To provide a communication system and a communication method, intending to an efficient use of a communication resource.

When a VoIP voice packet destined to a mobile IP terminal 37 from a mobile IP terminal 2 is being received by a receiving section 13 in a base station 12, on disconnecting a session between the base station 12 and the mobile IP terminal 37, a buffer data amount notification section 20 transmits a storage inquiry message to the mobile IP terminal 2. Then, when a storage request message, which is a response transmitted from the mobile IP terminal 2, is received by the receiving section 13, a data storage processing section 15 stores into a buffer 16 the VoIP voice packet destined to the mobile IP terminal 37 transmitted thereafter from the mobile IP terminal 2.