North American Network Operators Group
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Re: Comcast blocking p2p uploads

  • From: Sean Figgins
  • Date: Fri Oct 19 23:45:03 2007

Frank Bulk wrote:

2) DSL and fiber have limitations, too.  The modulation and spectrum width
can vary, but most MSOs have their forward configured with a maximum of
around 38 Mbps (256-QAM, 6 MHz wide) and the return in the 9 Mbps range
(64-QAM, 3.2 MHz wide).  Charts here:
Forward: http://www.cable360.net/images/articles/15131_1168455349.gif
Return: http://www.cable360.net/images/articles/15131_1168455396.gif

Thank you, Frank. I'm not a HFC engineer, but rather an IP/Network/Server/Security guy, that worked on the backbone and lab side of a large MSO. My HFC experience is exclusive of what is between the CMTS and the cable modem. I know just enough to be able to live there.

I got my figures reversed. For some reason I was thinking that it was about 100 meg on the upstream and 45 meg on the downstream, but looks like I remembered it wrong.

Anyways, regardless of that, you pretty much validated what I was saying as to the reason why a MSO would deploy such a device. It's possibly cheaper to do so than to deploy the hardware to split the HFC pland and increase available bandwidth to subscriber ratio. Not that I agree with such a practice.

-Sean