perm filename RFC828.TXT[RFC,NET] blob sn#696041
filedate 1982-11-24 generic text, type T, neo UTF8
Network Working Group K. Owen
Request for Comments: 828 IFIP
DATA COMMUNICATIONS: IFIP'S INTERNATIONAL "NETWORK" OF EXPERTS
(This report has been written for IFIP by Kenneth Owen, former
Technology Editor of The Times, London)
[ This RFC is distributed to inform the ARPA Internet community of the
activities of the IFIP technical committee on Data Communications, and
to encourage participation in those activities. ]
A vital common thread which runs through virtually all current advances
in implementing and operating computer-based systems is that of data
communications. The interconnection of the various elements of complete
systems in new ways has become the driving force behind a substantial
research and development effort.
In both national and international systems, a variety of new options has
been opening up in recent years. Increasingly the development of these
new systems involves people and groups from a variety of
backgrounds--the computer industry, the telecommunications industry, the
national telecommunications authorities and the national and
international standards bodies.
In an area where the formerly distinct technologies of computing and
telecommunications have so clearly converged, the new technology
presents both opportunities and problems. And this convergence of
technologies demands an "interconnection" also between the various
groups mentioned above.
For different purposes, and in different parts of the world, the
specific technological solutions will vary, though drawing on the same
basic research and development. πlobal, regional, national and local
systems are all involved. Systems are being designed at a time when the
technology itself is continuing to advance rapidly and there are many
uncertainties in choosing the best directions fo follow. Nonetheless,
international standards must be developed and agreed.
This background -- of interacting elements of a complex, rapidly
advancing technology -- lies behind the work of Technical Committee 6
(TC 6) of the International Federation for Information Processing
(IFIP). IFIP's membership consists of the appropriate national
professional organizations, one per country, and its aims include the
promotion of information science and technology and the advancement of
international cooperation in this field.
The broad field of information processing is subdivided for IFIP
purposes into a number of specialist areas, each of which is covered by
RFC 828 August 1982
one of the Federation's technical committees. TC 6 aims to promote the
exchange of information about data communication; to bridge some of the
gaps that exist between users, telecommunications administrations and
the manufactures of computers and equipment; and to cultivate working
contacts with other relevant international bodies.
Chairman of the committee is Professor Andre Danthine of the University
of Liege, Belgium. "The main interest of TC 6", he says, "is to have a
real exchange of technical information, on an international basis, in
two ways which are completely intermixed." In essence these two aspects
reflect the respective needs of people in the developed and the
In the developed countries where the technology is advancing most
rapidly, the basic need is for a full information exchange between the
researchers and the professional practitioners. The research will
include work which draws on voice and video communication; and the
practitioners will come from the traditional computer and
telecommunications industries (now competing with each other in this
area) and from the new "telematics" industry.
This interchange of ideas between experts in the developed nations is
complemented by the second category of the work of TC 6: the
interchange of information with the developing countries. "One of my
main objectives as a technical committee chairman", says Professor
Danthine, "is to try to keep a balance between meeting the needs of the
expert, and the responsibility of the expert to explain the state of the
art to people in the developing nations."
These "state of the art" or review conferences are an important part of
the TC 6 programme. Each of IFIP's technical committees is made up of
national representatives (plus working group chairmen, whose work is
described later in this article); and the strength of the TC 6
membership is such that, when necessary, the committee can mount
comprehensive "state of the art" conference programmes with speakers
drawn from its own ranks. In this role the committee is a technical
"travelling circus" -- one in which, as for IFIP activities generally,
the performers receive no fees.
The technical committee plans its overall programme of events and acts
as the driving mechanism for the TC 6 activity, Professor Danthine ponts
out, but the programme is normally implemented by the committee's
various specialist working groups as appropriate. The TC 6 working
groups are not small subcommittees in the conventional sense of the
term; each is a specialist community of perhaps 200 people who keep in
touch by mail (including electronic mail).
The working groups embrace a range of activities. First, there is the
RFC 828 August 1982
basic, routine process of information dissemination between members.
Each working group has a distribution system by which papers, reports
and notes can be "broadcast" to the group membership. This is much
wider in scope and more flexible than the mechanism of meetings; it can
be used to report research results, for example, prior to formal
Secondly, the working groups hold informal discussion "workshops" at
which a particular group of specialists will try to work towards a
consensus. Often timed to take place at a very early stage in the
development of a significant new technique or area of interest, these
meetings attempt to clarify the relevant terminology and methodology
that will be needed in moving towards a full understanding of the
A third activity is to hold relatively small "working conferences" -- an
IFIP term which defines a meeting of invited experts, at which each
participant presents a formal paper. The proceedings are subsequently
published to disseminate the results to the scientific world in general.
To gain a wider interaction than is possible at a working conference,
TC 6 pursues a fourth type of information exchange, that of the
"in-depth symposium". This, as its name implies, is a highly technical
open conference on a well-defined topical subject, designed to attract
as large an attendance as possible. For TC 6 the in-depth symposium is
an annual event.
Professor Danthine stresses the broad range of technology and of
interests that is represented on his technical committee. And he
stresses that it is technology rather than science that interests his
"We have very few people engaged in pure research in the sense that
their work is not application-oriented. Even those who work in protocol
verification have some application in mind. They try to find formal
methods in a way which may be characterized as basic applied research.
On the other hand, when advances are happening rapidly in computer
science, something which is theoretical becomes useful very quickly."
RFC 828 August 1982
Within data communications, no subject has aroused more general interest
in recent years than that of local computer networks, triggered by the
radical possibilities opened up by the Xerox Ethernet system. Within
TC 6, the subject of local computer networks is addressed by working
group WG 6.4, chaired by Greg Hopkins of Ungerman-Bass (while Robert
Metcalfe, inventor of Ethernet, is the United States representative on
the technical committee).
Local networks show all the signs of being a "bandwagon" subject at the
present time, with many people and organizations running to jump aboard.
The concept is not new; local networks were implemented in Canada, the
United States and Britain in the 1960s. But the appearance of Ethernet
started the bandwagon rolling. The message of Ethernet basically was
that new kinds of network structure existed, quite different from those
of large-area networks, which were appropriate to very high speeds of
transmission and rather limited geographical areas; and that by using
these high-speed networks one could reorganize the way that one
interconnected all parts of a computing system in a particular ofice, or
laboratory, or factory.
The aims of WG 6.4 are "to organize interest and promote the exchange of
information on networks of locally distributed digital computers" and
"to develop recommendations for international standardization of local
computer networking technology". A good example of what this means in
practice was the international symposium on local computer networks,
organized by WG 6.4 for TC 6, which attracted more than 500 delegates to
Florence earlier this year.
This was TC 6's "in-depth" event for 1982, covering such topics as VLSI
techniques, network reliability, voice distribution, LCN design and
applications, performance evaluation, protocols, gateways and standards.
Aspects of Ethernet, "slotted" ring networks such as the Cambridge Ring,
and "token" rings (pioneered in Canada in the mid-1960s and now the
subject of renewed interest) were discussed in detail. One of the
interesting developments reported at Florence concerned work on an
advanced token ring at IBM's research laboratories at Ruschlikon,
The relative characteristics of the Ethernet and ring categories of
local networks are still very much a matter for technical debate. And
the so-called broadband networks are a third competing category;
carrying far more information (at the cost of losing some logical
simplicity), they offer the prospect of combining cable television with
interactive computer-based services.
Thus the present time is one of intense marketing activity by the
RFC 828 August 1982
proponents of the respective technologies--and so a time when the
fullest international exchange of information on technical developments
is particularly important.
As interpreted by WG 6.4 local computer networks are "local" in that
they are concerned with communication over distances between ten metres
and 10,000 metres. Their "computers" are the devices which require and
provide the transmission of data in terminals and in large central
The "networks" may employ a variety of transmission media, including
twisted pairs, coaxial cable, fibre optics and local radio. Those of
most interest to WG 6.4 will use data rates above 100 kilobits per
second. Among the major topics tackled by the group are the role of
protocols in local computer networks and the interconnection of local
computer networks with remote networks.
International computer message systems and services form another rapidly
developing topic, Messages may be processed, stored and transmitted
between users who may be within the jurisdiction of separate carriers,
computer systems and/or computer networks. Technical, economic and
political issues must be resolved if a viable international computer
message service is to develop. Within TC 6, this is the concern of
working group WG 6.5, chaired by Ronald Uhlig of Bell-Northern Research,
This working group concentrates on standards for data structures,
addressing, and higher-level protocols to effect internatioanal
computer-mediated message services, Such services could have an impact
on existing international postal and communication agreements, and on
the economics of the worldwide communication system. Results of the
group's work are made available to users, manufacturers, common
carriers, PTTs, ISO and CCITT.
One of the most comprehensive moves by TC 6 and WG 6.5 to influence the
development of international computer-based message services was the
publication of a set of policy recommendations which came out of a
working-group workshop in Bonn in 1980 and was confirmed by the
technical committee. These concerned the right to operate such
services; restrictions on transborder data flow; and tariff issues.
Organizations should be free to operate their own computer-based message
services and to interconnect these services for messages between
organizations through public networks, TC 6 stated. (The aim here was
to preserve the basic freedom to communicate without entering into the
RFC 828 August 1982
more controversial subject of third-party traffic, which is regarded
differently in different countries.)
No restriction should be placed on the transmission across borders of
messages between persons. If restrictions were placed on the nature of
computer-based messages transmitted across a country's borders (the
forbidding of encipherment, for example), then the conditions should not
be more severe than those placed on letter post. (It was appreciated
that restrictions on the flow of data across borders could be regarded
as necessary to prevent the circumvention of national privacy laws by
the use of databases abroad but, the committee argued, the remedy should
be to rationalize the data privacy laws, not to restrict the data flow.)
On tarriff principles, TC 6 recommended that tariff levels should not
discriminate against computer-based message services, whether public or
private; there should be no heavy extra charge for international
messages; the principles of charging should not discourage the sensible,
expected pattern of usage; and charges for preparation and sending of
messages should be separated. (Here the background danger was that
public-service tariffs might be manipulated to achieve unfair
objectives, such as discouraging the use of new services or exploiting a
Policy aspects such as these represent one of three main themes which
are pursued within WG 6.5 in a formal structure of sub-groups. The
other two themes are the systems environment (overall systems issues of
computer messaging) and the user environment (the user interface and all
other aspects of user involvement). European and North American
sub-groups work in parallel in each of these two subject areas.
"We started out with the realization that computer messge systems were
coming along very rapidly, with many different systems appearing in
different parts of the world, and we could see the day coming when
people wree going to want all these systems to talk to each other", says
Ronald Uhlig. "That wasn't going to happen unless we started to get
people together. The first ones of the type we're talking about were on
the Arpanet in the United States. For TC 6, computer messaging was the
subject of the 1981 in-depth symposium which was held in Ottawa."
An important concept of mail messaging has emerged from WG 6.5's work on
systems environment. This divides computer messages from the systems
point of view into two parts, known respectively as the message transfer
agent and the user agent.
The user agent acts on behalf of the individual user. When the user
wishes to send a message he initially enters the user agent function.
The "agent" is probably software, but the concept is broad. The user
agent might be in a terminal, in a concentrator, in a PBX or in the
RFC 828 August 1982
network. It interacts with the user and handles everything up to the
point of composing the message.
The user then gives the user agent instructions to send the message. At
that point the message is in effect placed inside an electronic
envelope, and "posted" to a message transfer agent. The message may
pass from one messge transfer agent to another before finally passing to
the receiving user agent which handles functions concerned with reading
the message, filing it, etc.
The work of WG 6.5's systems environment group led to the formal
consideration of message-handling standards by a study group of CCITT.
The CCITT group is concentrating at present on devising standards fo the
protocols for the transfer of messages between message transfer agents.
"Once that becomes standardized", says Ronald Uhlig, "you've taken a
major step towards allowing anybody's message system to communicate with
anybody else's. Next we want to concentrate on obtaining some consensus
for standards on compatible sets of functions in user agents. You can
have many different kinds of user agents--those which will accept only
text messages, or voice messages, for example."
Another important development within WG 6.5 which is just getting under
way is concerned with messaging for developing nations. Here there are
two dimensions -- national and international. The international problem
is how to enable scientists (and in particular computer scientists) in
the developing nations to keep in touch with their colleagues in the
more advanced countries. An international message system could be the
Within individual developing countries there is the possibility of using
computer-based messaging as a superior type of internal telegram
service. People sending telegrams would go to a local post office to
dictate their messages. Post offices would be linked in a message
system, and at the receiving office the message would be printed out and
Dr. S. Ramani of India and Professor Liane Tarouco of Brazil are
co-chairmen of WG 6.5's new subgroup on messaging for developing
nations. Dr. Ramani has suggested that India might launch a small
satellite into a relatively low earth orbit, to be used for the
transmission of messages within developing countries (and possibly
Another subgroup within WG 6.5, it has been suggested, might be formed
to discuss messaging for the hearing impaired. This has been approved
in principle, but has not yet generated sufficient active interest for
it to move ahead.
RFC 828 August 1982
Thus working groups 6.4 and 6.5 have an active, continuing programme in
well-defined subject areas. TC 6's other two working groups, 6.1 and
6.3, are each in a state of flux at present as they review their scope
in order to respond to changing needs.
WG 6.1 has been concerned up to now with "international packet switching
for computer sharing". Formed in 1973 from the nucleus of an existing
non-IFIP international network working group (which itself had grown out
of a United States network working group within the Arpanet community),
it played a key role in the development of communication protocols for
The working group defined its original scope as follows. The group
would study the problems of the interworking of packet-switched computer
networks planned in various countries. The group's ultimate goal was to
define the technical characteristics of facilities and operating
procedures which would make it possible and attractive to interconnect
such networks. In pursuit of this goal, the group would attempt to
define and publish guidelines for the interconnection of
packet-switching networks. Where possible, it would test the guidelines
with experimental interconnections between cooperating networks.
Thus, the mainstream of WG 6.1 activity has been in the area of
protocols, an area where the emphasis has now shifted from the
investigative research and discussion of IFIP to the follow-on work of
the international standards bodies. In 1978 an in-depth symposium on
computer network protocols was held in Liege. In 1979 an in-depth
symposium on flow control in complex data networks was held in Paris;
the subject of flow control and overall network design is now regarded
as having largely moved out of the research area and into the area of
commercial exploitation. In 1981 a workshop on formal description and
verification techniques was held at the National Physical Laboratory,
For the outside scientific community, WG 6.1 has thus been the focus for
significant research and information exchange. Within TC 6 it has also
played a significant role as the parent of subgroups which have gone on
to develop into working groups in their own right. For the future, it
is the intention that WG 6.1 should continue this latter "umbrella"
role, probably under a general "architecture and protocols for networks"
title, with specific new areas being hived off into subgroups as
One such subgroup of the new 6.1 could well be concerned with satellite
systems. At first sight it might appear a little late for a group such
as TC 6 to begin to turn its attention to an established communication
RFC 828 August 1982
medium such as satellite systems, but the committee has in mind
significant new variations on the satellite theme.
"Satellites have been used up to now almost entirely to provide
telephone channels", says Dr. Donald Davies of the National Physical
Laboratory, England, who is the recently elected vice-chairman of TC 6.
"What we want to do now is to develop satellite systems that will mix
voice and vision and data in such a way as to get the most use out of
the channel. You can very often get the best use of the channel by
mixing different types of traffic in this way. But you get these
advantages only if you're prepared to design the multiplexing system
around the requirements.
"Satellite Business Systems does this already to a certain extent. But
I believe that new types of multiplexing schemes will be developed for
satellites which will make the future generation of mixed-media
satellites much more powerful."
"Then there's the question: if you do have a satellite system
integrated with a surface network, and then perhaps with a number of
local networks, how do you set up the hierarchy of protocols to connect
all that together, in a way that actually works conveniently? That's an
"We know how to make a satellite into a sort of substitute telephone
line, but what we don't know is how to make one of these rather more
intelligent satellite systems work in nicely with the local network.
That's one of the functions of the Universe project in the UK."
Another possible new topic which could come under the WG 6.1 umbrella is
that of data security, which is the area of research in which Dr. Davies
is working at NPL. It presents a difficult technical problem, the need
for standards, and above all a need to anaylze the user's requirements.
Dr. Davies points out that ring networks, Ethernet systems and satellite
systems all use broadcast transmissions, with obvious dangers of data
Working Group 6.3, whose title is "Human-computer interaction", is also
being reviewed at present for rather different reasons. The group was
formed in 1975, re-formed in 1981, and has been concerned with
developing a science and technology of the interaction between people
and computers. It was concerned in particular with computer users,
especially those who were not computer professionals, and with how to
improve the human-computer relationship for them.
Identified areas for study included the problems people have with
RFC 828 August 1982
computers; the impact of computers on individuals and organizations; the
determinants of utility, usability and acceptability; the appropriate
allocation of tasks between computers and people; modelling the user as
an aid to better system design; and harmonizing the computer to the
characteristics and needs of the user.
Clearly the scope of 6.3 was deliberately set wide, with a tendency
towards general principles rather than particular systems. But it was
recognized that progress would be achieved only through specific studies
on practical issues--for example, on interface design standards, command
language consistency, documentation, appropriateness of alternative
communication media and human factors guidelines for dialogue design.
Chairman of WG 6.3 in recent years has been Professor Brian Shackel of
Loughborough University of Technology, UK, who played the leading role
in re-forming the group in 1981.
The scope of 6.3 in fact goes beyond the scope of any single technical
committee. It is close to that of TC 9, for example, whose subject is
the relationship between computers and society; and of TC 8, which is
concerned with information systems. Activities which cut across
boundaries in this way can be organized jointly by working groups from a
number of TCs, but in the case of WG 6.3 the future status of the group
is now the subject of an ad hoc review.
Looking ahead, Professor Danthine sums up: "I think that the most
important developments that are ahead of us will involve local networks,
the digital PBX, and the concept of the Integrated Services Digital
Network (ISDN). It will be interesting to see what will finally come
out of the various pressures, coming from different directions, for the
same market. Some of the directions are technology-driven; some are
marketing-driven. It is not at all clear what will happen.
"The role of TC 6 -- or rather the working groups -- is to act as a
forum where experts can advocate, and assess, the various alternatives.
We do not restrict ourselves to the view of any one sector -- the
telecommunications authorities, say, or the manufacturers. We are much
more open-minded, and exposed to the opinions of people who are not
necessarily from our own domain of work."
One area in which TC 6 is seeking a fuller methodology and understanding
is that of office automation. "It is surprising to see that, at the
present time, we are only at the beginning of a real understanding of
office work," says Professor Danthine, "We have no model."
Thus, following the modelling work which TC 6 did in protocols, system
architectures and messaging systems, the committee chairman says, "we
RFC 828 August 1982
are now doing some modelling work in terms of office automation, in
order to understand what the problems are. Very often a solution
appears for a problem which is not understood -- that is, not completely
defined. That happens more often than you might think in computer
The next two years will be important ones for data communication: 1983
is World Communication Year, and 1984 will be important because of the
CCITT Integrated Services Digital Network standards which are expected
to be announced then. These standards will indicate the
telecommunication authorities' plans for their own "local networks" (by
which they mean the distribution systems at local level from the
telephone exchange out to the homes, offices and factories).
At present this local distribution is by multicore cable. In future it
will be by glass fibres coupled with complex electronics at the various
nodes. At the moment nobody knows what these nodes will look like, nor
what the actual mode of transmission will be. If the CCITT standards
are announced in 1984 they will affect everybody concerned with "local
networks" in the computing sense. They will influence the design of the
local computer networks of the late eighties.
These various threads of development in data communication are reflected
in TC 6's programme of meetings for 1982-85. Planned events include an
international conference on data communications (a "state of the art"
review) in Johannesburg, South Africa, in September 1982; a working
conference on interconnected personal computing systems in Tromso,
Norway, in 1983; an in-depth symposium on satellite and computer
communications in Paris, France, in 1983; and a working conference on
data communications in ISDN in Israel in 1985. TC 6 is also active in
providing speakers for the sixth International Conference on Computer
Communication (ICCC '82) in September 1982 in London, England.
Published by the IFIP Secretariat, 3 rue du Marche, CH-1204
GENEVA,Switzerland, August 1982.
For further information, please contact your National Computer Society
or the IFIP Secretariat.