Many functions for various network services (e.g. IP telephone, ISP connection and IP-VPN) are deployed on a broadband network, especially at the boundary between an access network and core network in the broadband network. The network service must be identified from each packet and the packet must be processed appropriately for that service. IP traffic in the broadband network is increasing sharply, so traffic distribution based on service identification may bottleneck when many different network services are provided in the network. Therefore, we propose an offload method for traffic distribution based on service identification to service processing parts, which process the packets for each network service appropriately. This method does not require additional functions in user terminals, and it more scalable than the method in which all traffic undergoes the service identification process. However, control of the proposed method is slightly more complex, so we established a control procedure and checked it in combination with user terminals. In addition, we evaluated by theoretical analysis the scalability of traffic distribution with offload compared to the method without offload. The results showed that the proposed offload method can increase the scalability of traffic distribution based on service identification.