<s>
The	O
DNS	B-Protocol
root	I-Protocol
zone	I-Protocol
is	O
the	O
top-level	O
DNS	B-Protocol
zone	I-Protocol
in	O
the	O
hierarchical	O
namespace	O
of	O
the	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Protocol
)	O
of	O
the	O
Internet	O
.	O
</s>
<s>
Before	O
October	O
1	O
,	O
2016	O
,	O
the	O
root	O
zone	O
had	O
been	O
overseen	O
by	O
the	O
Internet	B-Application
Corporation	I-Application
for	I-Application
Assigned	I-Application
Names	I-Application
and	I-Application
Numbers	I-Application
(	O
ICANN	B-Application
)	O
which	O
delegates	O
the	O
management	O
to	O
a	O
subsidiary	O
acting	O
as	O
the	O
Internet	O
Assigned	O
Numbers	O
Authority	O
(	O
IANA	O
)	O
.	O
</s>
<s>
Distribution	O
services	O
are	O
provided	O
by	O
Verisign	B-Application
.	O
</s>
<s>
Prior	O
to	O
this	O
,	O
ICANN	B-Application
performed	O
management	O
responsibility	O
under	O
oversight	O
of	O
the	O
National	O
Telecommunications	O
and	O
Information	O
Administration	O
(	O
NTIA	O
)	O
,	O
an	O
agency	O
of	O
the	O
United	O
States	O
Department	O
of	O
Commerce	O
.	O
</s>
<s>
Oversight	O
responsibility	O
transitioned	O
to	O
the	O
global	O
stakeholder	O
community	O
represented	O
within	O
ICANN	B-Application
's	O
governance	O
structures	O
.	O
</s>
<s>
A	O
combination	O
of	O
limits	O
in	O
the	O
DNS	B-Protocol
definition	O
and	O
in	O
certain	O
protocols	O
,	O
namely	O
the	O
practical	O
size	O
of	O
unfragmented	O
User	B-Protocol
Datagram	I-Protocol
Protocol	I-Protocol
(	O
UDP	O
)	O
packets	O
,	O
resulted	O
in	O
a	O
practical	O
maximum	O
of	O
13	O
root	B-Application
name	I-Application
server	I-Application
addresses	O
that	O
can	O
be	O
accommodated	O
in	O
DNS	B-Protocol
name	I-Protocol
query	O
responses	O
.	O
</s>
<s>
The	O
DNS	B-Protocol
root	I-Protocol
zone	I-Protocol
is	O
served	O
by	O
thirteen	O
root	B-Application
server	I-Application
clusters	O
which	O
are	O
authoritative	O
for	O
queries	O
to	O
the	O
top-level	O
domains	O
of	O
the	O
Internet	O
.	O
</s>
<s>
Thus	O
,	O
every	O
name	O
resolution	O
either	O
starts	O
with	O
a	O
query	O
to	O
a	O
root	B-Application
server	I-Application
or	O
uses	O
information	O
that	O
was	O
once	O
obtained	O
from	O
a	O
root	B-Application
server	I-Application
.	O
</s>
<s>
The	O
root	B-Application
servers	I-Application
clusters	O
have	O
the	O
official	O
names	O
a.root-servers.net	O
to	O
m.root-servers.net	O
.	O
</s>
<s>
To	O
resolve	O
these	O
names	O
into	O
addresses	O
,	O
a	O
DNS	B-Protocol
resolver	O
must	O
first	O
find	O
an	O
authoritative	O
server	O
for	O
the	O
net	O
zone	O
.	O
</s>
<s>
To	O
avoid	O
this	O
circular	B-Language
dependency	I-Language
,	O
the	O
address	O
of	O
at	O
least	O
one	O
root	B-Application
server	I-Application
must	O
be	O
known	O
for	O
bootstrapping	O
access	O
to	O
the	O
DNS	B-Protocol
.	O
</s>
<s>
For	O
this	O
purpose	O
,	O
operating	O
systems	O
or	O
DNS	B-Protocol
servers	O
or	O
resolver	O
software	O
packages	O
typically	O
include	O
a	O
file	O
with	O
all	O
addresses	O
of	O
the	O
DNS	B-Application
root	I-Application
servers	I-Application
.	O
</s>
<s>
Even	O
if	O
the	O
IP	O
addresses	O
of	O
some	O
root	B-Application
servers	I-Application
change	O
,	O
at	O
least	O
one	O
is	O
needed	O
to	O
retrieve	O
the	O
current	O
list	O
of	O
all	O
name	O
servers	O
.	O
</s>
<s>
This	O
address	O
file	O
is	O
called	O
named.cache	O
in	O
the	O
BIND	B-Protocol
name	O
server	O
reference	O
implementation	O
.	O
</s>
<s>
The	O
current	O
official	O
version	O
is	O
distributed	O
by	O
ICANN	B-Application
's	O
InterNIC	O
.	O
</s>
<s>
With	O
the	O
address	O
of	O
a	O
single	O
functioning	O
root	B-Application
server	I-Application
,	O
all	O
other	O
DNS	B-Protocol
information	O
may	O
be	O
discovered	O
recursively	O
,	O
and	O
information	O
about	O
any	O
domain	O
name	O
may	O
be	O
found	O
.	O
</s>
<s>
The	O
root	B-Application
DNS	I-Application
servers	I-Application
are	O
essential	O
to	O
the	O
function	O
of	O
the	O
Internet	O
,	O
as	O
most	O
Internet	O
services	O
,	O
such	O
as	O
the	O
World	O
Wide	O
Web	O
and	O
electronic-mail	O
,	O
are	O
based	O
on	O
domain	O
names	O
.	O
</s>
<s>
The	O
DNS	B-Protocol
servers	O
are	O
potential	O
points	O
of	O
failure	O
for	O
the	O
entire	O
Internet	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
multiple	O
root	B-Application
servers	I-Application
are	O
distributed	O
worldwide	O
.	O
</s>
<s>
The	O
DNS	B-Protocol
packet	O
size	O
of	O
512	O
octets	O
limits	O
a	O
DNS	B-Protocol
response	O
to	O
thirteen	O
addresses	O
,	O
until	O
protocol	O
extensions	O
(	O
see	B-Protocol
Extension	I-Protocol
Mechanisms	I-Protocol
for	I-Protocol
DNS	I-Protocol
)	O
lifted	O
this	O
restriction	O
.	O
</s>
<s>
Since	O
the	O
introduction	O
of	O
IPv6	B-Protocol
,	O
the	O
successor	O
Internet	B-Protocol
Protocol	I-Protocol
to	O
IPv4	B-Protocol
,	O
previous	O
practices	O
are	O
being	O
modified	O
and	O
extra	O
space	O
is	O
filled	O
with	O
IPv6	B-Protocol
name	O
servers	O
.	O
</s>
<s>
The	O
root	B-Application
name	I-Application
servers	I-Application
are	O
hosted	O
in	O
multiple	O
secure	O
sites	O
with	O
high-bandwidth	O
access	O
to	O
accommodate	O
the	O
traffic	O
load	O
.	O
</s>
<s>
Usually	O
each	O
DNS	B-Protocol
server	O
installation	O
at	O
a	O
given	O
site	O
is	O
a	O
cluster	O
of	O
computers	O
with	O
load-balancing	O
routers	O
.	O
</s>
<s>
As	O
of	O
February	O
20	O
,	O
2019	O
,	O
there	O
were	O
938	O
root	B-Application
servers	I-Application
worldwide	O
.	O
</s>
<s>
The	O
modern	O
trend	O
is	O
to	O
use	O
anycast	B-Protocol
addressing	O
and	O
routing	O
to	O
provide	O
resilience	O
and	O
load	O
balancing	O
across	O
a	O
wide	O
geographic	O
area	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
j.root-servers.net	O
server	O
,	O
maintained	O
by	O
Verisign	B-Application
,	O
is	O
represented	O
by	O
104	O
(	O
)	O
individual	O
server	O
systems	O
located	O
around	O
the	O
world	O
,	O
which	O
can	O
be	O
queried	O
using	O
anycast	B-Protocol
addressing	O
.	O
</s>
<s>
The	O
content	O
of	O
the	O
Internet	O
root	O
zone	O
file	O
is	O
coordinated	O
by	O
a	O
subsidiary	O
of	O
ICANN	B-Application
which	O
performs	O
the	O
Internet	O
Assigned	O
Numbers	O
Authority	O
(	O
IANA	O
)	O
functions	O
.	O
</s>
<s>
Verisign	B-Application
generates	O
and	O
distributes	O
the	O
zone	O
file	O
to	O
the	O
various	O
root	B-Application
server	I-Application
operators	O
.	O
</s>
<s>
A	O
1998	O
Commerce	O
Department	O
document	O
stated	O
the	O
agency	O
was	O
"	O
committed	O
to	O
a	O
transition	O
that	O
will	O
allow	O
the	O
private	O
sector	O
to	O
take	O
leadership	O
for	O
DNS	B-Protocol
management	O
"	O
by	O
the	O
year	O
2000	O
,	O
however	O
,	O
no	O
steps	O
to	O
make	O
the	O
transition	O
happen	O
were	O
taken	O
.	O
</s>
<s>
The	O
chairman	O
of	O
the	O
board	O
of	O
ICANN	B-Application
denied	O
the	O
two	O
were	O
connected	O
,	O
however	O
,	O
and	O
said	O
the	O
transition	O
process	O
had	O
been	O
ongoing	O
for	O
a	O
long	O
time	O
.	O
</s>
<s>
ICANN	B-Application
president	O
Fadi	O
Chehadé	O
called	O
the	O
move	O
historic	O
and	O
said	O
that	O
ICANN	B-Application
will	O
move	O
toward	O
multi-stakesholder	O
control	O
.	O
</s>
<s>
Various	O
prominent	O
figures	O
in	O
Internet	O
history	O
,	O
not	O
affiliated	O
with	O
ICANN	B-Application
,	O
also	O
applauded	O
the	O
move	O
.	O
</s>
<s>
NTIA	O
's	O
announcement	O
did	O
not	O
immediately	O
affect	O
how	O
ICANN	B-Application
performs	O
its	O
role	O
.	O
</s>
<s>
The	O
proposal	O
was	O
adopted	O
,	O
and	O
ICANN	B-Application
's	O
renewed	O
contract	O
to	O
perform	O
the	O
IANA	O
function	O
lapsed	O
on	O
September	O
30	O
,	O
2016	O
,	O
resulting	O
in	O
the	O
transition	O
of	O
oversight	O
responsibility	O
to	O
the	O
global	O
stakeholder	O
community	O
represented	O
within	O
ICANN	B-Application
's	O
governance	O
structures	O
.	O
</s>
<s>
As	O
a	O
component	O
of	O
the	O
transition	O
plan	O
,	O
it	O
created	O
a	O
new	O
subsidiary	O
called	O
Public	O
Technical	O
Identifiers	O
(	O
PTI	O
)	O
to	O
perform	O
the	O
IANA	O
functions	O
which	O
include	O
managing	O
the	O
DNS	B-Protocol
root	I-Protocol
zone	I-Protocol
.	O
</s>
<s>
Since	O
July	O
2010	O
,	O
the	O
root	O
zone	O
has	O
been	O
signed	O
with	O
a	O
DNSSEC	B-Protocol
signature	O
,	O
providing	O
a	O
single	O
trust	B-General_Concept
anchor	I-General_Concept
for	O
the	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
that	O
can	O
in	O
turn	O
be	O
used	O
to	O
provide	O
a	O
trust	B-General_Concept
anchor	I-General_Concept
for	O
other	O
public	B-Architecture
key	I-Architecture
infrastructure	I-Architecture
(	O
PKI	O
)	O
.	O
</s>
