From:  Klaus Mueller <m@klml.de>
Date:  01 Nov 2018 18:06:03 Hong Kong Time
Newsgroup:  news.mozilla.org/mozilla.dev.tech.network
Subject:  

does firefox failover on DNS Round Robin?

NNTP-Posting-Host:  63.245.210.105

Hi,

I realised that browsers do failover on alternative entries on DNS Round 
Robin. Also others noticed this, but [have found it very hard to get 
clear confirmation that they are supposed to.][article]

So I set up this setting myself http://dns-no-tcp.klml.org/ and this 
works with all my browsers.

wget even shows me, it is also doing the failover

wget http://dns-no-tcp.klml.org/
--2018-10-30 11:57:00--  http://dns-no-tcp.klml.org/
Resolving dns-no-tcp.klml.org (dns-no-tcp.klml.org)... 188.106.110.128, 
95.143.172.147
Connecting to dns-no-tcp.klml.org 
(dns-no-tcp.klml.org)|188.106.110.128|:80... failed: No route to host.
Connecting to dns-no-tcp.klml.org 
(dns-no-tcp.klml.org)|95.143.172.147|:80... connected.
HTTP request sent, awaiting response... 200 OK
....


Of course DNS round robin has no handling of server failures. But it is 
a common notion, that clients also do no failover.

[If a service at one of the addresses in the list fails, the DNS will 
continue to hand out that address and clients will still attempt to 
reach the inoperable 
service.](https://en.wikipedia.org/wiki/Round-robin_DNS)

But for me it seems, at least browsers, wget and curl do.


So my queston is: is this behavior a firefox feature? Is there some 
documentation, standard or RFC?



thank you very much
Klaus


[article]: 
https://blog.engelke.com/2011/06/07/web-resilience-with-round-robin-dns/

-- 
Klaus Mueller