PURPOSE: To realize the decentralization of a load by dividing a buffer pool managed by a monitor, into three, and managing them independently.

CONSTITUTION: In each part of terminal interface parts 2aW2n of a data transmission equipment, a network side interface part 3, and a system managing part 1, a buffer pool managed by a monitor 5 is provided by dividing into three such as a system buffer, an internal bus buffer, and a line buffer. Said each buffer is managed independently, respectively, therefore, even when a load is, for instance, concentrated to the network side interface part 3 and an idle buffer is eliminated from a bus pool, a data from a line side can be inputted to the line buffer.