we have at least 30 apple tv of various model, the apple tv are update to the last firmware, when we try to share screen with Airplay, we enter on the IPad the code digit, and the stream start for a while and than stop and we see a black screen.
This problem takes place only for apple tv model A1469.
The apple tv are wired connected and we have a bonjour forwarding configuration for the Airplay service on the WiFi.
Remember that mDNS is only for service discovery. Once your device starts up the stream it is a purely unicast stream. So I wouldn't focus on mDNS here. You'll have to find out where your stream is cutting off.
Maybe start a capture at the switchport at the Apple TV at start of stream and when stream fails. So you can determine if the device itself is still streaming. If it isn't then you should look at just before the failure if something happened like a TCP reset if it is TCP streaming.
Hey, the capture doesn't show the actual streaming. You can see that is a small TCP session that is almost immediately closed by the client. So if you're talking about losing the stream after a while you should already have seen hundreds of packets with a larger size before the failure.