SNMP Fundamentals

SNMP Overview

• Developed in 1988, widely supported in modern network hardware
• Designed to be simple with few commands
• Defined by IETF (Internet engineering task force)

SNMP and OSI Model

• Uses User Datagram Protocol (UDP) as transport mechanism
• Operates on two well-known ports: UDP Port 161 (SNMP Messages) and UDP Port 162 (SNMP Trap Message)

SNMP Compatible Devices

• Allows remote and local management of devices on the network
• Compatible devices include: servers, workstations, routers, switches, printers, and more

SNMP Functionality

• Fault Management
• Configuration Management
• Accounting Management
• Performance Monitoring and Management
• Security Management

SNMP Architecture

• Consists of SNMP Manager, SNMP Agent, and NMS (Network Management System)
• SNMP Manager collects and stores management information and makes it available to NMS
• SNMP Agent gathers and sends data about managed resources in response to manager requests
• NMS executes applications that monitor and control managed devices

SNMP Agent

• Small piece of code that runs on every managed device
• Collects information, stores it in MIB, and replies to manager with proper information
• Can initiate communication with SNMP manager using traps

SNMP Proxy

• Maintains information of one or more non-SNMP devices
• Converts control messages and runs on other NMS

NMS

• Executes applications that monitor and control managed devices
• Provides bulk of processing and memory resources required for network management

SNMP Internal Component

• SMI: Structure of Management Information
• MIBs: Management Information Base
• SNMP: Simple Network Management Protocol

SNMP Message

SNMP Trap

• Unrequested event reports sent to management system by SNMP agent process
• Generated when trappable event occurs and sent to trap destination
• Can be throttled (limited) and have priority associated with them

Issues with SNMP v2

• Multiple versions with no consensus
• Security improvements lacking
• Incompatibility with earlier versions
• Overhead implementing Bilingual Manager or Proxy Server

SNMP v2 Compatibility with SNMP v1

• Bilingual Manager: implements both SNMP v1 and v2 interpreter in manager
• Proxy Server: allows communication with SNMP v1 agent

SNMP v3

• General framework for all three SNMP versions
• Improved security feature: message integrity, authentication, and encryption

SNMP v3 Security

• Major security improvement: message integrity, authentication, and encryption
• Ensures data is not modified or tampered during transit

SNMP v3 Architecture

• SNMP engine provides services for sending, receiving, authenticating, and encrypting messages
• Dispatcher supports concurrent multiple SNMP message processing
• Message processing subsystem prepares message for sending and extracts information from received message
• Security subsystem provides security services
• Access Control System provides authorization services

SNMP v3 Application

• Command Generator: generates get-request, get-next-request, get-bulk, and set-request messages
• Command Responder: processes get and set requests destined for it
• Notification Receiver: receives asynchronous message and processes it
• Notification Originator: initiates asynchronous message or traps
• Proxy Forwarder: forwards requests and notifications to other SNMP engines