RFC - 1693

An Extension to TCP : Partial Order Service

Original:	ftp://ftp.isi.edu/in-notes/rfc1693.txt
Authors:	T. Connolly [University of Delaware], P. Amer [University of Delaware], P. Conrad [University of Delaware]
Date:	November 1994
Category:	Experimental Standard

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Referred by:	23 RFC
Refers to:	5 RFC

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Status

This memo defines an Experimental Protocol for the Internet community. This memo does not specify an Internet standard of any kind. Discussion and suggestions for improvement are requested. Distribution of this memo is unlimited

IESG Note

Note that the work contained in this memo does not describe an Internet standard. The Transport AD and Transport Directorate do not recommend the implementation of the TCP modifications described. However, outside the context of TCP, we find that the memo offers a useful analysis of how misordered and incomplete data may be handled. See, for example, the discussion of Application Layer Framing by D. Clark and D. Tennenhouse in, "Architectural Considerations for a New Generation of Protocols", SIGCOM 90 Proceedings, ACM, September 1990.

Abstract

This RFC introduces a new transport mechanism for TCP based upon partial ordering. The aim is to present the concepts of partial ordering and promote discussions on its usefulness in network communications. Distribution of this memo is unlimited.

A service which allows partial order delivery and partial reliability is one which requires some, but not all objects to be received in the order transmitted while also allowing objects to be transmitted unreliably (i.e., some may be lost).

The realization of such a service requires, (1) communication and/or negotiation of what constitutes a valid ordering and/or loss-level, and (2) an algorithm which enables the receiver to ascertain the deliverability of objects as they arrive. These issues are addressed here - both conceptually and formally - summarizing the results of research and initial implementation efforts.

The authors envision the use of a partial order service within a connection-oriented, transport protocol such as TCP providing a further level of granularity to the transport user in terms of the type and quality of offered service. This RFC focuses specifically on extending TCP to provide partial order connections.

The idea of a partial order service is not limited to TCP. It may be considered a useful option for any transport protocol and we encourage researchers and practitioners to investigate further the most effective uses for partial ordering whether in a next-generation TCP, or another general purpose protocol such as XTP, or perhaps within a "special purpose" protocol tailored to a specific application and network profile.

Finally, while the crux of this RFC relates to and introduces a new way of considering object ordering, a number of other classic transport mechanisms are also seen in a new light - among these are reliability, window management and data acknowledgments.

Keywords: partial order, quality of service, reliability, multimedia, client/server database, Windows, transport protocol

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