With people rely more on computer networks

the study on the dependability of networks is increasingly significant.First the paper provides insight about the main definitions and attributes related to dependability

and classifies and compares the general models for dependability.On the basis of the synthesis

the modeling and analysis methods using Stochastic Petri Net (SPN) for the network system dependability are mainly investigated.The service failure and fault tolerance SPN models and the calculating methods of main dependability attributes are examined.The existing problems and applications of SPN are concluded that concern the dependability of networks. And directions for future research are also indicated.