The LLQ in MDRR can work either in strict or alternate priority mode.
-Next_Queue is the next queue to be serviced after it is selected by the MDRR or PQ scheduler.
Figure 3 shows the network topology used in OPNET software to simulate the Reconfigurable Bandwidth MDRR scheduler model (RB-MDRR).
The performance of the RB-MDRR scheduler will be compared with the performance of Cisco MDRR. The assumptions to be used during simulation of the two schedulers are as follows:
* SchedMDRR and SchedPQ implement the scheduling algorithms MDRR and PQ respectively.
The performance of RB-MDRR will be compared with the performance of Cisco MDRR. As explained previously, to be fair, the input traffic, the buffer allocations and queue management schemes are set to the same under the two schedulers.
Figure 5 shows queueing delay (in seconds) of traffic classes (0-7) versus simulation time (in minutes) under RB-MDRR and MDRR schedulers.
Simulation results of packets drop under RB-MDRR and MDRR schedulers for various traffic classes are presented in Figure 6.
The packet loss at traffic classes (0-5) under RB-MDRR is increased, compared to the packet loss under the MDRR scheduler, as expected, with the increasing of the total offered load at the bottleneck link.
For example, Table 5 illustrates the differences in packet dropped under RB-MDRR and MDRR, at simulation time 1800 second.
However, MDRR is consistent throughout all traffic types.
Results shows that MDRR algorithm performs better than others, However in some cases, e.g., in case of VoIP traffic, resources were not allocated properly, specifically if BE service was selected, in few cases it does not transmit even a small amount of data that leads towards the unfair bandwidth sharing, but overall MDRR performs better.