[opendtv] Re: The New Mac Mini is All About Movies
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
- Date: Sun, 23 Jan 2005 17:59:03 -0500
Craig Birkmaier wrote:
>http://www.pbs.org/cringely/pulpit/pulpit20050120.html
>
> Did you read the entire story Bert?
>
> If Cringely is right, would you call this a walled
> garden IPTV deployment, or an effort to BYPASS the
> walled gardens?
First of all, this isn't IPTV. Unless I missed
something in the article, all he's talking about is
web sites where one would download HD movies. The
sites will be controlled access, but there's no
hint that this is an IPTV scheme. (It might be
that these web servers are contained in walled
gardens, in various ISP nets, but that's not
mandatory.)
Secondly, my definition of a walled garden is a
controlled access *network*. Almost by definition,
any network which supports multiple IP Multicast
groups is a walled garden. You might want to read
RFCs 2365 and 3171 to see what the thinking is.
Digital cable is a very good example not only of
a walled garden, but also a good model for how a
real world IPTV deployment would look, from the
perspective of bandwidth allocation and access.
Specifically, in a digital cable, you have only so
much bandwidth dedicated to Internet access, and
the bulk of bandwidth dedicated to high quality TV
streams. In an IPTV network, the network would
similarly dedicate a small portion of its total
bandwidth to Internet access for its subscribers,
and the the bulk would go to a pre-selected set
of high quality TV stream multicasts.
The only significant difference (from a user's
perspective) is that in digital cable, the end
user gets the entire fire hose delivered into
his home, to parse through as he sees fit. In
an IPTV network, the local loop is seriously
bandwidth challenged, and therefore the network
must do the intelligent parsing at some node
outside the home.
But fundamentally, there's no big difference.
The IPTV network will have a set of local IP
multicasts streams from which its subscribers
can choose. That's why the hype about IPTV is
simply overblown and uninformed.
IPv6 and much faster network cores could change
this picture in theory, but the problems have
to do with more than just speed and address
space. The bigger problem is settling time of
multicast trees and the amount of state
information routers would need to maintain to
support huge numbers of global multicasts. So
I'm not getting any indication that multicasts
will be done in dramatically different ways with
IPv6. The talk is still walled gardens. Routers
in the Internet do not forward multicasts by
default, only when and if specific groups are
selected.
Bert
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