Llamas it's probably not the servers fault, most likely your computer or internet speeds. Try using the basic or super basic pack if you have a slow computer. If you are experiencing lag where your character can move around but everything around you is frozen and stuff, that is the servers fault. If it is just FPS (frame rate drops) it may be your computer. Try using Optifine if you have a lot of frame rate drops or look into some better RAM cards or so.