Our organization uses the BridgeTab app for electronic bridge scoring. It's a simple data collection app which also presents feedback to the players. It works great on Amazon Fire tablets, barely taxing the memory, CPU, or network. Each tablet is a client with the server running on a Windows box. During a game, we have 15-20 tablets in use.
Occasionally the app is unable to receive the feedback, i.e. what other players did on the same hand of cards, sent from the server. My initial feeling was that this was due to wireless network contention, perhaps exacerbated by an inefficient client-server protocol, Fire OS pulling down OS or app updates during the game, or other network traffic. After capturing network traffic with Wireshark and comparing it to delays reported in the log generated by the server application, I strongly suspect that the problems occur when Amazon Fire devices generate a multicast DNS (mDNS) flood. The flood is never higher than 1,800 mDNS packets / sec and averages around 200 mDNS packets / sec during the half hour or so peak period of the mDNS storm. But this is worse than it seems because according to the WiFi specification the access point (AP) is supposed to transmit multicast packets at the slowest rate support by the AP to ensure that all wireless clients can receive the multicast packet.
I'm not very familiar with the mDNS protocol. There seem to a lot of queries for service 'amzn' and name '_amzn-wplay' which might be a search for the Amazon Fire TV based on other online reports. And there are a lot of query responses along the lines of:
amazon-4dfe67879.local 184.108.40.206 MDNS 308 Standard query response 0x0000 PTR amzn.dmgr:0F468773F342637FECAE76E824E515D1:xsiKnDvsK5:716763._amzn-wplay._tcp.local SRV, cache flush 0 0 57616 amazon-4dfe67879.local TXT, cache flush
I can send a Wireshark capture if helpful.
I don't think this mDNS traffic is being generated by the BridgeTab app. Is there some way to shut it down or at least reduced it? Could it be a bug in Fire OS?
FWIW, we use a mix of fifth and seventh generation Amazon Fires, all 7" models. They should all be running at least Fire OS 220.127.116.11 but had probably updated to 18.104.22.168 by the time I captured the network traffic.