First of all - if there is a better place to ask this, let me know. I simply want to make sure the audience has the technical chops to try to answer the question. So discussions.apple.com / macrumors are out.
I’m trying to figure out how OSX is behaving with regard to downgrading sent IGMP messages in the presence of “older” queriers. I.e. if a query is heard from a router (querier) that is v2, start a timer and only speak (IGMP) in v2 until it expires. From the definitions I’ve found of how to calculate this timer - that should be 260 seconds. After this time, assuming we haven’t heard any further v2 queries - we can start speaking v3 again. From my testing (using 10.9 Mavericks and the newest VLC) - this doesn’t happen. From the network side, I’m using a Cisco 3750 with snooping and querier turned on (i.e. not a real mcast router).
If I turn these off and reboot, VLC causes IGMP v3 to be sent. If I turn querier back on on my switch - OSX drops down to IGMP v2. It just never seems to bounce back to v3. I think I waited ~ 10 minutes on my last test, and it was still v2.
Thanks - and sorry this isn’t about systemd (although I am reading the thread and think it’s a great topic).