+7. Pessimistic external search.
+ * Valid bound becoming invalid on re-measurement with higher duration
+ is frequently a sign of SUT behaving in non-deterministic way
+ (from blackbox point of view). If the final width interval goal
+ is too narrow compared to width of rate region where SUT
+ is non-deterministic, it is quite likely that there will be multiple
+ invalid bounds before the external search finds a valid one.
+ * In this case, external search can be sped up by increasing interval width
+ more rapidly. As only powers of two ensure the subsequent internal search
+ will not result in needlessly narrow interval, a parameter *doublings*
+ is introduced to control the pessimism of external search.
+ For example three doublings result in interval width being multiplied
+ by eight in each external search iteration.
+
+### FD.io CSIT Input Parameters
+
+1. **maximum_transmit_rate** - Typical values: 2 * 14.88 Mpps for 64B
+ 10GE link rate, 2 * 18.75 Mpps for 64B 40GE NIC (specific model).
+2. **minimum_transmit_rate** - Value: 2 * 10 kpps (traffic generator
+ limitation).
+3. **final_trial_duration** - Value: 30 seconds.
+4. **initial_trial_duration** - Value: 1 second.
+5. **final_relative_width** - Value: 0.005 (0.5%).
+6. **packet_loss_ratio** - Value: 0.005 (0.5%).
+7. **number_of_intermediate_phases** - Value: 2.
+ The value has been chosen based on limited experimentation to date.
+ More experimentation needed to arrive to clearer guidelines.
+8. **timeout** - Limit for the overall search duration (for one search).
+ If MLRsearch oversteps this limit, it immediatelly declares the test failed,
+ to avoid wasting even more time on a misbehaving SUT.
+ Value: 600 (seconds).
+9. **doublings** - Number of dublings when computing new interval width
+ in external search.
+ Value: 2 (interval width is quadroupled).
+ Value of 1 is best for well-behaved SUTs, but value of 2 has been found
+ to decrease overall search time for worse-behaved SUT configurations,
+ contributing more to the overall set of different SUT configurations tested.
+
+## Example MLRsearch Run
+
+The following table shows data from a real test run in CSIT
+(using the default input values as above).
+The first column is the phase, the second is the trial measurement performed
+(aggregate bidirectional offered load in megapackets per second,
+and trial duration in seconds).
+Each of last four columns show one bound as updated after the measurement
+(duration truncated to save space).
+Loss ratio is not shown, but invalid bounds are marked with a plus sign.
+
+| Phase | Trial | NDR lower | NDR upper | PDR lower | PDR upper |
+| ----: | ---------: | --------: | --------: | --------: | --------: |
+| init. | 37.50 1.00 | N/A | 37.50 1. | N/A | 37.50 1. |
+| init. | 10.55 1.00 | +10.55 1. | 37.50 1. | +10.55 1. | 37.50 1. |
+| init. | 9.437 1.00 | +9.437 1. | 10.55 1. | +9.437 1. | 10.55 1. |
+| int 1 | 6.053 1.00 | 6.053 1. | 9.437 1. | 6.053 1. | 9.437 1. |
+| int 1 | 7.558 1.00 | 7.558 1. | 9.437 1. | 7.558 1. | 9.437 1. |
+| int 1 | 8.446 1.00 | 8.446 1. | 9.437 1. | 8.446 1. | 9.437 1. |
+| int 1 | 8.928 1.00 | 8.928 1. | 9.437 1. | 8.928 1. | 9.437 1. |
+| int 1 | 9.179 1.00 | 8.928 1. | 9.179 1. | 9.179 1. | 9.437 1. |
+| int 1 | 9.052 1.00 | 9.052 1. | 9.179 1. | 9.179 1. | 9.437 1. |
+| int 1 | 9.307 1.00 | 9.052 1. | 9.179 1. | 9.179 1. | 9.307 1. |
+| int 2 | 9.115 5.48 | 9.115 5. | 9.179 1. | 9.179 1. | 9.307 1. |
+| int 2 | 9.243 5.48 | 9.115 5. | 9.179 1. | 9.243 5. | 9.307 1. |
+| int 2 | 9.179 5.48 | 9.115 5. | 9.179 5. | 9.243 5. | 9.307 1. |
+| int 2 | 9.307 5.48 | 9.115 5. | 9.179 5. | 9.243 5. | +9.307 5. |
+| int 2 | 9.687 5.48 | 9.115 5. | 9.179 5. | 9.307 5. | 9.687 5. |
+| int 2 | 9.495 5.48 | 9.115 5. | 9.179 5. | 9.307 5. | 9.495 5. |
+| int 2 | 9.401 5.48 | 9.115 5. | 9.179 5. | 9.307 5. | 9.401 5. |
+| final | 9.147 30.0 | 9.115 5. | 9.147 30 | 9.307 5. | 9.401 5. |
+| final | 9.354 30.0 | 9.115 5. | 9.147 30 | 9.307 5. | 9.354 30 |
+| final | 9.115 30.0 | +9.115 30 | 9.147 30 | 9.307 5. | 9.354 30 |
+| final | 8.935 30.0 | 8.935 30 | 9.115 30 | 9.307 5. | 9.354 30 |
+| final | 9.025 30.0 | 9.025 30 | 9.115 30 | 9.307 5. | 9.354 30 |
+| final | 9.070 30.0 | 9.070 30 | 9.115 30 | 9.307 5. | 9.354 30 |
+| final | 9.307 30.0 | 9.070 30 | 9.115 30 | 9.307 30 | 9.354 30 |