<s>
Dynamic	B-Protocol
DNS	I-Protocol
(	O
DDNS	B-Protocol
)	O
is	O
a	O
method	O
of	O
automatically	O
updating	O
a	O
name	B-Protocol
server	I-Protocol
in	O
the	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Protocol
)	O
,	O
often	O
in	O
real	O
time	O
,	O
with	O
the	O
active	O
DDNS	B-Protocol
configuration	O
of	O
its	O
configured	O
hostnames	O
,	O
addresses	O
or	O
other	O
information	O
.	O
</s>
<s>
The	O
first	O
is	O
"	O
dynamic	B-Protocol
DNS	I-Protocol
updating	O
"	O
which	O
refers	O
to	O
systems	O
that	O
are	O
used	O
to	O
update	O
traditional	O
DNS	B-Protocol
records	O
without	O
manual	O
editing	O
.	O
</s>
<s>
These	O
mechanisms	O
use	O
TSIG	B-Protocol
to	O
provide	O
security	O
.	O
</s>
<s>
The	O
second	O
kind	O
of	O
dynamic	B-Protocol
DNS	I-Protocol
permits	O
lightweight	O
and	O
immediate	O
updates	O
often	O
using	O
an	O
update	O
client	B-Protocol
,	O
which	O
do	O
not	O
use	O
the	O
RFC2136	O
standard	O
for	O
updating	O
DNS	B-Protocol
records	O
.	O
</s>
<s>
These	O
clients	O
provide	O
a	O
persistent	O
addressing	O
method	O
for	O
devices	O
that	O
change	O
their	O
location	O
,	O
configuration	O
or	O
IP	B-Protocol
address	I-Protocol
frequently	O
.	O
</s>
<s>
In	O
the	O
initial	O
stages	O
of	O
the	O
Internet	O
(	O
ARPANET	O
)	O
,	O
addressing	O
of	O
hosts	B-Protocol
on	O
the	O
network	O
was	O
achieved	O
by	O
static	O
translation	O
tables	O
that	O
mapped	O
hostnames	O
to	O
IP	B-Protocol
addresses	I-Protocol
.	O
</s>
<s>
The	O
tables	O
were	O
maintained	O
manually	O
in	O
form	O
of	O
the	O
host	B-Protocol
file	I-Protocol
.	I-Protocol
</s>
<s>
The	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
brought	O
a	O
method	O
of	O
distributing	O
the	O
same	O
address	O
information	O
automatically	O
online	O
through	O
recursive	O
queries	O
to	O
remote	O
databases	O
configured	O
for	O
each	O
network	O
,	O
or	O
domain	O
.	O
</s>
<s>
Even	O
this	O
DNS	B-Protocol
facility	O
still	O
used	O
static	O
lookup	O
tables	O
at	O
each	O
participating	O
node	O
.	O
</s>
<s>
IP	B-Protocol
addresses	I-Protocol
,	O
once	O
assigned	O
to	O
a	O
particular	O
host	O
,	O
rarely	O
changed	O
and	O
the	O
mechanism	O
was	O
initially	O
sufficient	O
.	O
</s>
<s>
However	O
,	O
the	O
rapid	O
growth	O
of	O
the	O
Internet	O
and	O
the	O
proliferation	O
of	O
personal	O
computers	O
in	O
the	O
workplace	O
and	O
in	O
homes	O
created	O
the	O
substantial	O
burden	O
for	O
administrators	O
of	O
keeping	O
track	O
of	O
assigned	O
IP	B-Protocol
addresses	I-Protocol
and	O
managing	O
their	O
address	B-General_Concept
space	I-General_Concept
.	O
</s>
<s>
The	O
Dynamic	B-Protocol
Host	I-Protocol
Configuration	I-Protocol
Protocol	I-Protocol
(	O
DHCP	B-Protocol
)	O
allowed	O
enterprises	O
and	O
Internet	O
service	O
providers	O
(	O
ISPs	O
)	O
to	O
assign	O
addresses	O
to	O
computers	O
automatically	O
as	O
they	O
powered	O
up	O
.	O
</s>
<s>
In	O
addition	O
,	O
this	O
helped	O
conserve	O
the	O
address	B-General_Concept
space	I-General_Concept
available	O
,	O
since	O
not	O
all	O
devices	O
might	O
be	O
actively	O
used	O
at	O
all	O
times	O
and	O
addresses	O
could	O
be	O
assigned	O
as	O
needed	O
.	O
</s>
<s>
This	O
feature	O
required	O
that	O
DNS	B-Protocol
servers	I-Protocol
be	O
kept	O
current	O
automatically	O
as	O
well	O
.	O
</s>
<s>
The	O
first	O
implementations	O
of	O
dynamic	B-Protocol
DNS	I-Protocol
fulfilled	O
this	O
purpose	O
:	O
Host	O
computers	O
gained	O
the	O
feature	O
to	O
notify	O
their	O
respective	O
DNS	B-Protocol
server	I-Protocol
of	O
the	O
address	O
they	O
had	O
received	O
from	O
a	O
DHCP	B-Protocol
server	I-Protocol
or	O
through	O
self-configuration	O
.	O
</s>
<s>
This	O
protocol-based	O
DNS	B-Protocol
update	O
method	O
was	O
documented	O
and	O
standardized	O
in	O
IETF	O
publication	O
in	O
1997	O
and	O
has	O
become	O
a	O
standard	O
part	O
of	O
the	O
DNS	B-Protocol
protocol	I-Protocol
(	O
see	O
also	O
nsupdate	B-Protocol
program	O
)	O
.	O
</s>
<s>
The	O
explosive	O
growth	O
and	O
proliferation	O
of	O
the	O
Internet	O
into	O
homes	O
brought	O
a	O
growing	O
shortage	B-Protocol
of	I-Protocol
available	I-Protocol
IP	I-Protocol
addresses	I-Protocol
.	O
</s>
<s>
DHCP	B-Protocol
became	O
an	O
important	O
tool	O
for	O
ISPs	O
as	O
well	O
to	O
manage	O
their	O
address	B-General_Concept
spaces	I-General_Concept
for	O
connecting	O
home	O
and	O
small-business	O
end-users	O
with	O
a	O
single	O
IP	B-Protocol
address	I-Protocol
each	O
by	O
implementing	O
network	B-Protocol
address	I-Protocol
translation	I-Protocol
(	O
NAT	O
)	O
at	O
the	O
customer-premises	O
router	B-Protocol
.	O
</s>
<s>
The	O
private	B-Protocol
network	I-Protocol
behind	O
these	O
routers	B-Protocol
uses	O
address	B-General_Concept
space	I-General_Concept
set	O
aside	O
for	O
these	O
purposes	O
,	O
masqueraded	O
by	O
the	O
NAT	B-Protocol
device	I-Protocol
.	O
</s>
<s>
This	O
,	O
however	O
,	O
broke	O
the	O
end-to-end	B-Application
principle	I-Application
of	O
Internet	O
architecture	O
and	O
methods	O
were	O
required	O
to	O
allow	O
private	B-Protocol
networks	I-Protocol
,	O
with	O
frequently	O
changing	O
external	O
IP	B-Protocol
addresses	I-Protocol
,	O
to	O
discover	O
their	O
public	O
address	O
and	O
insert	O
it	O
into	O
the	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
in	O
order	O
to	O
participate	O
in	O
Internet	O
communications	O
properly	O
.	O
</s>
<s>
Today	O
,	O
numerous	O
providers	O
,	O
called	O
Dynamic	B-Protocol
DNS	I-Protocol
service	O
providers	O
,	O
offer	O
such	O
technology	O
and	O
services	O
on	O
the	O
Internet	O
.	O
</s>
<s>
DNS	B-Protocol
is	O
based	O
on	O
a	O
distributed	B-Operating_System
database	I-Operating_System
that	O
takes	O
some	O
time	O
to	O
update	O
globally	O
.	O
</s>
<s>
When	O
DNS	B-Protocol
was	O
first	O
introduced	O
,	O
the	O
database	O
was	O
small	O
and	O
could	O
be	O
easily	O
maintained	O
by	O
hand	O
.	O
</s>
<s>
As	O
the	O
system	O
grew	O
this	O
task	O
became	O
difficult	O
for	O
any	O
one	O
site	O
to	O
handle	O
,	O
and	O
a	O
new	O
management	O
structure	O
was	O
introduced	O
to	O
spread	O
out	O
the	O
updates	O
among	O
many	O
domain	B-Application
name	I-Application
registrars	I-Application
.	O
</s>
<s>
Registrars	O
today	O
offer	O
end-user	O
updating	O
to	O
their	O
account	O
information	O
,	O
typically	O
using	O
a	O
web-based	O
form	O
,	O
and	O
the	O
registrar	O
then	O
pushes	O
out	O
update	O
information	O
to	O
other	O
DNS	B-Protocol
servers	I-Protocol
.	O
</s>
<s>
Due	O
to	O
the	O
distributed	O
nature	O
of	O
the	O
domain	B-Protocol
name	I-Protocol
systems	I-Protocol
and	O
its	O
registrars	O
,	O
updates	O
to	O
the	O
global	O
DNS	B-Protocol
may	O
take	O
hours	O
to	O
distribute	O
.	O
</s>
<s>
Thus	O
DNS	B-Protocol
is	O
only	O
suitable	O
for	O
services	O
that	O
do	O
not	O
change	O
their	O
IP	B-Protocol
address	I-Protocol
very	O
often	O
,	O
as	O
is	O
the	O
case	O
for	O
most	O
large	O
services	O
like	O
Wikipedia	O
.	O
</s>
<s>
Servers	O
being	O
run	O
on	O
certain	O
types	O
of	O
Internet	O
service	O
provider	O
,	O
cable	B-Device
modems	I-Device
in	O
particular	O
,	O
are	O
likely	O
to	O
change	O
their	O
IP	B-Protocol
address	I-Protocol
over	O
very	O
short	O
periods	O
of	O
time	O
,	O
on	O
the	O
order	O
of	O
days	O
or	O
hours	O
.	O
</s>
<s>
Dynamic	B-Protocol
DNS	I-Protocol
is	O
a	O
system	O
that	O
addresses	O
the	O
problem	O
of	O
rapid	O
updates	O
.	O
</s>
<s>
The	O
term	O
DDNS	B-Protocol
is	O
used	O
in	O
two	O
ways	O
,	O
which	O
,	O
while	O
technically	O
similar	O
,	O
have	O
very	O
different	O
purposes	O
and	O
user	O
populations	O
.	O
</s>
<s>
The	O
first	O
is	O
standards-based	O
DDNS	B-Protocol
,	O
which	O
uses	O
an	O
extension	O
of	O
the	O
DNS	B-Protocol
protocol	I-Protocol
to	O
ask	O
for	O
an	O
update	O
;	O
this	O
is	O
often	O
used	O
for	O
company	O
laptops	O
to	O
register	O
their	O
address	O
.	O
</s>
<s>
The	O
second	O
is	O
proprietary	O
DDNS	B-Protocol
,	O
usually	O
a	O
web-based	O
protocol	O
,	O
normally	O
a	O
single	O
HTTP	B-Protocol
fetch	O
with	O
username	O
and	O
password	O
which	O
then	O
updates	O
some	O
DNS	B-Protocol
records	O
(	O
by	O
some	O
unspecified	O
method	O
)	O
;	O
this	O
is	O
commonly	O
used	O
for	O
a	O
domestic	O
computer	O
to	O
register	O
itself	O
by	O
a	O
publicly	O
known	O
name	O
in	O
order	O
to	O
be	O
found	O
by	O
a	O
wider	O
group	O
,	O
for	O
example	O
as	O
a	O
games	O
server	O
or	O
webcam	O
.	O
</s>
<s>
End	O
users	O
of	O
Internet	O
access	O
receive	O
an	O
allocation	O
of	O
IP	B-Protocol
addresses	I-Protocol
,	O
often	O
only	O
a	O
single	O
address	O
,	O
by	O
their	O
Internet	O
service	O
provider	O
.	O
</s>
<s>
Dynamic	O
IP	B-Protocol
addresses	I-Protocol
present	O
a	O
problem	O
if	O
the	O
customer	O
wants	O
to	O
provide	O
a	O
service	O
to	O
other	O
users	O
on	O
the	O
Internet	O
,	O
such	O
as	O
a	O
web	O
service	O
.	O
</s>
<s>
As	O
the	O
IP	B-Protocol
address	I-Protocol
may	O
change	O
frequently	O
,	O
corresponding	O
domain	O
names	O
must	O
be	O
quickly	O
re-mapped	O
in	O
the	O
DNS	B-Protocol
,	O
to	O
maintain	O
accessibility	O
using	O
a	O
well-known	O
URL	O
.	O
</s>
<s>
Many	O
providers	O
offer	O
commercial	O
or	O
free	B-Application
Dynamic	B-Protocol
DNS	I-Protocol
service	O
for	O
this	O
scenario	O
.	O
</s>
<s>
The	O
automatic	O
reconfiguration	O
is	O
generally	O
implemented	O
in	O
the	O
user	O
's	O
router	B-Protocol
or	O
computer	O
,	O
which	O
runs	O
software	O
to	O
update	O
the	O
DDNS	B-Protocol
service	O
.	O
</s>
<s>
The	O
standardized	O
method	O
of	O
dynamically	O
updating	O
domain	B-Protocol
name	I-Protocol
server	I-Protocol
records	O
is	O
prescribed	O
by	O
RFC	O
2136	O
,	O
commonly	O
known	O
as	O
dynamic	B-Protocol
DNS	I-Protocol
update	I-Protocol
.	O
</s>
<s>
The	O
method	O
described	O
by	O
RFC	O
2136	O
is	O
a	O
network	O
protocol	O
for	O
use	O
with	O
managed	O
DNS	B-Protocol
servers	I-Protocol
,	O
and	O
it	O
includes	O
a	O
security	O
mechanism	O
.	O
</s>
<s>
RFC	O
2136	O
supports	O
all	O
DNS	B-Protocol
record	O
types	O
,	O
but	O
often	O
it	O
is	O
used	O
only	O
as	O
an	O
extension	O
of	O
the	O
DHCP	B-Protocol
system	O
,	O
and	O
in	O
which	O
the	O
authorized	O
DHCP	B-Protocol
servers	I-Protocol
register	O
the	O
client	B-Protocol
records	O
in	O
the	O
DNS	B-Protocol
.	O
</s>
<s>
This	O
form	O
of	O
support	O
for	O
RFC	O
2136	O
is	O
provided	O
by	O
a	O
plethora	O
of	O
client	B-Protocol
and	O
server	O
software	O
,	O
including	O
those	O
that	O
are	O
components	O
of	O
most	O
current	O
operating	O
systems	O
.	O
</s>
<s>
Support	O
for	O
RFC	O
2136	O
is	O
also	O
an	O
integral	O
part	O
of	O
many	O
directory	O
services	O
,	O
including	O
LDAP	B-Protocol
and	O
Windows	B-Protocol
 '	I-Protocol
Active	I-Protocol
Directory	I-Protocol
domains	O
.	O
</s>
<s>
In	O
Microsoft	B-Application
Windows	I-Application
networks	O
,	O
dynamic	B-Protocol
DNS	I-Protocol
is	O
an	O
integral	O
part	O
of	O
Active	B-Protocol
Directory	I-Protocol
,	O
because	O
domain	B-Protocol
controllers	I-Protocol
register	O
their	O
network	B-Protocol
service	I-Protocol
types	I-Protocol
in	O
DNS	B-Protocol
so	O
that	O
other	O
computers	O
in	O
the	O
domain	O
(	O
or	O
forest	O
)	O
can	O
access	O
them	O
.	O
</s>
<s>
Increasing	O
efforts	O
to	O
secure	O
Internet	O
communications	O
today	O
involve	O
encryption	O
of	O
all	O
dynamic	O
updates	O
via	O
the	O
public	O
Internet	O
,	O
as	O
these	O
public	O
dynamic	B-Protocol
DNS	I-Protocol
services	O
have	O
been	O
abused	O
increasingly	O
to	O
design	O
security	O
breaches	O
.	O
</s>
<s>
Standards-based	O
methods	O
within	O
the	O
DNSSEC	B-Protocol
protocol	O
suite	O
,	O
such	O
as	O
TSIG	B-Protocol
,	O
have	O
been	O
developed	O
to	O
secure	B-Protocol
DNS	I-Protocol
updates	O
,	O
but	O
are	O
not	O
widely	O
in	O
use	O
.	O
</s>
<s>
Microsoft	O
developed	O
alternative	O
technology	O
(	O
GSS-TSIG	B-Protocol
)	O
based	O
on	O
Kerberos	B-Protocol
authentication	O
.	O
</s>
<s>
Some	O
free	B-Application
DNS	B-Protocol
server	I-Protocol
software	O
systems	O
,	O
such	O
as	O
dnsmasq	B-Protocol
,	O
support	O
a	O
dynamic	O
update	O
procedure	O
that	O
directly	O
involves	O
a	O
built-in	O
DHCP	B-Protocol
server	I-Protocol
.	O
</s>
<s>
This	O
server	O
automatically	O
updates	O
or	O
adds	O
the	O
DNS	B-Protocol
records	O
as	O
it	O
assigns	O
addresses	O
,	O
relieving	O
the	O
administrator	O
of	O
the	O
task	O
of	O
specifically	O
configuring	O
dynamic	O
updates	O
.	O
</s>
<s>
Dynamic	B-Protocol
DNS	I-Protocol
providers	O
offer	O
a	O
software	B-Protocol
client	I-Protocol
program	O
that	O
automates	O
the	O
discovery	O
and	O
registration	O
of	O
the	O
client	B-Protocol
system	O
's	O
public	O
IP	B-Protocol
addresses	I-Protocol
.	O
</s>
<s>
The	O
client	B-Protocol
program	I-Protocol
is	O
executed	O
on	O
a	O
computer	O
or	O
device	O
in	O
the	O
private	B-Protocol
network	I-Protocol
.	O
</s>
<s>
It	O
connects	O
to	O
the	O
DDNS	B-Protocol
provider	O
's	O
systems	O
with	O
a	O
unique	O
login	O
name	O
;	O
the	O
provider	O
uses	O
the	O
name	O
to	O
link	O
the	O
discovered	O
public	O
IP	B-Protocol
address	I-Protocol
of	O
the	O
home	O
network	O
with	O
a	O
hostname	O
in	O
the	O
domain	B-Protocol
name	I-Protocol
system	I-Protocol
.	O
</s>
<s>
Often	O
they	O
use	O
an	O
HTTP	B-Protocol
service	O
request	O
since	O
even	O
restrictive	O
environments	O
usually	O
allow	O
HTTP	B-Protocol
service	O
.	O
</s>
<s>
Most	O
providers	O
have	O
an	O
API	B-Application
similar	O
to	O
a	O
first	O
provider	O
DynDNS	O
(	O
Dyn.com	O
)	O
so	O
it	O
's	O
often	O
called	O
DynDNS2	O
.	O
</s>
<s>
Many	O
home	O
networking	O
modem/routers	B-Application
include	O
client	B-Protocol
applications	I-Protocol
in	O
their	O
firmware	B-Application
,	O
compatible	O
with	O
a	O
variety	O
of	O
DDNS	B-Protocol
providers	O
.	O
</s>
<s>
Dynamic	B-Protocol
DNS	I-Protocol
is	O
an	O
expected	O
feature	O
or	O
even	O
requirement	O
for	O
IP-based	O
security	O
appliances	O
like	O
DVRs	B-Application
and	O
IP	B-Algorithm
cameras	I-Algorithm
.	O
</s>
<s>
Many	O
options	O
are	O
available	O
for	O
today	O
's	O
manufacturer	O
,	O
and	O
these	O
include	O
the	O
use	O
of	O
existing	O
DDNS	B-Protocol
services	O
or	O
the	O
use	O
of	O
custom	O
services	O
hosted	O
by	O
the	O
manufacturers	O
themselves	O
.	O
</s>
<s>
In	O
almost	O
all	O
cases	O
,	O
a	O
simple	O
HTTP	B-Protocol
based	O
update	O
API	B-Application
is	O
used	O
as	O
it	O
allows	O
for	O
easy	O
integration	O
of	O
a	O
DDNS	B-Protocol
client	B-Protocol
into	O
a	O
device	O
's	O
firmware	B-Application
.	O
</s>
<s>
There	O
are	O
several	O
pre-made	O
tools	O
that	O
can	O
help	O
ease	O
the	O
burden	O
of	O
server	O
and	O
client	B-Protocol
development	O
,	O
like	O
MintDNS	O
,	O
cURL	B-Language
and	O
Inadyn	O
.	O
</s>
<s>
Most	O
web-based	O
DDNS	B-Protocol
services	O
use	O
a	O
standard	O
user	O
name	O
and	O
password	O
security	O
schema	O
.	O
</s>
<s>
This	O
requires	O
that	O
a	O
user	O
first	O
create	O
an	O
account	O
at	O
the	O
DDNS	B-Protocol
server	O
website	O
and	O
then	O
configure	O
the	O
device	O
to	O
send	O
updates	O
to	O
the	O
DDNS	B-Protocol
server	O
whenever	O
an	O
IP	B-Protocol
address	I-Protocol
change	O
is	O
detected	O
.	O
</s>
<s>
Some	O
device	O
manufacturers	O
go	O
a	O
step	O
further	O
by	O
only	O
allowing	O
their	O
DDNS	B-Protocol
Service	O
to	O
be	O
used	O
by	O
the	O
devices	O
they	O
manufacture	O
,	O
and	O
also	O
eliminate	O
the	O
need	O
for	O
user	O
names	O
and	O
passwords	O
altogether	O
.	O
</s>
<s>
Generally	O
this	O
is	O
accomplished	O
by	O
encrypting	O
the	O
device	O
's	O
MAC	O
address	O
using	O
an	O
cryptographic	O
algorithm	O
kept	O
secret	O
on	O
both	O
the	O
DDNS	B-Protocol
server	O
and	O
within	O
the	O
device	O
's	O
firmware	B-Application
.	O
</s>
<s>
Resources	O
for	O
the	O
development	O
of	O
custom	O
DDNS	B-Protocol
services	O
are	O
generally	O
limited	O
and	O
involve	O
a	O
full	O
software	O
development	O
cycle	O
to	O
design	O
and	O
field	O
a	O
secure	O
and	O
robust	O
DDNS	B-Protocol
server	O
.	O
</s>
