| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to obtain a protocol compatible with an existing protocol by maintaining encoding for existing parameters in the protocol and providing a system which increases the number of parameter identification that can be encoded by parameters of a message packet. SOLUTION: A telephone system 100 has a first exchange system 101 and a second exchange system 111. The exchange system 101 provides telephone services to two telephone terminals 131 and 132 through lines 141 and 142, and the exchange system 111 provides telephone services to telephone terminals 133 to 135 through lines 143 to 145. According to this system, a device which communicates by using an old version of protocol can receiver a message including a parameter which has an expanded encoding field. The device performs reading processing of the parameter which has encoding that indicates a command by the old protocol.
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