Additional Traffic Matrix Solver Information
Choosing a Period of Interface Traffic
Which period of interface traffic data should you use? Currently, it is recommended to select a few periods (for example, include one during general heavy load and one at light load), and run the Traffic Matrix tool once for each set of traffic data to create a couple different sets of end to end flows.
Avoid choosing the period called “Worst,” as the worst/peak case may occur at different times for different links, which is not as suitable for the Traffic Matrix tool. Rather, it is better to determine a few specific period numbers for which the loading was heavy.
There are a few ways to load traffic data into the network model. Note that the following applies to those users who use the online module / NorthStar Traffic Data Collectors to collect live traffic:
If you created your initial network project by saving it out from the live network view (File > Save Network), then the last 24 samples of traffic data at the time you saved it out will already be recorded in the default interfaceTraffic.in and interfaceTraffic.out ingress and egress files associated with your network project
If you have existing ingress and egress traffic files, you can read them in via File > Load Network Files (specify them in the Traffic Files section)
To retrieve historic traffic data, in View or Design mode, go to Traffic > Traffic Load, and select “Interface”. Select the “Start From” time and press “Fetch”. At this point, if you do File > Save Network, the corresponding interfaceTraffic.in and interfaceTraffic.out files will be created. Then, close and reopen the network project, or else use File > Load Network Files to load in the interface traffic files, before proceeding to the Traffic Matrix tool.
If you do not have the online module or an interface traffic file, but want to generate one based on the current network demands, select Traffic > Traffic Matrix > Save Interface Traffic.
Resetting Demand Bandwidth According to Demand Trafficload File
At any point in time you can reset the demand bandwidths to be the same as that of a specified period of the measured demand bandwidth in the trafficload file. Any demand that does not have measured demand bandwidth will not be changed in this process.
To do this, first select the General tab and select the desired Period of the Traffic Load File. Then click “Show Results.” A popup window will show how many demands have a current model bandwidth that is different from the measured demand bandwidth.
When asked to update the different entries, click Yes in order to update the model bandwidths to be exactly the same as the specified period of the traffic load. The Summary tab will be updated to reflect the changes.
Note that during the design, if you had set the Maximum Bandwidth Difference Ratio between the modeled demand bandwidth and the measured trafficload bandwidth to 0, then there should not be any differences when clicking “Show Results” if you are using the same trafficload period.
Traffic Matrix Parameters
The following parameters can be added to your project’s dparam file to stop the Traffic Matrix Solver when the solution is deemed good enough or if not enough improvements can be found per iteration.
TM_linkdiff = <ratio> : Stop earlier than the loopcount if the target LinkDiff is reached ( the difference between calculated demand traffic load and measured link used bandwidth.)
TM_minimprovement = <number> : Stop earlier than the loopcount if the improvement per iteration is less than this number for 100 iterations