IP multicasting
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... IP) to support multicasting. It is the
recommended standard for IP multicasting in the Internet.
Distribution of this memo is unlimited.
...
... >Level 0: no support for IP multicasting. ...
... requirement that all IP implementations
support IP multicasting. Level 0 hosts will, in general, be
unaffected by multicast ...
... destination address field; they should be quietly
discarded by hosts that do not support IP multicasting. Class D
addresses ...
... Level 2: full support for IP multicasting. ...
... IP. It is required to be
implemented by all hosts conforming to level 2 of the IP multicasting
specification. IGMP messages are encapsulated ...
...
This appendix is not part of the IP multicasting specification, but
provides background discussion of several issues related to IP ...