Network Management Protocol
An essential function in achieving the goal of network management is acquiring information about the networks. A standardised set of network management protocols has been developed protocols has been developed to help extract the necessary information from all network elements. There are two typical standardized protocols for network management
SNMP developed under internet sponsorship
CMIP developed under international telecommunication standardized sector.
SIMPLE NETWORK MANAGEMENT PROTOCOL(SNMP):
SNMP is designed to work with TCP/IP protocol stack and establishes standards for collecting and for performing security, performance, fault, accounting and configuration function associated with the network management. The common protocol for SNMP is UDP which is very simple, unacknowledged, connectionless protocol.
The SNMP is an application layer protocol that provides the exchange of management information between network devices and it is part of transmission control protocol/ internet protocol. SNMP guides network administrator to manage network performance, find and solve network problems and plan for network growth.
In SNMP two versions exist, there are SNMP version1 and SNMP version2. Both are having number of features as common, but in second version of SNMP overs enhancements such as additional protocol operations.
The basic components of SNMP managed networks are managed devices agents and network management systems
A managed device is a network node that contains an SNMP agent and that are resides on a managed devices. This device collects and store management information and makes this information available to Network management system (NMS) using SNMP. Sometimes managed devices are called as network elements, network elements such as computer, router, and terminal server connected to networks.
Agents are software modules that reside in network elements. They collect and store information such as the number of error packet received by a network element.
Network management system (NMS):
These device excutes management applications that monitor and control network elements. A management station hosts management software called the network management systems.
SNMP is a communication specification that defines how management information is exchanged between network management applications and management agents. SNMP itself does not define which information a managed system should offer, it uses an extensible design.
A management information base is a collection of information that is organised hierarchically. This data is accessed by using a network management protocol such as SNMP. They are of managed objects and are identified by Object Identifiers (OID). Each OID identifiers a variable that can read or set through SNMP.
A managed object sometimes called as MIB object. The Managed objects are made up of one or most object instances. The managed objects are made up of one or most object instances. There are two types of managed objects exist, the scalar objects define a single object instance and another is tabular objects that are grouped in MIB tables.
SNMP specifies five commands used to exchange information between network management application and management agents. They are
GET_REQUEST: These commands request a value or set of values from a management agent or MIB.
GET_NEXT_REQUEST: this command allows the management station to walk the entire MIB tree to get the values of all variables without specifying the identifies of any variables.
GET_RESPONSE: it is a response from the management agent to the management station the requested value.
GET_NEXT_REQUEST - Requests the next object instance from a table or list from an agent
TRAP: it is an unsolicited message from a management agent to management station. Agents can send a trap when a condition has occurred, such as changes in state of a device, device failure or agent initialization.
The SNMP architecture is
The main attributes of SNMP are, it is easy to implement, making it easy for a vendor to accommodate it into its device. It does not require large computational or memory resources.
The attractiveness of SNMP is its simplicity and relative ease of implementation. SNMP version 1 uses underlying User Datagram Protocol (UDP) for data delivery which does not ensure reliability of data transfer, there fore the loss of data is the limitation to network manager.
SNMP is best suited for network monitoring and capacity planning. SNMP does not provide the basic trouble shooting information because, SNMP agents do not analyze information they just collect information and provide it to the network management application. It provides a minimal security.
COMMON MANAGEMENT INFORMATION PROTOCOL (CMIP):
CMIP is designed to support a richer set of network management functions and work with all systems conforming to ISO standards. The common management information protocol is a network management protocol built on the open systems interconnection (ISO) communication model. It is an ISO protocol used with common management information services (CMIS), supports exchange information between network management applications and management agents. CMIS supplies a system of network management information services. CMIP supplies an interface that provides functions which may be used to support both ISO and user defined management protocols. CMIP specification for built on the open TCP/IP networks is called CMOT.
CMIP uses an ISO reliable connection-oriented transport mechanism and has built in security that supports access control, authorization and security logs. The management information is exchanged between management application and management agents through managed objects, managed objects are a characteristic of a managed device that can be monitored, modified or controlled and can be used to perform tasks.
CMIP does not specify the functionality of the network management application, it only defines the information exchange mechanism of the managed objects and not how the information into be used or interpreted. The network management application can initiate transactions with management agents using the following operations:
ACTION - Request an action to occur as defined by the managed object.
CANCEL_GET - Cancel an outstanding GET request.
CREATE - Create an instance of a managed object.
DELETE - Delete an instance of a managed object.
GET - Request the value of a managed object instance.
SET - Set the value of a managed object instance.
A management agent can initiate a transaction with the network management application using the EVENT_REPORT operation. This operation can be used to send notifications or alarms to the network management application based upon predetermined conditions set by the network management application using the ACTION operation. CMIP is divided into the following functions:
Accounting management Monitor and charge for network usage.
Configuration management View and manage system resources and management information. faults in the network.
Performance management Monitor and tune network performance.
Security Authenticate users, detect intrusions, and transmit data securely.
CMIS (Common Management Information Service) provides
Fault management Detects and corrects a way to share management information in the CMIP environment. A relatively new protocol, CIM (Common Information Model), is bringing interoperability among management protocols in general. It has many new features that go beyond features in SNMP and CMIP, while providing backward compatibility.
The major advantages of CMIP over SNMP are:
It is a more secure system with built in security that supports access control and authorization.
Polling is reduced or eliminated with CMIP improved event filtering reduces the number of event messages that are sent to the management work station.
Unlike SNMP, which manages device, CMIP manages relationship between devices. More function can be accomplished with a single request.
It provides better reporting of unusual network conditions.
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