An Extension to TCP : Partial Order Service
RFC 1693

Document Type RFC - Historic (November 1994; No errata)
Obsoleted by RFC 6247
Last updated 2013-03-02
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Network Working Group                                       T.  Connolly
Request for Comments: 1693                                       P. Amer
Category: Experimental                                         P. Conrad
                                                  University of Delaware
                                                           November 1994

              An Extension to TCP : Partial Order Service

Status of This Memo

   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.

Introduction

   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.

Connolly, Amer & Conrad                                         [Page 1]
RFC 1693       An Extension to TCP: Partial Order Service  November 1994

   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

Table of Contents

   1. Introduction and motivation ..................................  3
   2. Partial Order Delivery .......................................  4
   2.1 Example 1: Remote Database ..................................  4
   2.2 Example 2: Multimedia .......................................  8
   2.3 Example 3: Windows Screen Refresh ...........................  9
   2.4 Potential Savings ........................................... 10
   3. Reliability vs. Order ........................................ 12
   3.1 Reliability Classes ......................................... 13
   4. Partial Order Connection ..................................... 15
   4.1 Connection Establishment .................................... 16
   4.2 Data Transmission ........................................... 19
   4.2.1 Sender .................................................... 22
   4.2.2 Receiver .................................................. 25
   5. Quantifying and Comparing Partial Order Services ............. 30
   6. Future Direction ............................................. 31
   7. Summary ...................................................... 32
   8. References ................................................... 34
   Security Considerations ......................................... 35
   Authors' Addresses .............................................. 36

Connolly, Amer & Conrad                                         [Page 2]
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