Octet Sequences for Upper-Layer OSI to Support Basic Communications Applications
RFC 1698

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Network Working Group                                         P. Furniss
Request for Comments: 1698                                    Consultant
Category: Informational                                     October 1994

                  Octet Sequences for Upper-Layer OSI
              to Support Basic Communications Applications

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.

Abstract

   This document states particular octet sequences that comprise the OSI
   upper-layer protocols (Session, Presentation and ACSE) when used to
   support applications with "basic communications requirements". These
   include OSI application protocols such as X.400 P7 and Directory
   Access Protocol, and "migrant" protocols, originally defined for use
   over other transports.

   As well as the octet sequences which are the supporting layer headers
   (and trailers) around the application data, this document includes
   some tutorial material on the OSI upper layers.

   An implementation that sends the octet sequences given here, and
   interprets the equivalent protocol received, will be able to
   interwork with an implementation based on the base standard, when
   both are being used to support an appropriate application protocol.

Table of Contents

   1. Introduction ...................................................2
   2. General ........................................................3
    2.1 Subdivisions of "basic communication applications" ...........3
    2.2 Conformance and interworking .................................5
    2.3 Relationship to other documents ..............................5
   3. Contexts and titles ............................................6
    3.1 The concepts of abstract and transfer syntax .................6
    3.2 Use of presentation context by cookbook applications..........7
    3.3 Processing Presentation-context-definition-list ..............8
    3.4 Application context ..........................................9
    3.5 APtitles and AEqualifiers ....................................9
   4. What has to be sent and received ..............................10
    4.1 Sequence of OSI protocol data units used ....................10
    4.2 Which OSI fields are used ...................................12

Furniss                                                         [Page 1]
RFC 1698             ThinOSI Upper-Layers Cookbook          October 1994

    4.3 Encoding methods and length fields ..........................14
    4.3.1 Session items .............................................14
    4.3.2 ASN.1/BER items (Presentation and ACSE) ...................14
    4.4 BER Encoding of values for primitive datatypes ..............15
    4.5 Unnecessary constructed encodings ...........................16
   5. Notation ......................................................16
   6. Octet sequences ...............................................17
    6.1 Connection request message ..................................17
    6.2 Successful reply to connection setup ........................20
    6.3 Connection rejection ........................................22
    6.4 Data-phase TSDU .............................................23
    6.5 Closedown  - release request ................................24
    6.6 Closedown - release response ................................25
    6.7 Deliberate abort ............................................25
    6.8 Provider abort ..............................................27
    6.9 Abort accept ................................................27
   7. References ....................................................27
   8. Other notes ...................................................28
   9. Security Considerations .......................................29
   10. Author's Address .............................................29

1.  Introduction

   The upper-layer protocols of the OSI model are large and complex,
   mostly because the protocols they describe are rich in function and
   options. However, for support of most applications, only a limited
   portion of the function is needed. An implementation that is not
   intended to be a completely general platform does not need to
   implement all the features. Further, it need not reflect the
   structuring of the OSI specifications - the layer of the OSI model
   are purely abstract.

   This document presents the protocol elements required by the OSI
   upper layers when supporting a connection-oriented application with
   only basic communication requirements - that is to create a
   connection, optionally negotiate the data representation,
   send/receive data, close a connection and abort a connection.
   Optionally, data may be sent on the connection establishment, closing
   and abort messages.

   In this document, the protocol elements needed are given in terms of