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2.2 NEL
Network Element Layer


  1. Management versus Control

The main network management recommendation, M.3010, doesn't say much about the Network Element Layer except for: TMN Functional Blocks

network element (NE):
An architectural concept that represents telecommunication equipment (or groups/parts of telecommunication equipment) and supports equipments or any item or groups of items considered belonging to the telecommunications environment that performs network element functions (NEFs).
network element function:
A function block which represents the telecommunication functions and communicates with the TMN OSF function block for the purpose of being monitored and/or controlled {i.e. being managed}.
The NEF includes the telecommunications functions which are the subject of management.  These functions are not part of the TMN but are represented to the TMN by the NEF.  The part of the NEF that provides this representation in support of the TMN is part of the TMN itself, whilst the telecommunications functions themselves are outside.

So the functions of a Network Element are represented by Network Element Functions (NEFs):  the NEFs are the 'hooks' in the NE for management.  It also implies that the NE functions not represented by NEFs can not be managed by the TMN (which should be obvious).
In the section on Generic Components & Interfaces we will elaborate on NEFs, but it should be clear that NEFs are at the boundary of a TMN:  they form a defined interface to the TMN (the q-interface in the figure) but how they achieve their function in the NE is not part of the recommendation.  The NEL is not part of the TMN except for the apparent behaviour of the NEFs.

Management versus Control

The distinction between Management and operational Control is often confused.  To properly operate a system, both are required.  The basic distinction is:

is an intrinsic part of the operation and therefore embedded in it.  It requires continuous availability and real-time response (typically part of a stimulus/­response-loop).
stands above the operation (and its control) and is commonly located elsewhere.  It is not required for normal operation and can therefore be temporarily off-line.  Management typically issues directives/­commands/­requests/­set-points/­targets, and receives responses/­reports and unsollicited notifications (e.g. alarms).

Note that:

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