<s>
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
(	O
DoT	O
)	O
is	O
a	O
network	O
security	B-Protocol
protocol	I-Protocol
for	O
encrypting	O
and	O
wrapping	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Application
)	O
queries	O
and	O
answers	O
via	O
the	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
(	O
TLS	O
)	O
protocol	O
.	O
</s>
<s>
The	O
goal	O
of	O
the	O
method	O
is	O
to	O
increase	O
user	O
privacy	O
and	O
security	O
by	O
preventing	O
eavesdropping	O
and	O
manipulation	O
of	O
DNS	B-Application
data	O
via	O
man-in-the-middle	O
attacks	O
.	O
</s>
<s>
The	O
well-known	B-Protocol
port	I-Protocol
number	I-Protocol
for	O
DoT	O
is	O
853	O
.	O
</s>
<s>
While	O
DNS-over-TLS	B-Protocol
is	O
applicable	O
to	O
any	O
DNS	B-Application
transaction	O
,	O
it	O
was	O
first	O
standardized	O
for	O
use	O
between	O
stub	O
or	O
forwarding	O
resolvers	O
and	O
recursive	O
resolvers	O
,	O
in	O
in	O
May	O
of	O
2016	O
.	O
</s>
<s>
Subsequent	O
IETF	O
efforts	O
specify	O
the	O
use	O
of	O
DoT	O
between	O
recursive	O
and	O
authoritative	O
servers	O
(	O
"	O
Authoritative	O
DNS-over-TLS	B-Protocol
"	O
or	O
"	O
ADoT	O
"	O
)	O
and	O
a	O
related	O
implementation	O
between	O
authoritative	O
servers	O
(	O
Zone	O
Transfer-over-TLS	O
or	O
"	O
xfr-over-TLS	O
"	O
)	O
.	O
</s>
<s>
BIND	B-Protocol
supports	O
DoT	O
connections	O
as	O
of	O
version	O
9.17	O
.	O
</s>
<s>
Earlier	O
versions	O
offered	O
DoT	O
capability	O
by	O
proxying	O
through	O
stunnel	B-Protocol
.	O
</s>
<s>
Unbound	B-Protocol
has	O
supported	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
since	O
22	O
January	O
2018	O
.	O
</s>
<s>
With	O
Android	B-Application
Pie	I-Application
's	O
support	O
for	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
,	O
some	O
ad	O
blockers	O
now	O
support	O
using	O
the	O
encrypted	O
protocol	O
as	O
a	O
relatively	O
easy	O
way	O
to	O
access	O
their	O
services	O
versus	O
any	O
of	O
the	O
various	O
work-around	O
methods	O
typically	O
used	O
such	O
as	O
VPNs	O
and	O
proxy	O
servers	O
.	O
</s>
<s>
Simple	B-Protocol
DNS	I-Protocol
Plus	I-Protocol
,	O
a	O
resolving	O
and	O
authoritative	O
DNS	B-Application
server	O
for	O
Windows	B-Application
,	O
added	O
support	O
for	O
DoT	O
in	O
version	O
9.0	O
released	O
28	O
September	O
2021	O
.	O
</s>
<s>
Android	O
clients	O
running	O
Android	B-Application
9	I-Application
(	O
Pie	B-Application
)	O
or	O
newer	O
support	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
and	O
will	O
use	O
it	O
by	O
default	O
if	O
the	O
network	O
infrastructure	O
,	O
for	O
example	O
the	O
ISP	O
,	O
supports	O
it	O
.	O
</s>
<s>
In	O
April	O
2018	O
,	O
Google	B-Application
announced	O
that	O
Android	B-Application
Pie	I-Application
will	O
include	O
support	O
for	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
,	O
allowing	O
users	O
to	O
set	O
a	O
DNS	B-Application
server	O
phone-wide	O
on	O
both	O
Wi-Fi	O
and	O
mobile	O
connections	O
,	O
an	O
option	O
that	O
was	O
historically	O
only	O
possible	O
on	O
rooted	B-Application
devices	O
.	O
</s>
<s>
DNSDist	O
,	O
from	O
PowerDNS	B-Language
,	O
also	O
announced	O
support	O
for	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
in	O
version	O
1.3.0	O
.	O
</s>
<s>
Linux	B-Application
and	O
Windows	B-Application
users	O
can	O
use	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
as	O
a	O
client	O
through	O
the	O
NLnet	B-General_Concept
Labs	I-General_Concept
stubby	O
daemon	O
or	O
Knot	O
Resolver	O
.	O
</s>
<s>
The	O
unbound	B-Protocol
DNS	B-Application
resolver	O
by	O
NLnet	B-General_Concept
Labs	I-General_Concept
also	O
supports	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
.	O
</s>
<s>
Apple	O
's	O
iOS	B-Operating_System
14	I-Operating_System
introduced	O
OS-level	O
support	O
for	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
(	O
and	O
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
)	O
.	O
</s>
<s>
systemd-resolved	B-Application
is	O
a	O
Linux-only	O
implementation	O
that	O
can	O
be	O
configured	O
to	O
use	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
,	O
by	O
editing	O
/etc/systemd/resolved.conf	O
and	O
enabling	O
the	O
setting	O
DNSOverTLS	O
.	O
</s>
<s>
Most	O
major	O
Linux	B-Application
distributions	O
have	O
systemd	B-Application
installed	O
by	O
default	O
.	O
</s>
<s>
personalDNSfilter	O
is	O
an	O
open	B-License
source	I-License
DNS	B-Application
filter	O
with	O
support	O
for	O
DoT	O
and	O
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
(	O
DoH	O
)	O
for	O
Java-enabled	O
devices	O
including	O
Android	O
.	O
</s>
<s>
Nebulo	O
is	O
an	O
open	B-License
source	I-License
DNS	B-Application
changer	O
application	O
for	O
Android	O
which	O
supports	O
both	O
DoT	O
and	O
DoH	O
.	O
</s>
<s>
DNS-over-TLS	B-Protocol
was	O
first	O
implemented	O
in	O
a	O
public	O
recursive	O
resolver	O
by	O
Quad9	B-Protocol
in	O
2017	O
.	O
</s>
<s>
Other	O
recursive	O
resolver	O
operators	O
such	O
as	O
Google	B-Application
and	O
Cloudflare	B-Application
followed	O
suit	O
in	O
subsequent	O
years	O
,	O
and	O
now	O
it	O
is	O
a	O
broadly-supported	O
feature	O
generally	O
available	O
in	O
most	O
large	O
recursive	O
resolvers	O
.	O
</s>
<s>
DoT	O
can	O
impede	O
analysis	O
and	O
monitoring	O
of	O
DNS	B-Application
traffic	O
for	O
cybersecurity	O
purposes	O
.	O
</s>
<s>
DoT	O
has	O
been	O
used	O
to	O
bypass	O
parental	O
controls	O
which	O
operate	O
at	O
the	O
(	O
unencrypted	O
)	O
standard	O
DNS	B-Application
level	O
;	O
Circle	O
,	O
a	O
parental	O
control	O
router	O
which	O
relies	O
on	O
DNS	B-Protocol
queries	I-Protocol
to	O
check	O
domains	O
against	O
a	O
blocklist	O
,	O
blocks	O
DoT	O
by	O
default	O
due	O
to	O
this	O
.	O
</s>
<s>
However	O
,	O
there	O
are	O
DNS	B-Application
providers	O
that	O
offer	O
filtering	O
and	O
parental	O
controls	O
along	O
with	O
support	O
for	O
both	O
DoT	O
and	O
DoH	O
.	O
</s>
<s>
In	O
that	O
scenario	O
,	O
DNS	B-Protocol
queries	I-Protocol
are	O
checked	O
against	O
block	O
lists	O
once	O
they	O
are	O
received	O
by	O
the	O
provider	O
rather	O
than	O
prior	O
to	O
leaving	O
the	O
user	O
's	O
router	O
.	O
</s>
<s>
As	O
with	O
any	O
communication	O
,	O
encryption	O
of	O
DNS	B-Application
requests	O
by	O
itself	O
does	O
not	O
protect	O
privacy	O
.	O
</s>
<s>
Thus	O
,	O
DoT	O
does	O
not	O
qualify	O
as	O
an	O
end-to-end	O
encrypted	O
protocol	O
,	O
only	O
hop-to-hop	O
encrypted	O
and	O
only	O
if	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
is	O
used	O
consistently	O
.	O
</s>
<s>
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
(	O
DoH	O
)	O
is	O
a	O
similar	O
protocol	O
standard	O
for	O
encrypting	O
DNS	B-Protocol
queries	I-Protocol
,	O
differing	O
only	O
in	O
the	O
methods	O
used	O
for	O
encryption	O
and	O
delivery	O
from	O
DoT	O
.	O
</s>
<s>
DNSCrypt	B-Protocol
is	O
another	O
network	O
protocol	O
that	O
authenticates	O
and	O
encrypts	O
DNS	B-Application
traffic	O
,	O
although	O
it	O
was	O
never	O
proposed	O
to	O
the	O
Internet	O
Engineering	O
Task	O
Force	O
(	O
IETF	O
)	O
with	O
a	O
Request	O
for	O
Comments	O
(	O
RFC	O
)	O
.	O
</s>
