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X3S3.3/90-85R 20 April, 1990 ACCREDITED STANDARDS COMMITTEE X3 - INFORMATION PROCESSING SYSTEMS Proposed Standards Development Project for TRANSMISSION CONTROL PROTOCOL (TCP) SECRETARIAT: Computer and Business Equipment Manufacturers Association (CBEMA) Page 2 1 IDENTIFICATION OF PROPOSED PROJECT 1.1 Title: TRANSMISSION CONTROL PROTOCOL 1.2 Proposer: Task Group X3S3.3 (Network and Transport Layers) A. Lyman Chapin, Chairman Data General Corporation 4400 Computer Drive Westborough, MA 01580 (508) 870-6056 1.3 Date Submitted: 20 April, 1990 Page 3 2 JUSTIFICATION OF PROPOSED STANDARD 2.1 Needs The evolution of the Transmission Control Protocol (universally referred to as "TCP") began with the publication of Request for Comment (RFC) number 675 by Vinton Cerf in 1974, the result of work that Cerf and Robert Kahn performed in 1973 as part of Kahn's Internet program at the DARPA Information Processing Techniques Office. In its original form, TCP version 1 included the functions of both an end-to-end transport protocol and a connectionless internetwork protocol. Version 2 was published as Internet Experi- mental Note (IEN) 5 in 1977; Version 3 (which separated the tran- sport and internetwork functions, retaining the transport functions in TCP and moving the internetwork functions to a new protocol, the Internetwork Protocol (IP)) as IEN 21 in 1978; and Version 4 as IEN 40 in 1978. Version 4 became the basis for the TCP Internet Standard, published as RFC 793 in 1981, and for the US Department of Defense Military Standard for TCP, MIL-STD-1778, published in August 1983. Although there have been no further official versions of TCP, none of the three Version 4 documents (IEN 40, RFC 793, and MIL-STD-1778) is considered today to be a definitive specification of TCP, which has continued to evolve. The widespread availability of TCP after its incorporation into the University of California/Berkeley version of the Unix operating system in 1983 (release 4.2 of the Berkeley Software Distribution, commonly referred to as "4.2bsd") encouraged the development of many imple- mentation improvements to TCP. Current TCP implementations repre- sent a combination of the basic Version 4 internet standard, some or all of the extensions that have been documented since 1983 (in, for example, RFCs 813, 879, and 1072), and a set of agreements and conventions concerning the "best" way to implement TCP functions and algorithms, now documented in RFC 1122, "Requirements for Internet Hosts", which consolidates in a single document the implementation practices of the Internet community. The need for an American National Standard for TCP is based on the widespread market penetration and growing commercial importance of computer systems that use TCP for host-to-host communication. Users and vendors would benefit greatly from a consolidated speci- fication of TCP, drawn from the existing Internet Request for Comments (RFC) documentation, which could be used to evaluate the conformance of products that implement it and to place TCP in a formal context in which its relationship to other standard proto- Page 4 cols may be clearly established. 2.2 Recommended Scope of Standard The proposed standard will specify TCP as it is currently under- stood within the Internet engineering community. The scope of the proposed standards development project does not include the speci- fication of any function or feature that has not been accepted within the community that is currently implementing, deploying, and using TCP. 2.3 Existing Practice in Area of Proposed Standard The proposed standard will formalize accepted existing practice, based on existing documentation, in which TCP is used as the end-to-end transport protocol in conjunction with other protocols that are generally referred to as the "TCP/IP protocol suite". 2.4 Expected Stability of Proposed Standard Technological advance in the area of end-to-end transport protocols has been, and is expected to continue to be, very rapid. However, the architecture of TCP and the closely-related Internetwork Protocol is well understood and stable. New architectures for end-to-end communications are likely to generate entirely new sets of standards, rather than destabilize the standard for TCP. 3 DESCRIPTION OF PROPOSED PROJECT 3.1 Type of Document The proposed development project will produce an American National Standard for Transmission Control Protocol. 3.2 Definitions of Concepts and Special Terms Page 5 3.3 Expected Relationship with Approved X3 Reference Models The proposed standard will define a protocol that supports the end-to-end functions and capabilities associated with the Transport layer of the Open Systems Interconnection Reference Model (ISO 7498) architecture. It will not, however, define an "OSI Transport Layer Protocol". 3.4 Recommended Program of Work The program of work will consist of the preparation, from existing documentation concerning TCP, of a document that captures all of the currently accepted TCP practice, in a form that is as close to the existing internet documentation as the rules for the presenta- tion of American National Standards permit. 3.5 Resources The resources of Task Group X3S3.3, Network and Transport Layers, are expected to be available to carry out the program of work. X3S3.3 has 26 voting members, representing a broad spectrum of users and suppliers of computer and communications equipment and services. The resources of the Internet Activities Board, which administers the internet standards that apply to the operation of the internet, and of the Internet Engineering Task Force, which is responsible for the technical specification of TCP (and the other internet protocols), are also expected to be available. 3.6 Recommended X3 Development Technical Committee It is recommended that the proposed project, if approved, be assigned to Task Group X3S3.3, Network and Transport Layers, of X3 Technical Committee X3S3, Data Communications. The proposed project is closely related, both technically and administratively, to projects 332 and 674, which have previously been assigned to X3S3.3. 3.7 Anticipated Frequency and Duration of Meetings If the proposed project is pursued by task group X3S3.3, as recom- mended above, it is anticipated that the equivalent of half a day during each of the task group's 6 five-day meetings each year will Page 6 be devoted to work on the project. 3.8 Target Date for dpANS to X3 A draft proposal for an American National Standard Transmission Control Protocol could be conveyed to X3 by October 1, 1990. 3.9 Estimated Useful Life of Standard The useful life of the proposed standard coincides with the useful life of the set of internet standards that comprise the "TCP/IP protocol suite". This lifetime is expected to be very long, spanning at least several decades. 4 IMPLEMENTATION IMPACTS 4.1 Impact on Existing User Practices and Investments The proposed standard will formalize existing user practice in the area without modification. The impact of the proposed standard will therefore be limited to the salutary regularization of the documentation and points of reference for TCP. 4.2 Impact on Supplier Products and Support As above; with the additional benefit that suppliers of products that implement or use TCP will be able to focus their evaluation of TCP standard compliance requirements on a single reference point. 4.3 Techniques and Costs for Compliance Verification Verification of compliance with the proposed standard will require the development of test purposes and test suites in accordance with ISO 9646, "OSI Conformance Testing Methodology and Framework". The cost of conformance testing is expected to be similar to the costs associated with OSI Transport protocol conformance testing. Page 7 4.4 Legal Considerations No special legal issues are raised by the proposed project, which covers material that is non-proprietary and freely distributed. 5 CLOSELY RELATED STANDARDS ACTIVITIES 5.1 Existing Standards The proposed project will formalize the existing internet standard for TCP, for which the basic references are RFCs 793 and 1122. 5.2 X3 Standards Development Projects The proposed project is closely related to the work on the OSI Transport service and protocol under X3 projects 332 and 674. 5.3 X3/SPARC Study Groups The proposed project has no relationship to any existing X3/SPARC Study Group. 5.4 Other Related Domestic Standards Efforts The internet standards effort pursued by the Internet Engineering Task Force and its parent organization, the Internet Activities Board, is and will continue to be the source of technical input to the process of developing an American National Standard for TCP. 5.5 ISO Standards Development Projects There is no related ISO standards development project, and it is not anticipated that the proposed project will result in the initiation of any new work in ISO. Page 8 5.6 Other Related International Standards Development Projects As above. 5.7 Recommendations for Coordinating Liaison None. 5.8 Recommendations for Close Liaison Close liaison, in the form of joint development work and/or joint meetings, with the Internet Activities Board and the Internet Engineering Task Force (and/or its appropriate working groups) will be essential.