rfc828.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

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


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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
solution.

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
then hand-delivered.

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
internationally).

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.


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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.

PROTOCOLS

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
computer networks.

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,
Teddington, England.

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
appropriate.

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


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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
unsolved problem."

"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
insecurity.

HUMAN FACTORS

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


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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.

THE FUTURE

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


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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
science."

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.










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GENEVA,Switzerland, August 1982.

For further information, please contact your National Computer Society
or the IFIP Secretariat.


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