There are too many people logged in. The research and recruitment network is an authoritative channel for publishing graduate information and a necessary channel for graduate students to obtain information. Therefore, there will be too many people in each rush hour, which will lead to the failure of the research and recruitment network. This phenomenon can't appear in the general situation of R&D. Only in the early days of the research network, candidates signed up for the postgraduate entrance examination. Or when the system is first turned on. This may happen.