OSS architecture

A lot of the work on OSS has been centred on defining its architecture. Put simply, there are four key elements of OSS:
Processes
the sequence of events
Data
the information that is acted upon
Applications
the components that implement processes to manage data
Technology
how we implement the applications
During the 1990's, new OSS architecture definitions was done by the ITU-T in its TMN model. This established a 4-layer model of TMN applicable within an OSS:
Business Management Level (BML)
Service Management Level (SML)
Network Management Level (NML)
Element Management Level (EML)
(Note: a fifth level is mentioned at times being the elements themselves, though the standards speak of only four levels) This was a basis for later work. Network management was further defined by the ISO using the FCAPS model - Fault, Configuration, Accounting, Performance and Security. This basis was adopted by the ITU-T TMN standards as the Functional model for the technology base of the TMN standards M.3000 - M.3599 series. Although the FCAPS model was originally conceived and is applicable for an IT enterprise network, it was adopted for use in the public networks run by telecommunication service providers adhering to ITU-T TMN standards.
A big issue of network and service management is the ability to manage and control the network elements of the access and core networks. Historically many efforts have been spent in standardization fora (ITU-T, 3GPP) in order to define standard protocol for network management, but with no success and practical results. On the other hand IETF SNMP protocol (Simple Network Management Protocol) has become the de-facto standard for internet and telco management, at the EML-NML communication level.
From 2000 and beyond, with the growth of the new broadband and VoIP services, also the management of the home networks is entering the scope of OSS and network management. DSL Forum TR-069 specification has defined the CPE WAN Management Protocol (CWMP), suitable for managing home networks devices and terminals at the EML-NML interface.
Most recently the TeleManagement Forum (TMF) has developed a communications domain model that provides the basis for clarifying the distinction between OSS and BSS systems. As shown in the figure the OSS supports the traditional Resource and Resource Facing Service domains. Whereas the BSS supports the more Customer Facing domains.