Packet processing unit

A packet receiving circuit splits the packet received from a transmission channel into a fixed length of cells and outputs the cells, a search key extracting circuit extracts a predetermined search key from the above-mentioned cells, a CAM performs retrieval based on the above-mentioned search key and outputs a memory address corresponding to the search key, a matching entry address receiving and associative data address transmitting circuit calculates the memory address of an associative data memory based on the above-mentioned memory address and outputs the information stored in the associative data memory as associative data, a search result (associative data) receiving circuit receives the above-mentioned associative data and performs header updating and destination address of the above-mentioned cells, and a packet transmitting circuit outputs the above-mentioned cells in the form of a packet to a transmission channel.