RFC 942 (rfc942) - Page 1 of 68
Transport protocols for Department of Defense data networks
Alternative Format: Original Text Document
Network Working Group National Research Council
Request for Comments: 942
February 1985
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.
This RFC reproduces 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).
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
National Research Council [Page i]
RFC 942 February 1985
Report Transport on Protocols
NOTICE
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 this publication 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
National Research Council [Page ii]
RFC 942 February 1985
Report Transport on Protocols
BOARD ON TELECOMMUNICATIONS -- COMPUTER APPLICATIONS
COMMITTEE ON COMPUTER-COMPUTER COMMUNICATION PROTOCOLS
Chairman
C. CHAPIN CUTLER, Professor of Applied Physics, Stanford University,
Stanford, California
Members
HERBERT D. BENINGTON, Technical Director, System Development
Corporation, McLean, Virginia
DONALD L. BOYD, Director, Honeywell Corporate Computer Sciences Center,
Honeywell Corporate Technology Center, Bloomington, Minnesota
DAVID J. FARBER, Professor of Electrical Engineering and Professor of
Computer Science, Department of Electrical Engineering, University of
Delaware, Newark, Delaware
LAWRENCE H. LANDWEBER, Professor, Computer Sciences Department,
University of Wisconsin, Madison, Wisconsin
ANTHONY G. LAUCK, Manager, Distributed Systems Architecture and
Advanced Development, Digital Equipment Corporation, Tewksbury,
Massachusetts
KEITH A. LUCKE, General Manager of Control Data Technical Standards,
Control Data Corporation, Minneapolis, Minnesota
MISCHA SCHWARTZ, Professor of Electrical Engineering and Computer
Science, Columbia University, New York, New York
ROBERT F. STEEN, Director of Architecture, Communication Products
Division IBM Corporation, Research Triangle Park, North Carolina
CARL A. SUNSHINE, Principal Engineer, Sytek, Incorporated, Los Angeles
Operation, Culver City, California
DANIEL J. FINK, (Ex-officio), President, D.J. Fink Associates, Inc.,
Arlington, Virginia
JAMES L. FLANAGAN, (CETS LIAISON MEMBER), Head, Acoustics Research
Department, AT&T Bell Laboratories, Murray Hill, New Jersey
Staff
RICHARD B. MARSTEN, Executive Director
JEROME D. ROSENBERG, Senior Staff Officer and Study Director
LOIS A. LEAK, Administrative Secretary
National Research Council [Page iii]
RFC 942 February 1985
Report Transport on Protocols
National Research Council [Page iv]
RFC 942 February 1985
Report Transport on Protocols
COMMISSION ON ENGINEERING AND TECHNICAL SYSTEMS
BOARD ON TELECOMMUNICATIONS -- COMPUTER APPLICATIONS
Chairman
DANIEL J. FINK, President, D.J. Fink Associates, Inc., Arlington,
Virginia
Past Chairman
BROCKWAY MCMILLAN, Vice President (Retired), Bell Laboratories,
Sedgwick, Maine
Members
ARTHUR G. ANDERSON, Vice President (Retired), IBM Corporation, San
Jose, California
DANIEL BELL, Henry Ford II Professor of Social Sciences, Department of
Sociology, Harvard University, Cambridge, Massachusetts
HERBERT D. BENINGTON, Technical Director, System Development
Corporation, McLean, Virginia
ELWYN R. BERLEKAMP, Professor of Mathematics, Department of
Mathematics, University of California, Berkeley, California
ANTHONY J. DEMARIA, Assistant Director of Research for Electronics and
Electro-Optics Technology, United Technologies Research Center, East
Hartford, Connecticut
GERALD P. DINNEEN, Vice President, Science and Technology, Honeywell
Incorporated, Minneapolis, Minnesota
GEORGE GERBNER, Professor and Dean, The Annenberg School of
Communications, University of Pennsylvania, Philadelphia, Pennsylvania
ANNE P. JONES, Partner, Sutherland, Asbill and Brennan, Washington,
D.C.
ADRIAN M. MCDONOUGH, Professor of Management and Decision Sciences
(Retired), The Wharton School, University of Pennsylvania, Havertown,
Pennsylvania
WILBUR L. PRITCHARD, President, Satellite Systems Engineering, Inc.,
Bethesda, Maryland
MICHAEL B. PURSLEY, Professor of Electrical Engineering, University of
Illinois, Urbana, Illinois
IVAN SELIN, Chairman of the Board, American Management Systems, Inc.,
Arlington, Virginia
National Research Council [Page v]
RFC 942 February 1985
Report Transport on Protocols
MISCHA SCHWARTZ, Professor of Electrical Engineering and Computer
Science, Columbia University, New York, New York
ERIC E. SUMNER, Vice President, Operations System and Network Planning,
AT&T Bell Laboratories, Holmdel, New Jersey
KEITH W. UNCAPHER, Executive Director, USC-Information Sciences
Institute Associate Dean, School of Engineering, University of Southern
California, Marina del Rey, California
JAMES L. FLANAGAN, (CETS LIAISON MEMBER), Head, Acoustics Research
Department, AT&T Bell Laboratories, Murray Hill, New Jersey
Staff
Richard B. Marsten, Executive Director
Jerome D. Rosenberg, Senior Staff Officer
Karen Laughlin, Administrative Coordinator
Carmen A. Ruby, Administrative Assistant
Lois A. Leak, Administrative Secretary
National Research Council [Page vi]
RFC 942 February 1985
Report Transport on Protocols
CONTENTS
PREFACE ............................................................ ix
EXECUTIVE SUMMARY .................................................. xi
I Introduction .................................................. 1
II Review of NBS and DOD Objectives .............................. 3
III Comparison of DOD and ISO Protocols .......................... 13
IV Status of DOD and ISO Protocol
Implementations and Specifications .......................... 25
V Markets ...................................................... 31
VI Development of Standard Commercial versus
Special Commercial Products .................................. 39
VII Responsiveness of International Standards
Process to Change ............................................ 43
VIII Options for DOD and NBS ...................................... 45
IX Cost Comparison of Options .................................. 47
X Evaluation of Options ........................................ 53
XI Recommendations .............................................. 61
National Research Council [Page vii]
RFC 942 February 1985
Report Transport on Protocols
National Research Council [Page viii]
RFC 942 February 1985
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 and
National Research Council [Page ix]
RFC 942 February 1985
Report Transport on Protocols
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.
National Research Council [Page x]
RFC 942 February 1985
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
-----
(1) The Advanced Research Projects Agency (ARPA) was reorganized and
became the Defense Advanced Research Projects Agency (DARPA) in 1973.
National Research Council [Page xi]
RFC 942 February 1985
Report Transport on Protocols
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 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.
-----
(2) The ISO Transport Protocol and ISO Internetwork Protocol became
Draft International Standards in September 1983 and April 1984,
respectively. Commercial vendors normally consider Draft International
Standards to be ready for implementation.
(3) Except where noted, the abbreviation TCP generally refers to both
the DOD's Transmission Control Protocol and its Internet Protocol.
Similarly, the abbreviation TP-4 refers to both the ISO Transport
Protocol class 4 and its Internetwork Protocol. (Transport Protocol
classes 0 to 3 are used for special purposes not related to those of
this study.)
National Research Council [Page xii]
RFC 942 February 1985
Report Transport on Protocols
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;
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
4. Specific applications that use the above protocols for their
particular purpose.
Accordingly, if a network is developed using one transport protocol, it
would generally not be able to interoperate functionally with other
networks using the same transport protocol unless both networks were
also using the higher-level utility and application protocols. In
evaluating whether or not to convert to TP-4 and in developing a
transition plan, the following factors must be considered:
The DOD contains numerous communities of interest whose principal need
is to interoperate within their own members, independently. Such
communities generally have a specific, well-defined mission.
National Research Council [Page xiii]
RFC 942 February 1985
Report Transport on Protocols
The DOD Intelligence Information System (DODIIS) and the World Wide
Military Command and Control System (WWMCCS) are examples.
Interoperability is needed primarily between the higher layer
applications programs initially unique to each community of interest.
There are many different kinds of operations needed between
communities of interest. Examples of such operations are
headquarters' need for access to several subordinate communities and
the communities' need for some minimum functional interoperability
with each other (such as mail exchange).
The need for functional interoperability can arise, unexpectedly and
urgently, at a time of crisis or when improved management
opportunities are discovered. Widespread standardization of TP-4 and
higher-level protocols can readily help to achieve these needs.
Often, special development of additional applications that cost time
and money will be necessary.
The DOD needs functional interoperability with many important external
agencies that are committed to ISO standards: The North Atlantic
Treaty Organization (NATO), some intelligence and security agencies,
and other parts of the federal government.
The same objectives that have prompted the use of standardized
protocols at higher-level headquarters will lead to their use by
tactical groups in the field.
SOME COMPARISONS
A detailed comparison of the DOD Transmission Control Protocol and the
ISO Transport Protocol indicates they are functionally equivalent and
provide essentially similar services. Because it is clear that a great
deal of care and experience in protocol development have gone into
generating the specifications for TP-4, the committee is confident that
TP-4 will meet military requirements.
Although there are differences between the two protocols, they do not
compromise DOD requirements. And, although in several areas, including
the data transfer interface, flow control, connection establishment,
and out-of-band, services are provided in different ways by the two
protocols, neither seems intrinsically superior. Thus, while existing
applications may need to be modified somewhat if moved from TCP to
TP-4, new applications can be written to use either protocol with a
similar level of effort.
The TCP and TP-4 protocols are sufficiently equivalent in their
security-related properties in that there are no significant technical
points favoring the use of one over the other.
While TCP currently has the edge in maturity of implementation, TP-4 is
gaining rapidly due to the worldwide support for and acceptance of the
National Research Council [Page xiv]
RFC 942 February 1985
Report Transport on Protocols
Open System Interconnection (OSI) international standards.
Experimental TCP implementations were completed in 1974 at Stanford
University and BBN Communications Corporation. Between 1974 and 1982 a
large number of implementations were produced. The Defense Advanced
Research Projects Agency (ARPA) network switched to a complete use of
TCP in January 1983. Operations have been satisfactory and its use is
growing. A number of TCP implementations are also in commercial use in
various private networks.
In contrast, TP-4 has not yet been implemented in any large operational
system. It has been tested experimentally, however, and has received
endorsement by many commercial vendors worldwide. In addition,
substantial portions of TP-4 have been demonstrated at the National
Computer Conference in July 1984.
The Internet Protocol (IP) part of the standards is not believed to be
a problem. The ISO IP is not as far along as TP-4, but it is much less
complex. The ISO IP, based very strongly on the DOD IP, became a draft
international standard in April 1984.
The rapidity of the progress in ISO and the results achieved over the
past two years have surprised even the supporters of international
standards. The reasons for this progress are twofold: strong market
demands stemming from the growing integration of communications and
data processing and the progress in networking technology over the past
years as the result of ARPA and commercial developments.
Although the DOD networks have been a model upon which the ISO
transport standards have been built, the rest of the world is adopting
TP-4. Because the DOD represents a small fraction of the market and
because the United States supports the ISO standard, it is not
realistic to hope that TP-4 can be altered to conform with TCP. This
raises the question as to what action should be taken by the DOD with
respect to the ISO standard.
SOME ECONOMIC CONSIDERATIONS
The DOD has a large and growing commitment in operational TCP networks,
and this will increase by 50 to 100 percent in the next eighteen
months. This rate of investment will probably continue for the next
five years for new systems and the upgrading of current ones. The
current Military Network (MILNET) and Movement Information Network
(MINET) systems are expanding and will shortly be combined. The
Strategic Air Command Digital Information Network (SACDIN) and DODIIS
are undergoing major upgrading. When these changes are completed,
there are plans to upgrade the WWMCCS Intercomputer Network (WIN) and
to add separate SECRET and TOP SECRET networks. There are plans to
combine these six networks in the late 1980s, and they will become
interoperable and multilevel secure using an advanced technology now
under development. If these plans are implemented on schedule, a delay
of several years in moving to TP-4 would mean that the DOD networks in
the late 1980s would be virtually all TCP-based. Subsequent conversion
to international standards would be very expensive
National Research Council [Page xv]
RFC 942 February 1985
Report Transport on Protocols
if hastily attempted in order to maintain established DOD
interoperability and gain interoperability with a large body of users.
As the Department of Defense policy recognizes, there are significant
advantages in using commercial vendor products if they meet the
department's operational needs. The major advantages are as follows:
Costs to the DOD for development, production, and maintenance are
significantly lower because (1) vendors spread the cost over a much
larger user base, (2) commercial vendors are generally more efficient
in their operations, and (3) vendors look for ways to improve their
product to meet competition.
The department generally gets more effective products because vendors
integrate the protocol functions into their entire software and
hardware product line. Thus the DOD may be able eventually to use
commercial software products that are built on top of, and thereby
take advantage of, the transport protocols.
By depending on industry to manage the development and maintenance of
products, the department can use its scarce management and technical
resources on activities unique to its mission.
Because the costs of transport and internet protocol development and
maintenance are so intertwined with other factors, it is impossible to
give a precise estimate of the savings that would be achieved by using
commercial products. Savings will vary in individual cases. The
marginal savings should range from 30 to 80 percent.
RECOMMENDATIONS
The ISO protocols are now well specified but will not generally be
commercially available for many months. Nevertheless, this committee
believes that the principles on which they are based are
well-established, and the protocols can be made to satisfy fully DOD's
needs. The committee recommends that the DOD move toward adoption of
TP-4 as costandard with TCP and toward exclusive use of TP-4.
Transition to the use of the ISO standards, however, must be managed in
a manner that will maintain DOD's operational capabilities and minimize
risks. The timing of the transition is, therefore, a major concern.
Descriptions of two options that take this requirement into account
follow. A majority of the committee recommends the first option, while
a minority favors the second. A third option--to defer action--is also
described but not recommended.
Option 1
The first option is for the DOD to immediately modify its current
transport policy statement to specify TP-4 as a costandard along with
TCP. In addition, the DOD would develop a military specification for
National Research Council [Page xvi]
RFC 942 February 1985
Report Transport on Protocols
TP-4 that would also cover DOD requirements for discretionary options
allowed under the NBS protocol specifications. Requests for proposals
(RFPs) for new networks or major upgrades of existing networks would
specify TP-4 as the preferred protocol. Contracts for TP-4 systems
would be awarded only to contractors providing commercial products,
except for unique cases.
Existing networks that use TCP and new networks firmly committed to
the use of TCP-based systems could continue to acquire implementations
of TCP. The DOD should carefully review each case, however, to see
whether it would be advantageous to delay or modify some of these
acquisitions in order to use commercial TP-4 products. For each
community of users it should be decided when it is operationally or
economically most advantageous to replace its current or planned
systems in order to conform to ISO standards without excessively
compromising continued operations.
United States government test facilities would be developed to enable
validation of TP-4 products (4). The Department of Defense would
either require that products be validated using these test facilities
or that they be certified by the vendor. The test facilities could
also be used to isolate multivendor protocol compatibility problems.
The existing NBS validation tools should be used as the base for the
DOD test facilities.
Because under this option networks based on both TCP and TP-4 would
coexist for some time, several capabilities that facilitate
interoperability among networks would need to be developed. The
Department of Defense generally will not find them commercially
available. Examples are gateways among networks or specialized hosts
that provide services such as electronic mail. The department would
need to initiate or modify development programs to provide these
capabilities, and a test and demonstration network would be required.
Option 2
Under Option 2 the Department of Defense would immediately announce
its intention to adopt TP-4 as a transport protocol costandard with
TCP after a satisfactory demonstration of its suitability for use in
military networks. A final commitment would be deferred until the
demonstration has been evaluated and TP-4 is commercially available.
The demonstration should take at most eighteen months and should
involve development of TP-4 implementations and their installation.
This option differs from Option 1 primarily in postponing the adoption
of a TP-4 standard and, consequently, the issuance of RFPs based on
TP-4 until successful completion of a demonstration. The department,
-----
(4) Validation means a systematic and thorough state-of-the-art testing
of the products to assure that all technical specifications are being
achieved.
National Research Council [Page xvii]
RFC 942 February 1985
Report Transport on Protocols
however, should proceed with those provisions of Option 1 that may be
completed in parallel with the demonstration. Early issuance of a
TP-4 military specification, development of validation procedures, and
implementation of means for interoperability would be particularly
important in this regard.
Option 3
Under the third option the DOD would continue using TCP as the
accepted transport standard and defer any decision on the use of TP-4
indefinitely. The department would be expected to stay well informed
on the development and use of the new protocol in the commercial and
international arena and, with the National Bureau of Standards, work
on means to transfer data between the two protocol systems. Testing
and evaluation of TP-4 standards by NBS would continue. The DOD might
eventually accommodate both protocol systems in an evolutionary
conversion to TP-4.
Comparison of Options
The committee believes that all three options equally satisfy the
functional objectives of the DOD, including matters of security. It
believes the two protocols are sufficiently similar and no significant
differences in performance are to be expected if the chosen protocol
implementation is of equal quality and is optimized for the given
environment.
The primary motivation for recommending Option 1 is to obtain the
benefits of standard commercial products in the communication protocol
area at an early date. Benefits include smaller development,
procurement, and support costs; more timely updates; and a wider
product availability. By immediately committing to TP-4 as a
costandard for new systems, Option 1 minimizes the number of systems
that have to be converted eventually from TCP. The ability to manage
the transition is better than with Option 2 since the number of
systems changed would be smaller and the time duration of mixed TCP
and TP-4 operation would be shorter. Interoperability with external
systems (NATO, government, commercial), which presumably will also use
TP-4, would be brought about more quickly. Option 1 involves greater
risk, however, since it commits to a new approach without as complete
a demonstration of its viability.
As with Option 1, a primary benefit of following Option 2 would be
obtaining the use of standard commercial products. Unit procurement
costs probably would be lower than with Option 1 because the
commercial market for TP-4 will have expanded somewhat by the time DOD
would begin to buy TP-4 products. Risk is smaller, compared to Option
1, because testing and demonstration of the suitability for military
use will have preceded the commitment to the ISO protocols.
Transition and support costs would be higher than for Option 1,
however, because more networks and systems would already have been
implemented with TCP. Also this is perhaps the most difficult option
to manage since the largest number of system conversions and the
National Research Council [Page xviii]
RFC 942 February 1985
Report Transport on Protocols
longest interval of mixed TCP and TP-4 operations would occur. In
addition, interoperability with external networks through
standardization would be delayed.
The principal benefit of exercising Option 3 would be the elimination
of transition cost and the risk of faulty system behavior and delay.
It would allow the most rapid achievement of full internal
interoperability among DOD systems. Manageability should be good
because only one set of protocols would be in use (one with which the
DOD already has much experience), and because the DOD would be in
complete control of system evolution. Procurement costs for TCP
systems would remain high compared with standard ISO protocol
products, however, and availability of implementations for new systems
and releases would remain limited. External interoperability with
non-DOD systems would be limited and inefficient.
In summary, Option 1 provides the most rapid path toward the use of
commercial products and interoperability with external systems.
Option 2 reduces the risk but involves somewhat greater delay and
expense. Option 3 involves the least risk and provides the quickest
route to interoperability within the Defense Department at the least
short-term cost. These are, however, accompanied by penalties of
incompatibility with NATO and other external systems and higher
life-cycle costs.
National Research Council [Page xix]
RFC 942 February 1985
Report Transport on Protocols
National Research Council [Page xx]
RFC 942 February 1985
Report Transport on Protocols
I. INTRODUCTION
For the past two decades industry and government have experienced an
increasing need to share software programs, transfer data, and exchange
information among computers. As a result, computer-to-computer data
communications networks and, therefore, communication formats and
procedures, or protocols, have proliferated. The need to interconnect
these networks is obvious, but the problems in establishing agreements
among users on the protocols have heightened.
The Department of Defense (DOD) has been conducting research and
development on protocols and communication standards for more than
fifteen years. In December 1978 the DOD promulgated versions of the
Defense Advanced Research Projects Agency's (DARPA) Transmission Control
Protocol (TCP) and Internet Protocol (IP) as standards within DOD. With
the participation of major manufacturers and systems houses, the DOD has
implemented successfully over twenty different applications of these
standards in DOD operational data communications networks.
The Institute for Computer Sciences and Technology (ICST) of the
National Bureau of Standards (NBS) is the government agency responsible
for developing network protocols and interface standards to meet the
needs of federal agencies. The Institute has been actively helping
national and international voluntary standards organizations develop
sets of protocol standards that can be incorporated into commercial
products.
Working with both industry and government agencies, the ICST has
developed protocol requirements based, in terms of functions and
services, on the DOD's TCP. These requirements were submitted to the
International Standards Organization (ISO) and resulted in the
development of a transport protocol (TP-4) that has the announced
support of twenty computer manufacturers.
Although the ISO's TP-4 is based on the DOD's TCP, the two protocols are
not compatible. Thus manufacturers who wish to serve DOD, while
remaining able to capture a significant share of the worldwide market,
have to field two product lines that are incompatible but perform the
same function. The Institute for Computer Sciences and Technology would
like to have a single set of protocol standards that serves both the
DOD, other government agencies, and commercial vendors.
It would be to the advantage of the DOD to use the same standards as the
rest of the world. The dilemma, however, is understandable: The DOD
National Research Council