For you to not have constant buffering or lag in the content you need to have a good internet connection. Therefore for a smart TV to work effectively and smoothly you would require an internet speed of at least 2 MB/per second for standard content. Whereas, if you stream HD content, then you would require 4 MB/per second. And this connection should be continuous as well. It is mostly preferred for you to use ethernet while using a TV box or smart TV but Wi-Fi too works just fine.