an information model is concerned with the structure and storage of information

8/7/2019 An information model is concerned with the structure and storage of information

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PP..IINNDDRRAA RREEDDDDYY MMEEMMOORRIIAALL EENNGGIINNEEEERRIINNGG CCOOLLLLEEGGEE

TECHNICAL SEMINAR

ON

NETWORK MANAGEMENT SYSTEMS

BY

S.BALAKRISHNA REDDY

07J81A1207


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Network Management System

A Network Management System (NMS) is a combination of both

hardware and software used to monitor and administer a network.individual

network is a network are managed by an element managed system

Effective planning for a network management system requires that a number

of network management tasks be performed. The network management system

should discover the network inventory, monitor the health and status of devices

and provide alerts to conditions that impact system performance.NMS systems make use of various protocols for the purpose they serve. For

example, SNMP protocol allows them to simply gather the information from the

various devices down the network hierarchy. NMS software is responsible for

identification of a problem, the exact source(s) of the problem, and solving them.

NMS systems not only are responsible for the detection of faults, but also for

collecting device statistics over a period of time. An NMS may include a library of

previous network statistics along with problems and solutions that were successful

in the pastuseful if faults recur. NMS software can then search its library for the

best possible method to resolve a particular problem.

An NMS manages the Network Elements. These elements or devices are managed

by the NMS, so these devices used to call as managed devices. Device

management includes Faults, Accounting, Configuration, Performance, and

Security (FCAPS) management. Each of these five functions is specific to an

organization, but the basic idea to manage these devices is FCAPS.


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Network management is the top-level administration and maintenance of large

networks, often in areas such as computers or telecommunications, but not

including user terminal equipment. In network management, functions such as

security, monitoring, control, allocation, deployment, coordination and planning

are executed. Network management is governed by a large number of protocols

that exist for its support, including SNMP, CMIP, WBEM, Common Information

Model, Java Management Extensions, Transaction Language 1, and Netconf.

Routing, which refers to the process of selecting the paths in a computer network

on which to send data, is an important area of network management. In this area of

network management, logically addressed packets are passed from their source to

their destination through nodes, which are called routers, in a process called

forwarding. This is usually based on routing tables that maintain a record of the

most efficient routes


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INTRODUCTION TO SNMP

Simple Network Management Protocol (SNMP) is the protocol developed to manage

nodes (servers, workstations, routers, switches and hubs etc.) on an IP network. SNMP enables

network administrators to manage network performance, find and solve network problems, and

plan for network growth. Network management systems learn of problems by receiving traps or

change notices from network devices implementing SNMP.

An SNMP managed network consists of three key components: managed devices,

agents, and network-management systems (NMSs). A managed device is a network node that

contains an SNMP agent and that resides on a managed network. Managed devices collect and

store management information and make this information available to NMSs using SNMP.Managed devices, sometimes called network elements, can be routers and access servers,

switches and bridges, hubs, computer hosts, or printers. An agent is a network management

software module that resides in a managed device. An agent has local knowledge of management

information and translates that information into a form compatible with SNMP. An NMS

executes applications that monitor and control managed devices.

The Simple Network Management Protocol (SNMP) is an application service that

has evolved with the growth ofTCP/IP. It was derived from a low-overhead protocol designed to

monitor Internet routers. Its use has since mushroomed because of its wide availability and low

cost.

COMPONENTS OF SNMP:

An SNMP-managed network consists of three key components:

y Managed devicey Agent software which runs on managed devicesy Network management system (NMS) software which runs on the manager


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INFORMATION MODELAn information model is concerned with the structure and storage of information. Let

us consider, for example, how information is structured and stored in a library and is accessed by

all. A book is uniquely identified by an International Standard Book Number (ISBN). It is a ten-

digit number identification that refers to a specific edition of a specific book. For example, ISBN

0-13-437708-7 refers to the book Understanding SNMP MIBs by David Perkins and Evan

McGinnis.


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Currently, there are three versions of SNMP defined: SNMP v1 , SNMP v2 and SNMP

v3 . The following table provides the summary of the operations and features of the different

version SNMP:

SNMP v1 Basic Operations and Features :

Get Used by the NMS to retrieve the value of one or more object instances

from an agent

GetNext Used by the NMS to retrieve the value of the next object instance in a

table or a list within an agent

Set Used by the NMS to set the values of object instances within an agent.

Trap Used by agents to asynchronously inform the NMS of a significant

event.


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SNMPv1 Commands:

Communication between SNMP capable devices occurs via messages represented

entirely within a single UDP datagram. All messages are transmitted to UDP port 161 with the

exception of SNMP traps, which use port 162. Devices like switches and routers will have aservice listening to port 161 waiting for Get and Set related messages, and network management

stations will have a service listening to port 162 waiting for trap messages from switches and

routers.

y Get request: Issued by a network management console to get a single MIB entryy Get Next request: Issued by a network management console to get the next single MIB

entry. This command is useful in getting sequential data that has no predictable length.

Get response: Sent by an SNMP agent (e.g., switch router) in response to a Get request,

Get Next request, or Set request

y Set request: Sent by a network management station to change the value of a MIB entry toaffect a configuration change.

SNMPv1s architecture has some disadvantages.

y It is inefficient to retrieve large amounts of data from the managed device, as each MIBentry must be retrieved one at a time.

y All data must fit within the payload of a single UDP datagram, as there is no reorderingor guarantee of delivery service as part of UDP.

y SNMPv1s most significant shortcoming is the lack of any security options. SNMPmessages are not authenticated or encrypted.

Community Strings :

SNMPv1 and SNMPv2 only have simple authentication, based on a read

community string (i.e., a password) and a write community string, allowing for read only and

read write access, respectively. These passwords are sent in the SNMP request in clear textnot

the most ideal situation regarding security.


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MANAGEMENT INFORMATION BASE:

SNMP itself does not define which information (which variables) a managed system

should offer. Rather, SNMP uses an extensible design, where the available information is definedby management information bases (MIBs). MIBs describe the structure of the management data

of a device subsystem; they use a hierarchical namespace containing object identifiers (OID).

Each OID identifies a variable that can be read or set via SNMP. MIBs use the notation defined

by ASN.1.

A management information base (MIB) is a virtual database used for managing

the entities in a communications network. Most often associated with the Simple Network

Management Protocol (SNMP), the term is also used more generically in contexts such as in

OSI/ISONetwork management model. While intended to refer to the complete collection of

management information available on an entity, it is often used to refer to a particular subset,

more correctly referred to as MIB-module.

Objects in the MIB are defined using a subset of Abstract Syntax Notation One (ASN.1) called

"Structure of Management Information Version 2 (SMIv2)" RFC 2578.The software that

performs the parsing is a MIB compiler.

The database is hierarchical (tree-structured) and entries are addressed through object identifiers.

Internet documentation RFCs discuss MIBs, notably RFC 1155, "Structure and Identification of

Management Information for TCP/IP based internets", and its two companions, RFC 1213,

"Management Information Base for Network Management of TCP/IP-based internets", and RFC

1157, "A Simple Network Management Protocol".


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SNMPv1:

SNMPv1 is the first version of the SNMP protocol, providing a minimum network

management function. The Structure of Management Information (SMI) and MIB of SNMPv1

are rather simple and have many security defects.

SNMPv1 uses community name for authentication. A community name plays a

similar role as a password and can be used to control access from NMS to Agent. SNMP packets

with community names that do not pass the authentication on the device are simply discarded.

SNMPv1 Message:

Figure 4 SNMPv1 message format

The above figure indicates that an SNMP message is composed of Version, Community, and

SNMP PDU. The following describes the main fields in an SNMP message:

Version: SNMP version.

Community: Community name, used for the authentication between an agent and the

NMS. Community name falls into read and write. If NMS performs Get or GetNext operation,

read community name is used for authentication; if NMS performs Set operation, write

community name is used for authentication.


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Request ID: It is used to match a response to a request. SNMP assigns a unique ID to

each request.

Error status: It is used in a response to indicate the errors when the agent processes the

request, including noError, tooBig, noSuchName, badValue, readOnly, and genErr.

Error index: Provides the information of the variables that caused the error when an

error occurs.

Variable bindings: It is composed of a variable name and value.

enterprise: Type of the device that generates traps.

Agent addr: Address of the device that generates traps.

Generic trap: It includes coldStart, warmStart, linkDown, linkup,

authenticationFailure, egpNeighborLoss and enterpriseSpecific.

Specific trap: Specific trap information of a vendor.

Time stamp: The amount of time between the time when the SNMP entity sending this

message reinitialized and the time when traps were generated, that is, the value of sysUpTime.

SNMPv1 and SNMPv2c Mechanism:

SNMPv1 and SNMPv2c adopts almost the same mechanism. New error codes and

GetBulk operation are added in SNMPv2c. The following describes the SNMPv1/v2c

mechanisms.

1. Get operation:

NMS wants to obtain the value of the node sysName of a managed device (the

sysName object is in the accessible view), using public as the read community name:

(1) NMS sends a Get request to Agent. The main fields in the request are set as follows:

version to 1, community to public, name 1 in variable bindings in the PDU to sysName.0.


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(2) Agent sends a get response to NMS to tell NMS whether the values are successfully

obtained. If succeeded, the field Value1 in Variable bindings in the response PDU is the device

name (for example, Agent010-H3C); if failed, the reason for the error is filled into the Error

status field, and error location is filled into the Error index field.

Figure 7 Get operation

2. GetNext operation:

NMS wants to obtain the value of the node sysLocation next to node sysName of a

managed device (the sysName and sysLocation objects are in the accessible view), using public

as the read community name:

(1) NMS sends a GetNext request to Agent. The main fields in the request are set as

follows: Version to 1, Community to public, and Name 1 in variable bindings in the PDU to

sysName.0.

(2) Agent sends NMS a GetNext response. If succeeded, the value of Name 1 in Variable

bindings in the response PDU is the next node sysLocation.0 of node sysName.0, and the value

of Value 1 is, for example, Beijing China; if failed, the reason for the error will be added to the

Error status field, and position will be added to the Error index field.

Figure 8 GetNext operation


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3. Set operation:

NMS wants to set the value of node sysName of the managed device to Device01,

using private as the read community name:

(1) NMS sends a Set request to Agent. The main fields in the request are set as follows:

Version to 1, Community to private, Name 1 in variable bindings in the PDU to sysName.0, and

Value1 to Device01.

(2) Agent sends NMS a Set response. If succeeded, the value of Value1 in Variable

bindings in the response PDU is the new name of the device (for example, Device01); if failed,

the reason for the error will be added to the Error status field, and position will be added to the

Error index field.

Figure 9 Set operation

4. Trap operation:

If abnormalities occur on a device, Agent will notify NMS by sending unsolicited

traps. For example, if the cable on a port of the device is plugged out, Agent will send a

linkDown trap to NMS. In the trap, the value of the Version field is 1, that of the Community

field is public, that of the enterprise field is the value of sysObjectID.0 (for example,

enterprises.25506), that of the Generic trap field is linkDown, and the Variable bindings field

contains the interface information.

Figure 10 Trap operation


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REFERENCES

1.Network Management:Principles and Practice by

Mani Subramanian

2.www.ccse.kfupm.edu.sa

3. RFC3411:An Architecture for Describing Simple Network

Management Protocol(SNMP) Management frameworks

4.http://www.javvin.com/protocol/rfc3584

5.http.//slidefinder.net/c/chapter4

6.www.its.bth.se/courses/tnm204/tnm20404

7.www.answers.com


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