OSI IS-IS Intra-domain Routing Protocol
RFC 1142

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Network Working Group                                     D. Oran, Editor
Request for Comments: 1142                        Digital Equipment Corp.
                                                            February 1990

                OSI IS-IS Intra-domain Routing Protocol
 
Status of this Memo

   This RFC is a republication of ISO DP 10589 as a service to the
   Internet community.  This is not an Internet standard.
   Distribution of this memo is unlimited.
        

NOTE:  This is a bad ASCII version of this document.  The official
document is the PostScript file, which has the diagrams in place.
Please use the PostScript version of this memo.

ISO/IEC DIS 10589
 
Information technology Telecommunications and information exchange
between systems Interme diate system to Intermediate system
Intra-Domain routeing exchange protocol for use in Conjunction with
the Protocol for providing the Connectionless- mode Network Service
(ISO 8473) Technologies de l'information Communication de donnies et
ichange d'information entre systhmes Protocole intra-domain de routage
d'un systhme intermediare ` un systhme intermediare ` utiliser
conjointement avec le protocole fournissant le service de riseau en
mode sans connexion (ISO 8473) UDC 00000.000 : 000.0000000000
Descriptors:
 
Contents
        Introduction            iv
        1       Scope and Field of Application  1
        2       References      1
        3       Definitions     2
        4       Symbols and Abbreviations       3
        5       Typographical Conventions       4
        6       Overview of the Protocol        4
        7       Subnetwork Independent Functions        9
        8       Subnetwork Dependent Functions  35
        9       Structure and Encoding of PDUs  47
        10      System Environment      65
        11      System Management       67
        12      Conformance     95
        Annex A         PICS Proforma   99
        Annex B         Supporting Technical Material   105
        Annex C         Implementation Guidelines and Examples  109
        Annex D         Congestion Control and Avoidance        115
 
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 re quired to achieve such
interconnection.  This Protocol is positioned with respect to other
related standards by the layers defined in the ISO 7498 and by the
structure defined in the ISO 8648. In particular, it is a protocol of
the Network Layer. This protocol permits Intermediate Systems within a
routeing Domain to exchange configuration and routeing information to
facilitate the operation of the route ing and relaying functions of
the Network Layer.  The protocol is designed to operate in close
conjunction with ISO 9542 and ISO 8473.  ISO 9542 is used to establish
connectivity and reachability between End Systems and Inter mediate
Systems on individual Subnetworks. Data is carried by ISO 8473.  The
related algo rithms for route calculation and maintenance are also
described.  The intra-domain ISIS routeing protocol is intended to
support large routeing domains consisting of combinations of many
types of subnetworks. This includes point-to-point links, multipoint
links, X.25 subnetworks, and broadcast subnetworks such as ISO 8802
LANs.  In order to support large routeing domains, provision is made
for Intra-domain routeing to be organised hierarchically. A large
domain may be administratively divided into areas.  Each system
resides in exactly one area. Routeing within an area is referred to as
Level 1 routeing. Routeing between areas is referred to as Level 2
routeing.  Level 2 Intermediate systems keep track of the paths to
destination areas. Level 1 Intermediate systems keep track of the
routeing within their own area. For an NPDU destined to another area,
a Level 1 Intermediate system sends the NPDU to the nearest level 2 IS
in its own area, re gardless of what the destination area is. Then the
NPDU travels via level 2 routeing to the destination area, where it
again travels via level 1 routeing to the destination End System.
 
Information technology

Telecommunications and information exchange between systems
Intermediate system to Intermediate system Intra-Domain routeing
exchange protocol for use in Conjunction with the Protocol for
providing the Connectionless-mode Network Service (ISO 8473)
 
1 Scope and Field of Application

This International Standard specifies a protocol which is used by
Network Layer entities operating ISO 8473 in In termediate Systems to
maintain routeing information for the purpose of routeing within a
single routeing domain. The protocol herein described relies upon the
provision of a connectionless-mode underlying service.11See ISO 8473
and its Addendum 3 for the mechanisms necessary to realise this
service on subnetworks based on ISO 8208, ISO 8802, and the OSI Data
Link Service.
 
This Standard specifies: 

a)procedures for the transmission of configuration and 
routeing information between network entities resid
ing in Intermediate Systems within a single routeing 
domain; 

b)the encoding of the protocol data units used for the 
transmission of the configuration and routeing infor