Ohta-san:
| Because best effort service is flat rated, receivers are not motivated
| to use multicast. Senders learned to have more servers.
Yes, but some senders would like to send a bit less :-)
For instance, some are actually paying based on volume (Mbytes/month),
some are paying on peak usage (95th percentile of measured traffic load),
and some are paying flat rate available bandwidth. All would like
to have more happy eyeballs watching while paying less to send the
traffic towards them, and some of these people would not be opposed
to using IP multicast.
Unfortunately, while it's fun to think about a sender flooding out
on a group and paying for the volume only when the group is joined
towards, actually implementing this is stuck in the realm of "fun idea"
Don't hold your breath.
So, I think you're essentially right: if one wants to send a bit less,
one pays a unicast-CDN to do very-short-term caching at various points
in the network instead.
"A bit less" can be significant in the case of streaming content when
one considers the number of outbound copies one can save when doing
packet-replication or short-term-content-caching here and there in
the network. Or at least so many CDN companies argue with varying
degrees of success.
Sean.
CDN: buzzword, "content distribution network".