Authority Server Selection of DNS Caching Resolvers
Seen from this document , BIND Caching Name Servers seem to like slower Authoritative Name servers.
I checked this behavior with BIND and unbound.
Here’s the result I did.
[ recursive server info ]
I installed bind and unbound with apt-get.
|# lsb_release –a|
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.04.1 LTS
# uname -ri
# rndc status | head -1
# unbound-control status | head -1
[ conditions ]
I have prepared four auth servers.
queryperf sent unique 3,000 DNS queries to the recursive sever and I counted # of DNS queries which is sent to the Auth servers from BIND/unbound caching name server.
|queryperf -- recursive server -- ns1.foobar.com ( no delay )|
-- ns2.foobar.com ( delay 50msec )
-- ns3.foobar.com ( delay 500 msec )
-- ns4.foobar.com ( delay 1000 msec )
[ results ]
# of queries sent to Auth servers from BIND or unbound
In my testing result , BIND seems to like slower Auth servers..
total # of queries BIND/unbound sent to the Auth servers is more than 3,000 queries.
I guess this was caused by retransmission DNS queries.
Please note that this result might differ from the testing conditions.