Hitting just G or V without dragging the mouse will show the standard blue/yellow pings. These don't provide much information but they are a start. Tagging an enemy with a blue ping (G) will target them letting your team know they're are a priority. It will even show a target above their head for everyone on your side. Tagging an enemy with yellow (V) shows the opposite of that and tells your team to retreat from that champ. You can hit G, V, CTRL, or ALT and a direction to show the following pings. Note it says G-direction but as above you can use any of those keys to replace G.
G-up gives the danger ping similar to just pressing V and shows a red exclamation point. Use this to tell teammates to fall back from an area. Or use it on an enemy champion to tell your team to avoid them.
G-right gives the On My Way alert and will draw a green line from your hero to the location where you pinged (Note this just draws the shortest way to that location and does not necessarily show the path you are currently taking). Use it as a jungle or while roaming as mid to let your lanes know you are coming in for a gank.
G-down is the Assist Me ping and shows up as a blue flag. Use it to let your jungler know you need help with your lane opponent. Also can be used later if you get caught out and need your team to come and try to save you.
G-left signals Enemy Missing displayed as a question mark. Use it to show your lane opponent may have left lane to gank another.
Of course these aren't the only situations you would use these pings in however. There is plenty of times to use any sort of ping depending on situation.
NA Forums link to the smart ping system
This used to be happened to me too. It turns out I had a bad router, which cannot handle too much connection session.
Even though softwares like Skype don't take up a lot of bandwidth, it may require a lot of connection sessions.(I don't know how to explain, it's like passing a 1000g ball to a person, or passing 10 of 100g ball to 10 person.) If your router could not handle it, it may hang.
The first solution is to adjust the bitrate of streaming. How many bitrate did you use on your streaming? The suggested bitrate is 1800-2500Kb/s for 720p.
I would also like to suggest you to try the Open Broadcaster Software. It's a free, open source streaming software. I found it works better than Xsplit in my computer. It lags less, and video qualities are generally better(according to my friends/fans). It also provide 1080p streaming for free.
OBS Official Site
OBS Setting Guide by Twitch
If the above solution doesn't work, then it is most likely about your router. Try to close unused software that would use up your network(like Panda Media or whatever, I don't know why the other answer get downvoted so much). Or, buy a better router.
My English could be painful to watch. But hopefully it solves your problems.
Best Answer
Have you installed LoL a while ago?
There are often problems with logs starting to be too big and being 'too big to managed' by the OS.
https://support-leagueoflegends.riotgames.com/hc/en-us/articles/201752674-Network-System-and-League-of-Legends-Logs#section-windows
Basically, in windows, opening a 4k file on the fly? no sweat. Opening a 4gb file on the fly? that could cause problems.
So my guess is you might have huge log files, and when it needs to open it to write something in it, you experience the freeze.