|
|
|
You can avoid some anomalies in the display of HRTT data (show prefix hrtt CLI command output and HRTT snapshot reports) by using metric-data-oriented displays (show prefix metric output and Metric snapshot report).
In the following example of show prefix hrtt output, the s label in the link_1 column shows that link_1 is in the winner set for the 172.0.0.0/14 prefix, even though the delta between its HRTT and that of the winner (link_3, identified by the w label) is a relatively high 185.7 milliseconds:
Prefix link_1 Diff link_2 Diff link_3 Diff D 172.0.0.0/14 b s 221.7 185.7 s 41.7 5.7 w 36.1 0.0 D 172.241.128.0/18 b 94.3 13.2 w 81.1 0.0 s 82.0 0.9
Yet, for the 172.241.128.0/18 prefix, link_1 is not in the winner set even though the delta is a considerably lower 13.2 ms. (See the section Prefixes elsewhere in this chapter for a description of the D, b, s and w labels shown in the example.)
The reason for the anomaly is the amount of time it takes the CNA decision maker process to evaluate incoming data. The example output indicates that link_1 was in the winner set for the 172.0.0.0/14 prefix the last time the decision maker process evaluated the data for that prefix.
Because of the newly arrived HRTT score, it will not be in the winner set when the decision maker process completes its loop through the prefix list and evaluates data for this prefix again. But the show command output was displayed before this evaluation occurred. Executing the show prefix hrtt command again a couple of seconds later would have shown that link_1 no longer displayed an s label.
This anomaly is not present in the show prefix metric output or Metric snapshot report because metric values are not updated until after the prefix is evaluated by the CNA decision maker process. The metric value is calculated at the same time label codes are assigned, so the table entries will all represent the same moment in time.
|
|
|