Side_1_360

• Topology2)in terms of links, subnetworks and
  access groups3).


• Connectivity in terms of trails, link connec-
  tions, subnetwork connections, ports and ref-
  erence points.

Here, the topological representation will be
addressed.

[G.805] introduces a set of concepts for describ-
ing the various functional aspects of a transport
network:

Architectural component:An item that is used to
generically describe transport network function-
ality.

Network:All of the entities (such as equipment,
plant, facilities) which together provide commu-
nication services.

Transport network:The functional resources of
the network which convey user information
between locations.

Topological component:An architectural com-
ponent, used to describe the transport network in
terms of the topological relationships between
sets of points within the same layer network.
Here we focus on four topological components:

• Layer network;


• Subnetwork;


• Link;


• Access group.

Layer network:A “topological component” that
includes both transport entities and transport
processing functions that describe the genera-

tion, transport and termination of a particular

characteristic information. A layer network is

defined by the complete set of access groups of

the same type which may be associated for the

purpose of transferring information.

Subnetwork:A “topological component” used to

effect routing of a specific characteristic infor-

mation. A subnetwork is defined by the set of

ports (see [G.805]) which are available for the

purpose of transferring characteristic informa-

tion. A subnetwork exists within a single layer

network.

Link:A “topological component” which de-

scribes a fixed relationship between a “subnet-

work” or “access group” and another “subnet-

work” or “access group”.

Access group:A group of co-located trail termi-

nation functions that are connected to the same

subnetwork or link.

The topological view describes the geographical

distribution of the resources of a single layer net-

work. Layering is a method for splitting the

overall transport function into a hierarchy of

layer networks on top of each other where each

layer uses the service from the server layer to

provide its own service.

The topological concepts and their relationships

are illustrated in Figure 7.

3.2 The Enhanced RM-ODP

Framework

ITU-T SG4 has chosen the ISO Reference

Model – Open Distributed Processing (RM-

ODP) [X.901, X.902, X.903, X.904] as the basic

framework for management modelling on the

Figure 7 Network

Architecture

• the topological view

2)Of a layer network.
3)When modelling the topology of a subnetwork rather than a full layer network, one may replace the

access group with the connection point group containing a number of co-located connection points.

Subnetwork

Access

Group

Subnetwork

Access

Group

Subnetwork

Access

Group

Link

Subnetwork

Layer Network

Link

Link Link

Link