TCP-IP: The management-functional areas

Functional areas

The network management includes diverse functions that contribute to the detailed knowledge of the state of his components, which allows the trigger of suitable preventive and corrective actions. The above mentioned functions can be gathered together in areas that ISO standardized of the following way:

• Configuration Management - Set of facility for the control, the identification, and the communication of information with regard to the managed objects.

• Fault Management - Detection, isolation and correction of abnormal situations of the network resources.

• Performance Management - Evaluation of the behavior of the managed objects and effectiveness of the communications.

• Security Management - Protection of the managed objects, provision of redundancy and usage of it.

• Accounting Management - Accounting of the use of the network resources.

Manager-agent model -basic concepts

Network management system

The functions of network management are carried out with the support of an information system, which includes an operating system, a database platform, a communications protocol, a programs execution environment and a user's interface.

In the system there are two principal protagonists: the manager, who controls all the management activity, and the agent, that supervise and controls the managed objects that are under its responsibility, in accordance with the instructions of the manager, to whom it brings the results.

RFC 1157 defines the NMS (Network Management Station) as a station that executes Network Management Applications that supervise and control the Network Elements. In the above mentioned elements Management Agent is used to carry out these functions. SNMP allows the communication between the NMS and the MA.

Communications protocol

It enables communications between manager and agents. Its functions are:

• to read and update the attributes of the managed objects

• to order the execution of specific functions to the managed objects

• to report the results obtained by the managed objects

• to create and to suppress manageable objects

Management Information Base (MIB)

It is a simplified model that allows carrying the management out in complex environments. It is constituted by "objects", which correspond to the network resources that admit some type of management.

Examples: NIC of a PC, serial interface of a router, CPU of a server.

Common Management Information Protocol

Developed by ISO, it is of general intention not restricted to TCP/IP. It is sophisticated, it includes powerful but complex commands. It is more versatile but it is not so widely used. It is faced to connection. CMIP communicates the agents of every layer (Layer Management Entities) with the applications of management (System Management Application Entities). Every LME operates in a level OSI and does not give a global vision of the operation. In turn there is a SMAE for every LME. The SMAE of different devices communicate by means of CMIP to allow to the manager the compilation and the analysis of the information of the network as a whole, service called sometimes Common Management Information Service. The following operations are defined:

ACTION – It requests an action is executed at the managed station in accordance with the standard.

GET – It requests the value of an instance of a managed object.

SET – It establishes the value of an instance of a managed object.

CANCEL_GET – It cancels a GET request.

CREATE – It creates an instance of a managed object.

DELETE – It deletes an instance of a managed object.

CMIP over TCP/IP (CMOT)

It was defined by the Internet Architecture Board (IAB) as a long term solution that would replace SNMP.

Simple Network Management Protocol

Developed by IETF it is used widely in TCP/IP environments. It is not connection oriented, it uses UDP and corresponds to the application level.

The agent resides in the devices and uses minimal resources not to harm the performance. It collects information and stores them in the base that resides in the device. The management with SNMP is of type distributed, since every entity can get out of debt as agent or as agent, or as both. In turn, an agent can answer to multiple agents. It uses UDP for communications.

Comparison with CMIP

CMIP variables allow to execute tasks and not only to send information like in SNMP. CMIP is surer than SNMP because it supports authorization, accesses control, and security records (logs). CMIP achieves major efficiency than SNMP with only one request. CMIP reports unusual conditions of the network better.

Protocol to analyze

The SNMP protocol is at present of widest use.

 Alvaro Sánchez

Head of operation and maintenance of the public IP network, international links and e-mail (Adinet) and DNS (ANTEL-Uruguay)

Professor of several courses on data transmission  (University ORT)