Multicast and the ‘Super Bowl Problem’

It’s Super Bowl time, and for network technologists, the big action has little to do with the Broncos or the Seahawks and everything to do with how many people will watch the big game as a video stream over the Internet, vs. a traditional television broadcast.

In network terms, the Super Bowl is to technologists what Mother’s Day is to the people who built and maintain the original telephone network: the day the network gets stress-tested for maximum usage. Conversationally, network engineers tend to append the word “problem” to it — “the Super Bowl problem.”

Telephony engineers even came up with a unit of measure for it — the Erlang (for Agner Erlang, the guy who came up with it). The Erlang measures the average number of concurrent phone calls carried by a circuit over a period of time.

So far as we know, there’s still no official “video Erlang,” but the concept is the same. The numbers: In 2012, the big game hit the Internet as a live video stream for the first time. A little more than 1 million people tuned in that way; 111.3 million watched it on TV. Last year, about 3 million people watched the game as a live Internet stream vs. the TV audience of 108.4 million.

At issue is what happens when half or more of Super Bowl viewers tune in over the Internet, and/or using Internet protocol. What happens, for instance, when 50 million people are all watching the same thing as a live video stream? What happens when they pause or rewind?

“If it were something you could hear, what you’d hear is a giant flushing sound,” one technologist quipped about it last week.

Refresher: “Multicast” is the Internet-y way of saying “broadcast,” meaning one to many. Right now, when you stream anything over the Internet, you’re watching a “unicast.” A special session is set up between you and the server holding what you want to watch. If your neighbor chooses to watch the same thing, she gets a different unicast stream. One to one.

What if all 108 million football watchers needed a unicast stream of the same thing, all at the same time?

This is what people are talking about when they say the Internet would buckle.

So where are we with multicast? Cable technologists say they’re making steady progress, but are divided over models of when things go wrong. Some say the efficiencies enabled by multicast only kick in when 30% or more of viewers are watching the big game over the Internet. Others say the operational impacts, especially ad insertion, are going to be significant.

So here’s my prediction: Either the Broncos or the Seahawks will win, and 6 million people will watch the game as a live Internet stream.

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