially testing the VAN service, time the subscriber integrates his system onto a the user has selected to access these two terminals VAN, he may want to incorporate in it a software through the network. Therefore, the TIP, in the interface with more efficiency and flexibility than central office closest to the host computer, is pro- the emulation interface provides. If a customer gramed to emulate a multipoint, binary synchro- wants to connect several computers to one location nous line. (The terminals might actually be on a to the network, the carrier may determine that it is separate point-to-point line connected to their local to the user's advantage to install a Til' on the sub- central offices.) Accordingly, few changes in the scriber's premises. With regard to software modi- software macros have to be made by the user in the fications, the carrier may either contract to develop computer's communications software. the software for the user's computer or assist the System use of the VAN could stop with the as- subscriber in having its in-house personnel develop signment of just two terminals to the network. the software.

Reprinted from Data Communications, May/June 1974 Copyright 1974 by McGraw-Hill Inc. 1221 Avenue of the Americas 10020 The Telenet Report Telenet Communications Corporation, 1666 K Street, N.W., Washington, D.C. 20006, [202] 785-8444 Volume I, Number 1. Summer, 1974

In the FCC order. Telenet was author- Telenet "Intelligent Network" ized to establish packet-switching centers in 18 cities, and to lease the neces- Receives FCC Approval sary high-speed interconnecting links from other communications common carriers. Required transmission facilities The Federal Communications Commis- impact on the structure of the industry, include terrestrial lines operating at 50 sion announced its approval of Telenet's such entry should be permitted be- or 56 kilobits per second and a supple- "Intelligent Network" on April 18 of this cause it would introduce new and im- mental 1.544 megabit per second multi- proved means of satisfying the needs year-just six months after Telenet filed access satellite channel. This channel, of the public not otherwise available its application! This action clears the way from generalized or specialized car- leased from an approved domestic satel- for Telenet's operation as the first U.S. riers. lite carrier, will serve domsat earth sta- carrier offering switched high-speed data tions located near eight major metro- communications on a coast-to-coast Packet-Switching Gaining politan areas. basis. The Commission rejected a peti- Worldwide Acceptance tion by the Western Union Telegraph Commenting on the FCC action, Dr. Letters of Support Submitted to FCC Company to deny the Telenet application. Lawrence G. Roberts, Telenet's Presi- In opposition to the Western Union Western Union's contention that Tele- dent, stressed the fact that packet-switch- petition, letters of support were received net's application failed to meet the re- ing is quickly gaining worldwide accept- by the FCC from The National Library of quirements of the Communications Act ance as the most effective means of Medicine, The Interuniversity Communi- and the FCC's rules was found by the providing switched data service to com- cations Council, Inc., The Center for Commission to be without merit. In its puter users. The approach has been Advanced Computation at The Univer- approval of Telenet, the Commission adopted by many countries, including sity of Illinois as well as the Computer stated: Canada, England, France and Spain, all Corporation of America. Additionally, ... although the entry of packet-switch- currently implementing public packet- American Satellite Corporation sub- ing carriers into the market for com- switching networks similar in many re- mitted comments urging the FCC to act munications services would have an pects to Telenet's. on the Telenet Application. Telenet Will Offer Nationwide Service By means of the initial seven switching above, the Telenet system will encom- High End-To-End Reliability- centers which are planned to be installed pass: Atlanta, Cincinnati, Cleveland, A Prime Design Objective and operational by early 1975, the Intel- Detroit, Houston, Milwaukee, Minn- Each Central Office will be equipped ligent Network will offer coast-to-coast eapolis, Philadelphia, Pittsburgh, St. with standby equipment, for quick re- data communications service. These Louis, and Seattle. And, within four years, placement of faulty facilities. And, diag- switching centers, called Central Offices, Telenet plans to enter another 44 cities nostic testing and preventive mainten- will be located in Boston, Chicago, Dal- for a grand total of 62 switching centers. ance will be regularly performed by on- las, Los Angeles, New York, San Fran- When all these cities are within the net- site Telenet personnel. Additionally, cisco, and Washington. (As this news- work, more than 50% of the U.S. popula- line switchover units will provide for letter went to press, office space for four tion will be within 20 miles of a Telenet immediate recovery from equipment of the seven switching centers had been facility. Continued on page 4 obtained, and several sites in the re- TELENET PACKET-SWITCHING NETWORK maining three cities were under evaluation.) But potential subscribers need not be located in these particular cities to take advantage of Telenet's service! Users in different cities may either lease a channel or use a dial-up line to access the nearest switching center. And, as additional cities are added to the network, the length (and cost] of system access lines will be reduced. After the first seven Central Office facilities are constructed, Telenet plans to expand the Intelligent Network at a rate of one city per month-so that eighteen full-service switching centers will be operational by December, 1975. In addition to the seven cities mentioned JANUARY 1975 O DECEMBER 1975 oped by its parent company, Telenet's in seven cities this fall. System software incorporates important exten- Shortly after receiving formal FCC Implementation... sions to the basic IMP and TIP programs. authorization, Telenet ordered additional These enhanced programs, nearly com- packet switching computers from Prime. plete, are running successfully in a proto- The Prime Model 200 processors will be A Progress Report type Central Office at the company's used as IMPs and TIPs, while Prime development center. Model 300 processors will serve as the Telenet has been working on the de- Utilizing computer equipment supplied Network Control Center (NCC) ma- velopment of the software for its IMPs by Prime Computer Inc., the prototype chines. Software development has been and TIPs since last fall. Starting with the Central Office will serve as a model for done primarily on the Prime 200 field-proven ^ARPANET software devel- the actual Central Offices, to be installed computers. Data By The Packet... What It's All About The concept of packet-switching is a sage switching, packets are stored in relatively young, but performance-proven core memory, for only a few millisec- data transmission technique specifically onds, and are routed along dynamically designed for the unique requirements of determined paths. Each node maintains terminal-to-computer and computer-to- a continuously updated routing table so computer communications. Like most that packets can be easily routed at each other switching techniques [i.e., circuit switching center, or node, along the path and message switching) packet-switch- that most efficiently minimizes transmis- ing is designed to avoid the high cost of sion delay at that moment. providing dedicated connections among At each Central Office node, small all points of communication. computers—called Interface Message Circuit switching, for example, is used Processors (IMPs) or Terminal Interface by the telephone company. Upon receipt Processors (TIPs)... when terminal/host of dialing signals, the switching equip- interfacing capability has been added- ment establishes a dedicated connection perform the packet-switching function. between sender and receiver. Through- These IMPs and TIPs are interconnected out the duration of the call, this channel by leased high-speed transmission facili- is unavailable to other users. Circuit ties, and the TIPs provide direct access switching makes efficient use of trans- to the packet-switching network to heter- mission channels when the information ogeneous, autonomously operating flow is relatively continuous, but is highly computers and to terminals of many inefficient for irregular data flow patterns. types. Each participating "host" com- On the other hand, message switch- puter is connected to a nearby Central ing involves routing addressed mes- Office TIP. Each data terminal is con- A member of Telenet's technical staff tests a sages from sender to an intermediate nected to either a Central Office TIP or new software enhancement for the IMPs and TIPs. Each switching center will contain a to a host computer. .. for indirect access. switching center. Here, they are stored minimum of two IMP and two TIP computers. on disk drives-usually for a matter of In this case the host computer is, in turn, minutes-until they can be forwarded connected to a TIP. Both terminals and to their destination or to the next store- hosts are connected to Telenet Central to conventional land lines for data trans- and-forward switching center. Messages Office TIPs via local telephone company mission. In the multi-access "broadcast" are stored so that peak demand for lines. mode, satellites afford extremely efficient transmission facilities can be spread over use of the available bandwidth by many time and so transmission facilities can be Messages Subdivided Into Packets ground stations. Each ground station used more uniformly and efficiently When a TIP receives a message, it is occupies the channel for a brief period throughout the day. This technique is subdivided into packets (about 100 of time only-for the amount of time suitable when deferred message de- characters in length) and transmitted to needed to transmit a single packet. livery is O.K., but inappropriate for rapid the destination along any available net- Therefore, many ground stations can ef- computer interaction. work path. Each packet proceeds along fectively interleave their respective trans- its own path, from TIP to IMP and from missions. This efficient use of shared Packet-Switching Similar IMP to IMP, until it reaches the destina- satellite channels provides high peak to Message-Switching tion TIP, where all packets are stored. At data rate channels (up to 1.544 Mbps) Both message and packet-switching the destination TIP, the complete mes- among all ground stations at the cost use store-and-forward techniques and sage is reassembled for delivery to the of asingle channel. both make efficient use of transmission receiving host or terminal. Future full development of satellite lines. In packet-switching, however, mes- technology is certain to make low cost, sages are subdivided for efficiency in Data Transmission= small-scale, ground stations readily avail- transmission into short segments called Terrestrial Channels+ able to further enhance the economical "packets," which are transmitted Satellite Channels interconnection of computers in isloated through multiple switching centers from A recent packet-switching innovation areas—and the economics of data trans- source to destination. But unlike mes- is the use of satellite facilities in addition mission by packet-switching! A final advantage to a packet net in- Telenet Stages Double-Edged volves a distributed data base-affording more economical, direct terminal access to information stored in a cen- Participation At Interface 74 tralized location or distributed among many computer sites. The Telenet Intelligent Network and the can best be translated in terms of re- Dr. Roberts also explained how the benefits of packet switching to data com- duced communication and computing Telenet packet network can best meet munications users were the order of the costs and increased flexibility. computer communications wide flexi- day as Dr. Roberts led Telenet Communi- In the area of cost-effectiveness, Tele- bility requirements. Not only will Tele- cations Corporation in a successful net will help most users reduce commu- net have the capacity to absorb sub- dual stint at Data Communications In- nication line charges and better utilize stantial increases and fluctuations in terface 74 in Dallas this March. both computing and terminal resources; individual traffic loads, but also will As the only national conference and and also decrease operating and main- permit the subscriber "to choose the exposition devoted exclusively to the tenance expenses for all users by assum- type of terminal to be used at each loca- needs of datacomm users, Interface ing complete, end-to-end responsibility. tion virtually independently" —without 74 offered Telenet representatives three Attendees were also very interested to the need for additional host software. full days of valuable contact with major hear that the high reliability of the Tele- Finally, Dr. Roberts said, public packet data communications personnel from net System-through such features as networks will make direct interconnec- organizations nationwide. The attention- dynamic alternate routing and advanced tion of data processing computers more getting Telenet booth consistently at- error detection and correction —will practical and more economical than tracted large numbers of attendees provide users with further cost savings. ever before. throughout the exposition. And. Telenet's technical and marketing staff members responded to their questions with detailed information on immediate and future capabilities of the Telenet Network -and on how the use of sophisticated packet-switching techniques can solve many serious data transmission problems. Dr. Roberts' Speech Highlights Conference Sessions President Roberts provided data communications users with an informative presentation on Public Packet-Switching Carriers during the second day of Interface conference sessions. Dr. Roberts reported that Telenet belongs to "a new class of communications common carriers-Value-Added Carriers-which are authorized to lease raw communication trunks from the transmission carriers, augment these facilities with computerized switching, and provide enhanced or (value-added) We Thought You'd Like To Know. communication services." Telenet, he ... a little something about Telenet nization and design, computer commu- told attendees, plans to provide these Communications Corporation in case nications networks, automatic program- value-added services by taking advan- you happened to miss some of our ming, pattern recognition, computer tage of proven packet-switching tech- recent publicity. Telenet is a majority- problem-solving, natural language com- nology. owned subsidiary of Bolt Beranek and puter systems, information retrieval, and Dr. Roberts traced the development Newman, Inc., a company established research on man's interaction with the and application of packet-switching in 1948 for the purpose of consulting, machine—to name a few. Here's a quick- techniques through the Defense Depart- research and development in science look at a few more specific areas of ment's Advanced Research Projects and technology. Since that time, BBN BBN involvement: Agency Network (ARPANET)-which (a public company listed on the Ameri- • In 1962, BBN developed one of the was built and is currently operated by can Stock Exchange] has developed first time-sharing systems, which Bolt Beranek and Newman, Inc., Tele- advanced capabilities in the computer laid the groundwork for the future net's parent. He also pointed out that communications field. In fact, about half of this burgeoning industry. public packet-switching networks, like of BBN's 600 employees are involved • Today, BBN's advanced TENEX Telenet's, are currently being imple- with computer science and technology. time-sharing operating system is in mented in various countries in Europe use in a number of research and and in Canada. Recent BBN Activities . . . university computer installations The user benefits of packet-switching . . . include computer science projects across the U.S. networks, Dr. Roberts went on to say, from A to Z: advanced computer orga- Continued on page 4 Continued from page 3 manages the entire packet-switching poses of establishing value-added com- • BBN is responsible for the design of network from its Control Center. The mon carrier services, based on the the COMEX network-the Pacific success of ARPANET has been cited as packet-switching technique developed Stock Exchange securities handling "one of the most significant and valu- for ARPANET. As a BBN subsidiary, computer system. able advances in computer and com- Telenet Communications has enjoyed • Recently, BBN delivered specialized munications technology." Due to his corporate and technological support packet-switching systems to the contribution to this unprecedented suc- from its parent company during all Defense Communications Agency and cess, Dr. Lawrence G. Roberts, current phases of its efforts. Using the ARPANET to the National Security Agency. President and Chief Executive Officer as its model, and drawing upon BBN of Telenet Communications, has won know-how and experience, Telenet be- Dr. Lawrence G. Roberts international acclaim as a leader in com- gan the process of establishing a na- and the ARPANET success story munications technology and is widely tionwide packet-switching network In 1968, the Advanced Research Proj- known as the "father of packet-switch- offering high-performance data com- ects Agency (ARPA) selected BBN to ing." munications services to the public . . . design and implement the ARPA packet- the first coast-to-coast network of its switching network. Currently, BBN de- ARPANET . . . The Telenet Model kind. The result? Quick FCC action on signs, maintains, tests, and installs In 1972, Telenet Communications the Telenet application for approval as ARPANET hardware and software and Corporation was founded for the pur- a value-added common carrier.

Continued from page 1 Two co-located Network Control a malfunction, as in the ARPA Network. failure. Even where a particular trans- Center computers will receive automatic The Network Control Center (NCC) will mission channel within the network fails, feedback from each Central Office re- be located at the Washington, D,C. Cen- network service will not be interrupted, garding line utilization and any malfunc- tral Office. Aside from their performance since each Central Office will be doubly tions, to assure prompt corrective serv- monitoring function, billing data and cen- or triply connected to other Central icing. This data will be provided at one tralized customer support services will Offices. minute intervals, or at the occurrence of both be provided by the NCC computers. Telenet President Roberts Considered 11 "Architect of Packet-Switching Technology in many areas. These included computer commanding position in computer system design and architecture, graph- science. ics, artificial intelligence, signal process- Secretary Schlesinger also empha- ing, weather modeling, and man-ma- sized Dr. Roberts' chine interaction. . . . penetrating insight [that) has been Additionally, the world-famous ARPA responsible for the design, develop- computer network—the communica- ment, and implementation of the ARPA tions network that served as the Telenet Computer Network, a revolutionary concept which has set new standards model —was developed under his direc- of reliability, speed and economy in tion. The network represents a new the communications field .. . It appears concept in interconnecting autonomous certain that major national and world- computer systems for the purposes of wide communications systems of the sharing hardware, software, and data future will be based on the technologi- resources among all members of the cal foundation laid by Dr. Roberts. ARPA research community through the In conclusion, the citation stated, application of packet-switching tech- "Rarely have the insights of a single Dr. Lawrence G. Roberts nology. individual had a greater impact on the progress of a profession so vital to the Dr. Lawrence G. Roberts, President of Awarded Civilian Service Medal destiny of this country." Telenet Communications Corporation, by Secretary of Defense Prior to his Defense Department ex- has earned international recognition as Dr. Roberts' outstanding achieve- perience, Dr. Roberts headed the re- a leader in computer and communica- ments while acting as Director of this source-sharing research at MIT's Lincoln tions technology. Before joining Telenet research and development organization Laboratory which resulted in initial in 1973, as President and Chief Execu- with an annual budget of more than $40 packet-switching developmental efforts. tive Officer, Dr. Roberts held the post of million, earned him the Secretary of Author of many articles in professional Director for Information Processing Defense Meritorious Civilian Service journals on a variety of computer and Techniques with the Advanced Research Medal. Awarded by Secretary Schles- communications topics, Dr. Roberts Projects Agency of the Department of inger on September 19, 1973, the has lectured throughout the continental Defense. citation commended Dr. Roberts for United States and abroad. He holds During this time, Dr. Roberts was his ... Bachelor of Science, Masters of Science, primarily concerned with the research, . . . industry and ceaseless drive [that] and Doctoral degrees in Electrical Engi- development and evaluation of new tech- have been in large measure respon- neering from the Massachusetts Insti- niques for the processing of information sible for maintaining this Nation's tute of Technology. The Telenet Report Telenet Communications Corporation, 1666 K Street, N.W., Washington, D.C, 20006, C202J 785-8444 Volume 2, Number 1, February, 1975 Reid Installation of Telenet's "Intelligent Network"

Moves Into High Gear miles of transmission facilities from AT&T and other transmission carriers. Field installation and testing of the na- Network" in over 60 cities across the These links will operate at speeds rang- tion's first public packet-switched data country. ing from 9600 to 56,000 bits per second. communications network began with Where AT&T's all-digital Dataphone Telenet's Washington Central Office in Central Office Equipment Digital Service (DOS) is available, Tele- January, 1975. The establishment of Supplied by Prime net is using these high-quality facilities similar packet-switching exchanges in The equipment in a typical Telenet for both interoffice connections and New York and Boston—scheduled for Central Office consists of Interface Mes- subscriber access links. March—will allow final testing of addi- sage Processors, which store and route The FCC has approved Telenet's tional system elements, including the packets, and Terminal Interface Proces- use of 1.544 megabit per second multi- new high-speed Dataphone Digital sors, which interface subscriber com- access satellite channels to comple- Service (DOS) transmission facilities puters and terminals to the network. ment its terrestial lines, and Telenet leased by Telenet from AT&T. Live [See photo on page 5.] These IMPs plans to begin utilizing these high- subscriber data traffic will be used as and TIPs are fabricated from computer capacity, low-cost channels as soon as part of the test procedures. equipment supplied by Prime Computer traffic volume within the Network builds The backbone of the nationwide net- Inc. under an agreement which provides up to necessary thresholds.Telenet will work will be completed with the addition for the delivery of up to 125 computers lease these facilities from authorized of Telenet Central Offices in Chicago, during 1975. domestic satellite carriers and will install Dallas, San Francisco and Los Angeles In addition, each Central Office incor- Satellite IMP [SIMP] equipment at those during April and May—permitting Tele- porates Telenet-designed line switching carriers' earth stations. net to offer tariffed data communications equipment which immediately transfers service on a nationwide basis beginning subscriber and network lines to standby Telenet Receives Enthusiastic in June. IMPs and TIPs in the event of equip- Subscriber Reaction Continued expansion of the Network mentfailure. Line switching equipment is Subscriber reaction to Telenet's new from the initial seven cities is scheduled manufactured by Cooke Engineering service offering has been greater than to proceed rapidly through the latter Co. anticipated. Initial subscribers who are half of 1975, with facilities to be installed currently working closely with Telenet in all the 18 FCC-approved cities by AT&T DOS Transmission Links on the procedures for connecting their early 1976. Further expansion to 24 to be Used computers and terminals to the Net- cities is planned for the first half of 1976 To interconnect the initial seven Cen- work, have been assured of service and, by late 1977, Telenet anticipates tral Office sites, Telenet has ordered dates between June and September. providing local access to the "Intelligent approximately ' 15,000 voice-equivalent Commercial service begins in June.

Telenet Receives $2 Million Lehman Brothers, Inc., Telenet's invest- ment banker, which together with BBN Additional Equity Rnancing has made previous investments in the company. Telenet was founded by BBN, a prin- In January, Telenet received $2.1 mil- The investors participating in the pri- cipal developer of packet-switching lion in additional equity financing under vate financing include Time, Inc., the technology, in December 1972. BBN a recently arranged financing program diversified publishing company; Besse- remains Telenet's largest stockholder involving several institutional investors. mer Securities Corporation and The with equity in excess of 40 percent, and The program provides Telenet with the Palmer Organization, leading venture will continue to provide Telenet with capital necessary to finance the imple- capital firms; and Telenet's parent com- technical support, based upon its experi- mentation and operation of its nation- pany, Bolt Beranek and Newman Inc. ence in the development and operation wide data communications network. (BBN). The financing was arranged by of the research-oriented ARPA network. Computer Service Rims To Benefit From The Intelligent Network

Firms marketing computer-based ser- Cost Savings Emphasized communications hardware associated vices-including conversational time- Perhaps the most significant advan- with its Host computer. Typically, such sharing; special-purpose, application- tage offered by Telenet to computer Host computers have hundreds of low- oriented remote computing; data base service firms (with or without established speed "ports" at present, each of which inquiry services and remote batch proc- networks) is cost savings. Communica- is a hardware interface to a communica- essing-will find that Telenet's Intelligent tions costs, which may range anywhere tions channel. The alternative approach, Network represents a most attractive from 5 to 20 percent of a computer ser- offered by Telenet, involves the consolida- vehicle for providing users across the vice firm's total revenues, represent a tion of the traffic from many remote country with economical access to these substantial recurring cost, for which any points over a single [or dual) high-speed services. reduction contributes directly to profit- link between the Intelligent Network and Today, the computer service firm may ability. the Host computer. While this approach employ a variety of expensive communi- requires "demultiplexing" software in cations channels to serve remote users, Telenet will reduce the firm's communi- the service firm's computer (or front end cation costs in several ways. First, Tele- including ordinary dial telephone lines, processor), the number of ports is vastly foreign exchange lines, or WATS lines. net's charges per terminal-hour of usage reduced, as is the amount of processing If the firm's customers cluster in metro- will, in general, be lower than those cur- and memory required for handling ter- politan areas, these communications rently experienced by firms operating minal traffic. their own multiplexer/concentrator net- expenses can be reduced through the Processing and memory are reduced use of multiplexers and concentrators. works. For example, private multiplexer/ because the service firm's computer is concentrator networks typically have However, the firm then incurs capital now handling "blocks" of data—e.g., a costs in the range of $3 to $7 per ter- costs for equipment and program de- line of characters —rather than individual minal hour for asynchronous dial-in velopment, to say nothing of the recur- characters. Also, Telenet relieves the ring line changes and network operating terminals. In contrast, Telenet's charges Host of such functions as code conver- and maintenance costs. for comparable service will be approxi- sion, echoing, and simple editing. With the introduction of Telenet's mately $2. Other savings to the computer ser- Intelligent Network, computer service Great Flexibility vice firm, not reflected in a simple com- firms have a new option for serving their While the cost savings offered by Tele- parison of hourly communications costs, remote users. Such a firm, by connect- net are substantial, many computer ing its Host computers to the Network, are the savings which flow from reduced service firms will find the flexibility pro- network operating costs, elimination of can enable its present and potential vided by Telenet to be equally attractive. customers to dial in to local Telenet lost revenues due to network outages, For example, a computer service firm Central Offices around the country and and elimination of various items of utilizing the Telenet service can install obtain access to the firm's remote com- equipment. The network operation and new Host computers anywhere in the puter services. maintenance services performed by United States; it is not constrained to If the computer service firm does not Telenet's Network Control Center may install new systems in a centralized data presently operate a communications enable the user to reduce the number of center. All of the firm's customers will network, the use of the Intelligent Net- personnel which he would otherwise be able to access any of its Host com- require to perform these functions. work permits it to immediately market puters, despite the fact that the Hosts The computer service firm may also its services nationally, rather than only may be located in different cities or within obtain substantial cost savings in the locally-possibly even test marketing the same data center. The Network per- its services in several cities. No major continued on page 3 capital investments are required. The firm will, in fact, not incur any significant AT&T Tarriff Revisions Help communication costs until its service is actually used and generating revenues in Value-Added Carriers the remote cities, since Telenet charges AT&T has filed provisions in both its utilize both conventional and AT&T's are based primarily upon traffic volume. analog and digital private line tariffs new digital private line circuits, as well If the computer service firm presently which enable Telenet, as well as other as WATS lines, in their common carrier operates an extensive communication Value-Added Carriers certificated by networks. Value-Added Carriers such as network, a connection to Telenet may the FCC, to lease AT&T lines and to use Telenet may also utilize the transmission be implemented in parallel, providing these lines to "perform data switching facilities of other carriers; however, most access to additional cities, as well as for others." These tariff changes, which of Telenet's transmission links will initial- providing backup for both peak traffic AT&T tried to file in mid-1974, were ly be supplied by AT&T. loads and outages in the computer ser- delayed because of ambiguities in the Although these tariff changes were vice firm's own network. In most cases, tariff language, but finally went into effect anticipated by our staff for some time the economic attractiveness of the Intel- in October 1974. (they were OKed by the FCC over a ligent Network will cause the computer According to the new tariff provisions, year ago), we are pleased that they have service firm to gradually phase out its Value-Added Carriers, called "Composite now been officially filed with the Com- existing network. Data Service Vendors" by AT&T, may mission. only for access links. At the present time all network access links are committed to approximately 30 organizations including British Olivetti Ltd., ICL, Barclays Bank, National Computing Centre Ltd., Data Dynamics Ltd., Civil Service Depart- Telenet's Director of ment, Scicon Computer Bureau, and Sales explains the the University of Oxford. At the end of advantages of packet-switched data the two-year experimental period, the communications initial three exchanges will be expanded, service to an attendee and additional exchanges will be in- at the 1974 Tele- stalled as required. Communications In France, the Ministere des Postes Association Confer- et Telecommunications [PTT] is also ence in San Diego, establishing a public packet-switching California. network, initially with packet-switching exchanges in Paris, Rennes, and Lyon, and with multiplexers in Bordeaux, Marseille, and Lille. Initial provision of public service is expected in 1976. Packet Switching: In Japan, work is underway developing a data switching system which will provide both circuit and packet-switch- A Worldwide Answer ing services. Equipment for field trials Though commercial packet switching is at least 14 cities. The announced has been built and programmed at the new, it is by no means unique to the charges for Datapac service are struc- laboratories of Nippon Telephone and United States. Public packet-switching tured in the same way as Telenet charges Telegraph Company, in conjunction networks are currently being established —they are based primarily upon the with four Japanese manufacturers. This in many countries around the world — volume of data transmitted. public switched data network is sched- including Canada, England, France, and In the United Kingdom, the British Post uled to be operational by 1977. Japan-as well as in the United States. Office Corporation (which provides At the present time, Telenet is partici- In October 1974, the Trans-Canada public telephone, telegraph and data pating in discussions with these other Telephone System (TCTS), which in- communication services) is well along carriers, aimed at developing standards cludes Bell Canada, announced its in the implementation of its Experimental as well as technical and operating pro- operating schedule for the first Canadian Public Packet Switching service (EPSS). cedures for interconnection of public public packet-switched network, called The EPSS service will be offered ini- packet switching networks. These dis- the Datapac network. It will begin operat- tially in fall 1975, with packet-switching cussions are continuing under the aus- ing in mid-1976, with four network nodes exchanges in London, Manchester, and pices of the CCITT, the international -in Calgary, Toronto, Ottawa, and Mon- Glasgow. For a period of two years the coordinating and standards-making treal. During the nextx four years TCTS BPOC will limit the number of subscrib- organization for telephone, telegraph, plans to expand the Datapac network to ers, and during the first year, will charge and data communications. continued from page 2 increase in functional capabilities when mits the terminal user to select the par- hance the range of services which the accessing a remote Host through the ticular Host processor to use at a service firm could offer to its customers. Telenet system, but also a substantial particular instant of time, taking into Similarly, customers of the computer improvement in overall communications account machine availability, loading, service firm could submit jobs from service reliability and data transmission and file availability. standard remote batch terminals, as accuracy. Redundant subscriber access Second, the computer service firm well as from Host computers or key- and switching equipment at each Tele- can also use the Telenet service to trans- board terminals. fer jobs and/or large files at high speed Finally, the computer service firm will net node, the availability of multiple from one Host computer to another. The be able to offer an improved communi- paths between all destinations, the use of Host computers may both be owned cation service to its customers by utiliz- dynamic routing of traffic along the and operated by the computer service ing the Intelligent Network. First, it will optimum path, the powerful network firm; or, alternatively, one of the Host be able to support a wide range of ter- monitoring and diagnostic techniques computers may be owned and operated minal types, and the terminal user will employed combined with 24-hour by a customer of the firm. Thus, a cus- have many communications-related maintenance, and the powerful error detection and correction codes used in tomer could establish, when required, features available to him, provided by the network, all insure that the communi- very high-speed access links to the firm's Telenet, in addition to the features pro- Host computers, for the purpose of vided by the computer service firm itself. cation service which the terminal user experiences when communicating submitting jobs or batch data for proc- These features are offered in the form essing and/or file update. The ability of simple optional "commands" avail- through the Intelligent Network is mark- edly superior to that experienced when to establish such computer-to-computer able to the terminal user. using a private multiplexer/concentrator links, on an as-needed basis, would en- The terminal user will see not only an network. Hie Network Control Center ... Serves Users Telenet's Network Control Center (NCC) aminations to the NCC. Specialized ment in most private data communica- will substantially improve network per- computers in the NCC collect these re- tion networks, greatly lighten the bur- formance and reliability. And. while ports, determine the global state of the den of the Telenet subscriber in coping doing this, it will serve to reduce our sub- Network and, in case of line or equip- with the operational problems associ- scribers' need for network operations ment failure, immediately initiate repair ated with an extensive data communica- and maintenance personnel, network activities. These specialized computers tions system. monitoring consoles, and line testing also alert NCC operations staff via com- Automatic Traffic Reports equipment. puter printouts and audio-visual alarms Traffic data collected by the NCC as appropriate. The NCC performs two basic func- forms the basis for off-line traffic analysis tions, both directly benefiting Telenet reports prepared for individual subscrib- Remote Diagnostics subscribers. First, the NCC is the com- ers, as well as for Network planning The NCC, in exercising its monitoring mand and control center where failures purposes. function for the Network, is permitted of any type in the Network are detected For example, at the termination of a to initiate certain privileged programs in and diagnosed and where remedial subscriber's virtual connection, say be- any of the IMPs and TIPs. To guarantee action is initiated. Manned around the tween a terminal and a remote Host, a Network integrity, these programs, clock, seven days a week, constant message is sent to the NCC identifying mainly diagnostic in nature, cannot be surveillance at the NCC insures a higher the connection, its start and stop time, initiated by the operations staff at the level of service availability than is prac- and the number of packets sent and re- Central Offices, but only by NCC per- tical in most private data networks. ceived. From this information, Telenet sonnel. Some of the functions which the Second, the NCC is the data collec- is able to prepare traffic reports for sub- tion center for all Network traffic records NCC is able to initiate remotely include: • a snapshot program to record the scribers indicating traffic volume as a and statistical information. It will provide function of time and location. accurate measurements of Network status of designated IMPs and TIPs; • a trace program which can record In addition, traffic data collected by the performance, will give an early indica- NCC will be used to determine when tion of requirements for additional Net- the end-to-end path taken by a particular message or packet; Central Office facilities should be ex- work capacity, and will enable Telenet to panded, when and where additional link prepare a wide variety of traffic analysis • loopback tests for checking out modems and communication lines; capacity is required, which links are reports for individual subscribers, de- experiencing high error rates and re- pending upon their particular desires. • programs for initiating the dissemina- quire examination, and which IMPs and tion of a new program release through TIPs have been malfunctioning and Continuous Monitoring the Network. may require adjustment. Each IMP and TIP in the Network is These diagnostic programs provide We feel the Telenet NCC is an invalu- programmed to examine itself, its asso- the NCC personnel with powerful and able tool for network control and main- ciated lines, and the IMPs and TIPs to effective techniques for insuring unin- tenance. We think you, too, will agree. which it is connected, every few seconds terrupted service to Telenet subscribers. -and to report the results of these ex- These techniques, too costly to imple- Personality Highlight: MMM Communications and Time Sharing Christopher B. Newport Systems, and later as Chief Engineer Vice President, Engineering for Honeywell's Advanced Communi- cations Product Line. With a staff of ap- The development of the Intelligent Net- proximately 100, he was responsible work is a monumental responsibility. for the design and development of sev- And Dr. Christopher B. Newport, our eral Honeywell time-sharing computer V.P. of Engineering, is uniquely qualified systems, as well as for the system speci- to assume this responsibility. Dr. New- fication and world-wide integration of port and his staff are in charge of a mul- communication facilities for Honeywell's titude of inter-related tasks at Telenet new line of large-scale computers. including overall systems engineering, Prior to joining Honeywell, Dr. New- Central Office design, specification of port was Systems Manager for the Auto- hardware interfaces and communica- since 1968 when, while at Honeywell mation Division of the Marconi Com- tion protocols, hardware selection (in- Information Systems, he was respon- pany, and worked on the design and cluding computers, modems, multi- sible forthedesign and special engineer- implementation of a wide rang.e of real- plexers and terminals), and system ing of the Honeywell minicomputers time communications systems, for air testing. which were used by Bolt Beranek and traffic control, radar, and message Dr. Newport has 18 years of experi- Newman, Inc. as IMPs and TIPs in the switching. ence in the design, development, and ARPA network. Dr. Newport holds Bachelor of Sci- implementation of computer-based During his six years at Honeywell, prior ence and Doctoral degrees in electrical communication systems of all kinds. He to joining BBN and then Telenet in early engineering from Birmingham Univer- has worked on packet switching systems 1973, Dr. Newport served as Director, sity [England). Rexibility and Cost Savings for the Corporate Data Center Data processing management in today's flexibility to evolve his teleprocessing The ability to transfer data at very high corporation is seeking to serve the com- system in accordance with his corporate speeds, upon demand, to a selected pany's evolving requirements in the most requirements, in terms of traffic loads Host computer presents teleprocessing responsive and cost-effective manner and terminal/Host locations and types. system designers with many new op- possible. Telenet's Intelligent Network Whereas a terminal in a conventional tions and possibilities. It becomes prac- will help improve the cost effectiveness of teleprocessing network is typically dedi- tical for data or jobs to be sent directly corporate data processing resources by cated to a particular application and from one regional data center to any making these facilities more accessible linked to a specific remote Host com- other, possibly for backup or load shar- to users and by avoiding unnecessary puter, the Telenet service permits any ing purposes. It becomes very simple to duplication of computer and terminal terminal to establish a "virtual connec- transfer summary files from regional equipment, as well as computer pro- tion" with one remote computer, and to data centers to centralized data centers. grams and data files. later establish a "virtual connection" to a Similarly, very high-speed data transfers In many respects, the limited range of different remote Host computer. The from major data collection centers (such communication facilities which have same terminal is then more easily uti- as a claims processing office of a prop- traditionally been available has limited the lized for multiple purposes and applica- erty/casualty insurance company) to a effective use of data processing re- tions and can more easily obtain access central site become possible. sources. Partially due to the inflexibility to backup computing facilities when Once a corporation's Host computers of conventional communication facilities, necessary. At the same time the termi- are connected to the Intelligent Network, corporations have often been forced to nal retains all the functional capabilities a broad range of terminal-to-Host and establish a separate in-house network for to be linked to a single remote com- Host-to-Host data communication appli- each different data communications puter and operated in the same fashion cations become practical and easy to application. This constraint becomes in- as in a conventional teleprocessing sys- implement. The user is largely isolated creasingly serious as a corporation de- tem. from the problems of network design votes an increasing percentage of its In addition to improved terminal ana and operation, and is able to focus upon expenditures to data processing, as a Host utilization and capability, Telenet his particular data processing require- larger portion of the company's activities permits Host computers to establish ments. While Telenet offers substantial become automated, as a larger fraction virtual connections with other Host savings in communication costs, per- of its information files are stored in ma- computers, and to transfer data over haps the greater advantage in the long chine-readable form, and as the amount these links at rates up to 50 kilobits per term will be the much larger cost sav- of data exchange among organizations second. (A Host computer can have ings which flow from greater flexibility grows with the growing interdependency many simultaneous virtual connections and efficiency in the use of corporate of our society. to various terminals and Hosts on the data processing resources. Corporate data processing manage- Network; a terminal can have only a By utilizing the Telenet service, a ment will find that use of the Intelligent single virtual connection at a given incorporation could, in effect, integrate Network enables them to implement new stant of time.) Host computers may es- several otherwise separate teleprocess- teleprocessing applications quickly and tablish high-speed virtual connections ing systems (terminals, lines and Hosts) easily. The manager who plans his own whenever required, and will be charged into a single integrated teleprocessing teleprocessing network (without using only for traffic sent, rather than for a network, affording both greater flexibility Telenet) must provide for the cost of dedicated long-haul line facility, or for and improved overall utilization of cor- network design, equipment selection, the holding time associated with each porate data processing resources. installation, and network operation and switched connection. maintenance. Moreover, to allow for future traffic growth, the manager must install a network whose capacity exceeds the actual traffic load during the initial operating period. The network is typically designed for a specific application, and for specific terminal types, locations, and traffic types. The resulting design is necessarily inflexible. As the corporation's requirements change (as they often do before the network is even completed) it becomes difficult and costly to revise and reconfigure the teleprocessing network accordingly. In contrast, Telenet provides a ver- satile, general-purpose data communications network which can be quickly A member of Telenet's technical staff tests the control programs running in and easily utilized to support teleprocess- two IMPs and two TIPs. Also shown is the automatic line switching equipment ing applications; it affords the user great which is used to transfer subscriber access lines from a failed TIP to a standby unit. Easy and Adaptable Terminal Access Subscriber terminals can be physically entered on these terminals is accumu- trol characters such as edit- linked to Telenet's network in a variety lated in a TIP buffer, on a character, line ing (DELete and CANcel), of ways, depending upon individual cir- or message basis. Before this data is terminanting (End Of Mes- cumstances and needs. These include sent to the remote Host, the terminal sage or End Of Text), forms dial-up lines; multipoint, and point-to- operator may correct simple keyboard control (TABbing, line feed), point leased lines; or by using concen- input errors. Again, this editing facility etc. The user may also specify the maximum number of trating devices such as multiplexers, re- can be preset-or the user can issue characters that the Network mote data concentrators, and terminal short commands that define "edit" should buffer before trans- controllers. In some instances, Telenet- characters which, when typed, will de- mitting to the remote Host. provided multiplexers or TIPs may be lete the last preceding character from the installed at the user site. data just entered or all the data in the Editing Permits the terminal operator to specify special charac- In addition to establishing this physical current TIP buffer. ters to be used for editing link to Telenet's nearest Central Office, These and other functions are strictly optional; their ultimate utility depends on purposes, such as deletion the subscriber terminal will also estab- of incorrectly entered char- lish a "virtual connection" through the the nature of the user's particular appli- acters or lines of characters. Network to some destination computer. cation. In short, some terminal users will A terminal operator using an The virtual connection can be estab- want to become familiar with a limited unbuffered terminal will also lished in either of two ways, depending repertory of commands and facilities. be able to display at his ter- on whether the terminal has a dedicated For most others, the Network interface minal the entire buffer of or a dialed link to the Central Office. can be pre-initialized and the terminal data accumulated by the When a terminal on a dedicated line operator need not utilize any Network TIP. converses with only one particular com- commands, nor even be aware of the Terminal Permits the terminal operator puter on the Network, that terminal's Network, during routine usage. In either Characteristics to change the use of padding TIP port may be pre-initialized to the case, the Network can be adapted to the characters or line feed char- desired transmission parameters and user's needs. (A summary of the most acters, or the speed at which Host computer address. When the ter- frequently used command types is the Network sends to and minal is switched on-line, a virtual con- given below.) receives from an asynchronous terminal. User may also nection to the preselected computer will Optional Network Communication Aids request one of various local automatically be established in less than Command Network echoing conven- one second; the computer may then re- Groups Function tions. For unbuffered ter- spond by printing out its own name, or a Terminal Identifies the specific make minals, the use of local echo- "prompt" character, on the terminals' Identification and model of terminal which ing provides excellent error printer or display. Then the terminal- the operator is using. For control over the local access computer-terminal dialog can proceed asychronous terminals, the line. just as if there were a direct physical Network automatically de- Code Permits the terminal operator circuit between the two station sites. termines the transmission Conversion to transmit data as if the Net- For a dial-up terminal, the process is speed and code, and. unless work were transparent, or similar, except that the terminal operator otherwise instructed, as- to have the Network convert sumes default options for may first have to provide a short com- the terminal data into a stand- terminal type. mand identifying his terminal model and ardized Network Virtual Ter- a second command specifying the Host Virtual Establishes a virtual connec- minal (NVT) code. computer with which it is to be con- Connections tion with a designated ter- nected. minal or Host. Provides indi- In the majority of cases, the terminal cation to terminal operator if Host is not functioning, or not Keep Current operator will be concerned with, at most, currently accepting traffic. the Telenet command that defines his Our subscription list to The Telenet Re- terminal model and the commands re- Buffering The TIP stores characters port is growing daily. So we can get your quired to establish and break the con- entered by a terminal until a copy to you as quickly as possible, we "transmission character" is nections to Host computers. From time ask that you observe the following: encountered. At that point, to time, however, some users may wish all accumulated characters • Mailing List Changes: Send an old to communicate other instructions di- are transmitted to the Host mailing label with all changes clearly rectly to the TIP. This is accomplished to which a virtual connection indicated near the imprint [not on the by issuing additional commands, most of is open. These commands imprint). which set a transmission parameter or allow a user to define which • Additions to the List: Please mail us mode. For example, the operator may characters are to be consid- your name, title, organization and instruct the Network to convert the data ered "transmission charac- complete address —including zip code. from his terminal into a standardized ters." For example the user • Multiple Copies and Back Issues: Network Virtual Terminal code. can specify as transmission Requests for these must be made on Additionally, the Network offers a num- characters [1) all alpha- your letterhead and must include the ber of other useful communication op- numerics (each character is sent as a separate packet); intended usage. tions For example, local editing is (2) carriage return charac- Please address all requests concern- available for unbuffered typewriter- ters (each line is sent as a ing your subscription to: Editor, The oriented terminals and displays. Data packet); or (3) various con- Telenet Report.