ISO Transport Class 2 Non-use of Explicit Flow Control over TCP RFC1006 extension
RFC 1859

Document Type RFC - Informational (October 1995; No errata)
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Network Working Group                                        Y. Pouffary
Request For Comments: 1859                 Digital Equipment Corporation
Category: Informational                                     October 1995

    ISO Transport Class 2 Non-use of Explicit Flow Control over TCP
                           RFC1006 extension

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

Table of Contents

   1. Introduction - General recommendations.......................2
   2. The protocol.................................................3
   2.1 TCP service as a Network Service - The Primitives...........3
   2.2 Connection Establishment....................................4
   2.3 Data Transfer...............................................5
   2.4 Connection Release..........................................6
   3. Packet Format................................................6
   4. DIGITAL DECnet over TCP/IP...................................8
   Acknowledgements................................................9
   References......................................................9
   Author's Address................................................9

1. Introduction - General recommendations

   This document is an extension to STD35, RFC1006, a standard for the
   Internet community. The document does not duplicate the protocol
   definitions contained in RFC1006 and in International Standard ISO
   8073.  It supplements that information with the description of how to
   implement ISO Transport Class 2 Non-use of Explicit Flow Control on
   top of TCP.

   The document should be used in conjunction with the RFC1006 and ISO
   8073.

   The RFC1006 standard defines how to implement ISO 8073 Transport
   Class 0 on top of TCP. This memo defines how to implement ISO 8073
   Transport Class 2 Non-use of Explicit Flow Control on top of TCP.
   Like ISO Transport Class 0, Class 2 Non-use of Explicit Flow Control
   provides basic connection with minimal overhead.

   A Transport protocol class is selected for a particular Transport
   connection based upon the characteristics of the lower layers and the

Pouffary                     Informational                      [Page 1]
RFC 1859            ISO Transport and Flow Control          October 1995

   requirements of the upper layer. Use of class 2 Non-use of Explicit
   Flow Control is suitable when the use of separate virtual data
   channels for normal and expedited Data are desirable or when an
   explicit disconnection of the Transport connection is desirable.

   Hosts which choose to implement this extension are expected to listen
   on the well-known TCP port number 399.

   It is recommended that the well-known RFC1006 TCP port 102 not be
   used. This recommendation is done to minimise impact to an existing
   RFC1006 implementation.

   The memo also describes the use of this extension within the DIGITAL
   Network Architecture (DNA).

2. The protocol

   The protocol specified by this memo is fundamentally equivalent to
   the protocol ISO 8073 Transport Class 2 Non-use of Explicit Flow
   Control, with the following extensions:

   - Expedited Data service is supported.

   - Splitting and Recombining may be used for Expedited Data
     transmission.

   - The Network Service used is provided by TCP.

   The ISO 8073 Transport protocol Class 2 allows Multiplexing. It is
   recommended that this capability not be use for performance reasons.

   The ISO 8073 Transport protocol exchanges information between peers
   in discrete units of information called transport protocol data units
   (TPDUs).  The protocol defined in this memo encapsulates these TPDUs
   in discrete units called TPKTs.  The structure of these TPKTs and
   their relationship to TPDUs are discussed in the next sections.

2.1 TCP service as a Network Service - The Primitives

   The mapping between the TCP service primitives and the service
   primitives expected by ISO 8073 Transport when operation over
   Connection-oriented network service is straightforward.

Pouffary                     Informational                      [Page 2]
RFC 1859            ISO Transport and Flow Control          October 1995

   Note: The following description of the mapping is a repeat from the
   RFC1006 standard.

   network service                 TCP
   ---------------                 ---
   CONNECTION ESTABLISHMENT

           N-CONNECT.REQUEST       open completes

           N-CONNECT.INDICATION    listen (PASSIVE open) finishes

           N-CONNECT.RESPONSE      listen completes

           N-CONNECT.CONFIRMATION  open (ACTIVE open) finishes

   DATA TRANSFER

           N-DATA.REQUEST          send data

           N-DATA.INDICATION       data ready followed by read data

   CONNECTION RELEASE

           N-DISCONNECT.REQUEST    close
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