CIJ: 32463 M
Licklider, J.C.R.
Applications of information networks
Proceedings of the IEEI, v.66 (11) pp.
1330-1346
32%3
1330
£
PROCEEDINGS OF THE IEEE, VOL. 66 , NO. 11, NOVEMBER 1978
Applications of Information Networks
J. C. R. LICKLIDER member, ieee, and ALBERT VEZZA, member, ieee
Invited Paper
Abstract—The present and* projected applications of computer-
communication networks or information networks include electronic
mail, teleconferencing, “the office of the future,” management informa¬
tion systems, modeling, “computerized commerce,” monitoring of
patients, military command and control, home security, education, and
news. This paper briefly examines 30 such applications and the net¬
work capabilities they require. It presents a way of estimating the
relative importance of various network characteristics and of predicting
the suitability of a network or network architecture for a given set of
applications. The paper then considers several issues that relate to the
political, social, and economic impacts of networks. Among the issues
are privacy, security, compatibility, impact on productivity, the roles of
networks in international technology transfer and economic competi¬
tion, and the confluence or collision of the fields of computers and
telecommunications. j
I. Introduction
HE SUBJECT of this paper is applications of networks.
The networks involve the use of computers, but com¬
putation in the narrow sense does not necessarily domi¬
nate the applications. The scope of the paper includes, no less
than computation, computer-based applications in which the
main emphasis is on communication among people, on access
to information, or on control of systems, organizations, or—to
mention early one of the deepest though least imminent
concerns—societies. The applications of networks that we shall
examine include electronic message communication [ 1 ] —[4],
electronic funds transfer [5], access to information, computer-
based office work and “telework,” management of organiza¬
tions and command and control of operations, education,
entertainment and recreation, reservations and ticketing, and
several others.
Some of the problems and issues in network applications are
mainly technical and some are mainly nontechnical, but almost
all are mixtures of the two, and in most of them the technical
and nontechnical factors interact strongly. For example, the
relative merits of circuit switching and packet switching are
mainly a technical matter, but the fact that the electronic
switching stations of the existing telecommunications “plant”
are circuit switches surely is an economic factor in the circuit¬
switching/packet-switching issue. The determination of what
should be the individual citizen’s right to informational privacy
is mainly a nontechnical matter, but the pragmatics of pro¬
viding informational security, the technical basis for assurance
of privacy, must enter the decision process. The national
telecommunications plant-in-being of the U.S. figures strongly
in many of these problems and issues and forces them to in¬
volve both technical and nontechnical factors. The plant is
valued at something like $120 billion, and most of it was de¬
signed to carry analog voice signals, which are quite different
Manuscript received March 10, 1978;revised July 7, 1978.
The authors are with the Laboratory for Computer Science, Massa¬
chusetts Institute of Technology, Cambridge, MA 02139.
in their spectral and temporal parameters and in their require¬
ments for error handling and security, from digital computer
signals of the kinds that will flow through the networks of the
future. Because of its inherent redundancy, speech remains
intelligible even when mixed with considerable amounts of
noise, but even a single undetected error—a single bit—can
have extremely serious consequences in electronic funds trans¬
fer (EFT) or seriously degrade the performance of a network
carrying enciphered information.
One of the major motivations for networking is the need to
share resources. The main resources that are often advantageous
to share are communications facilities, computer facilities, and
information itself. The design of a network can make it easier
or more difficult to share resources and thus directly influence
the amount of resource sharing that will occur. The amount
of communication facilities sharing depends upon many design
factors, all of which influence how well the network is able to
allocate resources dynamically in response to changing needs
and availabilities. Though the need for sharing certain types
of computational facilities may diminish with the arrival of
the age of the personal computer, it is not at all likely that the
need to share resources will disappear altogether. Geographi¬
cally distributed users can share, through a computer network,
the costly high-performance computers that are required to
solve certain large computational problems. Even those using
personal computers to satisfy the bulk of their computing
needs may wish to avail themselves through a network of spe¬
cial software services provided by vendors—and they will cer¬
tainly wish to communicate with one another.
The sharing of information is the most important type of
resource sharing. The term “information sharing” immediately
conjures up the thought of sharing large data banks of in¬
formation among many users, but that is only one aspect of
information sharing. All the applications discussed in this
paper have aspects of information sharing. Applications con¬
cerned with communications, management, commerce, govern¬
ment, protection, education, and awareness all involve sharing.
The convenience and effectiveness with which sharing can be
accomplished and the facility with which information can flow
across the boundaries of individual application programs will
have profound effects on how well the applications serve their
intended purposes.
Many problems and issues arise from the interaction of in¬
formation sharing with information security. For example,
should EFT have a network or networks of its own to simplify
the problem of providing secure transmission, processing, and
storage of funds data, or should EFT messages be carried over
a general-purpose network so that a reservations and ticketing
operation can be completed in a single transaction involving
the traveler’s organization, the airline and the bank.
0018-9219/78/1 100-1330S00.75 © 1978 IEEE
iiLICKLIDER AND VEZZA: APPLICATIONS OF INFORMATION NETWORKS
1331
m
II. Applications
F" In the context of information networks, just as in the con¬
text of computer systems, an application is essentially the im¬
plementation of a purpose. Applications, like purposes, may
be defined narrowly or broadly. When the airlines began to
develop computer-based reservations systems and formed a
consortium, ARINC, to interconnect several of their systems,
the application was narrow: airline reservations. Now, after
. years of growth and augmentation, one can rent a car, reserve
a hotel room, and arrange to be greeted with flowers and
mariachi music. The broadened application might be defined
as reservations and ticketing for almost anything that flies to
or can be purchased at a distant place. One can project the
broader definition into the future and envision a general reser¬
vations and ticketing application, operating in a nationwide
or worldwide common-carrier network, through which anyone
could examine the availability of, and reserve or buy a ticket
to, almost anything in the broad class to which reservations
and tickets apply. But, of course, there is no reason to stop at
that particular class. One can expand the scope further and
arrive at “computerized commerce,” dealing with the wHole
gamut of things that can be bought and sold. The very broadly
defined application would include advertising, dynamic pricing,
and computer-based purchasing strategies. It might even make
a place for cartels of suppliers and cooperatives of consumers.
No doubt there would be vigorous competition among several
or many offerers of the application, and perhaps one can
imagine even a “meta-market,” an over-arching system that
interconnects and integrates the competing “computerized
commerce applications.”
In any event, that introduces -the notion of applications of
information networks. It might serve to introduce, also, the
notion of issues, which involve the interplay of the opportunity
and the threat aspects of applications. It is not difficult to
imagine the mischief that could be played by pranksters or
dissidents in a poorly protected, ,-publicly accessible, nation¬
wide reservations system.
A. Basic Applications
Computer-communication networks perform three basic
classes of operations upon information: transmission, process¬
ing, and storage. The earliest recognized applications of net¬
works were essentially separate exploitations of the three basic
classes of operations. Transmission of information through a
network from a program in one computer to a program in
another, of course, requires some processing and some storage
(memory), but in simple message communication and file
transfer interest is focused sharply on transmission. In every
practical computer, processing requires storage (memory or
registers), but in early time-sharing services such as Quiktran
[6] —[8], which when introduced did not provide intersession
file storage, the (dial telephone) network application was
essentially access to processing. In the Datacomputer [9]
service available through the ARPANET [10] —[ 12], although
processing is involved in both storage and retrieval, one of the
main applications is essentially access to storage in and of it¬
self: the Datacomputer is a place to park bits.
A fourth essential network function combines the basic
transmission, processing, and storage operations to provide
access to information—with the focus of interest on the in¬
formation itself, rather than on any of the three basic ele¬
mentary operations.
Simple message communication and file transfer, access to
time-shared processing, access to storage, and access to in¬
formation are important as well as fundamental network func¬
tions, but they are no longer typical of the activities or services
we associate with the term “application.” In present-day
parlance, “application” suggests something more highly differ¬
entiated and specialized and closer to some specific task or
mission.
B. Communication Applications
In the developmental history of the ARPANET, electronic
message service was a sleeper. Even before the network in¬
cluded a dozen computers, several message programs were
written as natural extensions of the “mail” systems that had
arisen in individual time-sharing systems in the early 1960’s.
By the Fall of 1973, the great effectiveness and convenience of
such fast, informal message services as SNDMSG [13] had
been discovered by almost everyone who had worked on the
development of the ARPANET—and especially by the then
Director of ARP A, S. J. Lukasik, who soon had most of his
office directors and program managers communicating with
him and with their colleagues and their contractors via the net¬
work. Thereafter, both the number of (intercommunicating)
electronic mail systems and the number of users of them on
the ARPANET increased rapidly.
lj Electronic Mail, Electronic Message Systems: It soon be¬
came obvious that the ARPANET was becoming a human-
communication medium with very important advantages over
normal U.S. mail and over telephone calls. One of the ad¬
vantages of the message systems over letter mail was that, in
an ARPANET message, one could write tersely and type im¬
perfectly, even to an older person in a superior position and
even to a person one did not know very well, and the recipient
took no offense. The formality and perfection that most
people expect in a typed letter did not become associated with
network messages, probably because the network was so much
faster, so much more like the telephone. Indeed, tolerance for
informality and imperfect typing was even more evident when
two users of the ARPANET linked their consoles together and
typed back and forth to each other in an alphanumeric con¬
versation. Among the advantages of the network message
services over the telephone were the fact that one could pro¬
ceed immediately to the point without having to engage in
small talk first, that the message services produced a pre-
servable record, and that the sender and receiver did not have
to be available at the same time. A typical electronic mail
system now provides a rudimentary editor to facilitate prepa¬
ration of messages, a multiple-addressee feature to make it
easy to send the same message to several people, a file-inclusion
scheme to incorporate already prepared text files into a mes¬
sage, an alerting mechanism to tell the user that he has new
mail in his mailbox, facilities for reading received messages,
and a “help” subsystem. The prospects of electronic mail ap¬
pear to have caught the attention of computer manufacturers
and software and time-sharing firms as well as telephone com¬
panies, national telecommunication authorities, and the U.S.
Post Office—and most of them now seem to be planning, de¬
veloping, or even offering some kind of electronic mail service.
Even before electronic mail was well established, it had be¬
come apparent that users would need computer aids for
scanning, indexing, filing, retrieving, summarizing, and re¬
sponding to messages. Indeed messages are usually not isolated
documents but documents prepared and transmitted in the
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PROCEEDINGS OF THE IEEE, VOL. 66, NO. 11, NOVEMBER
course of performing complex activities often called “tasks.”
Within task contexts, messages are related to other messages
and to documents of other kinds, such as forms and reports.
It seems likely that we shall see a progressive escalation of the
functionality and comprehensiveness of computer systems that
deal with messages. If “electronic mail” refers to an early
stage in the progression, “electronic message system” is appro¬
priate for a later stage and “computer-based office system” or
some comparable term for the stage of full integration. At
some intermediate point, message service will no doubt be
blended with direct user-to-user linking to provide for delay-
free conversation whenever both sender and receiver are on-line
at the same time an3 prefer conversation^ sequential ex¬
change of messages.
2) Duologue and Teleconferencing: Although there has not
been, .thus, far, very much use of networks for one-on-one
interaction between users, it seems likely that some kind of
computer-augmented two-person telephone communication
will one day be one of the main modes of networking. In
order to displace the conventional telephone, “teleduologue”
will probably have to offer speech, writing, drawing, typing,
and possibly some approximation to television, all integrated
into a synergic pattern with several kinds of computer support
and facilitation. The two communicators (and their supporting
programs) will then be able to control displays in certain
areas of each other’s display screens and processes in certain
sectors of each other’s computers. Throughout a duologue,
each communicator will be advised by his own programs and
will use information from his own data bases and other sources
accessible to him. The effect will be to provide each com¬
municator with a wide choice of media for each component of
his communication and with a very fast and competent sup¬
porting staff.
A teleconference [14]-[17] is an organized interaction,
through a communication system or network, of geographically
separated members of a group. The term “teleconference” has
been used recently mainly to refer to interactions organized
or presided over by or with the aid of programmed computers.
In some teleconferences, the members of the group participate
concurrently; in others, each member logs in when it is con¬
venient for him to do so, reviews what has happened in his
absence, makes his contribution, and logs out, perhaps to re¬
turn later in the day or later in the week.
During the last five years, a considerable amount of experi¬
ence has been gained with computer-facilitated teleconfer¬
encing, but it is evidently a complex and subtle art, and
teleconference programs still have a long way to go before
teleconferences approach the naturalness of face-to-face inter¬
action. On the other hand, we note the inefficiency of travel¬
ing to meetings and the inefficiency of letting one participant
take up the time of n - 1 participants when only m < n - 1
are interested in what he is saying. As teleconferencing is per¬
fected (especially n'onconcurrent teleconferencing), it will be¬
come an extremely important technique.
C. Neopaperwork
“Office automation,” “computer-based officework,” “the
high-technology office,” and a few other such phrases refer to
the aggregation and integration of several applications of com¬
puters and networks in office work. (“Automation” is in¬
tended in its weak sense, which includes computer “aiding”
and “semi-automation.”) Office automation includes every¬
thing presently called “word processing” (dictation, docun
preparation, etc.) plus computer-based filing (informs
storage and retrieval), communication (electronic mail, t
tronic message services, duologue, teleconferencing),
modeling (simulation), and it connects with electronic fu
transfer, management information systems, and parts—if
all—of computerized commerce.
Office automation is expected to make heavy use of ;
Works, both local and geographically distributed. Much of:
work is organized in an approximately hierarchical mam
with component desk functions such as transcription, editi
filing, retrieval, scheduling, and telephone answering at 1
echelons and corporate or divisional functions such as planni:
marketing, operations, and public relations at high echelo
Low-echelon functions typically are carried out locally, witl
a single office or suite of offices, and, when low-echelon fui
tions are supported by minicomputers or microcompute
local networks will be required in their integration,
geographically distributed organizations, of course, geograpl
cally distributed networks will be required as higher level fur
tions are integrated.
1) Telework: Networks will make it possible for people
do informational work effectively at locations remote fro
their managers, their co-workers, the people who report
them, and, indeed, even from customers and clients with who;
they must interact. Such telework will require facilities fc
duologue, teleconferencing, and all the other aspects of offic
automation—but little beyond what automation of a nondi:
persed office will require.
Telework will offer the possibility of saving the hours anc
the energy spent in commuting. It may burden some familie:
with more togetherness than was contracted for through the
marriage vows (“for richer or poorer, but not for lunch”). But
its strongest impact on individual lives will surely be felt by
persons immobilized by prolonged illness, physical handicap,
or children. For many of them, networks will open many
doors—including the door to gainful employment.
2) Augmentation of the Intellect: The at-a-distance aspect
of computer-based work that is emphasized by the term “tele¬
work” will be overshadowed, in the opinion of many, by what
Engelbart [18]-[21] has called “augmentation of the in¬
tellect.” Computers will help people do informational work
faster and better by providing fast and accurate tools to
supplement such slow and fallible human functions as looking
up words in dictionaries, copying references for citation,
stepping through checklists, and searching for matching pat¬
terns. Augmentation is needed at levels that range from
A) helping poor typists who cannot spell to put out neat and
accurate reports, to Z) improving the content and style of top-
level policy statements. Expectations differ concerning the
prospect for significant early contributions from artificial in¬
telligence, but it is clear that relatively unsophisticated aug¬
mentation systems can make major contributions. Consider
the help provided by descriptor-based and citation-index-based
information retrieval systems to a person looking for refer¬
ences pertinent to a particular fact or concept. Or consider
the impact that would be made, on writing such as this, by a
text editor that automatically displayed the Flesch Count [22]
of every paragraph it helped compose.
3) Task Management and Coordination: In addition to help¬
ing the individual worker, computers will facilitate teamwork.
Each office task will have its planned course of actions, in-
1333
LICKL1DER AND VEZZA: APPLICATIONS OF INFORMATION NETWORKS
volving particular workers at particular projected times. A
:: computer-based task management system will monitor the
task as it moves along the course, checking the actions as they
are taken, arranging that planned coordinations and approvals
are obtained, and revising the plan (or calling for human help)
when the schedule slips. In the early days of office automa¬
tion, the task management process will be mainly a matter of
maintaining orderly work queues for the office workers and
displaying for them at each moment 1) what needs to be done
and 2) the information needed in doing it. What will need to
be done will usually be, of course, to solve a problem or to
make a decision—ritost of the preliminary work will have been
performed automatically by computers. With the passage of
time, as people come to understand the problem-solving and
decision-making processes and the supporting.information in
programmers’ terms, computers will chip away at the problem¬
solving and decision-making substance of office work, but we
expect the now-rising wave of office automation to succeed or
fail on the measure of its help to human workers and to
human teamwork.
D. Management Applications
Office automation will have its impact upon management,
of course, as well as upon the office workers. Manage/nent
deals almost exclusively with information. (Money is essentially
information, of course.) The comptroller’s department was
computerized early. Electronic funds transfer will be a major
application of special-purpose, limited-purpose, or general-
purpose networks. On-line financial services may burgeon. In¬
ventory, ordering, production, pricing, and planning will all be
interrelated with the aid of networks and computer modeling.
1) Management Information Systems: The widespread feel¬
ing of disappointment in the management information systems
(MIS’s) [23]-[26] of the 1960’s and early 1970’s had, we be¬
lieve, a simple basis: the activities that generated the informa¬
tion required to support management decision making had not
yet been brought on line to computers, and, therefore, the re¬
quired information was not available to the management in¬
formation systems. To some extent, information important
to the manager is so global in scope that capturing it all on
line is still not possible. (It was not worthwhile to keypunch all
the basic operating data just to feed them into the manage¬
ment information system, for only a small fraction of the
totality would ever be used. It was impossible to anticipate
just what subsets or aggregations of the basic operating data
would be required.) As soon as all the informational activities
involved in operating an organization are on line, however, the
basis for an effective management information system will
exist. A few organizations are already approaching that state,
but most are just entering—or just beginning to contemplate—
office automation.
Local and geographically distributed networks will make it
possible, at a cost, for top management to access all the facts
and figures involved in the minute-to-minute operations of a
business. Top management should resist the temptation to
convert that possibility into actuality. The principle that
looks best at present is to let the data of a corporation reside
where the managers most conversant with them reside (“keep
the data near the truth points”) and to have conversant man¬
agers “sign off” on the release of data upwards in the corpo¬
rate tree. Certain data should be abstracted and moved upward
according to preset schedules; other data may be queried from
above—but queried through an authenticating release process.
Of course, the release process may in some instances be medi¬
ated by programs operating on behalf of the human conversant
manager rather than by the human conversant manager himself
or herself.
The foregoing discussion pertains, indeed, to most of the
data management functions in office automation. In dis¬
tributed organizations, data will be distributed, and one of the
main uses of networks will be to move data from points of
residence to points of use.
2) Modeling and Simulation: Computer-based modeling and
simulation are applicable to essentially all problem solving and
decision making. At present, however, modeling and simula¬
tion are computer applications much more than they are net¬
work applications—and they are far from ubiquitous even as
computer applications.
The trouble at present is that most kinds of modeling and
simulation are much more difficult, expensive, and time con¬
suming than intuitive judgment and are cost-effective only
under special conditions that can justify and pay for facilities
and expertise. But those are prime conditions for resource
sharing and, hence, networking. Whereas very large organiza¬
tions will be able to afford their own concentrations of facili¬
ties and expertise, small organizations will not. As management
grows tighter and more sophisticated, therefore, there may
come to be a place for management consultation and service
firms that specialize in modeling and simulation and offer very
large or special facilities—and deliver their products through
networks. Perhaps a glimpse of such a future has been given
by the large array-processing computer, Illiac IV [27], [28],
which has been used through the ARPANET in modeling the
world climate and the space shuttle. Similarly, MIND [29], a
system accessible through a value added packet network, is
being used to design communication networks.
E. Commerce
Shifting our attention from activities within an organization,
such as a business firm, to interactions among organizations,
we can see another kind of application for networks.
1 ] Electronic Markets: Networks will serve as marketplaces,
providing meeting grounds for buyers and sellers. At first,
networks will displace telephone and mail, which now serve
the marketplace function for most businesses. Later, networks
will begin to displace stock exchanges and commodity markets.
Ordinary office automation and funds transfer facilities will
adequately support negotiations and transactions when the
“commodities” bought and sold are purely informational or
sufficiently specifiable by words and figures. Wide-band facili¬
ties for examining products at the time of purchase (“squeezing
the grapefruit”) may extend the scope of the electronic market¬
place to commodities that must be selected or approved in¬
dividually by prospective purchasers. We can expect networks
to go beyond the role of the mere place or medium for trans¬
actions and, with the aid of sophisticated programs, actively
to “make a market” in the sense that certain stock brokers
make markets in certain stocks.
2) Computerized Commerce: Computerized commerce [30]
is based on the idea of electronic markets. It goes beyond pro¬
viding a marketplace and making a market—and back into the
primary motivation of the business firm—by using computers
to develop and carry out the strategies and tactics of buying
and selling. The concept of computerized commerce is appli-
IflCKLIDER AND VEZZA: APPLICATIONS OF INFORMATION NETWORKS
: 133 **
5 *¥-
* 5 ’
If
jmiactice [34], [35]. Human expert consultation will, of
Pfcouxse, be available to supplement the computer knowledge
biases, but considerations of cost and availability will almost
Isurely favor the computer. Difficult problems of legal re¬
sponsibility and liability may have to be solved: advice from a
^knowledge base may be similar to advice from a book, but a
|| knowledge-based program that controls the administration of
an anesthetic would appear to introduce a new factor.
Possibly even more far reaching in its implications than
. access to medical knowledge bases by physicans is access to
jjf- medical knowledge bases by ^laymen. Knowledge bases for
IT laymen would have to be quite different in content and pack-
aging from knowledge bases for physicians, and ideally the
two applications would complement each other. The layman-
oriented application might deal mainly with the complaints
not ordinarily taken to a doctor or with the decision process
that determines whether or not to seek a physician’s help. In
either case, if the knowledge-base program had access to the
individual’s medical record, and if it could make simple
observations such as temperature and pulse rate through the net¬
work, it could go rather far beyond the limits of the conven¬
tional book of medicine for the layman. Society should ex¬
amine such incursions by the computer into medicine ?r even
paramedicine very carefully before making up its collective
mind about them. They obviously mix benefits with dangers.
Unfortunately, they tend to be approached with prejudice.
G. Government Applications
Actual and potential government applications of networks
include military command and control, communications,
logistics, acquisition and interpretation of intelligence data,
dissemination of intelligence, law enforcement, delivery of
government services such as Social Security benefits to citizens,
knd converting the paperwork of the bureaucracy into bits.
Paperwork in the government is rather like paperwork in the
private sector, but earned a step or two further into detail.
The other government applications, on the other hand, seem
rather special. Military command and control, communica¬
tions, intelligence, and to a considerable extent logistics sys¬
tems’must be able to operate fast, move fast or hide, and
function in the presence of physical (as well as other) counter¬
measures. Law enforcement information systems are in some
ways like highly amplified credit reference systems: derrogatory
information seems especially crucial, for to be forewarned is to
be forearmed, and action must often be taken on the basis of
whatever data can be assembled in a few seconds. Serving all
the citizens and collecting taxes from most of them requires
that certain personal data be held about almost everyone-
enough in sum to make a several-trillion-character data base
that at least conceivably could be subverted to political or
economic exploitation. There are strong lessons about govern¬
ment applications of networks in the recent rejection by the
Office of Management and the Budget (OMB), at the well-
timed suggestion of several members of Congress, of the pro¬
posed new Tax Administration System of the Internal Revenue
Service
1) Military Command and Control and Military Communica¬
tions: Military command and control and military communi-
•••: »•.-*•-» ' r ' t, VC'lC ' ,r ^ic 5 it'0 T !S. Both interactive
?nu n'.ar.v * . ac .au
works. For reasons we do not fully understand— since.fasti
response to a changing situation is the essence of command;.:
and control-the World-Wide Military Command and Control;
System (WWMCCS)- is actually not very interactive, aud its "
computers, which use the GECOS operating system [36] do-
signed for batch processing, are not interconnected by an elec¬
tronic network. But surely WWMCCS will in due course be-up¬
graded. Autodin II is under development and will supplement
or replace Autodin I [37], the Department of Defense’s present
store-and-forward digital telecommunications network, with a
modem packet-switching network based on modified and
secured ARPANET technology. Networking is being pursued
actively, also, in the intelligence community. One of the most
significant possibilities for the military that is opened up by
advances in information technology is the achievement of a
much tighter coupling between intelligence and command and
control. One can envision a reduction in the time required for
the distribution of intelligence information from days or hours
to minutes or seconds. Such an advance would, of course, put
pressure on intelligence gathering and processing to operate on
faster time scales.
2) Military Logistics: There is less progress, but also less
pressure, in the logistics area, where more than 20 large batch
inventory systems can be counted, diverse in respect of hard¬
ware, programming language, and data management system.
Over the coming years, however, even the logistics situation
will probably be brought under control and onto a network.
The overall objective is to make the entire operation of a mili¬
tary effort responsive to coherent hierarchical command in the
fight of valid and current intelligence-with security against
enemy actions and countermeasures.
3) The Network of the National Crime Information Center
(NCIC): The NCIC is operated by the FBI and connects with
state and local police units in most of the states. The NCIC
contains, among other things, data on stolen cars and stolen
license plates and the police histories of convicted criminals.
The case of the NCIC network is an interesting study because,
in it, the informational needs of the police and the information-
providing capabilities of computers and telecommunications
run head-on into Congressional concern for the right of in¬
formational privacy. When a police officer stops a speeding
car and approaches it to make an arrest, he would like to know
something about the car and driver. Is the car stolen? Does
the owner have a history of resisting arrest? Forewarned is
forearmed. About two years ago, however, an innocent man
was killed by an arresting officer forearmed by forewarning
with incorrect information. In the most recent chapter, the
Senate Committee on Government Operations caused to be
rejected the NCIC’s request for permission to acquire a message-
switched network to speed up communication with state and
local police.
4} Social Security: In the U.S., the Social Security Adminis¬
tration (SSA) distributes more than $100 billion a year to
more than 20 million people and interacts with millions of
clients each year through about 1300 offices manned full-time
and 3000 manned part-time. The set of computer processible
data bases that support SSA operations contains more than a
trillion characters, and it is estimated that in those operations
-far several trillions of characters flow from one location
, u - a tenth of a trillion by a network and process-
vvrlr*’.- DARS system,” and the rest mainly
1336
PROCEEDINGS OF THE IEEE, VOL. 66, NO. 11, NOVEMBER 1978
In 1976, the SSA began planning the modernization of the
process through which it discharges its massive responsibilities
[38], The new process will make even heavier use of com¬
puters than does the present one and there will be much con¬
sultation and updating of central or regional data bases from
local offices. (The present process requires several computer
areas, each with multiple mainframes, more than a hundred
disk drives, and more than a hundred tape drives—and, in all,
approximately 400 000 magnetic tapes.) The new communica¬
tion subsystem will, therefore, be a network of very major
proportions, probably a dedicated SSA network operated by
the General Services Administration or (improbably in the near
term) a part of an even larger and more comprehensive net¬
work. Most technologically developed countries will sooner
or later have social security networks.
- H. Protection
If military, intelligence, and police networks are reckoned
as networks for protection, then protection is a very large
category of network applications. There is another member
of the class that deserves mention. i?
1) Home and Neighborhood Security: Several of ihe pro¬
jected applications of computers in the home relate tojsecurity:
sentry against intrusion, fire, and gas and water leakage, moni¬
toring the well-being of the elderly and infirm, and “electronic
babysitting.” In most of these applications, computers will
be better at detecting trouble than in correcting it, and there
will be a strong requirement for communication with remote
persons or agencies. At present, some burglar alarms are con¬
nected by dedicated lines to central security offices or police
stations and some “dial up” in the event of trouble. If a packet
network were available, it would probably be less expensive
; and it would provide a wider range of options, including absent
members of the family, friends, and neighbors as well as se¬
curity companies and public agencies.
It seems possible that a neighborhood communication
medium (with a broader fan-out or faster sequencing of calls
than the telephone) might be just what is required for the
elderly to help one another achieve a higher level of security
and peace of mind. CB radio or house-to-house (or apartment-
to-apartment) wiring or a multipurpose packet network could
provide the medium.
Probably just conversation of the kind that prevails on CB
radio interconnections would go a long way, but it could be
reinforced by slightly higher technology. Home computers
could be programmed to interpret a variety of indicators of
trouble—the sound of a fall, too long a flow of water, the re¬
frigerator door open, prolonged quiescence-and to ask for an
“all’s well” report whenever there was cause for concern. Fail¬
ing to be satisfied that all was indeed well, the computer could
call for help. It would have a list of participating neighbors
and a schedule of probable availability for each, and—by com¬
municating with their home computers—it could quickly find
someone to look in and check, or provide assistance. It has
been suggested that a neighborhood net could monitor its
clients while they were walking on the sidewalks as well as
while they were at home, and a small device has been demon¬
strated that sends out a radio signal when its wearer falls
down—or for some other reason becomes horizontal [31]. If
neighborhood networks existed, there would probably be no
end of inventions to exploit them in the interest of security:
heartbeat monitors, breathing monitors, footstep sensors, and
so on. And if the present trend of population statistics con¬
tinues, security applications might constitute a significant
sector of the network application pie.
I. Education and Awareness
Beginning with the last section and continuing now into this
one, the focus of interest has moved from the organization-or
the individual as a member of an organization—to the in¬
dividual as an individual in the primary family group in the
home. Probably the most important network prospects for
the individual in this century lie in education and training.
1) Computer-Based Education and Training: We assume
that advances in computer representation of knowledge and in
computer mediation of interactions between people and
knowledge bases will advance computer-based education and
training far beyond the “expensive page turners” and drill and
practice routines that are associated in many minds with the
term “computer assisted instruction.” We assume that knowl¬
edge bases accessible through networks will eventually accumu¬
late more knowledge, in each of many fields of learning, than
typical teachers are able to master and retain, and that the
knowledge in the knowledge bases will be well organized (by
experts in each field) and effectively accessible to students at
all levels of mastery and aptitude. However, computer-based
techniques for the representation, organization, and exploration
of knowledge are at present still topics of research-and even if
they were fully developed today, it would still take a decade or
two to translate the content of the many fields of learning into
computer-processible knowledge bases. During the coming
years, therefore, application of networks in the area of
computer-based education and training will be preliminary and
propaedeutic. Perhaps toward the end of the century it will
approach its ultimate volume and significance-and be among
the top three or four uses of networks.
2) News: At present, most people gain their awareness of
what is going on in the world mainly through mass media that
report on events rather than processes, that select a few news
items instead of covering the news, and that give everyone,
regardless of his or her interest pattern, the same few selec¬
tions. Networking has the potential of changing the news into
a multidimensional dynamic model of the world that each in¬
dividual can explore in his own way, selecting for himself the
topics, the time scales, the levels of depth and detail, and the
modes of interrogation and presentation. Interest profiles and
other techniques of selective dissemination may play im¬
portant roles, but networking in principle removes the neces¬
sity of disseminating (with its implication that the initiative
lies mainly with the transmitter) and opens the door to self-
directed exploration and investigation by the receiver of the
news. To provide the multidimensional dynamic model for
exploration and investigation would, of course, be a demand¬
ing responsibility for the gatherers and organizers of news, but
they gather and organize much more even now than they print
or (especially) broadcast. There will probably be a long slow
evolution from the newspaper/newsmagazine format and the
nightly news format through increasing levels of user initiative
toward truly user-dominated interaction with a whole-world
knowledge base.
III. Requirements Imposed Upon Networks
by Applications
Now that we have sketched out several applications we
should examine briefly the network characteristics they re¬
quire. The applications do not all require the same network
characteristics, of course. One application may require one
JCKLIDER AND VEZZA: APPLICATIONS OF INFORMATION NETWORKS
1337
Rttttero of characteristics, while another application may re-
Kjpire another pattern. Some of the frequently required char-
gacteristics are the following.
g-; 1 ) Bidirectional Transmission: Most applications require
»two-way communication—if not the capability of sending and
^receiving simultaneously (full duplex), then at least the capa-
i bility of alternating between sending and receiving (half duplex).
2) Freedom from Error: One wrong bit may completely
| change the meaning, especially if numerical data are repre-
•isented nonredundantly. In such cases, even though the basic
^communication channel itself is ijot error free, the end-to-end
I communications must be made error free through the use of
adequate error handling mechanisms.
3) Efficiency Despite Burstiness: A source that transmits
short bursts of information and is quiescent between bursts
typically does not wish to pay for channel time while it is
quiescent. Both human beings and computers are bursty
sources.
4) Low Cost per Bit: The cost of network service depends,
of course, upon many nontechnical factors as well as upon the
technical efficiency of the network in converting its resources
into services. But technical efficiency is a very strong and
basic factor. This characteristic refers to the cost of trans¬
mitting one bit from source to destination. The relation of
cost to distance is considered separately.
5) High Connectivity: A source may need to transmit, to any
one or more of many destinations. A destination (i.e., user)
may need to examine many sources.
6j High Information Rate: Wide-band channels are capable
of transmitting many bits per second. The criteria for “high,”
“wide,” and “many” vary widely with type of signal and level
of expectation. The 50 000-bits/s information rate of most of
the ARPANET channels seems like a high information rate for
ordinary interactive computing, but it is too low for con¬
venient transmission of large files (e.g., high-resolution photo¬
graphs) and far too low for moving pictures, even low-resolution
television pictures.
7) Security: Security is a complex of characteristics, some
of which provide the technical basis for the protection of
privacy. Others have to do with preventing disruption of
service and protecting against fraud and theft.
8) Privacy: In the U.S., this complex of informational
rights, including but by no means limited to protection against
eavesdropping, has been formulated by the President’s Com¬
mission on Privacy and, to a considerable extent, expressed in
legislation in the Privacy Act of 1977. Other nations also have
privacy laws, of course, some of them in some respects more
stringent than ours.
9) Authentication: A good authentication scheme provides
the electronic equivalent of a signature. Ideally, authentication
identifies the author of a document and makes it impossible
for him to escape responsibility for the authorship. Ideally,
also, authentication makes it impossible for anyone to change
even one character or bit of the document without destroying
the “signature.”
10} High Reliability: Low probability that network service,
as seen by the application, will be impaired by macroscopic
malfunctions. For present purposes, we distinguish between
macroscopic malfunctions and microscopic errors in bit
transmission.
11) Full-Duplex Transmission: Some applications require,
and most are favored by, the capability of sending to another
station and receiving from it at the same time.
12) Priority Service: Guaranteed or preferential service, es¬
pecially when the network is congested, is widely regarded as
essential for certain very important functions or for certain
very important persons.
13) Speech Capability: Present speech circuits transmit
alphanumeric information inefficiently, and most present data
networks were not designed to transmit speech. It will be ad¬
vantageous, however, to integrate speech with data.
14) Pictures: It will be advantageous to integrate pictures,
also, into the repertoire. Graphs, charts, diagrams, and simple
sketches fit readily into the pattern of data transmission, but
high-resolution pictures and, especially, moving pictures re¬
quire high information transmission rates. This characteristic
is essentially a second “information rate”—but scaled in such a
way as to be more demanding of very-wide-band capabilities.
15) Insensitivity to Distance: Synchronous satellites and
packet switching both tend to make the difficulty and cost of
transmission less dependent on distance than they are in tradi¬
tional communication systems. Rarely is it an absolute re¬
quirement that difficulty and cost be independent of distance,
but often it is desirable.
16) Short Transit Time Delay: If the sum of the signal-
transit time and the signal-waiting-in-buffer time is too great,
an application may be slowed down too much or disrupted.
The 0.2-s delay introduced by transmission via a synchronous
satellite somewhat disturbs two-way speech communication.
The delay introduced by transmission from one processor to
another may slow down the operation of a multiprocessor that
is a network of minicomputers or microcomputers.
1 7) Uniform Time Delay: In some applications, successive
segments of the signal must reach the destination in sequence
(or be put back into sequence if they arrive in scrambled
order). Note that reordering may cause all the segments to be
delayed as much as the most-delayed segment.
18) Broadcast Capability: Some applications require, and
some are favored by, the capability of transmitting to many or
all destinations concurrently.
19) Mobility: Some or all of the stations may need to move
from place to place and may need to communicate in transit.
To obtain rough measures of the requirements imposed upon
networks by the several applications, we filled in the body of
(an early version of) Table I. 1 Into each cell we entered a
number to indicate our intuitive rating of the importance of
the characteristic for the application. The rating scale we used
runs from 0 (lowest) to 5 (highest). For example, we con¬
sidered connectivity to rate at 4 in importance for mail and
message systems because mail and messages typically fan out
widely from senders to receivers and fan in to receivers from a
wide distribution of senders. We did not assign a 5 because
mail and message systems would still be valuable (cf., the plans
of Satellite Business Systems) if connectivity were limited to
within organizations. In the case of the column 6, information
rate, we used a somewhat special scheme. The numbers from
1 through 5 encode five class intervals of information rate in
1 In order to obtain a broader basis on which to think about, and
possibly model, the relations between networks and applications, we
suggest that you (the reader) photocopy Table I and fill in some rows
with your estimates of the importance of the characteristics to the ap¬
plications. We have also provided room for you to define additional
applications or characteristics. If you are willing to share your estimates
with us, despite the fact we are not bold enough to share our raw-data
estimates with you, please post them to J. C. R. Licklider and A. Vezza,
MIT-LCS Rm. 219, 545 Tech Sq., Cambridge, MA 02139.
PROCEEDINGS OF THE IEEE, VOL. 66, NO. 11, NOVEMBER 1978
TABLE I
Importance Coefficients op Network Characteristics for Various Classes of Network Applications (Each Cell Entry Should Be
Subjective Rating of Importance on a Scale from 0 (Low) to 5 (High))
NETWORK
CHARACTERISTICS
1.23456789
10 11 12 13 14 15 16 17 18 19 SPACE FOR ADDITIONAL
CHARACTERISTICS
NETWORK
APPLICATIONS
Information
COMMUNICATION
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CRUDER AND VEZZA: APPLICATIONS OF INFORMATION NETWORKS
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bits/s: 1) 75-300, 2) 300-1000, 3) 1000-10 000, 4) 10 000-
! 1 000 000, and 5) above 1 000 000. For the rough purposes
of our analysis, nevertheless, we shall interpret the entries in
column 6, as all the other entries, to be estimates of the im¬
portance of The (columnar) characteristic for the (row)
application.
Fig. 1 shows the relative importance of the 19 network char¬
acteristics. As one examines the average ratings of the charac¬
teristics, it comes as no surprise that bidirectionality is very
important. It is the “co” in “communication.”
It may be slightly surprising, however, that freedom from
error is so important. It is freedom from error as seen by the
PROCEEDINGS OF THE IEEE, VOL. 66, NO. 11, NOVEMBER 1978
.• application, of course. There are bound to be errors in the raw
-• network channels, but they may be detected and eliminated by
= error-correcting circuits or by retransmission. “Error-free”
■may in practice mean one bit error in 10 n or 10 14 bits, on
the average. The importance of achieving an extremely low
error rate stems in part from the fact that many of the applica¬
tions involve information, such as financial data,,in which
changing a single character could make a great difference.
Freedom from error is required, also, by most cryptographic
schemes. Where freedom from grror is not required by an
application, one can usually firfd error detecting and correcting
mechanisms within the application itself. Such mechanisms
are quite evident, for example, in human conversation. But it
greatly simplifies most network applications if the network
can be counted on to do the error handling.
Ability to handle bursty transmissions efficiently ranks third.
The advantage provided by this characteristic translates di¬
rectly into a cost advantage.
Low cost ranks fourth in importance. It did not rank higher
because we recognized that certain of the applications, such as
military command, control, and communication, are relatively
insensitive to cost. Also, other network applications such/as
mail and messages are already quite cost competitive with their
conventional counterparts and do not demand very-low-cost
facilities.
Connectivity ranks fifth in importance. The reason con¬
nectivity does not rank higher is that we assigned only a
medium score for connectivity to applications that required
only connectivity within an organization or within a region,
and many applications could function—though perhaps at
some disadvantage—with such limited connectivity.
Information rate ranks sixth. We interpret that to mean that
very wide-band transmission is not vital to most of the applica¬
tions and that most of them could be satisfied with an in¬
formation rate in the range 1000-10 000 bits/s. However, that
is the information rate seen by the application. To handle
heavy traffic, and to handle a few of- the applications, a net¬
work should have channels of considerably greater bandwidth
than that.
Security, the complex that includes assurance of service
when required and protection against fraud and theft, ranks
seventh.
Privacy, the complex that includes protection against dis¬
closure of personal information and unauthorized use of it,
ranks eighth.
Authentication, a characteristic closely associated with se¬
curity, ranks ninth.
v At the other end of the ranking, mobility (19th) is not re¬
quired by most of the classes of applications we considered—
but, of course, is essehtial for some applications. ■
Broadcast capability (18 th) was scored low because it is not
needed at all in many applications and is needed only oc¬
casionally in others such as mail and message systems—and,
when needed, usually can be simulated adequately by repeated
point-to-point transmissions.
Uniformity of time delay (17th) is important mainly for
speech transmission. If speech had been given a weighting pro¬
portional to its probable eventual importance in networking,
uniformity of time delay would have ranked higher.
The capability of giving preferential treatment to high
priority traffic (12th) ranks as high as it does because we
viewed priority in. the context of present-day systems that
dnay introduce considerable delays into the delivery of some
or:all of their messages. In the context of future systems in
which a whole transmission will take less than a second,
priority may be much less important. However, the need for
priority is unlikely to-vanish. Priority classes are useful in
queuing messages for processing by people and in indicating
the prioritizer’s sense of urgency or importance to the re¬
cipient. Moreover, even very wide-band systems tend to be
designed just barely to handle expected peak loads, and even
such systems can be overloaded—in which case, prioritization
might be helpful. On the other hand, it is conceivable that the
processing of priorities might slow a system down more than
eliminating low priority traffic could speed it up.
We do not want to attribute too much value to our no-
doubt-ideosyncratic subjective estimates of the importance of
network characteristics to applications, but we would like to
carry the analysis another step to illustrate what we think
might be a valuable method. It attempts to deal with the rela¬
tive merits of various networks or network architectures.
The method begins with a table of applications versus char¬
acteristics similar to Table I except that each application has
an importance weight and all its cell values are multiplied by
that weight before the columns are totaled. The method as¬
sumes, also, a table of networks or network architectures versus
network characteristics such as Table II. The entries in Table II
represent our very subjective impressions of the degrees to
which the characteristics at the top characterize the networks
at the left-hand side. The values are certainly not definitive. In
the case of the hypothetical augmentation of the ARPANET,
they assume major increases in number of subscribers and in
information rate, and they assume that advanced provisions are
made for security, privacy, authentication, and priority service.
They assume, also, that satellite relays are incorporated into the
network along with wide-band surface channels and that there
is a packet-radio subsystem to serve mobile applications.
In the case of the projected SBS service, indeed, they are
based only on the most informal information, and they make
rather optimistic estimates about the characteristics of the
hypothetical networks that would be developed on the basis
of the SBS facilities. The reader is invited to substitute his or
her own estimates.
To determine the suitability of a network or network archi¬
tecture to a set of applications, one simply multiplies each cell
value in its row in (the table like) Table II by the importance
of the corresponding characteristic at the bottom of (the table
like) Table I—and then finds the sum (across the row) of the
products.
To illustrate the use of the method, we worked with the four
networks of Table II and with four sets of applications. Appli¬
cation set 1 was the set shown in Table I. Sets 2, 3, and 4 were
subsets consisting of—set 2: speech and encrypted speech,
set 3: still and moving pictures, and set 4:. duologue and aug¬
mentation. (We gave equal or uniform weighting to the appli¬
cations in each set-to all 30 in the first set and to both of the
two in each of sets 2, 3, and 4.)
We obtained the 16 appropriateness indexes shown in Table
III. The dial telephone network performs best in the speech
applications, of course, but it does not appear to do badly in
the others. (Giving more weight to cost tends to reduce its
scores.) The experimental ARPANET appears to perform well
on speech, which surprised us despite the fact that experiments
on the transmission of compressed speech over the ARPANET
have been very successful, but best on duologue and augmenta¬
tion, which we expected. In the scoring, the ARPANET suffers
Because, being experimental, it was not developed in respect to
some of the important network characteristics. Assuming such
:KLIDER AND VEZZA: applications of information networks
1341
TABLE II
Estimated Degrees to Which Four Selected Networks Possess the 19 Network Characteristics
(The Ratings Are the Authors’ Intuitive Estimates on a Scale from 0 (Low) to 5 (High)
*A hypothetical network based on ARPANET technology but with very wide-band ground and satellite chan¬
nels, very many subscribers, advanced provisions /or security, an authentication scheme, arrange¬
ments /or priority, and a mobile/ponable radio adjunct based on the ARPA Radio Net.
**A hypothetical network of the kind that might be based on the projected facilities of the Satellite Business
Systems Corporation and used by a large corporation with geographically distributed branches, it is assumed
that this network is used only within the corporation and therefore has restricted connectivity.
TABLE III
^Appropriateness Scores for Four Selected Networks, Each Rated
qfr: on Four Different Sets of Applications (The Appropriateness
Scores Are Based on a Scale from 0 (Low) to 5 (High).
The Way They Were Determined Is Described in the Text.)
BaY'
'v APPLICATION
N. SETS
NETWORKS N.
30 Applications
of Table 1 '
Speech and Encrypted
Speech
Still and Moving
Pictures
Duologue and
Augmentation
Dial Telephone
2.5
2.8
2.4
2.6
Experimental ARPANET
2.8
2.8
2.5
3.0
Hypothetical Augmented
ARPANET .
4.1
3.9
4.0
3.8
Hypothetical Corporate
Net Based on SBS Service
3.8
3.5
3.9
3.8
Obviously, the result obtained with the method is no better
than the ratings it processes, and we do not make any claims
for our ratings. We believe, nonetheless, that the Scheme puts
into an orderly array some of the basic factors that determine
the relative appropriatenesses of various networks for various
sets of applications, and that it leads the users of the method—
or at least it led us, as we used it—to consider the factors care¬
fully and to think about how they act and interact. Upon
examining the interactions, it soon becomes clear that the
linear weighting scheme smooths over many nonlinear logical
interactions, and that a more advanced model would have to
be more like a computer program than three tables and a
pocket calculator. Nevertheless, the first step has to be to
survey the variables that are active in networking, and the
simple scheme provides a start on that.
IV. Issues
A. Brittleness
jr development (Hypothetical Augmented ARPANET) yields the
appropriateness scores in the third row of Table III, which are
all toward the upper end of the five-point scale. The hypo-
jjb thetical corporate network based on the projected SBS service
i. appears to perform almost as well as the hypothetically aug-
0,mented ARPANET, suffering in the comparison only because
^i. we assumed for it limited connectivity (intercorporate com-
munication only), no surface channels (and therefore always
jss!-. *h e 0.2-s satellite delay), and no mobility. Those lacks showed
jjk U P °hly in the average over the 30 applications and in the
s Peech applications.
Brittleness is approximately the inverse of the lauded com¬
plex of system attributes: flexibility, robustness, and graceful¬
ness of degradation. Brittleness often arises from a quest for
efficiency or economy. If you space the pony express posts
as far apart as a fresh pony can run, then the mail does not get
through when an emergency forces you to use a tired pony. A
socioeconomic unit with a minimum-capacitance supply sys¬
tem avoids the waste inherent in having products stagnate in
the pipeline but crumbles in a siege. Networks will almost
surely be more efficient than the systems they supplant.
Should not that expectation prompt us to ask whether they
will also be more brittle?
From an engineering point of view, the preferred approach
is to avoid brittleness through judicious choices in the archi¬
tecture and design of networks. The dynamic routing feature
1342
^ t ^ Le tf f' RPANET ’ for “ample, pennits the network to con-
power supply, and redundancy of information storage More
over, sophisticated uses of redundancy J•, M
B Electronic Imperialism or Technology Transfer to the World
kfesssssk
ready had working transportation, systems hefn* ,
™ £
WS opmg world with the concentrated supercritical inters of
the developed world, bringing the former deeply int Jhe Z°
action patterns of the latter and making it much“S“he'
ism, J f ~
^ may l0 ° k “» *> so™
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sms”~ irjr tF^
1 but of knowledge and it flows through h ^ ° mformation
• Perhaps the most effective pattern involves by
promising young people from developing co^Mes in w Y
graduate schools in developed countriM-fX ,h , g
experience in the developed countries and then return fo 7°^
foa of advanced technology in the a. , ™ to form
mained functionally and motivational mlhe , I6 '
s^Sr«®s2=
could as well be in foreign countries poStdoctoraI locations
technology, if only they had net ’ £ V6n Countries with little
cient funtog to keep local te^ , 0 COnnefiti °™ and suffi-
to pay for computing time and 0peration “d
Indeed, it seems likely that teeh i 8 somewhere on the net.
countries couM becomf j t0 devel °P^
than informal exSon 3 n ° m ° re
become well established in the ARPANEtTo*^ ^
Fo^aT 2 o rti 0 ons t0 Seen e
Uie^^^not-te^^iolo^'Kn^^^s^would^^'^^^^^^
Productiveness of the technology-transfer'ent^ST ^
cannot "hope to^ffer^olutito^t^th* ^ reSPeCt t0 ’ “ d we
the juxtaposition of “electro* ■ t0 the problem suggested by
we,- p '“ " a ° b ‘° i ™
working between the developed aild the d Pr !° SPeCt ° f Het '
deserves very serious study. From the potat f 0 *"” 8 Tf
jar how * ^ t6 '
S'\-
‘<efefe&3s&v
c - Unity, Federation, or Fragmentation
is: would we see a side ’ 01 3 fra 8 men tation? That
11 applications and fr^g “ C ° mp “ si ” s
coherent system ot intercommunicating neTOoriS' 0 /“
incoherent assortment of isolated ? ° r “
works, most of them d.dic.fcd 'J.TST'
single organizations’ The first le™« U " nS or semng
engender pluralistic solutions to mo t ’ Z wIuch seems to
alternative-many seMelit Pr ° blemS - ™ e ^
what woufd be rLchJd >V
fore, may be Judged rathe, probable butit woSbT ' T
Serbs’” ^ »d =o™b y „,°e f “ eP on;
combinatorial^ ^e^ddf^l ^ ^ grow
woblem of ho.°toacwTnt'gi She” „TS s^poi* £
ssr is “ " a i -ssx
Coherence” characterizes a system in Which ah the n , rt
culate well and function in synergy and in which th v, S
systems are compatible and cooperative.' In an in forma tT
network, coherence is desirable partly for*the same r ° n
is desirable in a telephone system: the* value to a ,. ea ^ on lf
mcreases as the number of other^ccessible users increases'
This is true no matter whether the users are nennie
Puters. The importance of coherence,'is amplified h** C ° m "
by the fact that some of the -'applications of ’ 0wever >
works will involve several functio&”operafino° mPUter net ’
information. Planning a trip]:*for:' > example will ° D . COI ^ mon
action among: your calenda&'pfogram and'th require
grams of people you will'/viStffthe, reserve« 6 C endar pro "
airlines, car rental services*md;hotels 'the r, ° nS I 510 ® 111118 of
terns of your banlcvan'd^venSFotherbani- trans ^ er sys-
■ ‘ your company’s
OER AND VEZZA: APPLICATIONS OF INFORMATION NETWORKS
office, and perhaps data bases pertinent to business to
cted on the trip. The computers could not be of
help in the planning if each function or service had its
iparate network or if their networks were physically
hnectable but incompatible at various levels of proto-
Indeed, coherent interconnection of diverse functions will
Essential if networks are to live up to expectations in elec-
nic message services, computerized commerce, delivery of
aal services that involve both federal'and state governments,
ministrative policies can be defined clearly and networks can
be designed responsively.
D. Privacy
It is now very widely understood that the collection of large
amounts of personal information in computer processible data
banks tends to jeopardize personal privacy. The main reason,
of course, is that aggregation and computerization open up the
possibility of invading privacy efficiently and on a massive
■d many military and intelligence applications.
Coherence, however, is a condition that has to be planned
(fstriven for. It does not arise in a short time through evolu-
h—at least not through evolution that conforms to the
ontaneous-variation-plus-natural-selection model. Will the
Srces that are operating in the present network situation
bster a sufficient degree of coherence for networks to fulfill
•their promise? On the positive side is the fact that a standard
packet-switching interface protocol X.25 [40] was formulated
and agreed upon in an unusually short time and that the inter¬
connection of such dissimilar networks as Telenet [3] and the
Canadian data network has already occurred. Also on the
;positive side is the possibility: that one or two commercial
networks, such as the one being developed by AT&T and t^e
v one being developed by Satellite Business Systems, vyill
■ dominate the network market and thereby create the kind of
.. coherence that IBM has created in a large part of the computer
■ software field.
However, the other factors seem to work against coherent
interconnection. First, the network situation is evolving with-
y out any national policy. (Within the U.S. government, it is
evolving without any federal policy.) Several countries are
■V building networks independently. Many companies are
building networks independently. Second, although the lines
may be leased from the same telephone company that leases
lines to everyone else, there is some security in having one’s
own dedicated network. The need for security in such areas
as EFT may be stronger than the nped for interconnection.
Third, wherever personal information is concerned, and
especially in the federal government, privacy has become a
major issue, and a simplistic interpretation of the privacy
problem sets interconnection into opposition with privacy.
Fourth, research and development in the area of network
security and privacy assurance have not been and are not being
supported at a high enough level to create-soon enough-a
technology that will let one say: "You can have both intercon¬
nection and security, both interconnection and privacy; you
can have your cake and eat it, too.” Actually, the technology
of communications security is rather well developed [41] —
[ 44 ] —except for uncertainties arising from the “56-bit contro¬
versy” [45] —as a result of many years of work in the military
• intelligence area, but the technology of computer security is
less well developed [46], and nontechnological aspects-plant,
personnel, and operational aspects—of network security are
not in good condition at all.
The conclusion with respect to unification, federation, or
fragmentation must be: we should strive for the kind of feder¬
ation of networks that will provide coherent interconnection
where needed and justified and, at the same time, provide
informational privacy and security. That will require planning
at national and international levels. It will require intensified
research and development in network security and in inter¬
netting. And it will require an elevation of the ongoing dis¬
course about privacy—to a level on which legislative and ad-
scale. At the same time, they open up the possibility of pro¬
tecting privacy tirelessly and algorithmically and of using the
personal data effectively in the effort to accomplish the legiti¬
mate purposes for which the data were collected. Indeed, the.
stage is set for a battle between the forces of good and evil.
The stage is, however, not set in reasonable balance. The
things required for the protection of privacy in information
networks are policy and technology: legislative and admin¬
istrative policy to define what is to be achieved and a tech¬
nological basis for achieving it. In the U.S., the legislation is
the Privacy Act of 1974 and the administrative policy is an
OMB Circular [47]. Both are cast in terms of absolutes. The
technological basis, as mentioned in the preceding section, is
a combination of communications security and computer
security. Because computer security is a relatively new and
neglected subject, it is difficult to provide convincing assur¬
ance to an intelligent skeptic that any proposed intercon¬
nection of personal data, transmission channels, information
processors, and interrogation-and-display facilities will not
jeopardize privacy. Repeatedly, indeed, the advocates of pro¬
posed federal data networks have failed to present convincing
analyses of the threats to privacy and of the trade-offs be¬
tween privacy and mission effectiveness—and, repeatedly, their
requests for permission to procure such networks (e.g., FED-
NET, NCIC upgrade, IRS Tax Administrative System) have
been sidetracked or denied with good reason.
At least in government circles, therefore, the issue of privacy
is a very real and central network issue. Before it can be
solved, three things have to be done. 1) The technology of
information security has to be improved to the point at which
reasonable analyses can be made and assurances can be given.
2) Network advocates have to develop plans and justifications
that take privacy into account and provide strong assurances
that it will be protected. And 3) the members of the oversight
committees and their staffs have to face the fact that to pro¬
tect privacy by precluding interconnection is not a very satis¬
factory solution for the long term. They should support and
foster the accomplishment of steps 1) and 2) with the aim of
receiving plans and proposals that they would not have to kill.
E. Other Issues
Space limitation precludes substantial discussion of other
issues, but there are several that should be discussed. We shall
discuss only a few of them, and those only very briefly.
1) Transborder Data Flow: Several European countries are
beginning to restrict the flow of personal (or personnel) data
across their borders on the ground that they must protect the
informational privacy of their citizens against threats implicit
in data processing in countries with less stringent privacy laws.
Some of the countries have laws or regulations that preclude
the transmission of encrypted information through their
public communication facilities. Many believe that such re¬
strictions may be used to discriminate against foreign (e.g.,
1344
PROCEEDINGS OF THE IEEE, VOL. 66, NO. 11, NOVEMBER 1978
American) data processing firms and against multinational
corporations.
2) Technology Export and Import: International networks
can be expected to facilitate greatly the transfer of scientific
and technical information and know-how among the tech¬
nologically developed nations. From a nationalistic point of
view, one can see both advantages and disadvantages in such
transfer to ideological, military, and economic competitors.
The advantages are mainly humanistic and short-term eco¬
nomic. The disadvantages are mainly security-related and
long-term economic. The interplay of advantages and dis¬
advantages is giving rise to issues that will probably intensify.
3) Competition Versus Monopoly and Free Enterprise
Versus Regulation: These are the issues of the “Bell Bill”
(Consumer Communications Reform Act), Computer Inquiry
II, and several recent decisions of the Federal Communications
Commission that have favored competition in the telecom¬
munications industry. How these issues are settled will to a
large extent determine who operates the networks of the
future in the U.S. and how such applications as electronic
message service and “the office of the future” are, imple¬
mented. /
4) Nature of Office Work and Workforce: Some of the net¬
work applications we have discussed would tend to- alter
markedly the nature of white-collar work and the knowledge
and skills required of members of the workforce. . That fact
will give rise to issues involving reeducation and retraining, pay
commensurate with responsibility, and displacement of labor
by automation.
5) Impact on Productivity: Many people are expecting that
applications such as electronic mail and office automation will
significantly increase productivity, but there are as yet few if
any definitive experiences with such applications or quantita¬
tive models of them that will convince skeptics. Impact-on-
productivity may become a major issue in and of itself.
6) Educational Applications of Networks: Packet-switched
and satellite networks, together^with the great advances being
made in computers, appear to open the door to revolutionary
improvements in education, but much more than mere access
and mere hardware will be required to achieve truly significant
results. The issue that is arising is whether the society values
education enough to support the long and difficult effort that
will be required to develop effective computer- and network-
based methods—or whether there will be' another wave of pre¬
mature exploitation followed by disappointment as there was
in the computer-assisted-instruction “revolution” of the early
■1960’s.
j: 7) Networks Versus Stand-Alone Systems: Why do we need
time sharing when everyone can have his or her own micro¬
computer?' What good is a network when one can have a
'whole library on a video disk? Those questions have answers,
of course, in such applications as electronic message systems,
distributed but cooperating “offices of the future,” and
computerized commerce, but the questions will nevertheless
constitute a major issue. Microcomputers and inexpensive
digital storage devices have significantly changed the network
concept. Less than a decade ago, a computer network was
something that provided access to a time-sharing system. Now
it is a facility to support communication among spatially dis¬
tributed people and computers and to supply people and
computers with common information bases and supple¬
mentary storage and processing capabilities.
Id Leadership: An important latent issue is implicit
people have quite different percep¬
tions of the importance of networking. A significant fraction
of the people who have had experience as developers or inten¬
sive users of a packet-switching network believe they have
been in on the beginning of a new era and that descendants of
the ARPANET will constitute the nervous system of the
world. On the other hand, most of the people who now deter¬
mine the kind of national policy that earlier fostered the
merchant marine, the railroads, the airlines, and the interstates
seem not to be aware that any significant new potential exists
or that there may be any reason to move rapidly to take
advantage of it. And, of course, if it is meanihgful at all to the
man in the street, the term “information network” still
suggests the telephone system, the radio, or a television net¬
work. In that situation, it is difficult to project as an issue the
importance of networks to world economic leadership. We
believe, nevertheless, that it is such an issue, and we hope that
it will soon be recognized as such an issue.
9) Totalitarian Control: If almost all the telecommunica¬
tions in an area were based on computerized networks con¬
trolled by an organization—say by a government—then, in the
absence of effective safeguards, that organization could map
the life space of every individual and record the business trans¬
actions of every company. The notion of telecommunications
in the hands of a “big brother with computers” goes beyond
the bounds of what is usually called “invasion of privacy” into
the realm of totalitarian control. One can detect at least a
trace of the “big brother” issue in the coldness of certain
members of Congress toward, and the rejection by the OMB
of, the plans (mentioned earlier) of the IRS to develop a
computer- and network-based Tax Administration System.
The mere possibility of subversion was enough to kill the
system. It is of the utmost importance, of course, to develop
truly effective safeguards against misuse of networks for pur¬
poses of social control. But such safeguards will be more
difficult to devise than safeguards against ordinary invasion of
privacy or against fraud and theft. Networks will have to be
designed in such a way that representatives of diverse interests
can satisfy themselves that there is no subversion and that the
audit trails are not dossiers. And the arrangements will have to
be dictator-proof. We think that that is a very great task and
that it is being neglected.
V. Conclusions
Shakespeare could have been foreseeing the present situation
in information networking when he said,” . . . What’s past is
prologue; what to come, in yours and my discharge” [48].
Most of the applications that will shape the future of net¬
working are now in the stage of conceptualization or in the
stage of early development. But it seems possible that a “net¬
work of networks” will, even in this century, become the
nervous system of the world and that its applications will
significantly change the way we live and work. The degree to
which the potentials of networking will be realized will depend
upon how we resolve some of the issues that have been
discussed.
The value of information networks will depend critically
upon their connectivity and their ability to connect any one
of many sources to any one or more of many destinations.
High connectivity will be precluded if conditions force the
development of many separate, independent, incompatible
networks. One condition that would force such an incoherent
development is the combination of 1) a need for security
against loss of “electronic funds” and (other) proprietary
IKLIDER AND VEZZA: APPLICATIONS OF INFORMATION NETWORKS
1345
formation and 2) the lack of a technology capable of pro-
,g security in an interconnected network or network.of
orks. That would lead to what we have called “frag-
itation.” Another such condition is based in a similar way
a combination of need for informational privacy and lack
the technology necessary to protect it except by isolating
: e- privacy-sensitive data. The rapid and intensive develop¬
ment of computer and network security technology is vital to
'any network applications.
y forces are fostering the development of networks to
'terconnect organization or branches of organizations and the
lopment of applications to serve organizations, but there
few forces that foster networks to interconnect individuals
.network applications to serve individuals. Perhaps the main
ipe for the provision of network services to individuals—
ecially network services to individuals at home—is that the
ill System will move (as obviously it would like to do) into
he processing, storage, and information-commodity parts of
ie overall information business. But the telephone companies
nil be very slow to provide high-in formation-rate services
use they have such large investments in narrow-band
lalities. To get inexpensive wide-band channels into homes
;ian early date, we need a new departure in cable (or fiberi
tics) communication, taking off from cable television, or
imething truly revolutionary like a nation-wide network 'of
'erostationary platforms: microwave platforms at 70 000 ft,
pported by helium plus helicopter vanes, and relaying signals
;om housetop “dishes” a meter in diameter.
Examination of 30 actual and potential applications of net¬
works suggests that the following network characteristics or
pabilities are especially important: bidirectionality, freedom
im undetected errors, efficiency despite “burstiness” in the
mission pattern, inherently low cost, high connectivity,
gh.information transmission rate, security, privacy, authen¬
tication, and reliability. Mobility and broadcast capability
ed out to be of the lowest priority in our analysis. Packet-
tching and time-division-multiple-access networks, espe-
:y such networks with satellite relays, were suggested by
e analysis to have the patterns of characteristics required to
irve best the full range of applications. The analysis suggests
^approach to the selection of the best network to serve any
ified application or set of applications.
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A Tutorial on Protocols
/
LOUIS POUZIN and HUBERT ZIMMERMANN
Invited Paper
Abstract—Protocols ate common tools for controlling information
transfer between computer systems. The concept of a protocol, which
grew out of experimental computer networking, is now fundamental to
system design. In this paper, basic protocol functions are explained and
discussed. Then, the concept of a distributed system architecture is
presented. It provides the framework for layers and protocols to operate
across heterogeneous systems. The purpose and functions of each
protocol layer such as, transmission, transport, virtual terminal, are
described. Interactions between design and performance are discussed,
and typical mechanisms are reviewed. CCITT and ISO relevant standards
are summarized. Finally, the similarity between protocob and program¬
ming languages is emphasized as it points to the major impact brought
about by protocob in system design.
I. Introduction
VERYONE has had the opportunity to overhear such
cryptic conversations exchanged over the radio by taxi
drivers, policemen, and aircraft pilots. Although upon
hearing these conversations at first do not mean much to the
layman, these abbreviated languages carry well-defined mean¬
ings and obey well-defined rules. Speakers give their name, ask
correspondents if they are listening, confirm reception, etc.
This form of conversation differs drastically from a face-to-face
chat. The communication channel is shared by many speakers.
To save bandwidth and reduce interferences, messages are short
and coded. External noise and other interferences are com¬
mon occurences, hence, repetition and confirmation are normal
practice. These rules are known as protocols.
Manuscript received February 27, t978; revised July 24, t978.
The authors are with IRLA, 78150 Rocquencourt, France.
The term protocol entered the computer jargon at the turn
of the 70’s, when the U.S. Defense Advanced Research Project
Agency set out to build a network of geographically distribute
heterogeneous computers [71 ]. Up to that time, communica¬
tion between computer programs or processes was limited to
processes which were located within the same machine. Inter¬
process communication was accomplished through the use of
shared memory and special signals exchanged through the
mediation of the operating system. This technique represented
the analog of a face-to-face chat between processes. Inter¬
process communication between geographically distant systems
would have left processes with the same kind of constraints
that taxi drivers encounter. They would have to interact
through a potentially hostile environment with limited band¬
width, delay and unreliable transmission. In addition, the
processes in the different computer systems did not even speak
the same native tongue, having been created by different
manufacturers.
Computer veterans remember the sinuous evolution that led
from binary programming to assembly code, to Fortran, Cobol,
Algol, and other high-level languages. Originally viewed as a
collection of tricks and hobbies, programming languages have
developed into a major branch of computer science. The
evolution of protocols has followed a strikingly similar path.
Indeed, Protocols are common tools designed for controlling
information transfer between computer systems. They are
made up of sequences of messages with specific formats and
meanings. These messages are equivalent to the instructions
of a programming language, although protocol languages are
still in an early stage of ad hoc development.
0018-9219/78/1100-1346S00.75 © 1978 IEEE
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