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Wireless Future - Telenor

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Terje Henriksen (58) is Research<br />

Scientist at <strong>Telenor</strong> R&D.<br />

He has been involved in standardization<br />

and R&D projects<br />

within the area of network level<br />

modelling since 1991; from 1996<br />

to 2001 as the rapporteur for<br />

Question 18 of SG4 within the<br />

ITU-T.<br />

terje-fredrik.henriksen<br />

@telenor.com<br />

Telektronikk 1.2001<br />

Network Level Modeling in ITU<br />

TERJE HENRIKSEN<br />

1 Introduction<br />

In the early nineties, influenced by the emerging<br />

object oriented methodology, SG XVIII (later<br />

SG 13) in ITU developed the overall network<br />

architecture defined in G.805 [1]. It provides a<br />

high level view of the network function based on<br />

a small set of architectural entities (functional<br />

blocks) interconnected via reference points. Two<br />

main network representations may be provided<br />

on the basis of this architecture:<br />

• Topology 1) in terms of links, subnetworks and<br />

access groups 2) ;<br />

• Connectivity in terms of trails, link connections,<br />

subnetwork connections, ports and reference<br />

points.<br />

The topological view describes the geographical<br />

distribution of the resources of a layer network.<br />

The access group is a container for a number of<br />

co-located access points. The subnetwork represents<br />

the routing capabilities within a site or<br />

grouping of sites and the link represents the<br />

transport capacity between subnetworks. Layering<br />

is a method for splitting the overall transport<br />

function into a hierarchy of layer networks on<br />

top of each other, each of which utilizing the service<br />

from the server layer to provide its own service.<br />

A topological view of a layer network consisting<br />

of three sites is shown in Figure 1.<br />

Following the definition of the overall network<br />

architecture, the development of the generic (i.e.<br />

technology neutral) network model started in<br />

1994 in Question 30 of SG 15. As a consequence<br />

Access<br />

Group<br />

Access<br />

Group<br />

Link<br />

Subnetwork<br />

Link Link<br />

Link Subnetwork<br />

Link<br />

Subnetwork<br />

of the decision to make SG 4 the “Study Group<br />

for Management” within the ITU organisation,<br />

network level modeling became Q.18 of SG 4 in<br />

1996.<br />

This status paper describes the foundations for<br />

the generic model, the functionality currently<br />

supported and the extensions planned. To<br />

demonstrate the capabilities of the model, the<br />

modeling methodology is described in some<br />

detail. The creation of a trail termination point<br />

is used as a modeling example to illustrate the<br />

usage of the different modeling constructs.<br />

The existing model is applicable to connectionoriented<br />

core network technologies like SDH,<br />

ATM and WDM. Work has started to include<br />

the access network and also connectionless communication<br />

such as IP.<br />

2 Modeling Methodology<br />

The modelling methodology [2] was developed<br />

by Q.18/4 on the basis of the Reference Model<br />

for Open Distributed Processing (RM-ODP)<br />

which is specified in [3, 4, 5, 6]. The overview<br />

of the resulting methodology given in [7] is the<br />

basis for this description.<br />

RM-ODP consists of five viewpoints:<br />

• The Enterprise Viewpoint;<br />

• The Information Viewpoint;<br />

• The Computational Viewpoint;<br />

• The Engineering Viewpoint;<br />

• The Technology Viewpoint (not addressed<br />

by the Q.18/4 group).<br />

Subnetwork<br />

Access<br />

Group<br />

Layer Network Figure 1 Network Architecture<br />

– the topological view<br />

1) of a layer network<br />

2) When modeling the topology of a subnetwork rather than a layer network, one may replace the<br />

access group with the connection point group containing a number of co-located connection<br />

points.<br />

147

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