[opendtv] Re: News: TV Braces for the Apple Tablet

  • From: Kon Wilms <konfoo@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Mon, 1 Feb 2010 16:44:06 -0800

On Mon, Feb 1, 2010 at 4:01 PM, Manfredi, Albert E
<albert.e.manfredi@xxxxxxxxxx> wrote:
> Heh heh. That's exactly the same problem with regular wired ISPs' acceptance 
> of multicast, turns out. I think IP multicast gets used mainly by the 
> providers THEMSELVES, e.g. if they want to use IP to emulate a cable TV 
> service, but it requires many additional bells and whistles. There is an I-D 
> floating around about all this. They don't give the answer in this I-D, just 
> state the problem.

Well I would personally like to term those 'legacy distribution
networks'. As a CDN provider we don't make use of any IP multicast.
This threw me for a loop for a while since I spent so many years doing
exclusively IP multicast, but right now, distribution mechanisms are
far different for unicasting than they were years ago.

The preferred distribution mechanism for CDNs that I currently see
(and one we ourselves implement) is that of stream push over UDP to
various POPs, and from there, HTTP caching on edge servers (or stream
caching/splitting at the unicast level).

There is absolutely no benefit to implementing multicast in a switched
fabric since you pay for the packet distribution regardless. In fact,
you're probably at a disadvantage since one has to cope with erasure
correction, possible packet flooding, TTL tuning (lets not even go
there), and tunneling for security/legacy purposes.

> That's true, with faster and faster wired (fibered) backbone nets becoming 
> available. And then you can make every session VOD.

Right. We can scale quite easily to anywhere in the globe using HTTP
caching and TCP reflection on localized edge clusters.

Cheers
Kon
 
 
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