ion delays are same in both networks. As the minimum application delay is dependent on the RAB rate. But when the load gets higher, it can be observed that the delay performance of the ATM-based lub gets worse than the IP-based one. This is because that with RAB 128 kbps the ATM based transport network generates more transport network overheads (lower bandwidth efficiency) for the same amount of application load, and in turn for the same link rate the resultant R in the M/G/R-PS model is smaller. This result also implies that the ATM transport requires more link bandwidth than the IP transport for achieving the same target application delay. This conclusion is proven with right graph in Figure 7.8, where the dimensioning results are derived from the analytical models. In this graph, the dimensioned link bandwidth is represented by the normalized capacity (defined in section 4.3) over different traffic loads. The result shows that with RAB 128 kbps, the required bandwidth for the ATM-based lub is higher than IP-based lub since it has relatively lower bandwidth efficiency. Similar conclusion is obtained for RAB 384 kbps in Figure 7.9 (right diagram), due to higher bandwidth efficiency with the IP transport than the ATM (see Figure 7.6). While for RAB 64 kbps as given in the right diagram of Figure 7.9, the dimensioning result is slightly better in the ATM-based lub as a result of higher bandwidth efficiency with the ATM transport (see Figure 7.6). In Appendix A.22, more comparisons of the ATM and IP based transport are given. Additionally, based on [LC 07] some examples of applying different multiplexing schemes are given in Appendix A.22. The results show that a balance should be given between the bandwidth efficiency and the transport network delay by optimizing the multiplexing scheme parameters. 7 Dimensioning for Single IP-Based lub 7.5 Summary In this chapter, analytical dimensioning approach was proposed for dimensioning the IP bandwidth for the IP-based lub interface applying the DiffServ QoS, for elastic N