Vernon Schryver wrote:
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?
'Internet' is about speaking IP and ICMP.
There are many variants of routing; none are required to be deployed
_throughout_ the Internet. Static routes are sufficient, and 'who speaks
what routing protocol' and 'what the routes mean' (CIDR included) is a
matter of consensus among parties exchanging a single routing protocol,
not an Internet-wide requirement.
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.
Under classic IP, class D was defined as unused/reserved;
under multicast IP, class D is now defined as multicast.
That is the purest form of the change of a definition.
While it affects only a portion of all IP packets, it did redefine
the meaning of that portion.
(it redefined the meaning of values of the space, not the partitioning
of the space).
Joe