Setting up the WAN
Rev 4 May.17
25
When C1's connection is re-established, its recovery period of 120 seconds
begins, during which C2 remains as the current WAN link, and C1's score
gradually increases. When C1's score finally becomes greater than C2 again, C1
is restored as the active link, even if its recovery period has not yet completed.
The graph also shows that a short time later, the vehicle enters the WiFi zone of a
depot, at which point the WiFi link, which is the most preferred link, becomes the
active link.
Figure 5-10: Basic example with WiFi and two Cellular links
Note: This graph is intended to provide a basic introduction to how policies use scoring to
switch between links. In practice, other factors such as a WiFi device's Association Settling
Period mean that switches won't happen instantaneously.
Tip:
A priority score of 100 with a penalty of 300 and a 120 second recovery time, make
for good, "granular" numbers to use because they make it easy to monitor switchovers
(e.g. via logging) when using the Dynamic Priority policy. In particular a 120 second
recovery time will allow for a ping monitor to occur every 30 seconds so that three pings
occur during the recovery period.
See
on page 64 for a summary of this policy's settings.