SNMP and MODBUS are both components of the application layer in the OSI model. Where MODBUS is a protocol that can be supported by different physical and data link layers, SNMP is exclusively an IP standard.
Unlike MODBUS IP, which typically uses the TCP transport layer, SNMP data is usually sent through UDP (User Datagram Protocol), which makes it faster, simpler and more efficient than the TCP used for Morningstar’s current MODBUS IP-enabled Ethernet stack.
If users are implementing a solar system in either an industrial environment such as a SCADA system or residential use, MODBUS typically has been the protocol of choice for its speed and reliability for both monitoring and control.
MODBUS is also the protocol platform for the SunSpec data standard widely used in legacy inverters and charge controllers, data logging hardware, and even storage systems for interoperability.
In many UPS, backup or telecommunication/network applications, SNMP may be a better choice as it will provide the greatest overall device compatibility and management.
When would I want to use SNMP over other protocols or methods of accessing MS device data?
SNMP would be a good choice for accessing data in systems with an existing IT infrastructure. It is useful for sites that have a centralized network management location or host computer. SNMP is ideal for simple ‘bulk’ status monitoring and data polling of many devices. It can also be useful for implementing system-level alert notifications.
However, if more complex system interaction is needed to alter system operation in real-time (i.e using bi-directional control), MODBUS may be preferable in those circumstances.
Mark Cerasuolo, Marketing Director, Morningstar Corporation
— Solar Builder magazine
[source: https://solarbuildermag.com/news/how-does-snmp-compare-to-modbus/]
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