Tag: Hybrid fibre-coaxial

Slaughtering the hogs

How much Internet is too much? Apparently it’s 250 gigabytes, enough Internet content to fill up a $55 hard disk drive.

Comcast made news today by announcing a usage cap for Internet users. You can read more about it at PC Magazine. See also the DSLReports coverage.

The reason for the cap isn’t economical, it’s technical. In a shared physical topology, there must be management of usage in order to prevent performance problems due to congestion. Cable networks today are Hybrid Fiber Coax (HFC) networks, where the video and data is carried on fiber to distribution nodes which serve 500 to 2000 homes. All of these homes are on a common coaxial cable network, and share the capacity of the network. An image is worth a thousand words, so please view a simple HFC network diagram now.

This is a bit before my time, but a cable network is like a telephone party line. Common until around the 1940s, shared party line telephone service was how most homes received telephone service. It was cost effective because they didn’t have to run wire from every home back to the central office. Instead, it ran from house to house, so the circuit was shared. Telephone companies abandoned party line configurations over fifty years ago, and this has given them/us a big edge over cable.

For the last few years, Comcast has managed heavy usage by warning customers who used “too much”, without defining what too much was. This practice has been called an “invisible cap”. My guess is that this invisible cap is actually more effective than one which is well defined and documented. If you know how much you’re allowed to use, it’s possible to use bandwidth monitoring software to run up to but not over the limit. When the limit was unknown, users simply lived in fear and would presumably curtail their usage. Notably, users in locations where Comcast was the only broadband option would really be motivated to avoid getting the boot, as they’d have nowhere else to go for broadband Internet.

Of course, telco’s response was to point this weakness out in the ads many of us fondly remember. PacBell was criticized by cable companies who claimed they really didn’t have a problem. In fact they do, and the issue then and now is the same, and caps are the only real solution. (see that diagram again, and think “shared network”. There’s only so much to go around between the 500-2000 homes.)

The other solution they tried was filtering peer to peer traffic. They got in trouble with the FCC for this, and the new openly documented and disclosed cap is the result. Also notable, the illegal filtering of P2P traffic by Comcast is what really kicked the net neutrality cause into high gear. The folks at Save the Internet are continuing to fight for uniform and unfettered Internet access.

So, sit back and relax, watch the old PacBell ads and enjoy the trip down memory lane. Comcast has finally stuck the pigs, and they sure are squealing!

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