The server has a 15ms tick if you try to send packets faster than that, or to have the server send you more, you get "choke."
You can also get choke if the total size of packets over a certain timeframe exceeds your rate.
You should always let interp ratio handle your lerp. 2 gives leeway for dropping a packet or if your fps dips below 67; 1 means greater accuracy but people will jump around a lot more on your screen as there is less smoothing.