Hmmmmm 99.999% I think in reality this is un obtainable...
This equates to
0.864 Seconds in a day of down time
315.36 Seconds in a year!
When a failover from one server to another occurs there is a pause in obtaining dial tone. This has been anywhere from 3 to 10 seconds.
This is a pause in only obtaining a NEW dial tone... Existing calls between the ip phone and the voice gateway are not dropped.
Now consider this... what happens if your voice gateway fails? What happens if the telephone company cuts your trunk lines...
99.999% is unrealistic...
You should get two servers and have a publisher and a subscriber so you don't loose the system if one fails...
You could get a 99.99% uptime and still have 8.64 seconds of downtime a day... probably enough for a failover
Or 99.9% and have upto 86.4 seconds almost a minute and a half
( 24 hours - 99.999% = 0.00024 * 60 min in a hour * 60 sec in a minute == 0.864 seconds per day)
