Subject: mboned: RE: comments on draft-hayashi-rac-issues-00

From: "Manfredi, Albert E" <[email-masked]>
Date: Mon, 7 Mar 2005 10:45:15 -0500

Pekka Savola [mailto:[email-masked]] wrote:

> Well.  We're talking about gigabit grade backbones here.  Even with 
> the bitstream of 5 Mbit/s per group, even 100 simultaneous groups 
> might not be a problem.  Do the content providers even offer that 
> many?  Is this a real concern in real networks?

Could be a problem. IPTV networks want to compete against cable networks, which means offering more than 100 channels, and each could be HDTV. Cable networks today can cram around 130 channels, 6 MHz wide, each one potentially modulated 256-QAM, which means 38.8 * 130 = 5 Gb/s of core bandwidth for the TV programs (when the plant is dedicated to digital TV).

To compete agsinst that, IPTV nets advertize more streams, video on demand, broadband Internet access, and so on. The cable to each home is restricted in something on the order of 25 Mb/s today, perhaps 100 Mb/s in the future. So clearly the end users need to conduct IGMP with edge routers up in the network somewhere. But even within the core network, if it's 1 Gb/s, you don't have a lot of room.

Bert

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