Re: BitTorrentvs MBONE

John Kristoff <jtk@northwestern.edu> Fri, 16 September 2005 03:30 UTC

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Date: Thu, 15 Sep 2005 22:30:14 -0500
From: John Kristoff <jtk@northwestern.edu>
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Subject: Re: BitTorrentvs MBONE
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On Thu, 15 Sep 2005 19:34:47 -0700
"Hallam-Baker, Phillip" <pbaker@verisign.com> wrote:

> I think that the reasonable question to ask here is 'does MBONE have a
> future?'

It doesn't even have a present.  It's long gone.  Native multicast
on the public Internet seems to continue to have a future, but only
for a continued subset of the global Internet.  I've heard some talk
of renewed interest in multicast deployment, but I'm skeptical.  If
you look at some statistics [1] you find:

  About 450 ASNs (and not just .edu's) representing about 5000 routes
  seen via MBGP.

  These routes expand to cover about 125,000,00 million possible
  addresses (compared to about 1.1 billion addresses covered by a
  current unicast table).

  There are about 1,300 (not totally and obviously bogus) SAs.

What is interesting is that these numbers haven't moved all that much
over the past few years.  Multicast deployment has peaked, but one
might consider 10% (using address coverage as one measure) to be
pretty widely deployed.

What seems to have pretty strong and probably growing interest is site
local multicast applications such as file/image distribution and Video
over IP.

> If I was asked to design a new media distribution protocol
> from scratch I certainly would not choose MBONE as a model. The
> technical and political problems both appear insoluble to me.

They are.  Even after the MBONE, large-scale multicast is still quite
hard.  I think this paper captures the general sentiment pretty well
and I bet a few other operators who have had similar multicast
deployment experience will be nodding their heads with a familiar
feeling of shared pain as they read through Section 2:

  <http://gravity.lbl.gov/grbell/docs/RIPQOS-GRBell.pdf>

Even if you could get past the complexity issue, I would contend
that you would also need to overcome the security fears real (and they
are in the multicast case) or imagined whenever it requires the netops
people to have turn 'something on'.  Today, it is more likely that
things get turned off, rather than turned on and that has real serious
implications for how new things get deployed, which I'm sure is no
secret to you and most others here.

[1] http://www.multicasttech.com/status/

John

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