Cisco's latest Visual Networking Index (VNI) forecast looks at the period of 2011-2016 and is based on data collected from service providers and analysts. The new forecast is predicting that in 2016 the total volume of Internet traffic will be 1.3 zettabytes (ZB). Just to put that into perspective somewhat, one zettabyte is equal to one trillion gigabytes (GB)!

In last year's VNI forecast, which looked at the 2011-2015 period, Cisco had forecast that Internet traffic would grow to 966 exabytes (EB) by 2015. The difference between what Cisco is forecast for 2015 and 2016 is approximately 330EB, which is slightly less than the 369EB of Internet traffic generated in all of 2011.

"The big news is that we are approaching the zettabyte era," Thomas Barnett, senior manager of Product and Solutions Marketing for Cisco, told Enterprise Networking Planet. "Last year, in the 2010-2015 forecast, the compound annual growth rate (CAGR) was about 32 percent over the forecast period, in contrast the CAGR for the 2011-2016 forecast is about 29 percent."

Barnett noted that while Cisco is seeing a tapering off of growth, in absolute terms there is still a tremendous amount of traffic coming down the pike. Growth is being fueled by more devices and more connections per person. By 2016, Cisco forecasts that 45 percent of the world's population or 3.4 billion people will be on the Internet.

Video continues to be a major driver of growth with 792 million users in 2011 expanding to 1.5 billion in 2016. While some of that video traffic will be driven by traditional computing devices, Cisco is also forecasting that Web-enabled TVs will account for six percent of global consumer Internet traffic by 2016. Desktop-based video conferencing will also be front and center in 2016, growing to 219 million users up from just over 36 million in 2011.

Growth in video as a percent of traffic stands in contrast to the growth of peer-to-peer (P2P) traffic. At the end of 2011 P2P traffic accounted for 77 percent of global consumer Internet traffic. That percentage is set to fall to 54 percent by 2016, as more traffic moves to video.

The shift to wireless networking

Another key shift that is occurring is the one towards wireless networking. Cisco is forecasting that 51 percent of all global Internet traffic will be Wi-Fi based by 2016 while an additional 10 percent of traffic will use mobile broadband.

Over the next five years, there is the potential for economic slowdowns in parts of the world, though Cisco doesn't expect that to impact Internet traffic demand too much. Barnett noted that Cisco doesn't factor economic conditions directly into the VNI forecast.

"Certainly a slowdown could have an impact and if people begin to see network based services as something they don't want to be spending their income on, that could slow things down," Barnett said. "What we've seen over the last two sets of forecasts is that traffic has continued to grow significantly."

While global Internet traffic is growing fast, it's important to remember that data center traffic is growing faster. Cisco's Global Cloud Index report released in November of 2011 forecast that traffic inside data centers was set to grow to 4.8ZB in 2015 up from 1.1ZB in 2010.

Sean Michael Kerner is a senior editor at InternetNews.com, the news service of the IT Business Edge Network, the network for technology professionals Follow him on Twitter @TechJournalist.