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EXECUTIVE SUMMARY Computer communication networks have become a very important part of military and commercial operations. Indeed, the nation is becoming depen- dent 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 redated to protocol standardization. This report is concerned primarily with recom- mendations 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.] These efforts led to the development of modern packet-switched network design concepts. Transmission between computers is generally ac- complished by packet switching using strict protocols for the control and exchange of messages. The Advanced Research Projects Agency network (ARPANET), implemented in the early l970s, provided a testing ground for research on communications protocols. In 1978, after four years of devel- opment, the DOD promulgated versions of its Transmission Control Protocol (TCP) and an Internet Protocol (IP) and mandated their use as standards within the DOD. TOP 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 TOP greatly increased the momentum within the DOD toward establishing inter- operability between networks within the DOD. International Standards Qrganization's Transport Protocol The NBS Institute for Computer Sciences and Technology (ICST), in co- operation with the DOD, many industrial firms, and the International Stan- dards Organization (ISO), has developed a new international standard iThe Advanced Research Projects Agency (ARPA) was reorganized and became the Defense Advanced Research Projects Agency (DARPA) in 1973. X1

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Transport Protocol (TP-4) and a new Internetwork Protocol.2 These pro- tocols will soon be available as commercial products. Although in part derived from TOP, the new protocols are not compatible with TCP.3 The U.S. standards organizations are supporting TP-4 in international opera- tions, and the Department of Commerce is proposing TP-4 as a Federal Information Processing Standard (F1PS) for use by al] 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, mobiliza- tion, 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 fad] or suffer much loss of cap- ability because of unpredicted situations, unexpected loads, or misuse. An international crisis is the strongest test of robust- ness, since the system must operate immediately and with virtua1- ly full performance when an international situation flares up unexpectedly. Availability--Elements of the system needed for operational read- iness 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. 2The ISO Transport Protocol and ISO Internetwork Protocol became Draft International Standards in September 1983 and April 1984, respec- tive~y. Commercial vendors normally consider Draft International Stan- dards to be ready for implementation. 3Except where noted, the abbreviation TOP generally refers to both the DOD's Transmission Control Protocol and its Internet Protocol. Simi- larly, the abbreviation TP-4 refers to both the ISO Transport Protocol - class 4 and its Internetwork Protocol. (Transport Protocol classes O to 3 are used for special purposes not related to those of this study.) X 1 1

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These operational needs reflect themselves into five technical or manage- rial 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 trans- port 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 appli- cations 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 TOP for the Defense Com- munication System's Defense Data Network (DON), unless waivers are granted. In addition, the Defense Communication Agency (DCA) is estau- lishing 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 operati onal need. It is very important, however, to recognize that functional interop- erability 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: l. Internet, using IP; 2. Transport, using TOP; 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, we]~-defined mission. . . x ~ ~ ~

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The DOD Intelligence Information System (DODITS) 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 com- munities of interest. Examples of such operations are headquar- ters' 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 applica- tions 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 wild 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 tnat a great deal of care and experience in protocol development have gone into gener- ating 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 TOP to TP-4, new applica- tions can be written to use either protocol with a similar level of effort. The TOP 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 TOP currently has the edge in maturity of implementation, TP-4 is gaining rapidly due to the worldwide support for and acceptance of the x~v

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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 im- p~ementations 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 net- works. In contrast, TP-4 has not yet been implemented in any large opera- tional 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 Interned 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 stan- dards. The reasons for this progress are twofold: strong market demands stemming from the growing integration of communications and data process- ing 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 mode] upon which the ISO trans- port 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 net- works, and this will increase by 50 to lOO 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) sys- tems are expanding and will shortly be combined. The Strategic Air Com- mand Digital Information Network (SACDIN) and DODITS 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 198Os, and they will become interoperable and multilevel secure using an advanced technology now under development. If these plans are imple- mented on schedule, a delay of several years in moving to TP-4 would mean that the DOD networks in the late 198Os would be virtually all TCP-based. Subsequent conversion to international standards would be very expensive xv

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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 depart- ment's operational needs. The major advantages are as follows: Costs to the DOD for development, production, and maintenance are significantly lower because (~) 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 soft- ware and hardware product line. Thus the DOD may be able even- tually 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 main- tenance of products, the department can use its scarce manage- ment 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 s av i ngs should range from 30 to SO 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 TOP 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 mini- mize 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 ~ The first option is for the DOD to immediately modify its current transport policy statement to specify TP-4 as a costandard along with TOP. In addition, the DOD would develop a military specification for xvi

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TP-4 that would also cover DOD requirements for discretionary options allowed under the NDS 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 TOP and new networks firmly committed to the use of TCP-based systems could continue to acquire implementations of TOP. 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 advan- tageous 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 mu1tivendor 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 TOP and TP-4 would coexist for some time, several capabilities that facilitate interoper- ability 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 TOP 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 in- volve development of TP-4 implementations and their installation. This option differs from Option ~ primarily in postponi ng 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, however, should Validation means a systematic and thorough state-of-the-art testing of the products to assure that all technical specifications are being achieved. xvl 1

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proceed with those provisions of Option ~ that may be completed in paral- lel with the demonstration. Early issuance of a TP-4 military specifica- tion, 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 inter- national arena and, with the National Bureau of Standards, work on means to transfer data between the two protocol systems. Testing and evalua- tion 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 ~ is to obtain the benefits of standard commercial products in the communication protocol area at an early date. Benefits include smaller development, procure- ment, and support costs; more timely updates; and a wider product avail- ability. By immediately committing to TP-4 as a costandard for new sys- tems, Option ~ 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 ~ 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 commerc i al products . Un i ~ procurement costs probably would be lower than with Option ~ 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 i, because testing and demonstration of the suitability for military use wild 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 longest interval of mixed TCP and TP-4 oper- ations would occur. In addition, interoperability with external networks through standardization would be delayed. . xv ~ ~ ~

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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 could be in use (one with which the DOD already has much exper- ience), and because the DOD would be in complete control of system evolu- tion. Procurement costs for TOP systems would remain high compared with standard ISO protocol products, however, and availability of implementa- tions for new systems and releases would remain limited. External inter- operability with non-DOD systems would be limited and inefficient. In summary, Option ~ 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 interoper- ability 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. Ax

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