Lately, the Mac nerd community has really become fed up with the networking shenanigans around the new Domain Name Service (DNS) networking protocol, discoveryd.
discoveryd, plays a part in how your Mac can find other devices, like Apple TVs and Apple AirPort networking gear, on your home network, other Wi-Fi networks you might connect to and Internet websites among other things. As to the trouble discoveryd has been causing, well, you should read Craig Hockenberry's blog post on it [strong language warning]. He's far more knowledgeable about what goes on inside your Mac than I am.
Some of you may know that I'm a member of the OS X Public Beta program (and for iOS also). In the most recent OS X 10.10.4 developer and public beta (build 14E26a) Apple replaced the discoveryd DNS service with the mDNSResponder DNS service that was used in OS X Mavericks and earlier.
Here's a screen shot of my MacBook Pro running the previous beta build of OS 10.10.4:
As you can see, the discoveryd service is alive and talking to my home network.
After I installed OS X 10.10.4 Public Beta build 14E26a, you can see that mDNSResponder is back on the beat making sure OS X networking is obeying all the posted traffic signs.
Just for good measure, after installing the latest beta build, and as discussed in Hockenberry's blog post, I powered down both of my third generation Apple TVs and my Apple AirPort Extreme and Express, rebooted my cable modem, and then, one-by-one, turned everything back on in the following order:
Cable Modem, Apple AirPort Extreme, Apple AirPort Express, MacBook Pro, Apple TV 1 and then Apple TV 2.
Since then, I've seen a marked improvement in my home network's performance. Hopefully, mDNSResponder will be sticking around on OS X for a while and makes it into the official general release version of OS X soon.