Okay, so we knew Netflix was popular. But maybe not this popular.

In fact, nearly one-third of all bandwidth belongs to Netflix users during primetime hours, making it the largest single source of Internet traffic overall, according to data from Sandvine, a broadband equipment company.

To put this into perspective, a single Netflix movie, streaming in high-definition, reportedly uses about 3,600MB; a standard-def movie is around 500 to 700MB.

In North America, Netflix is now 29.7 percent of peak downstream traffic and has become the largest source of Internet traffic overall. Currently, what Sandvine categorizes as “real-time entertainment” applications consume 49.2 percent of peak aggregate traffic, up from 29.5 percent in 2009 – a 60 percent increase. Sandvine forecasts that the real-time entertainment category will represent 55-60 percent of peak aggregate traffic by the end of 2011.

HTTP and YouTube applications follow Netflix, using up 18 percent and 11 percent of bandwidth, respectively. 

Since the company’s last report in the fall of 2010, it’s become evident a growing appetite for on-demand applications will continue to drive data consumption and network quality requirements, Sandvine said.

In Europe, real-time entertainment is continuing a steady ascent, rising to 33.2 percent of peak aggregate traffic, up from 31.9 percent last fall, according to Sandvine’s “Global Internet Phenomena Report: Spring 2011.”

BitTorrent, a peer-to-peer (P2P) file sharing protocol, is the largest single component of both upstream (59.7 percent) and downstream (21.6 percent) Internet traffic during peak periods.

In the UK, BBC’s iPlayer is 6.6 percent of peak downstream traffic, reflecting the demand for localized content in many markets. Overall, individual subscribers in Europe consume twice the amount of data as North Americans.