The role of active and passive monitoring in virtual networks

Active monitoring: Also known as synthetic monitoring, involves injecting test traffic into the network, typically with the same forwarding criteria as the user traffic (service) being monitored, and then measuring its performance. These tests can either be one-way (from site ‘A’ to site ‘D’ or round trip (from site ‘A’ to site ‘D’ and back to site ‘A’), depending on what you want to measure. Since test traffic mimics the service traffic, active testing is ideal for providing a real-time view of the end-to-end performance of a service with regards to such things as latency (or delay), jitter (or delay variation), or packet loss. It’s worth noting that active testing can be performed between any 2 sites along the service path, for example, from site ‘A’ to site ‘B’ or site ’A’ to site ‘C’. This means that, with some simple math, it’s possible to segment the overall end-to-end path so that performance indicators can be derived on a per segment basis, providing greater, real-time visibility into where issues might be located. Network Troubleshooting ways

Active monitoring is the primary method for policing SLAs, since it provides a real-time view of performance.

Passive monitoring: This technique involves capturing and analyzing live network traffic, or traffic statistics, at a specific point in the network – for example, the network interface to an application server. As its name suggests, passive monitoring does not require another site in the network to be involved, or even aware. At its simplest, passive monitoring may be nothing more than the periodic collecting of port statistics, like byte and packet transmit and receive numbers. More typically, it also involves capturing some, or all, of the traffic flowing through a port for detailed, non-real-time, analysis of things like signaling protocols, application usage or top bandwidth consumers.