TCP/IP network management

Functional areas

Network management encompasses various functions that contribute to detailed knowledge about the condition of its elements, triggering adequate preventive and corrective actions. 

These functions are grouped into areas that ISO has standardized as follows:

• Configuration Management – Series of facilities to monitor, identify, and transmit data regarding managed objects.

• Fault Management – Detection, isolation, and correction of abnormal network resource situations.

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

• Security Management – Protection of managed objects, supply and use of redundancy.

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

Management architecture

As a rule, a network’s management architecture includes:

• A central site where a group of management stations, a Network Management System (NMS), resides and from which it is possible to act on the remote equipment to be managed, to consult status and receive notifications of this equipment, and to roll out management information, normally in a graphic format.

• A set of network elements to be managed, where a software (agent) functions, in charge of gathering information, answering queries, and communicating with the central site.

• A communication protocol, in charge of transmitting information between the equipment’s software and the management stations.

Standard management protocols

The common management protocols that implement the functions of the central site, the remote and communication equipment are:

Simple Network Management Protocol (SNMP): Developed by IETF, it is widely used in TCP/IP environments.  It is not aimed at connection or application.  The agent resides in the devices and uses minimum resources so as not to undermine performance.  It gathers data and stores them in the base which resides in the device.  It uses UDP for communications.

Common Management Information Protocol (CMIP): Developed by ISO, it is an all-purpose protocol, which is not confined to TCP/IP. It is sophisticated and includes powerful but complex commands. It is more versatile but it is not as widespread.

Network management system (NMS)

The network management functions are carried out with support of the information system, which includes an operating system, a database platform, a communication protocol, a program implementation environment, and a user interface.

There are two leading players in the system: the manager, which controls all management activities, and the agent, which adjusts and controls the managed objects under its responsibility in accordance with the guidelines of the manager to which it reports results.

Management/agent communication protocol

A communication protocol between manager and agents is required.  Its functions are:

• Read and update the attributes of the managed objects.
• Order the implementation of the specific functions of the managed objects.
• Report the results obtained by the managed objects.
• Create and delete manageable objects

The SNMP is used for this purpose, as it is a protocol of the application layer that facilitates the exchange of administrative information between network devices.  It is part of the suite of TCP/IP protocols.  SNMP enables administrators to supervise the network’s performance, look for and resolve its problems, and plan its growth.

The two most widely SNMP versions are: SNMP version 1 (SNMPv1) and SNMP version 2 (SNMPv2). Both versions share several common features, but SNMPv2 offers improvements, such as additional operations.

SNMP in its latest version, that is, SNMPv3, has major changes compared to its predecessors, especially in terms of security; nevertheless it has not been widely accepted by the industry.

Structure of Management Information (SMI) y Management Information Bases (MIBs)

The Structure of Management Information (SMI) defines the rules to describe managed objects and how protocols subject to management can gain access to them.  Managed objects are described using a subset of ASN.1 (Abstract Syntax Notation 1, ISO 8824 Standard), a data description language. The definition of the object type appears in the five fields:

• Object:  textual name, called object descriptor, for the object type, along with its corresponding object identifier as defined below.
• Syntax: the abstract syntax for the object type.  The options are SimpleSyntax (integer, octet string, object identifier, null), ApplicationSyntax (network address, counter, gauge, timeticks, opaque) or another type of application syntax (see RFC 1155 for further details).
• Definition: textual description of the semantics of the type.
• Access: reading-only, writing-only, reading-writing, or not-accessible.
• Status: mandatory, optional or obsolete.

Not only does a managed object have to be described, it also has to be identified.  This is done using the object identifier ASN.1 as if it were a phone number, reserving groups of numbers for different localizations.  In the case of network management for TCP/IP, the reserved number was 1.3.6.1.2 and SMI uses it as the basis for the definition of new objects.

Management Information Base (MIB) is a structure or a model containing a hierarchical order of all managed objects.  Each managed object in an MBI has a unique identifier.  The identifier includes the type (such as counter, sequence, address, etc.), the access level (read/write), size restrictions, and additional information.

It defines the variables needed by the SNMP protocol to supervise and monitor components in a network.  The agents/managers bring or store in these variables.

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

 
Alvaro Sánchez
Head of operations and maintenance
ANTEL