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SNMP ( Simple Network Management Protocol ) based Network Management. Network Management: What is it?. Network management includes deployment,integration and coordination of the hardware, software, and human elements

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network management what is it
NetworkManagement: What is it?
  • Network management includes
    • deployment,integration and coordination of the hardware, software, and human elements
    • to monitor, test, poll, configure, analyze, evaluate and control the network and element resources
    • to meet the real-time, operational performance, and Quality of service requirements at a reasonable cost.
network management why is it needed
Network Management: Why is it needed?
  • Lowers costs by eliminating the need for many administrators at multiple locations performing the same function
  • Makes network administration and monitoring easier and more convenient
  • Coherent presentation of data
functional areas of network management according to osi network management model
Functional Areas of Network Management(According to OSI Network Management Model)

Performance Management– how smoothly is the network running

Fault Management- reactive and proactive network fault management (deals with problems and emergencies in the network)

Configuration Management– keeping track of device settings and how they function

Accounting Management- cost management and charge back assessment

Security Management- SNMP (Version 1 and 2) doesn’t provide much here

network management architectures
Network Management Architectures

1) Management Entity job is to provide access to management data, controls, and behaviors:

  • Regular polling or sampling of management data
    • the management entity requests updates from managed devices to reflect recent status of the network being managed.
  • When alerts are received, appropriate responses must be generated
network management architectures contd
Network Management Architectures (contd.)

2) Managed Device

  • At each managed device, a special piece of software(process) called a management agent responds to polls for collected data,
  • The management agent itself has custody of a management database (MDB) of information that it collects and maintains over time
network management architectures contd1
Network Management Architectures (contd.)

3) N/w Management Protocol

  • The protocol runs between managing entity and the managed device.
  • Allows the managing entity to query the status of the managed devices .
  • Agents can use the network management protocol to inform the managing entity of exceptional events.
  • Two major versions SNMPv1, SNMPv2
  • SNMPv1 is the recommended standard
  • SNMPv2 has become split into:
  • SNMPv2u - SNMPv2 with user-based security
  • SNMPv2* - SNMPv2 with user-based security and additional features
  • SNMPv2c - SNMPv2 without security
  • SNMPv3 - Security
client pull server push
Client Pull & Server Push
  • SNMP is a “client pull” model

The management system (client) “pulls” data from the agent (server).

  • SNMP is a “server push” model

The agent (server) “pushes” out a trap message to a (client) management system

the internet standard management framework
The Internet- Standard Management Framework
  • SNMP is a tool (protocol) that allows for remote and local management of items on the network including servers, workstations, routers, switches and other managed devices.
  • Comprised of agents and managers
  • Agent - process running on each managed node collecting information about the device it is running on.
  • Manager - process running on a management workstation that requests information about devices on the network.
the internet standard management framework contd
The Internet- Standard Management Framework (contd.)

SNMP network management consists of four parts:

  • Management Information Base (MIB)
  • A map of the hierarchical order of all managed objects and how they are accessed
  • Structure of Management Information (SMI)
  • Rules specifying the format used to define objects managed on the network that the SNMP protocol accesses
  • SNMP Protocol
  • Defines format of messages exchanged by management systems and agents.
  • Specifies the Get, GetNext, Set, and Trap operations
  • Security and administration capabilities
  • The addition of these capabilities represents the major enhancement in SNMPv3 over SNMPv2
mib 2

MIB-II Standard Internet MIB

  • Definition follows structure given in SMI
  • MIB-II (RFC 1213) is current standard definition of the virtual file store for SNMP manageable objects
  • Has 10 basic groups
    • system
    • interfaces
    • at
    • ip
    • icmp
    • tcp
    • udp
    • egp
    • transmission
    • snmp
  • If agent implements any group then is has to implement all of the managed objects within that group
ports udp
Ports & UDP
  • SNMP uses User Datagram Protocol (UDP) as the transport mechanism for SNMP messages


IP Packet

SNMP Message


UDP Datagram

  • Like FTP, SNMP uses two well-known ports to operate:
  • UDP Port 161 - SNMP Messages
  • UDP Port 162 - SNMP Trap Messages
four basic operations
Four Basic Operations
  • Get

Retrieves the value of a MIB variable stored on the agent machine

(integer, string, or address of another MIB variable)

  • GetNext

Retrieves the next value of the next lexical MIB variable

  • Set

Changes the value of a MIB variable

  • Trap

An unsolicited notification sent by an agent to a management application (typically a notification of something unexpected, like an error)

basic operations contd
Basic operations contd..



port 161


port 161





port 161



port 162

port 161

  • Traps are unrequested event reports that are sent to a management system by an SNMP agent process
  • When a trappable event occurs, a trap message is generated by the agent and is sent to a trap destination (a specific, configured network address)
  • Many events can be configured to signal a trap, like a network cable fault, failing NIC or Hard Drive, a “General Protection Fault”, or a power supply failure
  • Traps can also be throttled -- You can limit the number of traps sent per second from the agent
  • Traps have a priority associated with them -- Critical, Major, Minor, Warning, Marginal, Informational, Normal, Unknown
trap receivers
Trap Receivers
  • Management applications can handle the trap in a few ways:
  • Poll the agent that sent the trap for more information about the event, and the status of the rest of the machine.
  • Log the reception of the trap.
  • Completely ignore the trap.
languages of snmp
Languages of SNMP
  • Structure of Management Information (SMI)

specifies the format used for defining managed objects that are accessed via the SNMP protocol

  • Abstract Syntax Notation One (ASN.1)

used to define the format of SNMP messages and managed objects (MIB modules) using an unambiguous data description format

  • Basic Encoding Rules (BER)

used to encode the SNMP messages into a format suitable for transmission across a network

snmp message encoding
  • The description of MIBs and message formats is based on the ASN.1 syntax.
  • The mapping from an abstract syntax upon a transfer syntax is defined by BER.
basic message format
Basic Message Format

Message Length

Message Version

Message Preamble

Community String

PDU Header

SNMP Protocol Data Unit

PDU Body

snmp agents

Monolithic Agents

  • not extendible
  • optimized for specific hardware platform and OS
SNMP Agents

Two basic designs of agents

  • Extendible Agents
  • Open, modular design allows for adaptations to new management data and operational requirements
community names
Community Names
  • A community string is a password that allows access to a network device. It defines what "community of people" can access the SNMP information that is on the device.
  • Community names are used to define where an SNMP message is destined for.
  • Set up your agents to belong to certain communities.
  • Set up your management applications to monitor and receive traps from certain community names.
  • There are actually three community strings for SNMP-speaking devices:
    • The SNMP Read-only community string
    • The SNMP Read-Write community string
    • The SNMP Trap community string
proxy management
Proxy Management
  • A node may not support SNMP, but may be manageable by SNMP through a proxy agent running on another machine.
  • Nowadays the term proxy denotes a device that forwards SNMP messages, but doesn’t look at the individual objects.
advantages of using snmp
Advantages of using SNMP
  • Standardized
  • universally supported
  • extendible
  • portable
  • allows distributed management access
  • lightweight protocol