A method and apparatus for transmitting network traffic includes selecting a major node in a major ring, where the major node corresponds to a first transmission opportunity encoded in the major ring. The major node specifies a minor node in a minor ring representing a virtual port. The method and apparatus also includes transmitting network traffic to a virtual connection that uses the virtual port. Alternatively, transmitting network traffic involves processing a schedule that includes a sequence of transmission opportunities encoded in a schedule ring and satisfying a minimum data rate for a scheduled virtual connection by processing a corresponding first minimum number of transmission opportunities from the schedule, each such transmission opportunity allocated by a schedule node to the scheduled virtual connection, where the schedule node is included in the schedule ring.