Patent ID: 7489682

Claim:
A packet relay system for relaying packet communication, the packet relay system comprising: a request source packet relay apparatus comprising: a path establishment block which establishes a request path on which a received packet to be proxy-filtered is sent to a proxy apparatus requested to perform proxy filtering of the packet and a return path on which the packet proxy-filtered by the proxy apparatus is received; a request source filter status determination block which determines whether the received packet requires a request that another apparatus performs proxy filtering, does not require the request, or has already been proxy-filtered and, when the packet requires the request, obtains a request destination port used to send the packet to the proxy apparatus and a request path identifier; a filtering request block which inserts the request path identifier into the packet to generate a filtering request packet; a request source transmission block which sends the filtering request packet from the request destination port to the proxy apparatus; and a packet update block which receives a proxy filtering packet and, when the request source filter status determination block determines that the proxy filtering packet has already been proxy-filtered, deletes a return path identifier from the packet, updates header information, and relays the packet; and a proxy packet relay apparatus comprising: a proxy filter status determination block which receives the filtering request packet, which includes the request path identifier, determines whether the packet requires proxy filtering or not, and, when proxy filtering is required, obtains a proxy destination port used to send the packet to the request source packet relay apparatus and the return path identifier; a proxy filter table which specifies the conditions of filtering of the received packet; a proxy filtering block which determines whether the filtering request packet can be relayed or should be discarded by searching through the proxy filter table using the request path identifier as a key, when proxy filtering is performed; a filtering return block which generates the proxy filtering packet by deleting the request path identifier from the filtering request packet and inserting the return path identifier, when the packet can be relayed; and a proxy transmission block which performs loopback transmission of the proxy filtering packet from the proxy destination port to the request source packet relay apparatus.