Link Management and Timeout Mechanism for Content Audit

Content audit analyzes the messages of application layer communication between the peers, and matches the set security policies to ensure legitimate and effective use of network resources. The link management is one of the key issues in designing the content audit system. In order to achieve efficient management of TCP links and the correlation analysis of the same session, the hash list is proposed to manage the links and chained address method has been adopted to solve hash collisions. The link will become a zombie when the FIN packet is lost due to irregular interruption or closure of the connection. Therefore the timeout mechanism, which organizes the nodes of hash list into another timeout two-way chained list according to the timeout length, is introduced to prevent the zombie links consuming system resources. With updating the timeout chained list continuously by the timeout length, it will greatly improve the efficiency of checking out the links.