Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


Network Working Group R. Watson Request for Comments: 592 SRI NIC 20391 November 1973

   Some Thoughts on System Design to Facilitate Resource Sharing


 There is a growing interest in moving toward more resource sharing on
 the ARPANET.  Some resource sharing has been taking place by having
 systems open TELNET connections and generating user command strings.
 I think that this is fine for experimental use, but is not the way we
 want to operate in real usage.  What I believe network system
 builders should do is to develop mechanisms appropriately designed
 for computer-computer communication.


 The goal I would like to see us move toward is to view all systems on
 the network as offering certain service modules, any subset of which
 can be combined in building other systems.  Each service module would
 have a well advertised set of primitive service capabilities that it
 could provide.  It would have documented commands at the level of
 present Telnet or FTP commands for gaining access to its services.
 It would also have a defined network connection procedure.  Then any
 system builder wanting to avail himself of these services could do so
 and integrate them into his own user interface environment.
 At the present time when a system is built, the system builders tend
 to see it as a stand alone thing or at most something to be used
 within a specific environment.  What I would like to see fostered is
 the idea that any system built is not only a stand alone environment
 but also a network service or set of services.  The builders would
 define not only a user interface for their environment, but also a
 set of primitives and primitive commands that can be accessed by
 other systems around the network to get that service performed.
    For example, we are redesigning the NLS Journal in light of our
    experience and that of Network Mail as a set of protocols and
    services.  If one looks at the processes of the NLS Journal one
    can see a number of separate services that could be provided by
    different network sites or combined in varying combinations by a
    single site.  These being:
       Distribution (identification of addressees and maintainance of
       the required data bases being a related service), recording
       (numbering and storing of items), cataloging, and retrieval.

Watson [Page 1] RFC 592 System Design for Resource Sharing November 1973

 At the moment these services are fairly tightly interconnected in the
 NLS Journal and what we want to do is to decouple them and define
 their intercommunication by protocols that would allow them to be
 distributed in different hosts on the network.  Mechanisms would also
 be defined for the several hosts performing similar services around
 the network to work together cooperatively.
 As a further example, there are also other services that NLS could
 probably provide such as structured file creation and manipulation;
 information portrayal online or in hardcopy; database querying etc.
 However, at the moment the system is not explicitly structured from
 the point of view that outside systems could come into it anywhere
 but at the human user interface even though internally it is quite
 modular.  It would be straightforward for us to identify those NLS
 services that other system builders might possibly be interested in
 incorporating into their systems with their own user interface and
 then to do the restructuring and primitive command definition
 necessary.  Other groups building systems on the network could
 perform a similar examination.
 CCA, on the other hand as I understand it, has taken this point of
 view from the beginning, namely building the Datacomputer on the
 assumption that it is primarily a network resource and is to be used
 by other systems.  BBN is also moving in this direction in the design
 of Distributed TENEX.
 There is nothing new in the above ideas; they come from generalizing
 past successes we have all had with network protocol development and
 with good software engineering practices.  It will, however, take a
 change in the thinking of system designers, some concrete examples,
 and ongoing dialog to make such a design philosophy the normal
 network way of life.


 The area of dialog support may be the first area ripe to create such
 a synthesis with the several systems in or coming into existence,
 each solves part of the problem (with some overlap).  The dialog
 support systems on the network known to me are:
    The NLS Journal (supports recorded and cataloged dialog and linked
    networks of documents and messages).
    NLS Screen linking and splitting (supports close collaboration of
    two or more people working together in real time in NLS)

Watson [Page 2] RFC 592 System Design for Resource Sharing November 1973

    The network wide linking of terminals through BBN's RSEXEC.
    Tenex Sndmsg and Readmail and other mail systems support
    nonrecorded dialog and further manipulation of received messages.
    (Some interconnection between NLS and these facilities has been
    The communication system under design at USC-ISI to support a
    range of message services.
    The online conferencing system being built by Jim Calvin of Case,
    John Iseli of Mitre and others supports online conferencing of
    several members and has facilities to utilize various Tenex
    subsystems such as TECO and NLS to support conferees.
    The Hack system of CASE offers a bulletin board service.
    The Forum system of IFF supports online and distributed in time
    conferencing and other features.
 Other areas possibly ripe for synthesis are 1) file and data
 management, and information retrieval services; 2) editing and
 hardcopy portrayal with systems like Tenex RUNOFF, SU-AI's PUB and
 SRI-ARC's Output Processor.
 If the salient service features, concepts, goals of each could be
 defined clearly and appropriate service primitives, as per other
 ARPANET protocols, could be defined for each, anyone wishing to
 incorporate that service with a user interface appropriate to his
 environment or philosophy could do so.


 There are many detailed issues related to system interconnection as
 proposed above.  A number seem worth mentioning here.
 1) Types of Network Connections
    The number and type of network connections to be opened between
    classes of cooperating processes can probably be systematized.
    One of the important elements of the FTP and Graphics protocol
    efforts was to define the number and type of connections necessary
    for these classes of transaction.  Similar classification and
    connection definition will be required for other types of

Watson [Page 3] RFC 592 System Design for Resource Sharing November 1973

 2) Data Structure Translation
    The whole area of translation and transfer of data structures more
    complicated than sequential files needs vigorous thought and
    protocol development.
       Systems built around sequential files are presently dominant on
       the ARPANET and provide a base for simple useful economical
       tools.  I, however, do not believe that the longer run tool
       sharing can depend on communication between sequential files,
       but requires structured files.  Experience with NLS tree
       structured files shows that even this level of structuring may
       be inadequate for many uses and more sophistication may be
       required.  A similar trend exists in work with computer
       graphics and generalized data management systems.  Developing
       protocols for handling structured data bases or agreement on
       common structuring characteristics seems an important need.
 3) Responsiveness
    Factors influencing responsiveness to users in an environment of
    heavy geographically separated resource sharing need determination
    and discussion.
 4) Documentation of System Interfaces
    It is probably reasonably straightforward to define service
    interfaces, but they will be useless unless their activating
    command languages and other conventions are well documented and
    this documentation is kept up to date.
 5) Accounting
    A very difficult problem once you interconnect systems at lower
    levels is to design an appropriate network accounting and banking
    system that will not cause undue delays in accessing distributed
 6) Error Handling
    We need to develop mechanisms for passing error signals around
    when system environments are crossing machine boundaries.
 7) Standard Parameter Formats
    Data types such as strings, integers, floating point numbers,
    arrays, pointers, etc. need to have standard representations
    defined for passing parameters back and forth between machines.

Watson [Page 4] RFC 592 System Design for Resource Sharing November 1973

 8) HELP at the Procedure Call Level
    A HELP mechanism needs to be defined in the protocols to provide
    information that each designer can translate to his user
    interface.  Standards for requesting HELP information and
    structuring HELP data bases needs agreement.


 I wish to acknowledge the useful suggestions of Charles Irby and Jim
 White in the thoughts above.

Watson [Page 5]

/data/webs/external/dokuwiki/data/pages/rfc/rfc592.txt · Last modified: 2010/01/07 00:32 by

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki