The iBUS (inbuilt burstification urgency-driven scheduling) algorithm delivers packets in IP-over-WDM networks in an "accurate" and "timely" manner. It employs a flexible assembly process which can interact effectively with the urgency-driven process of the iBUS algorithm. In this letter, a hop-constraint timing assembly approach is proposed, where input packets are classified by their routing hops. Then, input packets whose routing hops are more than a threshold are assembled into multi-hop bursts. Multi-hop bursts have higher priority to be scheduled by their urgency degrees, and limitedhop packets (without assembly) can be filled in voids between multi-hop bursts. This approach gives freedom to the urgencydriven process to facilitate iBUS in IP-over-WDM networks.