[70882] in North American Network Operators' Group
Re: Cable networks RE: best effort has economic problems, maybe OT
daemon@ATHENA.MIT.EDU (Petri Helenius)
Sun May 30 14:20:21 2004
Date: Sun, 30 May 2004 21:19:33 +0300
From: Petri Helenius <pete@he.iki.fi>
To: "Christopher J. Wolff" <chris@bblabs.com>
Cc: nanog@merit.edu
In-Reply-To: <B0008668808@mail.bblabs.net>
Errors-To: owner-nanog-outgoing@merit.edu
Christopher J. Wolff wrote:
>Folks,
>
>This is a great discussion. I'm interested in understanding these types of
>limitations in the context of HFC cable networks. In my opinion, HDTV
>channel bandwidth (30mhz?) , increased demand for voip, and growing demand
>for IP connectivity is going to stress the cable network model as well,
>forcing cable operators to convert everything to IP before going out across
>the wire. Any input is appreciated.
>
>
>
The bandwidth you quote refers to the unencoded signal bandwidth. The
actual transmission has the same channel spacing than traditional
television, be that NTSC or PAL or SECAM. Terrestial applications
typically carry 20-25 megabits and cable & satellite applications
typically 40-50 megabits per channel/transponder. HDTV channel usually
consumes 19.8Mbps for video plus some extra for audio + multiplexing
information. So a channel that used to carry one NTSC analog channel
over the air can be used to carry one HDTV channel or in the case of
cable/satellite networks, two.
I´m all for encapsulating all transmission to IP packets, because it
would make a lot of things easier, but I would suspect some places need
to freeze first :-)
Pete
