From now on, the network is being developed into PSTN(public switched telephone network) and PDN(public data network), that is depend on the form of data. The former one pursues sending voice, and the latter one pursues sending data. But it causes big loss of the economy and efficiency. So, ISDN, processing voice and data at same time, gives a big profit to user. To enlarge the ISDN at the narrow area, it is necessary that study to send the mixture form of voice and data in LAN environment. So, this paper proposes the algorithm about the mixture form of voice and data in ethernet and token-ring. that is widely used in these days.