rfc942.txt

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  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.

  

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(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.)

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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.





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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



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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

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RFC 942                                                    February 1985
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 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


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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,

  
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(4)  Validation means a systematic and thorough state-of-the-art testing
of the products to assure that all technical specifications are being
achieved.

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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