** Description changed:

+ [Impact]
+ Users of bond and bridges devices requiring tuning of the default device 
parameters.
+ 
+ [Test case]
+ == Configure MII monitor interval ==
+ 1) Configure a bond device
+ 2) Add parameters:
+ 
+ bonds:
+   mybond0:
+     parameters:
+       mii-monitor-interval: 1
+ 
+ 3) Verify that the applied MII monitor interval is of 1ms, as opposed to
+ 1 second (1000ms), by verifying the contents of
+ /sys/class/net/mybond0/bonding/miimon
+ 
+ 
+ == Validate default behavior ==
+ 1) Configure a bond device without parameters.
+ 2) Verify that no special MII monitor interval is applied, the default value 
should be 0:
+ 
+ $ cat /sys/class/net/mybond0/bonding/miimon
+ 0
+ 
+ 
+ [Regression potential]
+ MII monitor behavior is changing with this SRU. Default behavior for an 
unqualified value (ie. a number alone), which was also the only way to specify 
parameters, was to interpret the values as *seconds*. This leads to relatively 
slow checking of the device link status (for MII monitor), much slower than 
generally expected. The same applies to other time-based values such as up 
delay, down delay, arp interval. The interpretation for these values changes to 
reading them as *milliseconds* when unqualified, and a new way of qualifying 
the values (adding a modifier) was added. This was, people who do require 
"slow" checking of the MII link status will be migrated to "fast" checking 
right now, moving from an interval of 1 second to 1 millisecond (more checking 
means less false-negatives for packet passing through an interface, should 
reduce packet loss, at the cost of potentially flapping the interfaces 
(bringing down a path often if MII status is bad or slow to be returned)). 
Users who require the old behavior may add "s" at the end of the value to make 
it read as "1 second" again, or modify the value to be "1000", which will be 
1000ms (1 second). We estimate the impact of this change to users to be 
minimal,  actually requiring a 1 second interval for MII monitoring / up/down 
delay, and ARP interval is very uncommon and counter-intuitive as all other 
systems work on a millisecond basis.
+ 
+ ---
+ 
  The manpage for netplan doesn't indicate what the unit for mii-monitor-
  interval is on bond devices. It appears to be in whole seconds, but at
  the kernel level, the unit is milliseconds.
  
  From my testing, it appears to be impossible to set a value for mii-
  monitor-interval with netplan that is <1s (e.g. I got a syntax error
  with a value of 0.1 for 100ms)

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https://bugs.launchpad.net/bugs/1745597

Title:
  mii-monitor-interval unit is undocumented, and may be wrong

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