Disconnected / Lag Spike in icecrown realm

Hi, this 2-3 days im having a bad latency which lead to disconnected 6-7 times daily. This matter are new to me, before this i never ever have this lag and disconnected while green latency. I tried to insist ISP to fix my area internet and its no problem with my connection. even i can watching youtube at 4K HD without lag. This just happend in Icecrown server, i tried onyxia and blackrock i never ever have this problem. Tried to run cmd also all good with warmane.