rfc939.txt

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Network Working Group                          National Research Council
Request for Comments: 939
                                                           February 1985

                           Executive Summary
                          of the NRC Report on
                        Transport Protocols for
                         Department of Defense
                             Data Networks


STATUS OF THIS MEMO

   This RFC is distributed for information only.  This RFC does not
   establish any policy for the DARPA research community or the DDN
   operational community.  Distribution of this memo is unlimited.

INTRODUCTION

   This RFC reproduces the material from the "front pages" of the
   National Research Council report resulting from a study of the DOD
   Internet Protocol (IP) and Transmission Control Protocol (TCP) in
   comparison with the ISO Internet Protocol (ISO-IP) and Transport
   Protocol level 4 (TP-4).  The point of this RFC is to make the text
   of the Executive Summary widely available in a timely way.  The order
   of presentation has been altered, and the pagination changed.

   The title of the full report is:

                                    

                        Transport Protocols for
                         Department of Defense
                             Data Networks

                  Report to the Department of Defense
                  and the National Bureau of Standards

         Committee on Computer-Computer Communication Protocols

   Board on Telecommunications and Computer Applications Commission on
                   Engineering and Technical Systems
                       National Research Council

                         National Academy Press
                    Washington, D.C.  February 1985

   





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RFC 939                                                    February 1985
Executive Summary of the NRC Report Transport on Protocols


                                OVERVIEW

   The project that is the subject of this report was approved by the
   Governing Board on the National Research Council, whose members are
   drawn from the councils of the National Academy of Sciences, the
   National Academy of Engineering, and the Institute of Medicine.  The
   members of the committee responsible for the report were chosen for
   their special competences and with regard for appropriate balance.

   This report has been reviewed by a group other than the authors,
   according to procedures approved by a Report Review Committee
   consisting of members of the National Academy of Sciences, the
   National Academy of Engineering, and the Institute of Medicine.

   The National Research Council was established by the National Academy
   of Sciences in 1916 to associate the broad community of science and
   technology with the Academy's purposes of furthering knowledge and of
   advising the federal government.  The Council operates in accordance
   with general policies determined by the Academy under the authority
   of its congressional charter of 1863, which establishes the Academy
   as a private, nonprofit, self-governing membership corporation.  The
   Council has become the principal operating agency of both the
   National Academy of Sciences and the National Academy of Engineering
   in the conduct of their services to the government, the public, and
   the scientific and engineering communities.  It is administered
   jointly by both Academies and the Institute of Medicine.  The
   National Academy of Engineering and the Institute of Medicine were
   established in 1964 and 1970, respectively, under the charter of the
   National Academy of Sciences.

   This is a report of work supported by Contract No. DCA-83-C-0051
   between the U.S. Defense Communications Agency and the National
   Academy of Sciences, underwritten jointly by the Department of
   Defense and the National Bureau of Standards.

   Copies of the full report are available from:

      Board on Telecommunications and Computer Applications Commission
      on Engineering and Technical Systems
      National Research Council
      2101 Constitution Avenue, N.W.
      Washington, D.C. 20418







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RFC 939                                                    February 1985
Executive Summary of the NRC Report Transport on Protocols


                                PREFACE

   This is the final report of the National Research Council Committee
   on Computer-Computer Communication Protocols.  The committee was
   established in May l983 at the request of the Department of Defense
   (DOD) and the National Bureau of Standards (NBS), Department of
   Commerce, to develop recommendations and guidelines for resolving
   differences between the two agencies on a data communications
   transport protocol standard.

   Computer-based information and transaction-processing systems are
   basic tools in modern industry and government.  Over the past several
   years there has been a growing demand to transfer and exchange
   digitized data in these systems quickly and accurately.  This demand
   for data transfer and exchange has been both among the terminals and
   computers within an organization and among those in different
   organizations.

   Rapid electronic transport of digitized data requires electronic
   communication links that tie the elements together.  These links are
   established, organized, and maintained by means of a layered series
   of procedures performing the many functions inherent in the
   communications process.  The successful movement of digitized data
   depends upon the participants using identical or compatible
   procedures, or protocols.

   The DOD and NBS have each developed and promulgated a transport
   protocol as standard.  The two protocols, however, are dissimilar and
   incompatible.  The committee was called to resolve the differences
   between these protocols.

   The committee held its first meeting in August l983 at the National
   Research Council in Washington, D.C.  Following this two-day meeting
   the committee held five more two-day meetings, a three-day meeting,
   and a one-week workshop.

   The committee was briefed by personnel from both agencies.  In
   addition, the committee heard from Jon Postel, University of Southern
   California's Information Sciences Institute; Dave Oran, Digital
   Equipment Corporation; Vinton Cerf, MCI; David Wood, The Mitre
   Corporation; Clair Miller, Honeywell, and Robert Follett, IBM,
   representing the Computer and Business Equipment Manufacturer's
   Association; and John Newman, Ultimate Corporation.  In most cases
   the briefings were followed by discussion.

   The committee wishes to thank  Philip Selvaggi of the Department of
   Defense and Robert Blanc of the NBS, Institute of Computer Sciences


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RFC 939                                                    February 1985
Executive Summary of the NRC Report Transport on Protocols


   and Technology, for their cooperation as their agency's liaison
   representatives to the committee.  The committee appreciates the
   contributions and support of Richard B. Marsten, Executive Director
   of the Board on Telecommunications -- Computer Applications (BOTCAP),
   and Jerome D. Rosenberg, BOTCAP Senior Staff Officer and the
   committee Study Director.  We also wish to thank Lois A. Leak for her
   expert administrative and secretarial support.










































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RFC 939                                                    February 1985
Executive Summary of the NRC Report Transport on Protocols


                           EXECUTIVE SUMMARY

   Computer communication networks have become a very important part of
   military and commercial operations.  Indeed, the nation is becoming
   dependent upon their efficiency and reliability, and the recent
   proliferation of networks and their widespread use have emphasized
   the importance of developing uniform conventions, or protocols, for
   communication between computer systems.  The Department of Defense
   (DOD) and the National Bureau of Standards (NBS) have been actively
   engaged in activities related to protocol standardization.  This
   report is concerned primarily with recommendations on protocol
   standardization within the Department of Defense.

   Department of Defense's Transmission Protocol

      The DOD's Defense Advanced Research Projects Agency (DARPA) has
      been conducting and supporting research on computer networks for
      over fifteen years (1).  These efforts led to the development of
      modern packet-switched network design concepts.  Transmission
      between computers is generally accomplished by packet switching
      using strict protocols for the control and exchange of messages.
      The Advanced Research Projects Agency network (ARPANET),
      implemented in the early 1970s, provided a testing ground for
      research on communications protocols.  In 1978, after four years
      of development, the DOD promulgated versions of its Transmission
      Control Protocol (TCP) and an Internet Protocol (IP) and mandated
      their use as standards within the DOD.  TCP is now widely used and
      accepted.  These protocols meet the unique operational and
      functional requirements of the DOD, and any changes in the
      protocols are viewed with some trepidation by members of the
      department.  DOD representatives have stated that standardizing
      TCP greatly increased the momentum within the DOD toward
      establishing interoperability between networks within the DOD.

   International Standards Organization's Transport Protocol

      The NBS Institute for Computer Sciences and Technology (ICST), in
      cooperation with the DOD, many industrial firms, and the
      International Standards Organization (ISO), has developed a new
      international standard

      Transport Protocol (TP-4) and a new Internetwork Protocol (2).
      These protocols will soon be available as commercial products.
      Although in part derived from TCP, the new protocols are not
      compatible with TCP (3).  The U.S. standards organizations are




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RFC 939                                                    February 1985
Executive Summary of the NRC Report Transport on Protocols


      supporting TP-4 in international operations, and the Department of
      Commerce is proposing TP-4 as a Federal Information Processing
      Standard (FIPS) for use by all federal agencies.

   DOD OPERATIONAL AND TECHNICAL NEEDS

      The DOD has unique needs that could be affected by the Transport
      and Internet Protocol layers.  Although all data networks must
      have some of these capabilities, the DOD's needs for operational
      readiness, mobilization, and war-fighting capabilities are
      extreme.  These needs include the following:

         Survivability--Some networks must function, albeit at reduced
         performance, after many nodes and links have been destroyed.

         Security--Traffic patterns and data must be selectively
         protected through encryption, access control, auditing, and
         routing.

         Precedence--Systems should adjust the quality of service on the
         basis of priority of use; this includes a capability to preempt
         services in cases of very high priority.

         Robustness--The system must not fail or suffer much loss of
         capability because of unpredicted situations, unexpected loads,
         or misuse.  An international crisis is the strongest test of
         robustness, since the system must operate immediately and with
         virtually full performance when an international situation
         flares up unexpectedly.

         Availability--Elements of the system needed for operational
         readiness or fighting must be continuously available.

         Interoperability--Different elements of the Department must be
         able to "talk" to one another, often in unpredicted ways
         between parties that had not planned to interoperate.

      These operational needs reflect themselves into five technical or
      managerial needs:

         1.   Functional and operational specifications (that is, will
              the protocol designs meet the operational needs?);

         2.   Maximum interoperability;

         3.   Minimum procurement, development, and support costs;



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RFC 939                                                    February 1985
Executive Summary of the NRC Report Transport on Protocols


         4.   Ease of transition to new protocols; and

         5.   Manageability and responsiveness to changing DOD
              requirements.

      These are the criteria against which DOD options for using the ISO
      transport and internet protocols should be evaluated.

      Interoperability is a very important DOD need.  Ideally, DOD
      networks would permit operators at any terminal to access or be
      accessed by applications in any computer.  This would provide more
      network power for users, integration of independently developed
      systems, better use of resources, and increased survivability.  To
      increase interoperability, the Office of the Secretary of Defense
      has mandated the use of TCP for the Defense Communication System's
      Defense Data Network (DDN), unless waivers are granted.  In
      addition, the Defense Communication Agency (DCA) is establishing
      standards for three higher-level "utility" protocols for file
      transfer, terminal access, and electronic mail.  Partly as a
      result of these actions, it has become clear that there is growing
      momentum toward accepting interoperability and a recognition that
      it is an important operational need.

      It is very important, however, to recognize that functional
      interoperability is only achieved with full generality when two
      communication nodes can interoperate at all protocol levels.  For
      the DOD the relevant levels are as follows:

         1.   Internet, using IP;

         2.   Transport, using TCP;

         3.   Utility, using file, terminal, or mail protocols; and