How browsers handle multiple IPs
- by Sandman4
Can someone direct me to information on exact browsers behavior when browser gets multiple A records for a given hostname (say ip1 and ip2), and one of them is not accessible.
I interested in EXACT details, like (but not limited to):
Will browser get 2 IPs from OS, or it will get only one ?
Which ip will browser try first (random or always the first one) ?
Now, let's say browser started with the failed ip1
For how long will browser try ip1 ?
If user hits "stop" while it waits for ip1, and then clicks refresh
which IP will browser try ?
What will happen when it times-out - will it start trying ip2 or
give error ? (And if error, which ip will browser try when user
clicks refresh).
When user clicks refresh, will any browser attempt new DNS lookup ?
Now let's assume browser tried working ip2 first.
For the next page request, will browser still use ip2, or it may randomly
switch ips ?
For how long browsers keep IPs in their cache ?
When browsers sends a new DNS request, and get SAME ips, will it
CONTINUE to use the same known-to-be-working IP, or the process starts from
scratch and it may try any of the two ?
Of course it all may be browser dependent, and may also vary between versions and platforms, I'd be happy to have maximum of details.
The purpose of this - I'm trying to understand what exactly users will experience when round-robin DNS based used and one of the hosts fails.
Please, I'm NOT asking about how bad DNS load balancing is, and please refrain from answering "don't do it", "it's a bad idea", "you need heartbeat/proxy/BGP/whatever" and so on.
