Infographic
Comparison of SNMP, Packet Sniffing and Netflow
Depending on your infrastructure you can monitor the usage of your network using the three different protocols supported by PRTG Network Monitor: SNMP, Packet Sniffing, and Netflow. The animations below illustrate for each option how PRTG collects the data.
SNMP-Monitoring
The Simple Network Management Protocol (SNMP) is the most basic method of gathering bandwidth and network usage data. It can be used to monitor bandwidth usage of routers and switches port-by-port, as well as device readings like memory, CPU load, etc.
Data Acquisition Using SNMP
When this technology is used PRTG queries the devices (e.g. routers, switches, and servers) for the traffic counters of each port. This option creates the least CPU load and network load of the three methods.
Packet Sniffing in LANs and WLANs
If you need to know what applications or IP-addresses are causing the traffic in your network you can use a Packet Sniffer which looks at every single data packet travelling in your network for accounting purposes. PRTG can analyze the packets passing the network card of a PC or it can be connected to a so-called monitoring port of a switch. Also WLAN networks can be monitored this way.
Data Acquisition Using Packet Sniffing (LAN)
In order to calculate bandwidth usage PRTG inspects all network data packets either passing the PC's network card (shown on the left side) or the data packets sent by a monitoring port of a switch (right side) with its built-in Packet Sniffer. From the three technologies shown here this one creates the most CPU and network load. For larger networks PRTG offers remote probes that distribute the load and assure maximum performance.
Data Acquisition Using Packet Sniffing (WLAN)
In order to calculate bandwidth usage for a WLAN, PRTG inspects all network data packets acquired using a specialized WLAN USB dongle (available from the manufacturer's website cacetech.com). This USB adapter acts as a network card for WLANs and allows PRTG to read transmitted data packages of a WLAN while remaining invisible to other network subscribers.
NetFlow Protocol
Another option to measure bandwidth usage "by IP address" or "by application" is to use Cisco's NetFlow protocol which is especially suited for high traffic networks. Many routers and switches from Cisco support this protocol.
Data Aquisition Using Cisco's NetFlow Protocol
Cisco devices with NetFlow support track the bandwidth usage of the network internally and then only send pre-aggregated data to the PRTG system for accounting purposes. This way the computing load for PRTG is much lower. This option is recommended for high traffic networks.
More Information
If you are interested in a more detailed description of bandwidth monitoring for various network infrastructures please check out the following knowledge base articles:
