Ambiguity in H.225.0 Appendix D

Rajesh Patwardhan pats at TRILLIUM.COM
Thu Jan 14 13:40:58 EST 1999

Just FYI on multicast/unicast taken from Stevens book:

"...Some applications also bind the multicast address to the socket, in addition
to the port. This prevents any other datagrams that might be received for
that port from being delivered to the socket.

Historically, Berkeley-derived implementations only require that
some socketon the host join the mcast group, not necessarily the socket
that binds the port and then receives the mcast datagram. There is a
potential, however, with these implementations for mcast datagrams to be
delivered to the applications that are not mcast aware. Newer mcast
kernels now require that the process bind the port and set any mcast
socket option for the socket, the latter being an indication that the
application is mcast aware. Solaris 2.5 differs slightly and
only delivers received mcast datagrams to a socket that has both joined
the group and bound the port. For portability, all mcast apps should
join a group and bind the port.
Some older mcast-capable hosts do not allow the bind of mcast addr
to a socket. For portability an application may wish to ignore a bind
error for a mcast address...."


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