Starting a few weeks ago, at seemingly random intervals, 3 of 5 PCs will lag at the same time for a few seconds to the extent where mouse and keyboard input is delayed and VoIP calls are dropped.
After ruling out a few potential root causes, I suspected that something on the network was causing it.
So, a few times, I ran a constant Wireshark capture, waited for the problem to recur, and found that a large number (~1,500) of the following packets were transmitted over ~5 seconds and at the same time that the PCs lagged:
No. Date Time Source Destination Protocol Length Info
1361246 13:11.3 16889.25912 172.16.100.29 224.0.0.251 MDNS [427 | 442 | 475] Standard query response 0x0000 PTR Chromecast-1440b1ad27c2e70400c69c7c7900ee49._googlecast._tcp.local TXT, cache flush SRV, cache flush 0 0 8009 1440b1ad-27c2-e704-00c6-9c7c7900ee49.local A, cache flush 172.16.100.29
We do have a Chromecast plugged into a TV and a laptop (one of the affected PCs) casts BBC News to it all day but we've been doing this for months with no problems.
Can anyone advise?
I'm aware that there are known problems with Chromecasts slowing down networks at the moment (https://www.theverge.com/2018/1/16/16897426/wi-fi-google-home-chromecast-archer-router, https://9to5google.com/2018/01/15/google-chromecast-home-wifi-outage/) but the scenarios don't match exactly, if only because our Chromecast is in use when the problems recur.
