Is Simple Network Management Protocol (SNMP) really simple?

SNMP (Simple Network Management Protocol) is the common language of network monitoring and an essential component of any network management solution.

SNMP (Simple Network Management Protocol) is the common language of network monitoring and an essential component of any network management solution. It is used mostly in network management systems to monitor network-attached devices for conditions that warrant administrative attention. It governs how management data is retrieved and processed from network devices by a network management system (NMS) and how network devices send management information back to an NMS.

There is a view within the industry, however, that SNMP is a simple protocol to understand and implement. This ranks as the number one deception in the industry. SNMP is by no means simple, even for a seasoned network engineer. Getting useful and meaningful data for your NMS via SNMP is a challenge and this is where vendors can hinder or help you in this regard.

1. Get specifics on a vendors SNMP capability.
Most network management vendors claim to be SNMP-capable. But often, what they only offer is simple SNMP GET requests. This asks a network device to return the current value of a specific object identifier (OID) such as “packets IN.” This simplistic polling yields data such as “packets in = 5,992.” What can you do with this information? Not much.

A true NMS assembles appropriate OID values into statistics that are meaningful and useable. This is where it can get complex. A good example of this is “bandwidth utilization”. Contrary to what some vendors tell you, the statistic for bandwidth utilization is not a single OID object, but two OIDs, with appropriate mathematics built in. The actual statistic is created by using the formula: ((IN pkts in Octets OUT pkts in Octets) * 8)/1024. So where meaningful, useable statistics are required, expect complexity.

2. Get a demonstration on any functionality claims
Many vendors will say they can provide statistics like bandwidth utilization, but in truth, they leave it up to you to figure out which OIDs you need, and then how to perform the appropriate mathematics. If you are unclear about their claims, simply ask to see the functionality demonstrated.

3. Request that any statistics you need are built in to the NMS
If you don’t know what statistics are important, it may be that you have never properly implemented this powerful monitoring capability. True SNMP is not easy to implement so unless you are a programmer or SNMP expert, you should have the statistics built in.

4. Understand how they decipher SNMP polling and SNMP monitoring output
SNMP polling means that a network management system polls (sends SNMP GET requests) to the remote device. In other words, it asks the device for information and the device responds with a value. SNMP monitoring means that the network device is configured to send SNMP traps (ie: messages) to an NMS without a specific request.

Again, the problem is, as it is with most network monitoring information, there may be numerous trap messages which, in their raw form, are cryptic. Deciphering these messages appropriately relies on the experience of the network engineer and the depth to which SNMP is enabled.

SNMP is a powerful component of any NMS, but getting the best from the protocol can be complex and time-consuming. A truly SNMP capable vendor can remove the associated burden and deliver tangible value to your network management practice.

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