2002 - cesnet

We tried to divide the capacity of the output line to 35 % for the test flow and65 % for the background flow, by configuring the MDRR algorithm. We sent thetest flow packets with an IP priority set to 1 (the value of TOS Byte was 0x20).The background flow packets had a standard IP priority, that is 0. We used thefollowing configuration:interface GigabitEthernet0/2ip address 195.113.147.33 255.255.255.248no negotiation autotx-cos group1!cos-queue-group group1precedence 1 queue 1queue 0 65queue 1 35The development of the throughput and delay of a testing flow with the MDRRconfiguration was entirely identical to that without MDRR configuration. Thedivision of the line capacity was therefore ineffective. The possible reason wasthat we exceeded the capacity of „tofab“ queues before the packet switching engine,which are available for packets of a certain size scope always at a limitednumber. Both used data flows comprised packets of an identical length, whichwas unfortunately necessary, as the performance of the used PCs was not sufficientto generate large data flows even in shorter packets.We tried adding a WRED algorithm, designed primarily for the prevention ofdata flow control synchronization for parallel TCP flows. But it can be also usedfor the discarding of packets, depending on the volume of incoming data. Weused the following configuration:cos-queue-group group1precedence 0 random-detect-label 0precedence 1 random-detect-label 1random-detect-label 0 1000 2000 1random-detect-label 1 2000 3000 1For the development of throughput and delay of the test flow with MDRR andWRED configuration, see Figure 9.5. The throughput of the test flow was maintainedeven with the application of a background flow, with exception of a shortdrop toward the end of the background flow. This was, however, not thanks tothe MDRR algorithm. Because we configured WRED so that the dropping probabilityof 1 was reached for the background stream just at the beginning of thedropping range for the testing stream (when its dropping probability was still 0),as much traffic of the background stream was dropped as needed to forward alltesting stream traffic.High-speed National Research Network and its New Applications 2002125