I found that, via PingPlotter, there are a lot of packet loss ( the red line in the figure are packet loss).
The ping starts at Hop 1, and reaches the destination after 11 hops. Notice that the majority of the packet loss occurs between hop 5- 11, indicating that the network connection at those points are poor.
The question is, can we thus conclude that this is the ISP's problem?
Maybe a second screenshot will give a better overview picture on what's going on: