On 2014-02-13 Sean Walberg wrote:
Hosts speak IGMP, too. It's used to indicate interest in a multicast group. Normally the host would send something saying "hey sign me up for the stream at 229.1.1.1" and they'd start getting the stream. Every minute you'd then see a query to 229.1.1.1 from the router saying "hey local segment, is there anyone here that still wants this?" and it's the host's job to say "I do!". The 224.0.0.1 is a special case, basically a "hey are they any multicast listeners out here?" kind of thing.
Thanks for the tutorial, I've always been real hazy on multicast, having never had a need for it. Your theories are most likely correct.
Correct me if I'm wrong though: while hosts may speak IGMP for multicast, it's something that is basically never used by average-Joe home users and thus Shaw would most likely disable. As per one of your theories, it would really only make sense if Shaw was testing a multicast TV-over-IP concept.