BS ISO/IEC 10028:1993

Foreword
Introduction
1 Scope
2 Normative references
3 Definitions
4 Abbreviations and names of NILS elementary sequences
5 The model of relaying by an intermediate system
6 Features of the Network internal layer service
7 Primitives and parameters of the Network internal
   layer service
8 Sequences of primitives
9 Autonomous behaviour of relaying components
Annexes
A Sequence of primitives at one NISAP
B Architectural framework (ISO 7498 and ISO 8648)
C Examples of typical sequences of NILS primitives

Defines the abstract operation of the relaying functions of a Network entity in an intermediate system, as needed to support the OSI connection mode Network service. Coverage includes; the model of relaying by an intermediate system; primitives and parameters of the network internal layer service; autonomous behaviour of relaying components. Also includes detailed definitions and annexes.

This International Standard defines the abstract operation of the relaying functions of a Network entity in an intermediate system, as needed to support the OSI connection-mode Network service.

As the principal means for expressing the definition, the concept of the Network Internal Layer Service is used. This is similar to an OSI layer service, but adapted to expressing the invariants of the information flow within and throughout the layer, rather than just the external functionality of the layer provided between two service access points.

The definition includes the invocation of Network routing functions as a necessary element of the Network relaying functions, but it does not specify how those routing functions are to be realized.

The definition of Network relaying functions applies both to a subnetwork supporting all elements of the Network Service (as defined in ISO8648), and to a Network relay system interconnecting two subnetworks according to any of the three approaches defined in ISO8648. In the case of the hop-by-hop harmonization approach to interconnection, the definition of Network relaying functions applies to the result of harmonizing the subnetwork service(s) to the level of the Network Service. The harmonization functions, which require protocol mechanisms to be specified, are outside the scope of this International Standard.

This International Standard is intended for use in guiding the design and application of real interworking units and real subnetworks (eg, local area networks and private packet switched networks) which are to support the OSI NS. It is also intended for use in the development of standards for the Network layer, to ensure that the requirements deriving from the need for Network layer relaying are taken into account.

There are no requirements for conformance to this International Standard.

NOTE— Conformance requirements relating to Network layer relaying are to be found in the spécifications for mappings between the Network Internal Layer Service and Network protocols.