package handling module ( package _ server ) is responsible for assigning all received messages, which can advance real time capability; communication agent module ( sp _ agent & smc _ agent ) is responsible for communicating with external entities, but does n't identify message contents, which can lighten burden of package handling module; store-and-forward module ( store _ server ) completes store-and-forward mechanism by setting up timer, and implements overtime retransferring and failure handling; routing module ( route _ server ) is responsible for maintaining the links with the other ismgs to implement routing; feeing module only consists of some functions which can be called to record message items 其中,业务处理模块(package_server)负责分派所有收到的外来消息,提高实时性;通信代理模块(sp_agent&smc_agent)负责与外界实体通信,不具体识别消息,可减轻业务处理模块负荷过重的压力;存储转发模块(store_server)通过设置计时器完成存储转发机制,实现超时重传和失败处理;路由模块(route_server)负责维护与其他网关的通信链路,实现路由;计费模块只是一些可供调用的函数,用来完成话单记录的功能。