Simple Network Management Protocol

SNMP communication principles diagram

Simple Network Management Protocol (SNMP) is an Internet Standard protocol for collecting and organizing information about managed devices on IP networks and for modifying that information to change device behavior. Devices that typically support SNMP include routers, switches, servers, workstations, printers, modems, and more.

Overview

SNMP is part of the Internet Protocol Suite as defined by the Internet Engineering Task Force (IETF). It consists of a set of standards for network management, including an application layer protocol, a database schema, and a set of data objects.

Components

SNMP has three key components:

• Managed devices: Network nodes that contain an SNMP agent and reside on a managed network. These devices collect and store management information and make it available using SNMP.
• Agents: Software modules that reside within managed devices. An agent translates information into a form compatible with SNMP.
• Network management systems (NMS): Applications that monitor and control managed devices. NMS execute applications that monitor and control managed devices.

Versions

There are three significant versions of SNMP:

• SNMPv1: The original version of the protocol, defined in RFC 1157.
• SNMPv2c: An enhanced version, defined in RFC 1901, which includes improvements in performance, security, and manager-to-manager communications.
• SNMPv3: The current version, defined in RFC 3410, which adds security and remote configuration enhancements to SNMPv2c.

Operation

SNMP operates in the application layer of the Internet Protocol Suite. It uses the User Datagram Protocol (UDP) as its transport protocol. SNMP messages are sent to the agent on the managed device, which then processes the request and sends a response back to the NMS.

SNMP Messages

SNMP uses several types of messages to communicate between the NMS and the agents:

• GetRequest: Used by the NMS to retrieve one or more values from the managed device.
• SetRequest: Used by the NMS to set a value on the managed device.
• GetNextRequest: Used by the NMS to retrieve the next value in a table or list.
• GetBulkRequest: Used by the NMS to retrieve large blocks of data.
• Response: Sent by the agent in reply to a GetRequest, SetRequest, GetNextRequest, or GetBulkRequest.
• Trap: Sent by the agent to the NMS to report an event.
• InformRequest: Similar to a Trap, but requires an acknowledgment from the NMS.
• Report: Used for SNMPv3-specific communication.

Security

SNMPv3 provides significant security enhancements over previous versions, including:

• Message integrity: Ensures that a packet has not been tampered with in transit.
• Authentication: Verifies that the message is from a valid source.
• Encryption: Scrambles the contents of a packet to prevent it from being read by unauthorized sources.

Related Pages

• Network management
• Internet Protocol Suite
• User Datagram Protocol
• Router
• Switch
• Server
• Workstation
• Printer
• Modem

See Also

• Management Information Base
• Remote Monitoring
• Network Management System