1. Field of the Invention
The present invention relates to a charging system in public and private data communication networks, and in particular to a charging system in which a negotiation of shares of the communication charge can be beforehand conducted when a data communication is achieved between terminals via such networks.
2. Description of the Related Art
According to the conventional charging system, as described in the Japanese patent unexamined publication JP-A-60-28360 published on Feb. 13, 1985, in a case where a calling subscriber and a called subscriber connected to an automatic exchange of a common control method are both to be charged for calls effected therebetween, the charging operation is achieved depending on a message rate specified by the calling subscriber. However, considerations have not been given to an operation to conduct a negotiation of the charging ratio at an establishment of a call between a calling subscriber and a called subscriber and to an operation of the common control automatic exchange to charge both of the calling and called subscribers for the call.