lost and found ( for me ? )

BIND caching servers like slower Auth servers ?

I’ve found an interesting document about BIND recursive servers.

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
Release:        12.04
Codename:       precise

# uname -ri
3.5.0-030500-generic x86_64

# rndc status | head -1
version: 9.8.1-P1

# unbound-control status | head -1
version: 1.4.16

[ 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
no delay
delay 50msec
delay 500msec
delay 1000msec
BIND 9.8.1-P12472130425603
Unbound 1.4.16148015094643

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.

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