SNMP works in the application layer (the highest level of OSI), and has been on the marketing since 1988 and has been evolving ever since. Where SNMP v1 was the original design, the latest version we have currently is now SMTP v3.
The SNMP protocol is the most commonly used protocol for configuring and monitoring the health of a number of networking devices. As SNMP has been the standard for decades; there are many SNMP agents that are compatible with most devices. Such examples include routers, WI-FI, firewalls, servers, UPS, switches, printers and more.
So how does SNMP work, there are 3 main components:
- Managed devices that currently contain an agent are used to support the SNMP protocol.
- Agents: the agent is a small piece software that is responsible for receiving the configuration instructions from the NMS (Network Management System) – this acts like a Manager who has the correct credentials to access to the device. The Agent receives this information in an understandable format for the NMS and the two communicate over the network in this way.
- Network Management System (NMS): A centralised system that monitors and controls the devices located through the network using the SNMP protocol.
The NMS performs some important tasks:
- Issues a GetRequest which is sent to the agent in order to take one or more values.
- Issues a GetNextRequest to take the next value in a table or list of values within the agent.
- GetBulk is used to take a lot of data from the managed device.
- Receives a GetResponse from the agent indicating the results of a GetRequest or an error that may have resulted during a SetRequest.
- Issues a SetRequest to set one or multiple values within the managed device via the agent.
- Receives traps from the agent. A trap is a message that may indicate an error, a problem with the device or that a predefined threshold has been exceeded. Traps are typically turned on and / or configured by the NMS so that the NMS can be notified of some event occurring on the device. Traps are often a better way to go than polling a device for some event as a trap is immediate while polling is done at some predefined interval which may miss something.
The art of network management has been around for as long as networks have been around. Network management systems, tools and methodologies will continue to evolve as the size and complexity of networks will continue to grow. SNMP is a standard that is supported by the majority of network devices and should be supported by the centralised NMS so that a single NMS can manage the entire network.