A method in which a high-quality packet telephony terminal apparatus performing low-latency and lossless packet communication with a counterpart packet telephony terminal apparatus operates in an integrated network structure in which a time sensitive network (TSN) and a packet communication network are combined may be disclosed. The packet telephony terminal apparatus may perform packet telephony call processing, perform a TSN stream reservation procedure when the counterpart packet telephony terminal apparatus is capable of performing a TSN function for lossless packet communication, adjust a size of a dejitter buffer when the TSN stream reservation procedure is successful, and perform low-latency packet telephony communication through the minimized size of the dejitter buffer.