Wireless Sensor Networks : Technology, Protocols, and Applications

TRADITIONAL NETWORK MANAGEMENT MODELS 263
the reasons for management functions are manifold and may be summarized as
follows:
1. There are many heterogeneous devices and software entities that comprise
the network, and some may fail. It is the NM responsibility to determine
when, where, and why the fault had occurred and how to restore these
entities.
2. Optimization of system performance as a distributed system require NM to
collaborate in the process. For example, in some networks, congestion control
through admission control, by changing routes, or through device upgrade
occurs by NM functions.
3. For most networks, NM functions can be used to gather and analyze the
behavior of user interaction during network interface, which is very
important in planning the long-term evolution of network capacity and its
performance.
Generally speaking, network management consist of a set of functions to monitor
network status, detect network faults and abnormalities, manage, control, and
help configure network components, maintain normal operation, and improve network
efficiency and application performance. To perform these tasks, NM needs to
collect real-time information in network devices, analyze the information, and
apply control based on the information. Information is often organized as a management
information base (MIB) in each network device. Usually, there is an agent
in each device to collect the information and report to a network management
center that has a view of the entire network information. Therefore, network
management can be considered as an application.
9.3 TRADITIONAL NETWORK MANAGEMENT MODELS
9.3.1 Simple Network Management Protocol
The simple network management protocol (SNMP) for managing networks is in
broad use today. It includes three components: a network management system
(NMS), managed elements, and agents. NMS is a set of applications that monitor
and/or control managed elements. It can request management information (or
attributes) from the agent and present the results to NM users in the form of figures
or tables. It can also set attributes within the agent. The managed elements
are the network devices that are managed. SNMP agents run on each managed
element. The managed elements collect and store management information in
the MIB and provide access through SNMP to the MIBs. Examples of managed
elements include routers, switches, servers, and hosts. SNMP agents are management
software modules that reside on managed elements. Agents collect and
store the state of the managed elements and translate this information into a
form compatible with SNMP MIB. Exchanges of network management information
are through messages called protocol data units (PDUs). These are sent to