rfc926.txt

RFC 相关的技术文档

Network Working Group                                                ISO
Request for Comments: 926                                  December 1984

 
 
    Protocol for Providing the Connectionless-Mode Network Services
 
                         (Informally - ISO IP)

                              ISO DIS 8473

Status of this Memo:

 This document is distributed as an RFC for information only.  It does
 not specify a standard for the ARPA-Internet.  Distribution of this
 memo is unlimited.

Note:

 This document has been prepared by retyping the text of ISO DIS 8473 of
 May 1984, which is currently undergoing voting within ISO as a Draft
 International Standard (DIS).  Although this RFC has been reviewed
 after typing, and is believed to be substantially correct, it is
 possible that typographic errors not present in the ISO document have
 been overlooked.

 Alex McKenzie
 BBN





RFC 926                                                    December 1984





RFC 926                                                    December 1984


                           TABLE OF CONTENTS

 1   SCOPE AND FIELD OF APPLICATION........................ 2

 2   REFERENCES............................................ 3

 3   DEFINITIONS........................................... 4
 3.1   Reference Model Definitions......................... 4
 3.2   Service Conventions Definitions..................... 4
 3.3   Network Layer Architecture Definitions.............. 4
 3.4   Network Layer Addressing Definitions................ 5
 3.5   Additional Definitions.............................. 5

 4   SYMBOLS AND ABBREVIATIONS............................. 7
 4.1   Data Units.......................................... 7
 4.2   Protocol Data Units................................. 7
 4.3   Protocol Data Unit Fields........................... 7
 4.4   Parameters.......................................... 8
 4.5   Miscellaneous....................................... 8

 5   OVERVIEW OF THE PROTOCOL.............................. 9
 5.1   Internal Organization of the Network Layer.......... 9
 5.2   Subsets of the Protocol............................. 9
 5.3   Addressing......................................... 10
 5.4   Service Provided by the Network Layer.............. 10
 5.5   Service Assumed from the Subnetwork Service
    Provider.............................................. 11
 5.5.1   Subnetwork Addresses............................. 12
 5.5.2   Subnetwork Quality of Service.................... 12
 5.5.3   Subnetwork User Data............................. 13
 5.5.4   Subnetwork Dependent Convergence Functions....... 13
 5.6   Service Assumed from Local Evironment.............. 14

 6   PROTOCOL FUNCTIONS................................... 16
 6.1   PDU Composition Function........................... 16
 6.2   PDU Decomposition Function......................... 17
 6.3   Header Format Analysis Function.................... 17
 6.4   PDU Lifetime Control Function...................... 18
 6.5   Route PDU Function................................. 18
 6.6   Forward PDU Function............................... 19
 6.7   Segmentation Function.............................. 19
 6.8   Reassembly Function................................ 20
 6.9   Discard PDU Function............................... 21






ISO DIS 8473 (May 1984)                                         [Page i]





RFC 926                                                    December 1984


 6.10   Error Reporting Function.......................... 22
 6.10.1   Overview........................................ 22
 6.10.2   Requirements.................................... 23
 6.10.3   Processing of Error Reports..................... 24
 6.11   PDU Header Error Detection........................ 25
 6.12   Padding Function.................................. 26
 6.13   Security.......................................... 26
 6.14   Source Routing Function........................... 27
 6.15   Record Route Function............................. 28
 6.16   Quality of Service Maintenance Function........... 29
 6.17   Classification of Functions....................... 29

 7   STRUCTURE AND ENCODING OF PDUS....................... 32
 7.1   Structure.......................................... 32
 7.2   Fixed Part......................................... 34
 7.2.1   General.......................................... 34
 7.2.2   Network Layer Protocol Identifier................ 34
 7.2.3   Length Indicator................................. 35
 7.2.4   Version/Protocol Identifier Extension............ 35
 7.2.5   PDU Lifetime..................................... 35
 7.2.6   Flags............................................ 36
 7.2.6.1   Segmentation Permitted and More Segments Flags. 36
 7.2.6.2   Error Report Flag.............................. 37
 7.2.7   Type Code........................................ 37
 7.2.8   PDU Segment Length............................... 37
 7.2.9   PDUChecksum...................................... 38
 7.3   Address Part....................................... 38
 7.3.1   General.......................................... 38
 7.3.1.1     Destination and Source Address Information... 39

 7.4   Segmentation Part.................................. 40
 7.4.1   Data Unit Identifier............................. 41
 7.4.2   Segment Offset................................... 41
 7.4.3   PDU Total Length................................. 41
 7.5   Options Part....................................... 41
 7.5.1   General.......................................... 41
 7.5.2   Padding.......................................... 43
 7.5.3   Security......................................... 43
 7.5.4   Source Routing................................... 44
 7.5.5   Recording of Route............................... 45
 7.5.6   Quality of Service Maintenance................... 46
 7.6   Priority........................................... 47







ISO DIS 8473 (May 1984)                                        [Page ii]





RFC 926                                                    December 1984


 7.7   Data Part.......................................... 47
 7.8   Data (DT) PDU...................................... 49
 7.8.1   Structure........................................ 49
 7.8.1.1   Fixed Part..................................... 50
 7.8.1.2   Addresses...................................... 50
 7.8.1.3   Segmentation................................... 50
 7.8.1.4   Options........................................ 50
 7.8.1.5   Data........................................... 50
 7.9   Inactive Network Layer Protocol.................... 51
 7.9.1   Network Layer Protocol Id........................ 51
 7.9.2   Data Field....................................... 51
 7.10   Error Report PDU (ER)............................. 52
 7.10.1   Structure....................................... 52
 7.10.1.1   Fixed Part.................................... 53
 7.10.1.2   Addresses..................................... 53
 7.10.1.3   Segmentation.................................. 53
 7.10.1.4   Options....................................... 54
 7.10.1.5   Reason for Discard............................ 54
 7.10.1.6   Error Report Data Field....................... 55

 8   FORMAL DESCRIPTION................................... 56
 8.1   Values of the State Variable....................... 57
 8.2   Atomic Events...................................... 57
 8.2.1   N.UNITDATA_request and N.UNITDATA_indication..... 57
 8.2.2   SN.UNITDATA_request and SN.UNITDATA_indication... 58
 8.2.3   TIMER Atomic Events.............................. 59
 8.3   Operation of the Finite State Automation........... 59
 8.3.1   Type and Constant Definitions.................... 61
 8.3.2   Interface Definitions............................ 65
 8.3.3   Formal Machine Definition........................ 67

 9   CONFORMANCE.......................................... 84
 9.1   Provision of Functions for Conformance............. 84
















ISO DIS 8473 (May 1984)                                       [Page iii]





RFC 926                                                    December 1984



















































ISO DIS 8473 (May 1984)                                        [Page iv]





RFC 926                                                    December 1984


INTRODUCTION

 This Protocol is one of a set of International Standards produced to
 facilitate the interconnection of open systems. The set of standards
 covers the services and protocols required to achieve such
 interconnection.

 This Protocol Standard is positioned with respect to other related
 standards by the layers defined in the Reference Model for Open Systems
 Interconnection (ISO 7498). In particular, it is a protocol of the
 Network Layer. The Protocol herein described is a Subnetwork
 Independent Convergence Protocol combined with relay and routing
 functions as described in the Internal Organization of the Network
 Layer (ISO iiii). This Protocol provides the connectionless-mode
 Network Service as defined in ISO 8348/DAD1, Addendum to the Network
 Service Definition Covering Connectionless-mode Transmission, between
 Network Service users and/or Network Layer relay systems.

 The interrelationship of these standards is illustrated in Figure 0-1
 below:

      ______________OSI Network Service Definition______________  
                    |                             ^               
                                                  |               
                    |                             |               
         Protocol     Reference to aims __________|               
                    |                                             
                                                                  
      Specification | Reference to assumptions ___                
                                                  |               
                    |                             |               
                                                  |               
                    |                             |               
                                                  |               
                    |                             v               
      ______________Subnetwork Service Definition(s) ___________  

              Figure 0-1.  Interrelationship of Standards











ISO DIS 8473 (May 1984)                                         [Page 1]





RFC 926                                                    December 1984


1  SCOPE AND FIELD OF APPLICATION

 This International Standard specifies a protocol which is used to
 provide the Connectionless-mode Network Service as described in ISO
 8348/DAD1, Addendum to the Network Service Definition Covering
 Connectionless-mode Transmission. The protocol herein described relies
 upon the provision of a connectionless-mode subnetwork service.

 This Standard specifies:

  a)  procedures for the connectionless transmission of data and control
      information from one network-entity to a peer network-entity;

  b)  the encoding of the protocol data units used for the transmission
      of data and control information, comprising a variable-length
      protocol header format;

  c)  procedures for the correct interpretation of protocol control
      information; and

  d)  the functional requirements for implementations claiming
      conformance to the Standard.

 The procedures are defined in terms of:

  a)  the interactions among peer network-entities through the exchange
      of protocol data units;

  b)  the interactions between a network-entity and a Network Service
      user through the exchange of Network Service primitives; and

  c)  the interactions between a network-entity and a subnetwork service
      provider through the exchange of subnetwork service primitives.
















ISO DIS 8473 (May 1984)                                         [Page 2]





RFC 926                                                    December 1984


2  REFERENCES

 ISO 7498       Information Processing Systems - Open Systems
                Interconnection - Basic Reference Model

 DP 8524        Information Processing Systems - Open Systems
                Interconnection - Addendum to ISO 7498 Covering
                Connectionless-Mode Transmission

 DIS 8348       Information Processing Systems - Data Communications -
                Network Service Definition

 ISO 8348/DAD1  Information Processing Systems - Data Communications -
                Addendum to the Network Service Definition Covering
                Connectionless-Mode Transmission

 ISO 8348/DAD2  Information Processing Systems - Data Communications -
                Addendum to the Network Service Definition Covering
                Network Layer Addressing

 DP iiii        Information Processing Systems - Data Communications -
                Internal Organization of the Network Layer

 DP 8509        Information Processing Systems - Open Systems
                Interconnection - Service Conventions

 ISO TC97/SC16  A Formal Description Technique based on an N1825
                Extended State Transition Model





















ISO DIS 8473 (May 1984)                                         [Page 3]





RFC 926                                                    December 1984


SECTION ONE.  GENERAL

3  DEFINITIONS

 3.1  Reference Model Definitions

  This document makes use of the following concepts defined in ISO 7498:

   a) Network layer
   b) Network service
   c) Network service access point
   d) network service access point address
   e) Network entity
   f) Routing
   f) Service
   h) Network protocol
   i) Network relay