As per Relevance of the word transport, we have this rfc below:
Network Working Group National Research
Request for Comments: 942
February 1985
TRANSPORT PROTOCOLS
DEPARTMENT OF
DATA
STATUS OF THIS
This RFC is distributed for information only. This RFC does
establish any policy for the DARPA research community or the
operational community. Distribution of this memo is unlimited
This RFC reproduces the National Research Council report resulting
a study of the DOD Internet Protocol (IP) and Transmission
Protocol (TCP) in comparison with the ISO Internet Protocol (ISO-IP)
Transport Protocol level 4 (TP-4).
Transport Protocols
Department of
Data
Report to the Department of
and the National Bureau of
Committee on Computer-Computer Communication
Board on Telecommunications and Computer Applications Commission
Engineering and Technical
National Research
National Academy
Washington, D.C. February 1985
National Research Council [Page i
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The project that is the subject of this report was approved by
Governing Board on the National Research Council, whose members
drawn from the councils of the National Academy of Sciences,
National Academy of Engineering, and the Institute of Medicine.
members of the committee responsible for the report were chosen
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
of members of the National Academy of Sciences, the National Academy
Engineering, and the Institute of Medicine
The National Research Council was established by the National Academy
Sciences in 1916 to associate the broad community of science
technology with the Academy's purposes of furthering knowledge and
advising the federal government. The Council operates in
with general policies determined by the Academy under the authority
its congressional charter of 1863, which establishes the Academy as
private, nonprofit, self-governing membership corporation. The
has become the principal operating agency of both the National
of Sciences and the National Academy of Engineering in the conduct
their services to the government, the public, and the scientific
engineering communities. It is administered jointly by both
and the Institute of Medicine. The National Academy of Engineering
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
the U.S. Defense Communications Agency and the National Academy
Sciences, underwritten jointly by the Department of Defense and
National Bureau of Standards
Copies of this publication are available from
Board on Telecommunications and Computer Applications Commission
Engineering and Technical
National Research
2101 Constitution Avenue, N.W
Washington, D.C. 20418
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BOARD ON TELECOMMUNICATIONS -- COMPUTER
COMMITTEE ON COMPUTER-COMPUTER COMMUNICATION
C. CHAPIN CUTLER, Professor of Applied Physics, Stanford University
Stanford,
HERBERT D. BENINGTON, Technical Director, System
Corporation, McLean,
DONALD L. BOYD, Director, Honeywell Corporate Computer Sciences Center
Honeywell Corporate Technology Center, Bloomington,
DAVID J. FARBER, Professor of Electrical Engineering and Professor
Computer Science, Department of Electrical Engineering, University
Delaware, Newark,
LAWRENCE H. LANDWEBER, Professor, Computer Sciences Department
University of Wisconsin, Madison,
ANTHONY G. LAUCK, Manager, Distributed Systems Architecture
Advanced Development, Digital Equipment Corporation, Tewksbury
KEITH A. LUCKE, General Manager of Control Data Technical Standards
Control Data Corporation, Minneapolis,
MISCHA SCHWARTZ, Professor of Electrical Engineering and
Science, Columbia University, New York, New
ROBERT F. STEEN, Director of Architecture, Communication
Division IBM Corporation, Research Triangle Park, North
CARL A. SUNSHINE, Principal Engineer, Sytek, Incorporated, Los
Operation, Culver City,
DANIEL J. FINK, (Ex-officio), President, D.J. Fink Associates, Inc.,
Arlington,
JAMES L. FLANAGAN, (CETS LIAISON MEMBER), Head, Acoustics
Department, AT&T Bell Laboratories, Murray Hill, New
RICHARD B. MARSTEN, Executive
JEROME D. ROSENBERG, Senior Staff Officer and Study
LOIS A. LEAK, Administrative
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National Research Council [Page iv
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COMMISSION ON ENGINEERING AND TECHNICAL
BOARD ON TELECOMMUNICATIONS -- COMPUTER
DANIEL J. FINK, President, D.J. Fink Associates, Inc., Arlington
Past
BROCKWAY MCMILLAN, Vice President (Retired), Bell Laboratories
Sedgwick,
ARTHUR G. ANDERSON, Vice President (Retired), IBM Corporation,
Jose,
DANIEL BELL, Henry Ford II Professor of Social Sciences, Department
Sociology, Harvard University, Cambridge,
HERBERT D. BENINGTON, Technical Director, System
Corporation, McLean,
ELWYN R. BERLEKAMP, Professor of Mathematics, Department
Mathematics, University of California, Berkeley,
ANTHONY J. DEMARIA, Assistant Director of Research for Electronics
Electro-Optics Technology, United Technologies Research Center,
Hartford,
GERALD P. DINNEEN, Vice President, Science and Technology,
Incorporated, Minneapolis,
GEORGE GERBNER, Professor and Dean, The Annenberg School
Communications, University of Pennsylvania, Philadelphia,
ANNE P. JONES, Partner, Sutherland, Asbill and Brennan, Washington
D.C
ADRIAN M. MCDONOUGH, Professor of Management and Decision
(Retired), The Wharton School, University of Pennsylvania, Havertown
WILBUR L. PRITCHARD, President, Satellite Systems Engineering, Inc.,
Bethesda,
MICHAEL B. PURSLEY, Professor of Electrical Engineering, University
Illinois, Urbana,
IVAN SELIN, Chairman of the Board, American Management Systems, Inc.,
Arlington,
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MISCHA SCHWARTZ, Professor of Electrical Engineering and
Science, Columbia University, New York, New
ERIC E. SUMNER, Vice President, Operations System and Network Planning
AT&T Bell Laboratories, Holmdel, New
KEITH W. UNCAPHER, Executive Director, USC-Information
Institute Associate Dean, School of Engineering, University of
California, Marina del Rey,
JAMES L. FLANAGAN, (CETS LIAISON MEMBER), Head, Acoustics
Department, AT&T Bell Laboratories, Murray Hill, New
Richard B. Marsten, Executive
Jerome D. Rosenberg, Senior Staff
Karen Laughlin, Administrative
Carmen A. Ruby, Administrative
Lois A. Leak, Administrative
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PREFACE ............................................................
EXECUTIVE SUMMARY ..................................................
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
Implementations and Specifications .......................... 25
V Markets ...................................................... 31
VI Development of Standard Commercial
Special Commercial Products .................................. 39
VII Responsiveness of International
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
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This is the final report of the National Research Council Committee
Computer-Computer Communication Protocols. The committee
established in May l983 at the request of the Department of
(DOD) and the National Bureau of Standards (NBS), Department
Commerce, to develop recommendations and guidelines for
differences between the two agencies on a data communications
protocol standard
Computer-based information and transaction-processing systems are
tools in modern industry and government. Over the past several
there has been a growing demand to transfer and exchange digitized
in these systems quickly and accurately. This demand for data
and exchange has been both among the terminals and computers within
organization and among those in different organizations
Rapid electronic transport of digitized data requires
communication links that tie the elements together. These links
established, organized, and maintained by means of a layered series
procedures performing the many functions inherent in the
process. The successful movement of digitized data depends upon
participants using identical or compatible procedures, or protocols
The DOD and NBS have each developed and promulgated a transport
as standard. The two protocols, however, are dissimilar
incompatible. The committee was called to resolve the
between these protocols
The committee held its first meeting in August l983 at the
Research Council in Washington, D.C. Following this two-day meeting
committee held five more two-day meetings, a three-day meeting, and
one-week workshop
The committee was briefed by personnel from both agencies. In addition
the committee heard from Jon Postel, University of Southern California'
Information Sciences Institute; Dave Oran, Digital
Corporation; Vinton Cerf, MCI; David Wood, The Mitre Corporation;
Miller, Honeywell, and Robert Follett, IBM, representing the
and Business Equipment Manufacturer's Association; and John Newman
Ultimate Corporation. In most cases the briefings were followed
discussion
The committee wishes to thank Philip Selvaggi of the Department
Defense and Robert Blanc of the NBS, Institute of Computer Sciences
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Technology, for their cooperation as their agency's
representatives to the committee. The committee appreciates
contributions and support of Richard B. Marsten, Executive Director
the Board on Telecommunications -- Computer Applications (BOTCAP),
Jerome D. Rosenberg, BOTCAP Senior Staff Officer and the committee
Director. We also wish to thank Lois A. Leak for her
administrative and secretarial support
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EXECUTIVE
Computer communication networks have become a very important part
military and commercial operations. Indeed, the nation is
dependent upon their efficiency and reliability, and the
proliferation of networks and their widespread use have emphasized
importance of developing uniform conventions, or protocols,
communication between computer systems. The Department of Defense (DOD
and the National Bureau of Standards (NBS) have been actively engaged
activities related to protocol standardization. This report
concerned primarily with recommendations on protocol
within the Department of Defense
Department of Defense's Transmission
The DOD's Defense Advanced Research Projects Agency (DARPA) has
conducting and supporting research on computer networks for
fifteen years (1). These efforts led to the development of
packet-switched network design concepts. Transmission
computers is generally accomplished by packet switching using
protocols for the control and exchange of messages. The
Research Projects Agency network (ARPANET), implemented in the
1970s, provided a testing ground for research on
protocols. In 1978, after four years of development, the
promulgated versions of its Transmission Control Protocol (TCP) and
Internet Protocol (IP) and mandated their use as standards within
DOD. TCP is now widely used and accepted. These protocols meet
unique operational and functional requirements of the DOD, and
changes in the protocols are viewed with some trepidation by members
the department. DOD representatives have stated that standardizing
greatly increased the momentum within the DOD toward
interoperability between networks within the DOD
International Standards Organization's Transport
The NBS Institute for Computer Sciences and Technology (ICST),
cooperation with the DOD, many industrial firms, and the
Standards Organization (ISO), has developed a new
-----
(1) The Advanced Research Projects Agency (ARPA) was reorganized
became the Defense Advanced Research Projects Agency (DARPA) in 1973.
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Transport Protocol (TP-4) and a new Internetwork Protocol (2).
protocols will soon be available as commercial products. Although
part derived from TCP, the new protocols are not compatible
TCP (3). The U.S. standards organizations are supporting TP-4
international operations, and the Department of Commerce is
TP-4 as a Federal Information Processing Standard (FIPS) for use by
federal agencies
DOD OPERATIONAL AND TECHNICAL
The DOD has unique needs that could be affected by the Transport
Internet Protocol layers. Although all data networks must have some
these capabilities, the DOD's needs for operational readiness
mobilization, and war-fighting capabilities are extreme. These
include the following
Survivability--Some networks must function, albeit at
performance, after many nodes and links have been destroyed
Security--Traffic patterns and data must be selectively
through encryption, access control, auditing, and routing
Precedence--Systems should adjust the quality of service on the
of priority of use; this includes a capability to preempt services
cases of very high priority
Robustness--The system must not fail or suffer much loss of
because of unpredicted situations, unexpected loads, or misuse.
international crisis is the strongest test of robustness, since
system must operate immediately and with virtually full
when an international situation flares up unexpectedly
Availability--Elements of the system needed for operational
or fighting must be continuously available
Interoperability--Different elements of the Department must be able
"talk" to one another, often in unpredicted ways between parties
had not planned to interoperate
-----
(2) The ISO Transport Protocol and ISO Internetwork Protocol
Draft International Standards in September 1983 and April 1984,
respectively. Commercial vendors normally consider Draft
Standards to be ready for implementation
(3) Except where noted, the abbreviation TCP generally refers to
the DOD's Transmission Control Protocol and its Internet Protocol
Similarly, the abbreviation TP-4 refers to both the ISO
Protocol class 4 and its Internetwork Protocol. (Transport
classes 0 to 3 are used for special purposes not related to those
this study.)
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These operational needs reflect themselves into five technical
managerial needs
1. Functional and operational specifications (that is, will
protocol designs meet the operational needs?);
2. Maximum interoperability
3. Minimum procurement, development, and support costs
4. Ease of transition to new protocols;
5. Manageability and responsiveness to changing DOD requirements
These are the criteria against which DOD options for using the
transport and internet protocols should be evaluated
Interoperability is a very important DOD need. Ideally, DOD
would permit operators at any terminal to access or be accessed
applications in any computer. This would provide more network
for users, integration of independently developed systems, better
of resources, and increased survivability. To
interoperability, the Office of the Secretary of Defense has
the use of TCP for the Defense Communication System's Defense
Network (DDN), unless waivers are granted. In addition, the
Communication Agency (DCA) is establishing standards for
higher-level "utility" protocols for file transfer, terminal access
and electronic mail. Partly as a result of these actions, it
become clear that there is growing momentum toward
interoperability and a recognition that it is an important
need
It is very important, however, to recognize that
interoperability is only achieved with full generality when
communication nodes can interoperate at all protocol levels. For
DOD the relevant levels are as follows
1. Internet, using IP
2. Transport, using TCP
3. Utility, using file, terminal, or mail protocols;
4. Specific applications that use the above protocols for
particular purpose
Accordingly, if a network is developed using one transport protocol,
would generally not be able to interoperate functionally with
networks using the same transport protocol unless both networks
also using the higher-level utility and application protocols.
evaluating whether or not to convert to TP-4 and in developing
transition plan, the following factors must be considered
The DOD contains numerous communities of interest whose principal
is to interoperate within their own members, independently.
communities generally have a specific, well-defined mission
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The DOD Intelligence Information System (DODIIS) and the World
Military Command and Control System (WWMCCS) are examples
Interoperability is needed primarily between the higher
applications programs initially unique to each community of interest
There are many different kinds of operations needed
communities of interest. Examples of such operations
headquarters' need for access to several subordinate communities
the communities' need for some minimum functional
with each other (such as mail exchange).
The need for functional interoperability can arise, unexpectedly
urgently, at a time of crisis or when improved
opportunities are discovered. Widespread standardization of TP-4
higher-level protocols can readily help to achieve these needs
Often, special development of additional applications that cost
and money will be necessary
The DOD needs functional interoperability with many important
agencies that are committed to ISO standards: The North
Treaty Organization (NATO), some intelligence and security agencies
and other parts of the federal government
The same objectives that have prompted the use of
protocols at higher-level headquarters will lead to their use
tactical groups in the field
SOME
A detailed comparison of the DOD Transmission Control Protocol and
ISO Transport Protocol indicates they are functionally equivalent
provide essentially similar services. Because it is clear that a
deal of care and experience in protocol development have gone
generating the specifications for TP-4, the committee is confident
TP-4 will meet military requirements
Although there are differences between the two protocols, they do
compromise DOD requirements. And, although in several areas,
the data transfer interface, flow control, connection establishment
and out-of-band, services are provided in different ways by the
protocols, neither seems intrinsically superior. Thus, while
applications may need to be modified somewhat if moved from TCP
TP-4, new applications can be written to use either protocol with
similar level of effort
The TCP and TP-4 protocols are sufficiently equivalent in
security-related properties in that there are no significant
points favoring the use of one over the other
While TCP currently has the edge in maturity of implementation, TP-4
gaining rapidly due to the worldwide support for and acceptance of
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Open System Interconnection (OSI) international standards
Experimental TCP implementations were completed in 1974 at
University and BBN Communications Corporation. Between 1974 and 1982
large number of implementations were produced. The Defense
Research Projects Agency (ARPA) network switched to a complete use
TCP in January 1983. Operations have been satisfactory and its use
growing. A number of TCP implementations are also in commercial use
various private networks
In contrast, TP-4 has not yet been implemented in any large
system. It has been tested experimentally, however, and has
endorsement by many commercial vendors worldwide. In addition
substantial portions of TP-4 have been demonstrated at the
Computer Conference in July 1984.
The Internet Protocol (IP) part of the standards is not believed to
a problem. The ISO IP is not as far along as TP-4, but it is much
complex. The ISO IP, based very strongly on the DOD IP, became a
international standard in April 1984.
The rapidity of the progress in ISO and the results achieved over
past two years have surprised even the supporters of
standards. The reasons for this progress are twofold: strong
demands stemming from the growing integration of communications
data processing and the progress in networking technology over the
years as the result of ARPA and commercial developments
Although the DOD networks have been a model upon which the
transport standards have been built, the rest of the world is
TP-4. Because the DOD represents a small fraction of the market
because the United States supports the ISO standard, it is
realistic to hope that TP-4 can be altered to conform with TCP.
raises the question as to what action should be taken by the DOD
respect to the ISO standard
SOME ECONOMIC
The DOD has a large and growing commitment in operational TCP networks
and this will increase by 50 to 100 percent in the next
months. This rate of investment will probably continue for the
five years for new systems and the upgrading of current ones.
current Military Network (MILNET) and Movement Information
(MINET) systems are expanding and will shortly be combined.
Strategic Air Command Digital Information Network (SACDIN) and
are undergoing major upgrading. When these changes are completed
there are plans to upgrade the WWMCCS Intercomputer Network (WIN)
to add separate SECRET and TOP SECRET networks. There are plans
combine these six networks in the late 1980s, and they will
interoperable and multilevel secure using an advanced technology
under development. If these plans are implemented on schedule, a
of several years in moving to TP-4 would mean that the DOD networks
the late 1980s would be virtually all TCP-based. Subsequent
to international standards would be very
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if hastily attempted in order to maintain established
interoperability and gain interoperability with a large body of users
As the Department of Defense policy recognizes, there are
advantages in using commercial vendor products if they meet
department's operational needs. The major advantages are as follows
Costs to the DOD for development, production, and maintenance
significantly lower because (1) vendors spread the cost over a
larger user base, (2) commercial vendors are generally more
in their operations, and (3) vendors look for ways to improve
product to meet competition
The department generally gets more effective products because
integrate the protocol functions into their entire software
hardware product line. Thus the DOD may be able eventually to
commercial software products that are built on top of, and
take advantage of, the transport protocols
By depending on industry to manage the development and maintenance
products, the department can use its scarce management and
resources on activities unique to its mission
Because the costs of transport and internet protocol development
maintenance are so intertwined with other factors, it is impossible
give a precise estimate of the savings that would be achieved by
commercial products. Savings will vary in individual cases.
marginal savings should range from 30 to 80 percent
The ISO protocols are now well specified but will not generally
commercially available for many months. Nevertheless, this
believes that the principles on which they are based
well-established, and the protocols can be made to satisfy fully DOD'
needs. The committee recommends that the DOD move toward adoption
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
a manner that will maintain DOD's operational capabilities and
risks. The timing of the transition is, therefore, a major concern
Descriptions of two options that take this requirement into
follow. A majority of the committee recommends the first option,
a minority favors the second. A third option--to defer action--is
described but not recommended
Option 1
The first option is for the DOD to immediately modify its
transport policy statement to specify TP-4 as a costandard along
TCP. In addition, the DOD would develop a military specification
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TP-4 that would also cover DOD requirements for discretionary
allowed under the NBS protocol specifications. Requests for
(RFPs) for new networks or major upgrades of existing networks
specify TP-4 as the preferred protocol. Contracts for TP-4
would be awarded only to contractors providing commercial products
except for unique cases
Existing networks that use TCP and new networks firmly committed
the use of TCP-based systems could continue to acquire
of TCP. The DOD should carefully review each case, however, to
whether it would be advantageous to delay or modify some of
acquisitions in order to use commercial TP-4 products. For
community of users it should be decided when it is operationally
economically most advantageous to replace its current or
systems in order to conform to ISO standards without
compromising continued operations
United States government test facilities would be developed to
validation of TP-4 products (4). The Department of Defense
either require that products be validated using these test
or that they be certified by the vendor. The test facilities
also be used to isolate multivendor protocol compatibility problems
The existing NBS validation tools should be used as the base for
DOD test facilities
Because under this option networks based on both TCP and TP-4
coexist for some time, several capabilities that
interoperability among networks would need to be developed.
Department of Defense generally will not find them
available. Examples are gateways among networks or specialized
that provide services such as electronic mail. The department
need to initiate or modify development programs to provide
capabilities, and a test and demonstration network would be required
Option 2
Under Option 2 the Department of Defense would immediately
its intention to adopt TP-4 as a transport protocol costandard
TCP after a satisfactory demonstration of its suitability for use
military networks. A final commitment would be deferred until
demonstration has been evaluated and TP-4 is commercially available
The demonstration should take at most eighteen months and
involve development of TP-4 implementations and their installation
This option differs from Option 1 primarily in postponing the
of a TP-4 standard and, consequently, the issuance of RFPs based
TP-4 until successful completion of a demonstration. The department
-----
(4) Validation means a systematic and thorough state-of-the-art
of the products to assure that all technical specifications are
achieved
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however, should proceed with those provisions of Option 1 that may
completed in parallel with the demonstration. Early issuance of
TP-4 military specification, development of validation procedures,
implementation of means for interoperability would be
important in this regard
Option 3
Under the third option the DOD would continue using TCP as
accepted transport standard and defer any decision on the use of TP-4
indefinitely. The department would be expected to stay well
on the development and use of the new protocol in the commercial
international arena and, with the National Bureau of Standards,
on means to transfer data between the two protocol systems.
and evaluation of TP-4 standards by NBS would continue. The DOD
eventually accommodate both protocol systems in an
conversion to TP-4.
Comparison of
The committee believes that all three options equally satisfy
functional objectives of the DOD, including matters of security.
believes the two protocols are sufficiently similar and no
differences in performance are to be expected if the chosen
implementation is of equal quality and is optimized for the
environment
The primary motivation for recommending Option 1 is to obtain
benefits of standard commercial products in the communication
area at an early date. Benefits include smaller development
procurement, and support costs; more timely updates; and a
product availability. By immediately committing to TP-4 as
costandard for new systems, Option 1 minimizes the number of
that have to be converted eventually from TCP. The ability to
the transition is better than with Option 2 since the number
systems changed would be smaller and the time duration of mixed
and TP-4 operation would be shorter. Interoperability with
systems (NATO, government, commercial), which presumably will also
TP-4, would be brought about more quickly. Option 1 involves
risk, however, since it commits to a new approach without as
a demonstration of its viability
As with Option 1, a primary benefit of following Option 2 would
obtaining the use of standard commercial products. Unit
costs probably would be lower than with Option 1 because
commercial market for TP-4 will have expanded somewhat by the time
would begin to buy TP-4 products. Risk is smaller, compared to
1, because testing and demonstration of the suitability for
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
implemented with TCP. Also this is perhaps the most difficult
to manage since the largest number of system conversions and
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longest interval of mixed TCP and TP-4 operations would occur.
addition, interoperability with external networks
standardization would be delayed
The principal benefit of exercising Option 3 would be the
of transition cost and the risk of faulty system behavior and delay
It would allow the most rapid achievement of full
interoperability among DOD systems. Manageability should be
because only one set of protocols would be in use (one with which
DOD already has much experience), and because the DOD would be
complete control of system evolution. Procurement costs for
systems would remain high compared with standard ISO
products, however, and availability of implementations for new
and releases would remain limited. External interoperability
non-DOD systems would be limited and inefficient
In summary, Option 1 provides the most rapid path toward the use
commercial products and interoperability with external systems
Option 2 reduces the risk but involves somewhat greater delay
expense. Option 3 involves the least risk and provides the
route to interoperability within the Defense Department at the
short-term cost. These are, however, accompanied by penalties
incompatibility with NATO and other external systems and
life-cycle costs
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I.
For the past two decades industry and government have experienced
increasing need to share software programs, transfer data, and
information among computers. As a result, computer-to-computer
communications networks and, therefore, communication formats
procedures, or protocols, have proliferated. The need to
these networks is obvious, but the problems in establishing
among users on the protocols have heightened
The Department of Defense (DOD) has been conducting research
development on protocols and communication standards for more
fifteen years. In December 1978 the DOD promulgated versions of
Defense Advanced Research Projects Agency's (DARPA) Transmission
Protocol (TCP) and Internet Protocol (IP) as standards within DOD.
the participation of major manufacturers and systems houses, the DOD
implemented successfully over twenty different applications of
standards in DOD operational data communications networks
The Institute for Computer Sciences and Technology (ICST) of
National Bureau of Standards (NBS) is the government agency
for developing network protocols and interface standards to meet
needs of federal agencies. The Institute has been actively
national and international voluntary standards organizations
sets of protocol standards that can be incorporated into
products
Working with both industry and government agencies, the ICST
developed protocol requirements based, in terms of functions
services, on the DOD's TCP. These requirements were submitted to
International Standards Organization (ISO) and resulted in
development of a transport protocol (TP-4) that has the
support of twenty computer manufacturers
Although the ISO's TP-4 is based on the DOD's TCP, the two protocols
not compatible. Thus manufacturers who wish to serve DOD,
remaining able to capture a significant share of the worldwide market
have to field two product lines that are incompatible but perform
same function. The Institute for Computer Sciences and Technology
like to have a single set of protocol standards that serves both
DOD, other government agencies, and commercial vendors
It would be to the advantage of the DOD to use the same standards as
rest of the world. The dilemma, however, is understandable: The
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has well satisfied its requirements by its own tried and
protocols, the agency has invested heavily in systems
successfully with TCP, and the Armed Forces is increasingly adopting
protocol. Thus, although DOD's policy is to use commercial
whenever suitable, it is hesitant about converting to the ISO TP-4
protocols. In addition, the DOD is not certain whether the ISO TP-4
completely satisfies military requirements
In 1983 both DOD and the ICST agreed that an objective study of
situation was needed. Each requested assistance from the
Research Council. The National Research Council, through its Board
Telecommunications and Computer Applications (BOTCAP), appointed
special Committee on Computer-Computer Communication Protocols to
the issues and develop recommendations and guidelines for ways
resolve the differences in a mutually beneficial manner
The six items composing the committee's scope of work are as follows
1. Review the technical aspects of the DOD transmission control
ICST transport protocols
2. Review the status of the implementation of these protocols
3. Review the industrial and government markets for these protocols
4. Analyze the technical and political implications of the DOD
ICST views on the protocols
5. Report on time and cost implications to the DOD, other
entities, and manufacturers of the DOD and ICST positions
6. Recommend courses of action toward resolving the
between the DOD and ICST on these protocol standards
The committee devoted considerable effort to reviewing the
and goals of the DOD and NBS that relate to data communications,
technical aspects of the two protocols, the status of
implementation in operating networks, and the market
pertaining to their use. This process included hearing government
industry presentations and reviewing pertinent literature. The
of this part of the study are presented in Sections II through VII
Concurrent with this research and analysis, the committee developed
possible options that offered plausible resolutions of the problem
These ranged from maintaining the status quo to an immediate
from one protocol to the other. From these ten initial options
were determined to hold the greatest potential for resolving
problem
Section VIII describes the three options, Section IX provides a
comparison, and Section X provides an overall evaluation of the
options. Section XI presents the committee's basic and
recommendations for how best the DOD might approach the
between its protocol and the ISO protocol
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II. REVIEW OF NBS AND DOD
The National Bureau of Standards and the Department of Defense are
disparate organizations that the committee felt it needed to begin
study with a definition of the roles and expectations of each
regard to the protocol issues in question. The following provides
review of each organization's objectives (5).
NBS
The National Bureau of Standards has three primary goals in
networking
1. To develop networking and protocol standards that meet U.S
government and industry requirements and that will be
in off-the-shelf, commercial products
2. To develop testing methodologies to support development
implementation of computer network protocols
3. To assist government and industry users in the application
advanced networking technologies and computer and
equipment manufacturers in the implementation of
protocols
Development of Networking and Protocol
The Bureau accomplishes the first objective through close
and cooperation with U.S. computer manufacturers and
system developers. Technical specifications are
cooperatively with U.S. industry and other government agencies
provided as proposals to voluntary standards organizations
Because the Department of Defense is potentially the
government client of these standards, DOD requirements are
factored into these proposals. In addition, protocols
computer-to-computer communications developed within the DOD
community are used as
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(5) The objectives were reviewed by representatives of NBS and DOD
respectively
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exact statement of DOD functional needs for a particular protocol
form a basis for the functions, features, and services of NBS-
standards
To further the development of commercial products that
standards, the NBS gives priority to the needs of U.S.
manufacturers who wish to market their products nationally
internationally, not just to the U.S. government. The
participates, therefore, in national and international
standards organizations toward the development of an
consensus based on United States needs. Specifications,
description techniques, testing methodologies, and test
developed by the NBS are used to further the
standardization process
Development of Testing
The National Bureau of Standards has laboratory activities
prototypes of draft protocol standards are implemented and tested in
variety of communications environments supporting
applications on different kinds and sizes of computers
Communications environments include, for example, global networks
local networks, and office system networks. Applications may,
example, include file transfer or message processing. The
purposes are to advance the state of the art in
methodologies for advanced computer networking technologies
determine protocol implementation correctness and performance
The NBS views testing as a cooperative research effort and works
other agencies, private-sector companies, and other countries in
development of methodologies. At this time, this cooperation
five network laboratories in other countries and over twenty
manufacturers
The testing methodologies developed at the NBS are well documented
and the testing tools themselves are developed with the objective
portability in mind. They are made available to many
engaged in protocol development and implementations
Assisting Users and
The NBS works directly with government agencies to help them
evolving network technologies effectively and apply international
government networking standards properly. When large amounts
assistance are required, the NBS provides it under contract
Assistance to industry is provided through cooperative
efforts and by the availability of NBS testing tools, industry
workshops, and cooperative demonstration projects. At this time,
NBS is working directly with over twenty computer manufacturers in
implementation of network protocol standards
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Consistent with overall goals, NBS standards developments, research
testing methodologies, and technical assistance are characterized
direct industry and
cooperation and mutual support
DOD
The DOD has unique needs that could be affected by the Transport
Internet Protocol layers. Although all data networks must have some
these capabilities, the DOD's needs for operational readiness
mobilization, and war-fighting capabilities are extreme. These
include the following
Survivability--Some networks must function, albeit at
performance, after many nodes and links have been destroyed
Security--Traffic patterns and data must be selectively
through encryption, access control, auditing, and routing
Precedence--Systems should adjust the quality ot service on the
of priority of use; this includes a capability to preempt services
cases of very high priority
Robustness--The system must not fail or suffer much loss of
because of unpredicted situations, unexpected loads, or misuse.
international crisis is the strongest test of robustness, since
system must operate immediately and with virtually full
when an international situation flares up unexpectedly
Availability--Elements of the system needed for operational
or fighting must be continuously available
Interoperability--Different elements of the Department must be able
"talk" to one another, often in unpredicted ways between parties
had not planned to interoperate
These operational needs reflect themselves into five technical
managerial needs
1. Functional and operational specifications (that is, will
protocol designs meet the operational needs?);
2. Maximum interoperability
3. Minimum procurement, development, and support costs
4. Ease of transition to new protocols;
5. Manageability and responsiveness to changing DOD requirements
These are the criteria against which DOD options for using the
transport and internet protocols should be evaluated
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Performance and
The performance and functionality of the protocols must provide
the many unique operational needs of the DOD. The
paragraphs discuss in some detail both these needs and the ways
can impact protocol design
Survivability includes protecting assets, hiding them, and
them for redundancy. It also includes endurance--the assurance
those assets that do survive can continue to perform in a
environment for as long as needed (generally months rather
hours); restoral--the ability to restore some of the damaged assets
operating status; and reconstitution--the ability to
fragmented assets into a surviving and enduring network
The DOD feels that an important reason for adopting international
commercial standards is that under cases of very widespread damage
its own communications networks, it would be able to support
functions by using those civil communications that survive.
would require interoperability up to the network layer, but
TCP nor TP-4 would be needed. The committee has not considered
extent to which such increased interoperability would
survivability through better restoral and reconstitution
Availability is an indication of how reliable the system and
components are and how quickly they can be repaired after a failure
Availability is also a function of how badly the system has
damaged. The DDN objective for system availability in peacetime
according to whether subscribers have access to l or 2 nodes of
DDN. For subscribers having access to only one node of the DDN,
objective is that the system be available 99.3 percent of the time
that is, the system will be unavailable for no more than 60 hours
year. For subscribers having access to 2 nodes, the objective is
the system be available 99.99 percent of the time, that is, the
will be unavailable for no more than one hour per year
Robustness is a measure of how well the system will
successfully in face of the unexpected. Robustness attempts to
or minimize system degradation because of user errors,
errors, unusual load patterns, inadequate interface specifications
and so forth. A well designed and tested system will limit the
caused by incorrect or unspecified inputs to affect only
performance of the specific function that is requested.
protocols are very complex and can be in very many "states",
robustness is an important consideration in evaluating
implementing protocols
Security attempts to limit the unauthorized user from gaining both
information communicated in the system and the patterns of
throughout the system. Security also attempts to prevent spoofing
the system: an agent attempting to appear as a legitimate user
insert false traffic, or deny services to users by repeatedly
system services
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Finally, Security is also concerned with making sure that
measures cannot seriously degrade the system, confuse its performance
or cause loss of security in other ways
Encryption of communication links is a relatively
element of security. It is widely used, fairly well understood
constantly undergoing improvement, and becoming less expensive.
the other hand, computer network security is a much newer field
considerably more complex. The ability of computer network
to provide security is a very critical issue. In the past decade
has been learned about vulnerability of computer operating systems
development of trusted systems, different levels of protection,
of proving that security has been achieved, and ways to
multilevel systems or a compartmented mode. This is a dynamic field
however, and new experience and analysis will probably place
requirements on network protocols
Crisis-performance needs are a form of global robustness. The
of a national security crisis is that it is fraught with
unexpected. Unusual patterns of communication traffic emerge
Previously unstressed capabilities become critical to
leaders. Individuals and organizations that had not
communicating must suddenly have close, secure, and
communications. Many users need information that they are not
exists, and if it does, they do not know where it is or how to get it
The development of widely deployed, interoperable computer
can provide important new capabilities for a crisis, particularly
there is some investment in preplanning, including the higher-
protocols that facilitate interoperability. Presidential
call for this. This will become a major factor in DOD's need
interoperability with other federal computer networks. The DOD,
one of the most affected parties, has good reason to be concerned
its network protocols will stand the tests of a crisis
In addition, there are performance and functionality features that
measures of the capability of the network when it is not damaged
stressed by unexpected situations. Performance includes
measures such as time delays, transmission integrity, data rates
efficiency, throughput, numbers of users, and other features
understood in computer 