Link Faults

Note: This topic applies to Advanced Tests only – not to Quick Tests.

Link faults consist of effects caused by physical link malfunctions, specifically bit errors and disconnections. Bit errors are emulated by instructing NV Test Manager to toggle bits at a given frequency. To achieve "disconnection" in the WAN Cloud, you can instruct NV Test Manager to stop responding for a given period. Click the Link Faults tab to set the parameters that help emulate the link faults.

You can emulate any of the link errors or all of them. Select the check box of the fault type that you want to emulate, and then enter the parameters.

Bit Error

In the Average Frequency box, type a number of bits (from 1/102– 1/1012). Bit toggling will occur every time that the indicated number of bits (on average) has crossed the WAN Cloud.

In the Minimum and Maximum parameters (Number of toggled bits), enter a range of numbers from 1 to 500. NV Test Manager randomly picks a number in the range and toggles as many bits.

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The parameters in this group allow you to emulate a physical disconnection of the network. In the Average Frequency box type the desired number of seconds (from 3 to 300). NV Test Manager will emulate a disconnection once every so many seconds on average. In the Minimum and Maximum boxes (Disconnection time span), indicate a time range in milliseconds (from 10 to 30,000 ms). NV Test Manager will randomly pick a time value from this range and the lines will remain "disconnected" during this time, by dropping all packets that go through the WAN Cloud during this period.

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The Congestion feature helps you emulate a periodic and momentary rise in WAN Cloud traffic, which results in increased latency and packet loss.

Note: The Latency and Packet Loss values during the congestion event override the original values (either manually defined or imported).

Congestion Parameter Description
Average congestion frequency Type the frequency in seconds (from 1 to 300). For example, entering 20 means that the NV Test Manager will increase latency and packet loss every 20 seconds on average.
Congestion time span The duration of the event in milliseconds (from 10 to 65,535). Type a range in the Maximum and Minimum parameters. NV Test Manager randomly picks a value from this range and sets the latency and packet loss to the values you indicate in the Fixed Latency and Loss fields (below), for the selected duration. After this time, latency and packet loss return to their original settings (as described under the Latency and Packet Loss branches).
Congestion event properties
Fixed Latency Enter the latency, in milliseconds, that will prevail during the congestion time (from 0 to 8,000 ms). This value replaces the original latency setting.
Lose x% of all packets Enter a percentage of packets to be lost during the congestion time (from 0% to 90%). This value replaces the original setting for packet loss.

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