Dynamic bandwidth allocation method employing tree algorithm and ethernet passive optical network using the same

A DBA (Dynamic Bandwidth Allocation) method employing a tree algorithm in an E-PON including an OLT and a plurality of ONUs connected to the OLT, the DBA method being based on steps comprising:

• a) arranging a plurality of logical DBA Control Nodes (DBACNs) in hierarchical stages of a tree with the ONUs being positioned in a lowermost stage thereof, and connecting DBACNs or ONUs positioned in an intermediate stage to a DBACN positioned in a stage higher than that intermediate stage;
• b) sequentially performing a process of causing a DBACN to collect bandwidth request information inputted from DBACNS or ONUs connected thereto from a lower stage, starting from a lowermost DBACN up to an uppermost DBACN in the hierarchy;
• c) causing the uppermost DBACN to allocate a smaller one of a total available allocation-bandwidth and a total requested bandwidth to DBACNs connected thereto from a lower stage in a priority order of said DBACNS connected thereto from a lower stage;
• and
• d) causing DBACNs positioned in stages below that of the uppermost DBACN to each allocate a bandwidth allocated by a DBACN connected thereto from a higher stage to DBACNs or ONUs connected thereto from a lower stage in a priority order of said DBACNS or ONUs connected thereto from a lower stage.