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.

Network Working Group                                            K. Owen
Request for Comments:  828                                          IFIP
                                                             August 1982

    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.  Global, 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


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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
developing nations.

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


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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
publication.

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
subject area.

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
members.

"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."












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RFC 828                                                      August 1982


LOCAL NETWORKS

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,
Zurich, Switzerland.

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


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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
processing systems.

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.

MESSAGING

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,
Ottawa, Canada.

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



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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
monopoly.)

Policy aspects such as these represent one of three main themes which