A first table used for compression of a message to be transmitted to another communication apparatus and decompression of a compressed message received from the other communication apparatus is generated. After the first table is generated, the first table is updated based on data contained in a message to be transmitted to the other communication apparatus. The other communication apparatus is guided to transmit a predetermined message corresponding to a specific index in the first table. Integrity of the updated first table and a second table used in the other communication apparatus by referring to the predetermined message received from the other communication apparatus. The second table is used for compression of a message to be transmitted to the communication apparatus and decompression of a compressed message received from the communication apparatus in the other communication apparatus.