failover peer why only for 60 seconds?

Simon Hobson dhcp1 at
Wed Apr 4 09:49:28 UTC 2007

S Kalyanasundaram wrote:

>      In the failover setup why are we checking in the peer only for 
>60 seconds? Subtracting the [cur_time and link->imsg->time] in 
>failover.c can not exceed the 60 seconds. Other wise the peer 
>rejects the connection by saying time offset too large!. May be i am 
>asking a very basic question, but it is not striking.

DHCP stuff is heavily dependent on times, if the two servers disagree 
on what time it is then they are going to end up disagreeing on when 
leases expire etc. Since by definition, a failover pair MUST be 
networked together, it is trivially easy to keep their clocks 
syncronised to at worst a fraction of a second difference - so a 
whole minute is actually quite generous !

One of the first things I do when configuring a new server is to 
configure NTP on it, then I can just forget about time. IMHO, time 
differences between the servers are a non-issue simply because no 
server qualifies as well managed if it doesn't have the right time. 
Even Windows supports NTP !

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