How do you put a TV station on the Mbone?

William Herrin bill at
Wed May 4 22:20:09 UTC 2011

On Fri, Apr 29, 2011 at 4:40 PM, Tim Durack <tdurack at> wrote:
> Multicast is a great technical solution in search of a good business problem.

It's a useful replacement for broadcast on a local link. It's of
limited utility elsewhere.

On Fri, Apr 29, 2011 at 5:21 PM, George Bonser <gbonser at> wrote:
> Multicast is perfect for a live event.  Unicast is best for "on demand"
> viewing of something.

A layered cache implemented via unicast would work better and enable
local fills for lost packets too. More, it sits to the side of the
routers rather than in line, so it allows your routers to focus on
what they do well: routing unicast packets.

Some time ago I sketched out a notion for a layered opportunistic
caching system that finds its nearest caches via anycast and validates
the cached data via a very small signature stream from the original
source. Even if your viewing is off-sync with others using the caches
in your hierarchy the probability of bandwidth savings increases
rapidly with the popularity of the content.

The idea is that you deploy these caches as deep in your system as is
cost effective. Regionally. The local CO. In the box with the
neighborhood fiber terminal if you find the traffic savings beats the
equipment cost.

And of course such a cache system could work well for popular
non-streamed content as well.

Never quite linked up with someone interested in seeing an
implementation though...

Bill Herrin

William D. Herrin ................ herrin at  bill at
3005 Crane Dr. ...................... Web: <>
Falls Church, VA 22042-3004

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