Remote Monitoring & Control
"We build to your specs"
1-800-693-0351

SNMP Tutorial Part 3: Understanding Packet Types and Structure



Part 1 - What is SMNP? | Part 2 - The Management Information Base | Part 3 All 3 parts for easy printing

This article in our series on the Simple Network Management Protocol (SNMP) examines the communication between managers and agents. Basic serial telemetry protocols, like TBOS, are byte oriented with a single byte exchanged to communicate. Expanded serial telemetry protocols, like TABS, are packet oriented with packets of bytes exchanged to communicate. The packets contain header, data and checksum bytes. SNMP is also packet oriented with the following SNMP v1 packets (Protocol Data Units or PDUs) used to communicate:

  1. Get
  2. GetNext
  3. Set
  4. Trap

The manager sends a Get or GetNext to read a variable or variables and the agent's response contains the requested information if managed. The manager sends a Set to change a variable or variables and the agent's response confirms the change if allowed. The agent sends a Trap when a specific event occurs.

SNMP Products:

Pricing info

The image below shows the packet formats. Each variable binding contains an identifier, a type and a value (if a Set or response). The agent checks each identifier against its MIB to determine whether the object is managed and changeable (if processing a Set). The manager uses its MIB to display the readable name of the variable and sometimes interpret its value.

SNMP Packet Formats
SNMP Packet Formats

Part 1 - Intro to SNMP | Part 2 - The Management Information Base | Part 3
All 3 parts for easy printing

"Ask us anything"
(we're experts)

-Ron, Mark, & Marshall
DPS Engineers

Most Popular Pages

Ask a DPS Expert
50 SNMP/SCADA Tutorials
Master Stations
RTUs
Environmental Sensors
Electronic Door Control

Popular White Papers

SNMPv3 Tutorial
SNMP MIB Tutorial
SCADA Tutorial
Building Access Control
Battery Monitoring Guide

Top Case Studies

National Grid
RT Communications
Duke Energy
Wyoming PBS
US Cellular

Learning Resources

DPS News
Knowledge Library
Application Diagrams
Real-World Examples
Meeting Rooms
Weekly E-magazine