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Cisco’s Virtual Networking Index, in a report Entering the Zettabyte Era (pdf) issued today Jun 1 2011, predicts that annual global IP traffic (Internet and non-Internet) will grow 400% by 2015 to reach 966 exabytes or nearly 1 zettabyte. The chart below represents Internet traffic.

Other predictions for 2015:

• There will be 3 billion global Internet users, with average bandwidth of 27mbps.
• The number of devices connected to IP networks will be twice as high as the global population.
• There will be 6 million Internet households worldwide generating over a terabyte per month in Internet traffic, up from just a few hundred thousand in 2010 (but most of them will be in Asia).
• Traffic from wireless devices will exceed traffic from wired devices.
• Peak traffic will be equivalent to 500 million people streaming a high-definition video continuously.

Over 60% of the traffic will be video, broken down as follows:

Interestingly the report tackles the topic of possible changes to the asymmetric bandwidth status quo:

With the exception of short-form video and video calling, most forms of Internet video do not have a large upstream component.

As a result, traffic is not becoming more symmetric as many expected when user-generated content first became popular. The emergence of subscribers as content producers is an extremely important social, economic, and cultural phenomenon, but subscribers still consume far more video than they produce. Upstream traffic has been flat as a percentage for several years, according to data from the participants in the Cisco VNI Usage program.

It appears likely that residential Internet traffic will remain asymmetric for the next few years. However, there are a number of scenarios that could result in a move toward increased symmetry.
• Content providers and distributors could adopt P2P as a distribution mechanism. There has been a strong case for P2P as a low-cost content delivery system for many years, yet most content providers and distributors have opted for direct distribution, with the exception of applications such as PPStream and PPLive in China, which offer live video streaming through P2P, and have had great success. If content providers in other regions follow suit, traffic could rapidly become highly symmetric.
• High-end video communications could accelerate, requiring symmetric bandwidth. PC-to-PC video calling is gaining momentum, and the nascent mobile video calling market appears to have promise. If high-end video calling becomes popular, this will move traffic toward symmetry again.

Generally, if service providers provide ample upstream bandwidth, applications that use upstream capacity will begin to appear.