This Recommendation covers the functional requirements of optical transport network functionality within equipment. Some examples of the functionality are:
– optical transmission section termination and line amplification functionality;
– optical multiplex section termination functionality;
– optical channel termination functionality;
– optical channel cross-connect functionality.
This Recommendation uses the specification methodology defined in [ITU-T G.806] in general for
transport network equipment and is based on the architecture of optical transport networks defined
in [ITU-T G.872] and the interfaces for optical transport networks defined in [ITU-T G.709]. The
description is generic and no particular physical partitioning of functions is implied. The
input/output information flows associated with the functional blocks serve for defining the functions
of the blocks and are considered to be conceptual, not physical.
The OCh layer as defined in [ITU-T G.872] is divided into an OCh layer, an OTU layer and an
ODU layer with tandem connection sub-layers as defined in [ITU-T G.709].
The functionality defined in this Recommendation can be applied at user to network interfaces
(UNIs) and network node interfaces (NNIs) of the optical transport network. It is recognized that for
interfaces used within optical sub-networks, aspects of the interface are optical technology
dependent and subject to change as technology progresses. Therefore, optical technology dependent
aspects (for transverse compatibility) are not defined for functional blocks used for these interfaces
to allow for technology changes. The overhead processing functionality necessary for operations
and management of optical sub-networks is defined.
Not every functional block defined in this Recommendation is required for every application.
Different subsets of functional blocks from this Recommendation and others (e.g., [ITU-T G.783])
may be assembled in different ways according to the combination rules given in these
Recommendations to provide a variety of different capabilities. Network operators and equipment
suppliers may choose which functions must be implemented for each application.
The internal structure of the implementation of this functionality (equipment design) need not be
identical to the structure of the functional model, as long as all the details of the externally
observable behaviour comply with the EFS.
Equipment developed prior to the production of this Recommendation may not comply in all details
with this Recommendation.
Equipment which is normally stated to be compliant with this Recommendation may not fulfil all
the requirements in the case that it is interworking with old equipment that is not compliant with
this Recommendation.
ITU-T G.798-2006 history
2006ITU-T G.798-2006 Characteristics of optical transport network hierarchy equipment functional blocks Study Group 15