Throttling seems to work as a workaround to allow you to send messages with media while also limiting the amount of online backup that occurs.   You should be able to set up a traffic shaping rule for individual groups in group policy settings (Network Wide -> Group Policies -> [desired policy] -> Traffic Shaping) or do it globally (Security & SD-WAN -> SD-WAN & Traffic Shaping).   This doesn't block iCloud backup but it does reduce the bandwidth used. **I have not tested media message sending for large numbers of people while also attempting iCloud backup. That is something you will need to do, but I do hope that if you do it you will post an update here and let us know how it goes. ... View more

Yes, I can confirm this is still an issue for me.   Earlier today I applied the block to a group policy my phone didn't belong :). as of v14.40 I still suffer from this issue... if I envoke it.   I am going to throttle this and try again later. ... View more

It worked for me this morning. I tried it twice. ... View more

Hi Rumor, I do. at the time of posting my solution I was able to toggle the icloud backup block several times and either produce the issue or allow sending on my end. However... now that I am on v14.40 I am unable to get imessages with media to fail at all. Sorry that isn't much help. ... View more

I do believe it is what fixed it. This was a long time issue for us. We did not have functioning media sending on iphones using iMessage for at least a month, and at the time of writing my solution above I was able to re-enable the icloud backup block and cause all imessage transactions with media to fail. Disabling the function allowed media messages to pass through. I flipped the switch several times to check and double check with the same results each time. However, that being said... Now that I am on v14.40 I cannot get media messages to fail at all. Sorry I can't be of more help. ... View more

That would have been a good question to answer: 14.38 ... View more

I've done several packet captures now.   With Media attached: Apple Messages on these networks is having "Spurious retransmission", "TCP Previous segment not captured",  and "TCP ACKed unseen segment" and "TCP Dup ACK" errors when sending media over these networks.   Without Media attached: Apple messages on these networks is not having "Spurious retransmission" "TCP Dup ACK"   I don't know if that is helpful at all. I must admit I am not the best with wireshark.     with media without media "Screenshots of two packet captures' graphical representation of events, one with media and the other without."     I have moved a teacher off their network (meraki controlled) to our staff network (server controlled) and they are able to send and receive media. I put them back on Teacher and they are not . If I whitelist any of these phones in the MX, media is then able to be sent and received over Messages. So it's definitely a configuration setting blocking only media in Apple messages on these networks. So, now I'm not thinking it is a server/meraki differentiation, but a network/network differentiation.   I have disabled AMP, I have also disabled all traffic shaping rules. I am beginning to come to a loss here. I am heading out for the day, and will reapproach this tomorrow afternoon and attempted to go through every setting I can think of on one of these networks.   Any other pointers would be appreciated.   thanks again   ... View more

Thanks guys, I appreciate the help. I've narrowed it down to VLANs specifically controlled in all ways by the MX. VLANS that have DHCP and DNS handled by a server are unaffected. I am going to investigate policies and break out the packet sniffer and update this thread.   thanks ... View more