<s>
This	O
article	O
presents	O
a	O
comparison	O
of	O
the	O
features	O
,	O
platform	O
support	O
,	O
and	O
packaging	O
of	O
many	O
independent	O
implementations	O
of	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Application
)	O
name	B-Protocol
server	I-Protocol
software	O
.	O
</s>
<s>
Each	O
of	O
these	O
DNS	B-Protocol
servers	I-Protocol
is	O
an	O
independent	O
implementation	O
of	O
the	O
DNS	B-Protocol
protocols	I-Protocol
,	O
capable	O
of	O
resolving	O
DNS	B-Protocol
names	I-Protocol
for	O
other	O
computers	O
,	O
publishing	O
the	O
DNS	B-Protocol
names	I-Protocol
of	O
computers	O
,	O
or	O
both	O
.	O
</s>
<s>
Excluded	O
from	O
consideration	O
are	O
single-feature	O
DNS	B-Application
tools	O
(	O
such	O
as	O
proxies	O
,	O
filters	O
,	O
and	O
firewalls	O
)	O
and	O
redistributions	O
of	O
servers	O
listed	O
here	O
(	O
many	O
products	O
repackage	O
BIND	B-Protocol
,	O
for	O
instance	O
,	O
with	O
proprietary	O
user	O
interfaces	O
)	O
.	O
</s>
<s>
DNS	B-Protocol
servers	I-Protocol
are	O
grouped	O
into	O
several	O
categories	O
of	O
specialization	O
of	O
servicing	O
domain	B-Protocol
name	I-Protocol
system	I-Protocol
queries	O
.	O
</s>
<s>
Authoritative	O
server	O
:	O
authoritative	O
name	B-Protocol
servers	I-Protocol
publish	O
DNS	B-Application
mappings	O
for	O
domains	O
under	O
their	O
authoritative	O
control	O
.	O
</s>
<s>
"	O
Acme	O
Example	O
Widgets	O
"	O
)	O
would	O
provide	O
its	O
own	O
authority	O
services	O
to	O
respond	O
to	O
address	O
queries	O
,	O
or	O
for	O
other	O
DNS	B-Application
information	O
,	O
for	O
www.example.int	O
.	O
</s>
<s>
Authoritative	O
name	B-Protocol
servers	I-Protocol
can	O
be	O
primary	O
name	B-Protocol
servers	I-Protocol
,	O
also	O
known	O
as	O
master	O
servers	O
,	O
i.e.	O
</s>
<s>
they	O
contain	O
the	O
original	O
set	O
of	O
data	O
,	O
or	O
they	O
can	O
be	O
secondary	O
or	O
slave	O
name	B-Protocol
servers	I-Protocol
,	O
containing	O
data	O
copies	O
usually	O
obtained	O
from	O
synchronization	O
directly	O
with	O
the	O
primary	O
server	O
,	O
either	O
via	O
a	O
DNS	B-Application
mechanism	O
,	O
or	O
by	O
other	O
data	O
store	O
synchronization	O
mechanisms	O
.	O
</s>
<s>
Recursive	O
server	O
:	O
recursive	O
servers	O
(	O
sometimes	O
called	O
"	O
DNS	B-Application
caches	O
"	O
,	O
"	O
caching-only	O
name	B-Protocol
servers	I-Protocol
"	O
)	O
provide	O
DNS	B-Protocol
name	I-Protocol
resolution	O
for	O
applications	O
,	O
by	O
relaying	O
the	O
requests	O
of	O
the	O
client	O
application	O
to	O
the	O
chain	O
of	O
authoritative	O
name	B-Protocol
servers	I-Protocol
to	O
fully	O
resolve	O
a	O
network	O
name	O
.	O
</s>
<s>
They	O
also	O
(	O
typically	O
)	O
cache	O
the	O
result	O
to	O
answer	O
potential	O
future	O
queries	O
within	O
a	O
certain	O
expiration	O
(	O
time-to-live	B-Protocol
)	O
period	O
.	O
</s>
<s>
Most	O
Internet	O
users	O
access	O
a	O
recursive	O
server	O
provided	O
by	O
their	O
internet	O
service	O
provider	O
to	O
locate	O
internet	B-Device
hosts	I-Device
such	O
as	O
www.example.com	O
.	O
</s>
<s>
F5	O
Networks	O
product	O
offers	O
DNS	B-Application
as	O
an	O
authoritative	O
server	O
,	O
recursive	O
and	O
adds	O
additional	O
security	O
measures	O
.	O
</s>
<s>
Key	O
advantage	O
is	O
to	O
use	O
the	O
same	O
application	O
delivery	O
controller	O
to	O
support	O
DNS	B-Application
and	O
application	O
acceleration	O
.	O
</s>
<s>
BIND	B-Protocol
is	O
the	O
de	O
facto	O
standard	O
DNS	B-Protocol
server	I-Protocol
.	O
</s>
<s>
It	O
is	O
a	O
free	B-Application
software	I-Application
product	O
and	O
is	O
distributed	O
with	O
most	O
Unix	O
and	O
Linux	B-Application
platforms	O
,	O
where	O
it	O
is	O
most	O
often	O
also	O
referred	O
to	O
as	O
named	O
(	O
name	O
daemon	O
)	O
.	O
</s>
<s>
It	O
is	O
the	O
most	O
widely	O
deployed	O
DNS	B-Protocol
server	I-Protocol
.	O
</s>
<s>
Historically	O
,	O
BIND	B-Protocol
underwent	O
three	O
major	O
revisions	O
,	O
each	O
with	O
significantly	O
different	O
architectures	O
:	O
BIND4	O
,	O
BIND8	O
,	O
and	O
BIND9	B-Protocol
.	O
</s>
<s>
BIND9	B-Protocol
is	O
a	O
ground-up	O
rewrite	O
of	O
BIND	B-Protocol
featuring	O
complete	O
DNSSEC	B-Protocol
support	O
in	O
addition	O
to	O
other	O
features	O
and	O
enhancements	O
.	O
</s>
<s>
Internet	O
Systems	O
Consortium	O
started	O
development	O
of	O
a	O
new	O
version	O
,	O
BIND	B-Protocol
10	O
.	O
</s>
<s>
Its	O
first	O
release	O
was	O
in	O
April	O
2010	O
,	O
but	O
ISC	O
involvement	O
concluded	O
with	O
the	O
release	O
of	O
BIND	B-Protocol
10	O
version	O
1.2	O
in	O
April	O
2014	O
.	O
</s>
<s>
ISC	O
cited	O
a	O
lack	O
of	O
resources	O
to	O
continue	O
development	O
of	O
BIND	B-Protocol
10	O
,	O
and	O
they	O
reaffirmed	O
their	O
commitment	O
to	O
BIND9	B-Protocol
.	O
</s>
<s>
The	O
BIND	B-Protocol
10	O
codebase	O
continues	O
on	O
as	O
an	O
open	B-License
source	I-License
project	O
.	O
</s>
<s>
CNR	O
includes	O
a	O
commercial	O
DNS	B-Protocol
server	I-Protocol
from	O
Cisco	O
Systems	O
usually	O
used	O
in	O
conjunction	O
with	O
the	O
CNR	O
DHCP	B-Protocol
(	O
Dynamic	B-Protocol
Host	I-Protocol
Configuration	I-Protocol
Protocol	I-Protocol
)	O
server	O
.	O
</s>
<s>
CoreDNS	O
is	O
the	O
recommended	O
DNS	B-Protocol
server	I-Protocol
for	O
Kubernetes	B-General_Concept
and	O
graduated	O
from	O
the	O
CNCF	O
in	O
2019	O
.	O
</s>
<s>
Dnsmasq	B-Protocol
is	O
a	O
lightweight	O
,	O
easy	O
to	O
configure	O
DNS	B-Application
forwarder	O
,	O
designed	O
to	O
provide	O
DNS	B-Application
(	O
and	O
optionally	O
DHCP	B-Protocol
and	O
TFTP	B-Device
)	O
services	O
to	O
a	O
small-scale	O
network	O
.	O
</s>
<s>
It	O
can	O
serve	O
the	O
names	O
of	O
local	O
machines	O
which	O
are	O
not	O
in	O
the	O
global	O
DNS	B-Application
.	O
</s>
<s>
Dnsmasq	B-Protocol
accepts	O
DNS	B-Protocol
queries	I-Protocol
and	O
either	O
answers	O
them	O
from	O
a	O
small	O
,	O
local	O
cache	O
or	O
forwards	O
them	O
to	O
a	O
real	O
,	O
recursive	O
DNS	B-Protocol
server	I-Protocol
.	O
</s>
<s>
It	O
loads	O
the	O
contents	O
of	O
/etc/hosts	B-Protocol
,	O
so	O
that	O
local	O
host	O
names	O
which	O
do	O
not	O
appear	O
in	O
the	O
global	O
DNS	B-Application
can	O
be	O
resolved	O
.	O
</s>
<s>
Djbdns	B-Protocol
is	O
a	O
collection	O
of	O
DNS	B-Application
applications	O
,	O
including	O
tinydns	B-Protocol
,	O
which	O
was	O
the	O
second	O
most	O
used	O
free	B-Application
software	I-Application
DNS	B-Protocol
server	I-Protocol
in	O
2004	O
.	O
</s>
<s>
It	O
was	O
designed	O
by	O
Daniel	O
J	O
.	O
Bernstein	O
,	O
author	O
of	O
qmail	B-Application
,	O
with	O
an	O
emphasis	O
on	O
security	O
considerations	O
.	O
</s>
<s>
In	O
March	O
2009	O
,	O
Bernstein	O
paid	O
$1000	O
to	O
the	O
first	O
person	O
finding	O
a	O
security	O
hole	O
in	O
djbdns	B-Protocol
.	O
</s>
<s>
As	O
of	O
March	O
2009	O
,	O
there	O
are	O
three	O
forks	B-Application
and	O
more	O
than	O
a	O
dozen	O
patches	O
to	O
add	O
additional	O
features	O
to	O
djbdns	B-Protocol
.	O
</s>
<s>
gdnsd	O
is	O
a	O
DNS	B-Protocol
server	I-Protocol
designed	O
for	O
geographic	O
balancing	O
.	O
</s>
<s>
gdnsd	O
is	O
the	O
DNS	B-Protocol
server	I-Protocol
used	O
by	O
Wikipedia	O
for	O
its	O
servers	O
and	O
networking	O
.	O
</s>
<s>
Knot	B-Protocol
DNS	I-Protocol
is	O
a	O
free	B-Application
software	I-Application
authoritative	O
DNS	B-Protocol
server	I-Protocol
by	O
CZ.NIC	B-Protocol
.	O
</s>
<s>
Knot	B-Protocol
DNS	I-Protocol
aims	O
to	O
be	O
a	O
fast	O
,	O
resilient	O
DNS	B-Protocol
server	I-Protocol
usable	O
for	O
infrastructure	O
(	O
root	O
and	O
TLD	O
)	O
and	O
DNS	B-Application
hosting	O
services	O
.	O
</s>
<s>
Knot	B-Protocol
DNS	I-Protocol
supports	O
DNSSEC	B-Protocol
signing	O
and	O
among	O
others	O
hosts	B-Protocol
root	O
zone	O
(	O
B	O
,	O
K	O
,	O
and	O
L	O
root	B-Application
name	I-Application
servers	I-Application
)	O
,	O
several	O
top-level	O
domains	O
.	O
</s>
<s>
Knot	O
Resolver	O
is	O
an	O
open	B-License
source	I-License
modern	O
resolver	O
implementation	O
designed	O
for	O
scalability	O
,	O
resiliency	O
,	O
and	O
flexibility	O
.	O
</s>
<s>
MaraDNS	B-Protocol
is	O
a	O
free	B-Application
software	I-Application
DNS	B-Protocol
server	I-Protocol
by	O
Sam	O
Trenholme	O
that	O
claims	O
a	O
good	O
security	O
history	O
and	O
ease	O
of	O
use	O
.	O
</s>
<s>
In	O
order	O
to	O
change	O
any	O
DNS	B-Application
records	O
,	O
MaraDNS	B-Protocol
needs	O
to	O
be	O
restarted	O
.	O
</s>
<s>
Like	O
djbdns	B-Protocol
dnscache	O
,	O
the	O
MaraDNS	B-Protocol
2.0	O
stand-alone	O
recursive	O
resolver	O
(	O
"	O
Deadwood	O
"	O
)	O
does	O
not	O
use	O
threads	O
.	O
</s>
<s>
Windows	B-Application
DNS	B-Protocol
Server	I-Protocol
component	O
of	O
Microsoft	B-Protocol
DNS	I-Protocol
.	O
</s>
<s>
The	O
software	O
is	O
integrated	O
with	O
Active	B-Protocol
Directory	I-Protocol
which	O
makes	O
it	O
the	O
default	O
DNS	B-Application
software	O
for	O
many	O
enterprise	O
networks	O
that	O
are	O
based	O
on	O
Active	B-Protocol
Directory	I-Protocol
.	O
</s>
<s>
It	O
also	O
allows	O
creating	O
zones	O
by	O
the	O
standard	O
DNS	B-Application
zone	B-Protocol
file	I-Protocol
.	O
</s>
<s>
The	O
software	O
comes	O
packaged	O
as	O
a	O
role	O
in	O
Windows	B-Device
Server	I-Device
.	O
</s>
<s>
The	O
server	O
software	O
is	O
shipped	O
with	O
a	O
command	B-Application
line	I-Application
application	O
dnscmd	O
,	O
a	O
DNS	B-Application
management	O
GUI	B-Application
wizard	O
,	O
and	O
a	O
DNS	B-Application
PowerShell	B-Application
package	O
.	O
</s>
<s>
In	O
Windows	B-Device
Server	I-Device
2012	I-Device
,	O
the	O
Windows	B-Application
DNS	B-Application
added	O
support	O
for	O
DNSSEC	B-Protocol
,	O
with	O
full-fledged	O
online	O
signing	O
,	O
with	O
Dynamic	B-Protocol
DNS	I-Protocol
and	O
NSEC3	O
support	O
,	O
along	O
with	O
RSASHA	O
and	O
ECDSA	O
signing	O
algorithms	O
.	O
</s>
<s>
User	O
interface	O
and	O
PowerShell	B-Application
support	O
for	O
managing	O
DNS	B-Application
and	O
DNSSEC	B-Protocol
were	O
improved	O
as	O
well	O
.	O
</s>
<s>
In	O
the	O
Windows	B-Device
Server	I-Device
2016	O
,	O
the	O
DNS	B-Protocol
Server	I-Protocol
supports	O
DNS	B-Application
policies	O
using	O
which	O
the	O
admins	O
can	O
have	O
more	O
control	O
over	O
the	O
name	O
resolution	O
process	O
.	O
</s>
<s>
NSD	B-Protocol
is	O
a	O
free	B-Application
software	I-Application
authoritative	O
server	O
provided	O
by	O
NLNet	O
Labs	O
.	O
</s>
<s>
NSD	B-Protocol
is	O
a	O
test-bed	O
server	O
for	O
DNSSEC	B-Protocol
;	O
new	O
DNSSEC	B-Protocol
protocol	O
features	O
are	O
often	O
prototyped	O
using	O
the	O
NSD	B-Protocol
code	O
base	O
.	O
</s>
<s>
NSD	B-Protocol
hosts	B-Protocol
several	O
top-level	O
domains	O
,	O
and	O
operates	O
three	O
of	O
the	O
root	B-Application
nameservers	I-Application
.	O
</s>
<s>
Pdnsd	B-Application
is	O
a	O
caching	O
DNS	B-Application
proxy	O
server	O
that	O
stores	O
cached	O
DNS	B-Application
records	O
on	O
disk	O
for	O
long	O
term	O
retention	O
.	O
</s>
<s>
Pdnsd	B-Application
is	O
designed	O
to	O
be	O
highly	O
adaptable	O
to	O
situations	O
where	O
net	O
connectivity	O
is	O
slow	O
,	O
unreliable	O
,	O
unavailable	O
,	O
or	O
highly	O
dynamic	O
,	O
with	O
limited	O
capability	O
of	O
acting	O
as	O
an	O
authoritative	O
nameserver	B-Protocol
.	O
</s>
<s>
It	O
is	O
licensed	O
under	O
the	O
GPL	B-License
.	O
</s>
<s>
Posadis	B-Protocol
is	O
a	O
free	B-Application
software	I-Application
DNS	B-Protocol
server	I-Protocol
,	O
written	O
in	O
C++	O
,	O
featuring	O
Dynamic	B-Protocol
DNS	I-Protocol
update	I-Protocol
support	O
.	O
</s>
<s>
PowerDNS	B-Language
is	O
a	O
free	B-Application
software	I-Application
DNS	B-Protocol
server	I-Protocol
with	O
a	O
variety	O
of	O
data	O
storage	O
back-ends	O
and	O
load	O
balancing	O
features	O
.	O
</s>
<s>
DNS	B-Application
Authority	O
is	O
commercial	O
authoritative	O
name	B-Protocol
server	I-Protocol
software	O
from	O
Secure64	B-Protocol
,	O
the	O
company	O
that	O
built	O
Genuinely	O
Secure	B-Protocol
DNS	I-Protocol
applications	O
and	O
operating	B-General_Concept
system	I-General_Concept
and	O
completely	O
automated	O
the	O
deployment	O
of	O
DNSSEC	B-Protocol
.	O
</s>
<s>
DNS	B-Application
Cache	O
is	O
scalable	O
,	O
highly	O
secure	O
recursive	O
DNS	B-Application
software	O
from	O
Secure64	B-Protocol
which	O
provides	O
built-in	O
protection	O
against	O
high-volume	O
denial	O
of	O
service	O
attacks	O
,	O
including	O
Pseudo	O
Random	O
Sub	O
Domain	O
(	O
PRSD	O
)	O
attacks	O
.	O
</s>
<s>
Simple	B-Protocol
DNS	I-Protocol
Plus	I-Protocol
is	O
a	O
commercial	O
DNS	B-Protocol
server	I-Protocol
product	O
that	O
runs	O
under	O
Microsoft	B-Application
Windows	I-Application
with	O
an	O
emphasis	O
on	O
a	O
simple-to-use	O
GUI	B-Application
.	O
</s>
<s>
Unbound	B-Protocol
is	O
a	O
validating	O
,	O
recursive	O
and	O
caching	O
DNS	B-Protocol
server	I-Protocol
designed	O
for	O
high	O
performance	O
.	O
</s>
<s>
It	O
was	O
released	O
on	O
May	O
20	O
,	O
2008	O
(	O
version	O
1.0.0	O
)	O
as	O
free	B-Application
software	I-Application
licensed	O
under	O
the	O
BSD	B-Operating_System
license	I-Operating_System
by	O
NLnet	O
Labs	O
.	O
</s>
<s>
It	O
is	O
installed	O
as	O
part	O
of	O
the	O
base	O
system	O
in	O
FreeBSD	B-Operating_System
starting	O
with	O
version	O
10.0	O
,	O
and	O
in	O
NetBSD	B-Device
with	O
version	O
8.0	O
.	O
</s>
<s>
A	O
version	O
is	O
also	O
available	O
in	O
OpenBSD	B-Operating_System
version	O
5.6	O
and	O
beyond	O
.	O
</s>
<s>
(	O
Previous	O
versions	O
of	O
FreeBSD	B-Operating_System
shipped	O
with	O
BIND	B-Protocol
.	O
)	O
</s>
<s>
YADIFA	B-Protocol
is	O
a	O
BSD-licensed	O
,	O
memory-efficient	O
DNS	B-Protocol
server	I-Protocol
written	O
in	O
C	O
.	O
The	O
acronym	O
YADIFA	B-Protocol
stands	O
for	O
Yet	O
Another	O
DNS	B-Application
Implementation	O
For	O
All	O
.	O
</s>
<s>
Some	O
DNS	B-Application
features	O
are	O
relevant	O
only	O
to	O
recursive	O
servers	O
,	O
or	O
to	O
authoritative	O
servers	O
.	O
</s>
<s>
Some	O
DNS	B-Protocol
servers	I-Protocol
provide	O
support	O
for	O
both	O
server	O
roles	O
in	O
a	O
single	O
,	O
"	O
monolithic	O
"	O
program	O
.	O
</s>
<s>
As	O
in	O
the	O
classic	O
Computer	O
Science	O
microkernel	B-Operating_System
debate	O
,	O
the	O
importance	O
and	O
utility	O
of	O
this	O
distinction	O
is	O
hotly	O
debated	O
.	O
</s>
<s>
The	O
feature	O
matrix	O
in	O
this	O
article	O
does	O
not	O
discuss	O
whether	O
DNS	B-Application
features	O
are	O
provided	O
in	O
a	O
single	O
program	O
or	O
several	O
,	O
so	O
long	O
as	O
those	O
features	O
are	O
provided	O
with	O
the	O
base	O
server	O
package	O
and	O
not	O
with	O
third-party	O
add-on	O
software	O
.	O
</s>
<s>
A	O
major	O
category	O
of	O
DNS	B-Protocol
server	I-Protocol
functionality	O
,	O
see	O
above	O
.	O
</s>
<s>
A	O
major	O
category	O
of	O
DNS	B-Protocol
server	I-Protocol
functionality	O
,	O
see	O
above	O
.	O
</s>
<s>
Servers	O
with	O
this	O
feature	O
provide	O
control	O
over	O
which	O
hosts	B-Protocol
are	O
permitted	O
DNS	B-Application
recursive	O
lookups	O
.	O
</s>
<s>
Authoritative	O
servers	O
can	O
publish	O
content	O
that	O
originates	O
from	O
primary	O
data	O
storage	O
(	O
such	O
as	O
zone	B-Protocol
files	I-Protocol
or	O
databases	O
connected	O
to	O
business	O
administration	O
processes	O
)	O
--sometimes	O
also	O
called	O
'	O
master	O
 '	O
servers--or	O
can	O
be	O
secondary	O
(	O
or	O
slave	O
)	O
servers	O
,	O
republishing	O
content	O
fetched	O
from	O
and	O
synchronized	O
with	O
such	O
primary	O
servers	O
.	O
</s>
<s>
This	O
is	O
typically	O
,	O
though	O
not	O
always	O
,	O
provided	O
using	O
the	O
AXFR	B-Protocol
DNS	B-Protocol
protocol	I-Protocol
.	O
</s>
<s>
Servers	O
with	O
this	O
feature	O
provide	O
recursive	O
services	O
for	O
applications	O
,	O
and	O
cache	O
the	O
results	O
so	O
that	O
future	O
requests	O
for	O
the	O
same	O
name	O
can	O
be	O
answered	O
quickly	O
,	O
without	O
a	O
full	O
DNS	B-Application
lookup	O
.	O
</s>
<s>
This	O
is	O
an	O
important	O
performance	O
feature	O
,	O
as	O
it	O
significantly	O
reduces	O
the	O
latency	O
of	O
DNS	B-Application
requests	O
.	O
</s>
<s>
Servers	O
with	O
this	O
feature	O
implement	O
some	O
variant	O
of	O
the	O
DNSSEC	B-Protocol
protocols	O
.	O
</s>
<s>
DNSSEC	B-Protocol
is	O
becoming	O
more	O
widespread	O
as	O
the	O
deployment	O
of	O
a	O
DNSSEC	B-Protocol
root	B-Application
key	I-Application
has	O
been	O
done	O
by	O
ICANN	B-Application
.	O
</s>
<s>
Deployment	O
to	O
individual	O
sites	O
is	O
growing	O
as	O
top	O
level	O
domains	O
start	O
to	O
deploy	O
DNSSEC	B-Protocol
too	O
.	O
</s>
<s>
The	O
presence	O
of	O
DNSSEC	B-Protocol
features	O
is	O
a	O
notable	O
characteristic	O
of	O
a	O
DNS	B-Protocol
server	I-Protocol
.	O
</s>
<s>
Servers	O
with	O
this	O
feature	O
typically	O
provide	O
DNSSEC	B-Protocol
services	O
.	O
</s>
<s>
In	O
addition	O
,	O
they	O
support	O
the	O
TSIG	B-Protocol
(	O
Transaction	O
SIGnature	O
)	O
protocol	O
,	O
which	O
allows	O
DNS	B-Application
clients	O
to	O
establish	O
a	O
secure	O
session	O
with	O
the	O
server	O
to	O
publish	O
Dynamic	B-Protocol
DNS	I-Protocol
records	O
or	O
to	O
request	O
secure	B-Protocol
DNS	I-Protocol
lookups	O
without	O
incurring	O
the	O
cost	O
and	O
complexity	O
of	O
full	O
DNSSEC	B-Protocol
support	O
.	O
</s>
<s>
Servers	O
with	O
this	O
feature	O
are	O
capable	O
of	O
publishing	O
or	O
handling	O
DNS	B-Application
records	O
that	O
refer	O
to	O
IPv6	B-Protocol
addresses	O
.	O
</s>
<s>
In	O
addition	O
to	O
be	O
fully	O
IPv6	B-Protocol
capable	O
they	O
must	O
implement	O
IPv6	B-Protocol
transport	O
protocol	O
for	O
queries	O
and	O
zone	B-Protocol
transfers	I-Protocol
in	O
secondary/primary	O
relationships	O
and	O
forwarder	O
functions	O
.	O
</s>
<s>
Servers	O
with	O
this	O
feature	O
can	O
publish	O
information	O
for	O
wildcard	B-Protocol
records	I-Protocol
,	O
which	O
provide	O
data	O
about	O
DNS	B-Protocol
names	I-Protocol
in	O
DNS	B-Application
zones	O
that	O
are	O
not	O
specifically	O
listed	O
in	O
the	O
zone	O
.	O
</s>
<s>
Servers	O
with	O
the	O
split-horizon	B-Protocol
DNS	I-Protocol
feature	O
can	O
give	O
different	O
answers	O
depending	O
on	O
the	O
source	O
IP	O
address	O
of	O
the	O
query	O
.	O
</s>
<s>
Server	O
Authoritative	O
Recursive	O
Recursion	O
ACL	O
Secondary	O
mode	O
Caching	O
DNSSEC	B-Protocol
TSIG	B-Protocol
IPv6	B-Protocol
Wildcard	B-Protocol
Free	B-Application
Software	I-Application
Interface	O
split	O
horizonDNS	O
over	O
HTTPSDNS	O
over	O
QUIC	O
BIG-IP	O
DNS	B-Application
API	O
,	O
command	B-Application
line	I-Application
BIND	B-Protocol
(	O
since	O
9.x	O
)	O
(	O
since	O
4.x	O
)	O
Web	O
,	O
command	B-Application
line	I-Application
PowerDNS	B-Language
(	O
since	O
3.0	O
)	O
(	O
since	O
3.0	O
)	O
REST	O
,	O
Web	O
,	O
command	B-Application
line	I-Application
:	O
dnsdist	O
only	O
CoreDNS	O
via	O
proxying	O
API	O
djbdns	B-Protocol
via	O
generic	O
records	O
.	O
</s>
<s>
In	O
this	O
overview	O
of	O
operating	B-General_Concept
system	I-General_Concept
support	O
for	O
the	O
discussed	O
DNS	B-Protocol
server	I-Protocol
,	O
the	O
following	O
terms	O
indicate	O
the	O
level	O
of	O
support	O
:	O
</s>
<s>
Included	O
indicates	O
that	O
the	O
server	O
comes	O
pre-packaged	O
with	O
or	O
has	O
been	O
integrated	O
into	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Server	O
BSD	B-Operating_System
Solaris	B-Application
Linux	B-Application
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
Windows	B-Application
BIND	B-Protocol
Microsoft	B-Protocol
DNS	I-Protocol
djbdns	B-Protocol
Dnsmasq	B-Protocol
Simple	B-Protocol
DNS	I-Protocol
Plus	I-Protocol
NSD	B-Protocol
Knot	B-Protocol
DNS	I-Protocol
Knot	O
Resolver	O
PowerDNS	B-Language
MaraDNS	B-Protocol
pdnsd	B-Application
"	O
pdnsd	B-Application
was	O
started	O
on	O
Linux	B-Application
,	O
and	O
has	O
since	O
been	O
ported	O
to	O
FreeBSD	B-Operating_System
(	O
and	O
Cygwin	O
and	O
Darwin	O
)	O
.	O
</s>
<s>
90%	O
of	O
the	O
source	O
code	O
should	O
be	O
easily	O
portable	O
to	O
POSIX	O
-	O
and	O
BSD-compatible	O
systems	O
,	O
provided	O
that	O
those	O
systems	O
support	O
the	O
POSIX	O
threads	O
(	O
pthreads	O
)	O
.	O
</s>
