Network Management: Snmp

Network Management: SNMP

1   NETWORK MANAGEMENT SYSTEM We can say that the functions performed by a network management system can be divided into five broad categories: configuration management, fault management, performance management, security management, and accounting management.

 NETWORK MANAGEMENT SYSTEM Configuration management:Initial configuration which can change Status of each entity and its relation to other entities Reconfiguration:Adjusting the network components Three types:- hardware, software, user-account Documentation:- hardware, software, user-account

 NETWORK MANAGEMENT SYSTEM Performance management:Capacity:- of the network which is limited Traffic:-internally and externally Throughput:Response time:- the time a user requests a service to the time the service is granted.

 NETWORK MANAGEMENT SYSTEM Fault management:Reactive:Detecting, isolating, correcting and recording faults. Steps:- detect the location of the fault, isolate the fault, correct the fault , document the fault. Proactive:- prevent faults from occurring Security Management:- defined security policy Accounting Management:- Control of user’s access to network resources through charges.

Functions of a network management system

 SIMPLE NETWORK MANAGEMENT            PROTOCOL (SNMP) The Simple Network Management Protocol (SNMP) is a framework for managing devices in an internet using the TCP/IP protocol suite. It provides a set of fundamental operations for monitoring and maintaining an internet.

SNMP concept

1.A manager checks an agent by requesting information that reflects the behavior of the agent. 2.A manger forces an agent to perform a task by resetting values in the agent database. 3.An agent contributes to the management process by warning the manager of an unusual situation.

Components of network management on the Internet

SNMP defines the format of packets exchanged between a manager and an agent. It reads and changes the status (values) of objects (variables) in SNMP packets.

SMI defines the general rules for naming objects, defining object types (including range and length), and showing how to encode objects and values. SMI does not define the number of objects an entity should manage or name the objects to be managed or define the association between the objects and their values.

MIB creates a collection of named objects, their types, and their relationships to each other in an entity to be managed.

We can compare the task of network management to the task of writing a program. ❏ Both tasks need rules. In network management this is handled by SMI. ❏ Both tasks need variable declarations. In network management this is handled by MIB. ❏ Both tasks have actions performed by statements. In network management this is handled by SNMP.

Management overview

 MANAGEMENT OVERVIEW A manager wants to send a message to an agent to find the number of UDP user datagrams received by the agent (done by MIB) SMI – encoding the name of the object SNMP – creating a GetRequest message and encapsulating the encoded message

Structure of Management Information Object attributes

NAME

SMI requires that each managed object has a name. For this ,it uses an object identifier Integer-dot representation is used in SNMP Name-dot representation is used by people.

Object identifier

All objects managed by SNMP are given an object identifier. The object identifier always starts with 1.3.6.1.2.1.

Data type

Data types

Conceptual data types

Encoding format

SMI uses Basic Encoding Rules (BER), to encode data BER specifies that each piece of data be encoded in triplet format:tag,length and value. Classes:- universal(00), application-wide(01),context-specific(10),private(11) Format:- data is simple(0) or structured(1). Number:- divides simple or structured data into sub groups.

Codes for data types

Length format

Length:- 1 or more bytes. If 1 byte: then MSB = 0;other 7 bits define the length

If > 1 byte: then MSB of the first byte = 1;other 7 bits define the number of bytes needed to define the length

Management Information Base (MIB) MIB2 – Version 2 Each agent has its own MIB2, a collection of all the objects a manager can manage. Objects are categorised under 10 groups:-

System Interface Address translation:-information about ARP table Ip:- routing table and ip address icmp transmission

udp group

udp variables and tables

Indexes for udpTable

Lexicographic ordering

Tables are ordered according to column-row rules; column by column; top to bottom

SNMP It is an application program that allows: a manager to retrieve the value of an object defined in an agent A manager to store a value in an object in an agent An agent to send an alarm message about an abnormal situation to the manager

SNMP PDUs

SNMP PDU’s GetRequest:-to retrieve the value of a variable or a set of variables GetNextRequest:-to retrieve values of entries in a table GetBulkRequest:- to retrieve a large amount of data SetRequest:-to set a value in a variable Response:- response to get commands Trap:-to report an event. InformRequest:- to get the value of some variables from agents under the control of the remote manager; who the responds with a response . Report:- to report errors between managers.

SNMP PDU format

SNMP PDU Format PDU type:Codes for SNMP messages

Request Id:- sequence no. used by the manager in a request and repeated by an agent in a response

SNMP PDU Format  Error status:- used only in responses; 0 in requests Types of errors

Error Index:- an offset that tells the manager which variable caused the error.  Var-Bind List:-set of variables with the corresponding values the manager wants to retrieve or set. Values are null in GetRequest and GetNextRequest

SNMP message

PDU embedded in a message  4 elements:- version (3), header, security parameters (message digest), data( includes encoded PDU)

Port numbers for SNMP