SNMP Tutorial Part 3: Understanding Packet Types and Structure

Show Me Products That Do This ...

Part 1 | Part 2 | Part 3 | Part 4 | Part 5
All 5 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.

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

Part 1 | Part 2 | Part 3 | Part 4 | Part 5
All 5 parts for easy printing

Show Me Products That Do This ...

 top

What Do You Want To Do With SNMP?

1. Mediate SNMP and Other Protocols
2. Display SNMP Alarm Data at Your NOC and in Your Web Browser
3. Monitor Discrete, Analog, and Ping Alarms via SNMP
4. Automatically Dispatch Repair Personnel
5. Control Remote Equipment via SNMP
6. Use Dial-Up Connections to Link SNMP Remotes to LAN
7. Find the SNMP Alarm Monitoring Capacity That's Right for Your Size Site
8. Use T1 Connection to Link SNMP Remotes to LAN

What Do You Want To Learn About SNMP?

1. SNMP Tutorials - Learn More About SNMP
2. 8 things you need to know before selecting an SNMP proxy agent to monitor your non-SNMP managed devices