4.6Simulation Outputs
The simulator output is a file for each direction – upstream and downstream – that lists the precise arrival time and delay of each packet in the stream under test from model ingress to egress. Packets that are dropped because of network congestion are noted. [What does Delay mean when the packet is dropped?] See the example in Table .
Table : Example Simulator Output [replace with recent output]
Source:
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TIA-921-B
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Creation Date:
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5/5/2010
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Description:
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Misc Downstream 2
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Content-Encoding :
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ASCII
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Delay Unit:
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ms
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Time
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Delay
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Drop
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2
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62.540836
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0
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2.064531
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62.5377494
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0
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2.068719
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62.106312
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0
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2.083353
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62.21563497
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0
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2.103442
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62.40617898
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0
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2.129744
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62.154648
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1
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2.136147
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62.401416
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0
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2.160704
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63.0072554
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1
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2.276267
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62.69638617
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1
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2.306837
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63.43353741
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1
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2.331988
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62.41461574
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1
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2.36096
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62.09868
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1
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2.443818
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63.41120351
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0
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The simulator may generate a pcap file containing the same information, suitable for processing by any program that recognizes the pcap file format.The simulator can be configured to monitor points throughout the network under test. Typically, the standard cases have monitors at the outputs of the various flows. At these monitor points, the simulator will generate produce pcap files that represent the traffic perturbed by the delay and loss through the simulator as well as a separate csv file of the simulator time, delay, and loss of each packet to the monitor point.
The CSV file can be plotted and analyzed to show a time series of the delay patterns and loss bursts. Furthermore, Packet Delay Variation (PDV) histograms and Cumulative Distribution Functions (CDF) can be generated for these files to analyze network characteristics. Examples of some of these plots are shown for the standard test scenarios.
The generated pcap files represent the input packets as perturbed by the network simulation. Payloads, if present in the input pcap files, are passed with the packets thereby enabling possible further analysis of the contribution of network impairments on traffic. This analysis goes beyond the scope of this standard.
[Should examples of PDV and time series be included here, or in an informative Annex?]
[Show time series and PDV from the same simulation]
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