The
AA website gives an example of a ppp object that has the settings
lcp-rate="1" lcp-timeout="5" .
I am assuming that this means that the Firebrick is doing PPP LCP ping link detection, checking that the (entire ?) link is really up? If so, this is like the CQM link state checking that AA’s routers do to check that the links are working and measure the links’ latency, but presumably is in the reverse direction. Is this correct?
There does not seem to be much documentation but I assume that
lcp-rate is the interval between PPP LCP pings being sent out and
lcp-timeout is the time before the Firebrick gives up and declares that the link is down following
n seconds with no responses to LCP pings.
How does one choose suitable values for these? Any suggestions?
If I were to reduce the
lcp-timeout value slightly then it would give me faster link down detection so that switchover to using other PPP links or failover to 3G would be quicker and things would go more smoothly after a DSL link goes down. Reducing it too much might cause spurious switchovers if LCP pings are lost because of errors even yet the link has not gone down.
Do you think that shortening it would be a good or very bad idea? Perhaps down to 3 or even 2 seconds from the suggested 5? Since I have many DSL links it won’t cause a risk of disaster even if I shorten it a bit too much.