TMN architecture: There are three architectural perspectives: functional, physical, and information, as shown in Figure1.

• The functional architecture identifies functional modules or blocks in the TMN environment, including the reference point between them. The requirements for interface are specified.

• The physical architecture defines the physical blocks and interfaces between them.

• Information architecture deals with the information exchange between managed objects and management systems, using a distributed object-oriented approach.

Functional Architecture:

i. TMN architecture made up of five function blocks: operations systems function, network element function (NEF), mediation function (MF), workstation function (WSF), and Q-adapter function (QAF), as shown in Figure2.

ii. The TMN operations systems function (OSF) is implemented in operations systems. Operations systems (OS) such as network transmission OS and traffic measurement OS help monitor, manage, and control telecommunication networks and services.

iii. Network management, both as a manager and an agent, is also considered to be an OS. This would include MIB in Internet management and naming tree in OSI management as a function of the OSF.

iv. The TMN NEF is concerned with the managed network elements. Network elements themselves are not part of TMN, but are supported by TMN over the standard interfaces. Network elements would include hardware, software, and systems such as hubs, routers, switches, processes, etc.

v. The network management agent and the associated MIB are part of the NEF. Network elements providing information for management, such as packets dropped, collision rate, etc., are considered as part of TMN, i.e. NEF.

vi. The TMN MF block addresses the operations performed on the information content passing between the network elements and operations systems. Such operations include filtering, store and forward, protocol conversion, threshold detection, etc.

vii. A physical entity in which the MF is implemented can be shared between multiple operations systems and network elements. The TMN WSF provides an interface between human personnel and TMN activities. More specifically, this function addresses the presentation aspect. The conversion function that converts machine-readable information to human-interpretable format in the presentation function belongs in one of the other three function blocks, OSF, MF, and QAF.

Physical Architecture:

i. Model for the TMN physical architecture, shown in Figure3. A TMN physical block could be an embodiment of one or more blocks, besides its equivalent function block. For example, an operations system could have its operation function as well as mediation device, which does filtering of information.

ii. There are five types of physical blocks representing the five functions discussed. Operations systems are embodiments of TMN OSF. It is connected to the mediation device, placing the MF on a data communication network.

iii. The data communication network is the physical implementation of DCF, which to repeat, is not a function block, but a TMN function, DCF. The network elements, Q adapter, and workstations reflect their respective TMN functions

iv. The Q, F, and X TMN interfaces between the physical devices are also shown in Figure3, representing the physical implementation of the respective TMN reference points. The Q3 interface is used between the OS and either an NE or a QA.

v. The Qx interface is shown between MD and QA/NE. An example of this would be an MD being a proxy server communicating with legacy systems via the QA interface. The F interface is implemented to connect a workstation to TMN. The X interface is between the operations systems belonging to two different TMNs.

Information Architecture:

i. Figure4 shows the information exchange between the two types of entities.

ii. The manager performs operations or makes requests from an agent. The agent executes the operations on the network elements that it is managing and sends responses to the manager. The agent also sends unsolicited messages to the manager indicating alarm events.

iii. Information models specified by SNMP and OSI management deal with the management of network elements. The TMN information model has been used in specific technology such as ATM and SDH/ SONET.

iv. The information architecture should transport information reliably across the functional boundaries. There are two types of communication services between interfaces: interactive and file oriented. Interactive service is supported in OSI by CMISE over Remote Operations Service Element (ROSE).

v. In the Internet distributed computing environment (DCE), this will be handled by Remote Procedure Call (RPC). The file-oriented category is supported by File Transfer Access Management (FTAM) in OSI and in the Internet by File Transfer Protocol (FTP).

vi. In the OSI model, Association Control Services Element (ACSE) is needed to establish, release, and abort application associations. In the Internet model, this is integrated in RPC presentation service.

• Networks are increasingly becoming complex and distributed. As a result, problems like hardware failures, performance degradation, resource allocation, bandwidth monitoring and assignment and service provisioning are harder to solve and become real challenges for Network Operation Centers (NOC).

• The NOC is in constant search for efficient integrated network management systems required to monitor, interpret, and control the behavior and performance of the network, its hardware devices and software resources.

• The network management architecture consists of the following:

1. Network management system (NMS): A system that executes applications that monitor and control managed devices. NMSs provide the bulk of the processing and memory resources that are required for network management.

2. Network management protocol: A protocol that facilitates the exchange of management information between the NMS and managed devices, including SNMP, MIB, and RMON.

3. Managed devices: A device (such as a router) managed by an NMS.

4. Management agents: Software, on managed devices, that collects and stores management information, including SNMP agents and RMON agents.

5. Management information: Data that is of interest to a device's management, usually stored in MIBs.

• The three network management architectures are:

1. Centralized Network Management

2. Distributed Network Management

3. Hierarchical Network Management

4. Centralized Network Management Architecture

• With a centralized architecture a single management system installation monitors the whole network.

• This installation may consist of one or more servers due to hardware limitations.

• If more than one server is used, it is considered as a centralized architecture when all servers are located at the same NOC.

• A distributed network that spans multiple geographical regions is managed from a single Network Operations Center (NOC).

• NOC operators from each of the regions use clients to remote connect to the centralized management servers located in another region.

• With this architecture, the network management system consists of:

1. One or more NMS server(s), located in a single NOC. The servers manage the network of the three regions, meaning that they will require Data Communications Network infrastructure (DCN) i.e., routers, switches and Ethernet connectivity from the single NOC they are installed to the remote regions where the network devices are installed to be able to establish management communication.

2. One or more clients located at all regions. These clients communicate remotely over DCN to the central server.

3. Advantage :

o only one management system is needed

o simplifying the architecture and reducing costs

o has a variety of management tools associated with it.

1. Trade-offs:

o single point of failure

o causing congestion or failure on the Network Interface.

1. Distributed Network Management Architecture

• With a distributed architecture, multiple installations of management systems are used to monitor the whole network. Each management system is installed at a NOC that is responsible to monitor a geographical or administration region / domain, i.e. it is a Domain Manager.

• A distributed network that spans three regions, is managed from three NMS servers each one located at a regional Network Operating Center (NOC). NOC operators of a region use clients to locally connect to their server that manages the part of the network installed at their region.

With this architecture, the network management system consists of:

1. Three NMS servers, each located in a separate NOC. Each server manages the (sub) network of the region it belongs, meaning that it will NOT require Data Communications Network infrastructure (DCN) i.e., routers, switches and Ethernet connectivity, from the NOC region to remote regions.

2. Clients located at all regions. These communicate locally to their server.

3. Hierarchical Network Management Architecture

• With a hierarchical architecture, multiple installations of management systems are used to monitor the whole network.

• Each management system is installed at a NOC that is responsible to monitor a geographical or administration region / domain, i.e. it is a Domain Manager.

• So far this is exactly the same as the distributed architecture, except that the hierarchical architecture adds an additional layer, the Manager of Managers (MoM). This Manager of Managers sits at a higher level and requests information from domain managers.

• There is no communication between domain managers, information flow follows the hierarchy. The hierarchy can be further expanded by adding additional layers of MoMs and therefore is quite scalable.

• Advantages:

1. every component can be made redundant

2. every component can be independent of the other components

3. can be tailored to the specific needs of the network

4. several display devices

5. several processing devices

6. several storage devices

• A trade-off:

1. Cost

2. Complexity

3. Overhead