[Nanog] ATT VP: Internet to hit capacity by 2010

Brandon Butterworth brandon at rd.bbc.co.uk
Tue Apr 22 07:06:22 CDT 2008


> So why would anyone plug an ATSC feed directly into the Internet?

Because we can. One day ISPs might do multicast and it might become
cheap enough to deliver to the home. If we don't then they probably
will never bother fixing those two problems

I've been multicasting the BBCs channels in the UK since 2004. The full
rate are mostly used by NOCs with our news on their projectors, we have
lower rate h264, WM and Real for people testing multicast over current
ADSL. The aim is by 2012 to be able to do all our Olympics sports in HD
(a channel per simultaneous event rather than the usual just one with
highlights of each) something we can't do on DTT (= ATSC) due to lack
of spectrum (there's enough but it's being sold for non TV use after
analogue switch off)

> Are there any devices that can play it other than a TV set?

Sure, STB for TV and VLC etc for most OS. It's trivial

> No ISP is going to allow subscribers to pull in 8gigs
> per day of video stream. And no broadcaster is going to pay for the
> bandwidth needed to pump out all those ATSC streams.

That's because they don't have a viable business model (unlimited
use...). Cable companies are moving to IP, they already carry
it from their core to the home just the transport is changing.

> And nobody is
> going to stick IP multicast (and multicast peering) in the core just
> to deal with video streams to people who leave their TV on all day
> whether they are at home or not.

When people do it unicast regardless then not doing multicast is silly

> At best you will see IP multicast on a city-wide basis in a single
> ISP's network.

Unlikely, too much infrastructure and not all content is available
locally

> Also note that IP multicast only works for live broadcast TV. 

See Sky Movies for a simulation of multicast VoD

> IP multicast
> does not help you when you have 1000 subscribers all pulling in 1000
> unique streams.

True but the 10000000 watching BBC1 may as well be multicast, at
least you save a bit.

> In the 1960's it was reasonable to think that you could deliver the
> same video to all consumers because everybody was the same in one big
> melting pot. But that day is long gone.

Evidence is a lot of people still like to vegetate in front of a
tv rather than hunt their content. Once they're all dead we'll
find out if linear TV is still viable, by then IPv6 roll out may
have completed too.

> On the other hand, P2P software could be leveraged to download video
> files during off-peak hours on the network.

Sure but P2P isn't a requirement for that and currently saves you no
money (UK ADSL wholesale model) over unicast. If people are taking
random content you won't be able to predict and send it in advance. If
you can predict then you can multicast it and save some transport cost
vs P2P/unicast

> Better yet, the ISP's P2P manager could arrange
> for one full copy of that file to get across the congested peering
> circuit during
> the time period most favorable for that single circuit, then distribute
> elsewhere.

Or they could just run an http cache and save a lot more traffic
and not have to rely on P2P apps playing nicely.

Apologies for length, just "no" seemed too rude

brandon




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