There is, practically, imperfect communication network (e.g., time delay and packet loss/switching) in haptic interaction (or teleoperation) systems. It is well known that such imperfect communication degrades teleoperator's performance as well as stability. We hypothesis that as an imperfectness level in the communication network is increasing, the teleoperator's performance is decreasing monotonically. In this paper, we verified the hypothesis via a human-centered evaluation of the teleoperator's perceptual performance in terms of just noticeable difference (JND), point of subject equality (PSE), and perception time using two psychophysical experiments: experiment of packet separation time and experiment of packet loss. In the experiment of packet separation time, there were significant increases of JND and PSE as the packet separation time was increased. However, interestingly, there was no significant decrease of teleoperator's perceptual performance in the experiment of packet loss although the packet loss rate was increased until 75 %. The experimental results clearly shows that the packet separation time affects on the teleoperator's perceptual performance more than the packet loss rate.