2002 - cesnet

was sending ARP queries to the IP address of PC3, which responded correctlywith its MAC address; however, the router failed to process this response.Testing stream sourcePC1195.113.147.18/29rude -s script.cnfBackground stream source1000BASE-SXge1/1PC21000BASE-SX195.113.147.26/29rude -s script.cnfge1/0ge1/21000BASE-SXGSR12008 +3-Port GE LCIOS 12.0(18.6)S195.113.147.35/29Background stream destinationTesting stream destinationPC3195.113.147.34/29crude -p 2000 -l crude.logFigure 9.3: Configuration of experiments with Cisco GSR routerAfter many hours of debugging and repeated contacts with the representativesof Cisco Systems, we came to the conclusion that the problem was caused byan improper version of the IOS system. We therefore replaced this systemwith version 12.0(8)S and the problem no longer appeared (we replaced onedevelopment version – early deployment – with another development version,as there is only development software available for the router worth approx.USD 120,000).Figure 9.4: Throughput (left) and delay (right) without QoS configurationFor the development of throughput and delay of the testing flow without QoSconfiguration, see Figure 9.4. The background flow was applied at 5 to 10 seconds.The router maintained full throughput of the test flow two seconds afterthe start of the background flow, thanks to the queuing. The delay of the testedflow increased to 0.45 seconds. As the entire input traffic equalled 1,150 Mbpsand the output flow was 1,000 Mbps, a difference of 150 Mbps was accumulatedin the queue. As a result, the queue size is 300 Mb, i.e., 37.5 MB. Unfortunately,we did not find how to configure the queue size. At the end of the backgroundflow, there was a dramatic fall in the test flow throughput, to approximately100 Mbps, for a period of approx. 0.7 s. We are not aware of the reason for thisphenomenon.124 High-speed National Research Network and its New Applications 2002