From: Joe Touch <touch(_at_)ISI(_dot_)EDU>
...
would pacbell filtering all multicast at all CPE equipemt fall into your
bucket, where do you draw the line?
At IP, as Bob Braden said.
SMTP is _over_ IP.
Multicast _redefines_ IP (or portions of the address space thereof); it
could be argued that a service provider sells 'Internet' without selling
multicast IP.
That grossly overstates the difference between multicast IP services and
classic IP services. For one thing, many multicast applications work
fine, albeit with rather reduced scope, when sent to the local IP broadcast
address instead of a multicast address. For another, since CIDR
"_redefines_ IP (or portions of the address space thereof", are ISP's
that sell non-classful blocks not in the IP business?
It's also a of a stretch to call the 1985 change of class D from
"unused" or "reserved" to the multicast space a redefinition of the
IP address space. (RFC 966 mentions the change. RFC 960 still
said "Note: No addresses are allowed with the three highest-order bits
set to 1-1-1. These addresses (sometimes called "class D") are reserved.")
Vernon Schryver vjs(_at_)rhyolite(_dot_)com