An Introduction to the Ericsson Transport Network Architecture ...

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switch fabric. The characteristics of an object
class are specified in terms of
- read/write attribute values in objects,
e.g. values of configuration parameters
and relations to other objects, represented
as lines between objects in Fig. 1 2 3
- create/delete operations of objects
- actions that can be performed on the object
- notifications (i.e. spontaneous messages)
sent from the object.
In an executing system, manageable resources
are represented as instances of
these object classes. The collection of instantiated
objects is referred to as the Management
Information Base (MIB). 2 There
are two types of object in the MIB: Managed
Objects and Support Objects. A Managed
Object (MO) represents a physical or
logical resource in the Network Element.
A Support Object (SO) represents a log or
an alarm filter, for example.
The link between the TMN management
functions and the IM is the implementation
of each management function as one or
more operations, actions or notifications in
the objects that build up the MIB.
A Network Element has what is called a
TMN Agent, which can be seen as a process
(function) acting on behalf of the managing
system(s), relaying messages in
both directions, Fig. 2.
A generic Information Model is essential
for the generation of management standards
concerning configuration, fault, performance
and security management functions.
A common network model,
identifying the generic resources in the
network - in this case the Transport Network-
and their associated attribute types,
events, actions and behaviour, provides a
basis on which to explain the interrelationships
between these resources and the
network management system. Without
this common view, a multi-vendortelecommunication
network will not be achieved.
The Information Model provided by Ericsson
and describing the SDH NE complies
with the information model developed by
CCITT's SG XV SDH Model (G.774), 6 and
with the SG IV Generic Network Information
Model (M.3100). 5 In general, the configuration
management part is derived
from G.774, while the fault management
and performance management parts are
derived from M.3100 and Q.821. By and
large, SG IV follows the CCITT X.700 series
of recommendations.
The SDH Information Model is a subset of
the ETNA Information Model common to
all Ericsson transport network elements
connected to the FMAS, including PDH
equipment and AXD I/O NEs.
The Data Communication Perspective
As well as providing telecommunications
services, the SDH NEs also provide powerful
data communications and network
layer routing functions. The TMN function
block that performs these functions is called
the Message Communication Function
(MCF).
The MCF is based on the OSI reference
model, which makes it possible for an
SDH NE to work as a data communication
node in an open network architecture. 7
Each of Ericsson's SDH NEs can be
equipped with a Q-interface and provide
for Embedded Control Channel (ECC) access,
which means that each NE can be
connected to any Operations System that
conforms to OSI and TMN standards, without
the need for additional Mediation Devices
or Q-adapters.
The MCF performs network layer routing
functions between the Q-interface and any
Fig. 2
Interworking between Manager, Agent and Managed
Objects
ERICSSON REVIEW No. 3, 1992