<s>
IPv4	B-Protocol
address	I-Protocol
exhaustion	I-Protocol
is	O
the	O
depletion	O
of	O
the	O
pool	O
of	O
unallocated	O
IPv4	O
addresses	O
.	O
</s>
<s>
This	O
depletion	O
is	O
one	O
of	O
the	O
reasons	O
for	O
the	O
development	O
and	O
deployment	B-Architecture
of	I-Architecture
its	I-Architecture
successor	I-Architecture
protocol	I-Architecture
,	O
IPv6	B-Protocol
.	O
</s>
<s>
IPv4	O
and	O
IPv6	B-Protocol
coexist	O
on	O
the	O
Internet	O
.	O
</s>
<s>
The	O
IP	B-Protocol
address	I-Protocol
space	O
is	O
managed	O
globally	O
by	O
the	O
Internet	O
Assigned	O
Numbers	O
Authority	O
(	O
IANA	O
)	O
,	O
and	O
by	O
five	O
regional	O
Internet	O
registries	O
(	O
RIRs	O
)	O
responsible	O
in	O
their	O
designated	O
territories	O
for	O
assignment	O
to	O
end	O
users	O
and	O
local	O
Internet	O
registries	O
,	O
such	O
as	O
Internet	O
service	O
providers	O
.	O
</s>
<s>
The	O
main	O
market	O
forces	O
that	O
accelerated	O
IPv4	B-Protocol
address	I-Protocol
depletion	I-Protocol
included	O
the	O
rapidly	O
growing	O
number	O
of	O
Internet	O
users	O
,	O
always-on	O
devices	O
,	O
and	O
mobile	O
devices	O
.	O
</s>
<s>
The	O
anticipated	O
shortage	O
has	O
been	O
the	O
driving	O
factor	O
in	O
creating	O
and	O
adopting	O
several	O
new	O
technologies	O
,	O
including	O
network	B-Protocol
address	I-Protocol
translation	I-Protocol
(	O
NAT	O
)	O
,	O
Classless	B-Protocol
Inter-Domain	I-Protocol
Routing	I-Protocol
(	O
CIDR	B-Protocol
)	O
in	O
1993	O
,	O
and	O
IPv6	B-Protocol
in	O
1998	O
.	O
</s>
<s>
All	O
RIRs	O
have	O
exhausted	O
their	O
address	O
pools	O
,	O
except	O
those	O
reserved	O
for	O
IPv6	B-Protocol
transition	I-Protocol
;	O
this	O
occurred	O
on	O
15	O
April	O
2011	O
for	O
the	O
Asia-Pacific	O
(	O
APNIC	O
)	O
,	O
on	O
10	O
June	O
2014	O
for	O
Latin	O
America	O
and	O
the	O
Caribbean	O
(	O
LACNIC	O
)	O
,	O
on	O
24	O
September	O
2015	O
for	O
North	O
America	O
(	O
ARIN	O
)	O
,	O
on	O
21	O
April	O
2017	O
for	O
Africa	O
(	O
AfriNIC	O
)	O
,	O
and	O
on	O
25	O
November	O
2019	O
for	O
Europe	O
,	O
Middle	O
East	O
and	O
Central	O
Asia	O
(	O
RIPE	O
NCC	O
)	O
.	O
</s>
<s>
Individual	O
ISPs	O
still	O
have	O
pools	O
of	O
unassigned	O
IP	B-Protocol
addresses	I-Protocol
,	O
and	O
could	O
recycle	O
addresses	O
no	O
longer	O
needed	O
by	O
subscribers	O
.	O
</s>
<s>
Every	O
node	B-Protocol
of	O
an	O
Internet	B-Protocol
Protocol	I-Protocol
(	O
IP	O
)	O
network	O
,	O
such	O
as	O
a	O
computer	O
,	O
router	B-Protocol
,	O
or	O
network	O
printer	O
,	O
is	O
assigned	O
an	O
IP	B-Protocol
address	I-Protocol
for	O
each	O
network	O
interface	O
,	O
used	O
to	O
locate	O
and	O
identify	O
the	O
node	B-Protocol
in	O
communications	O
with	O
other	O
nodes	O
on	O
the	O
network	O
.	O
</s>
<s>
Internet	B-Protocol
Protocol	I-Protocol
version	O
4	O
provides	O
232	O
(	O
4,294,967,296	O
)	O
addresses	O
.	O
</s>
<s>
However	O
,	O
large	B-Protocol
blocks	I-Protocol
of	I-Protocol
IPv4	I-Protocol
addresses	I-Protocol
are	O
reserved	O
for	O
special	O
uses	O
and	O
are	O
unavailable	O
for	O
public	O
allocation	O
.	O
</s>
<s>
The	O
transition	O
from	O
classful	B-Protocol
network	I-Protocol
addressing	O
to	O
Classless	B-Protocol
Inter-Domain	I-Protocol
Routing	I-Protocol
delayed	O
the	O
exhaustion	O
of	O
addresses	O
substantially	O
.	O
</s>
<s>
In	O
addition	O
,	O
network	B-Protocol
address	I-Protocol
translation	I-Protocol
(	O
NAT	O
)	O
permits	O
Internet	O
service	O
providers	O
and	O
enterprises	O
to	O
masquerade	O
private	B-Protocol
network	I-Protocol
address	O
space	O
with	O
only	O
one	O
publicly	O
routable	O
IPv4	B-Protocol
address	I-Protocol
on	O
the	O
Internet	O
interface	O
of	O
a	O
main	O
Internet	B-Protocol
router	I-Protocol
,	O
instead	O
of	O
allocating	O
a	O
public	O
address	O
to	O
each	O
network	O
device	O
.	O
</s>
<s>
While	O
the	O
primary	O
reason	O
for	O
IPv4	B-Protocol
address	I-Protocol
exhaustion	I-Protocol
is	O
insufficient	O
capacity	O
in	O
the	O
design	O
of	O
the	O
original	O
Internet	O
infrastructure	O
,	O
several	O
additional	O
driving	O
factors	O
have	O
aggravated	O
the	O
shortcomings	O
.	O
</s>
<s>
New	O
specifications	O
of	O
4G	B-Architecture
devices	O
require	O
IPv6	B-Protocol
addressing	O
.	O
</s>
<s>
The	O
rapid	O
increase	O
in	O
the	O
number	O
of	O
the	O
dial-up	O
networks	O
increased	O
address	O
consumption	O
rates	O
,	O
although	O
it	O
was	O
common	O
that	O
the	O
modem	O
pools	O
,	O
and	O
as	O
a	O
result	O
,	O
the	O
pool	O
of	O
assigned	O
IP	B-Protocol
addresses	I-Protocol
,	O
were	O
shared	O
amongst	O
a	O
large	O
customer	O
base	O
.	O
</s>
<s>
By	O
2007	O
,	O
however	O
,	O
broadband	B-General_Concept
Internet	I-General_Concept
access	I-General_Concept
had	O
begun	O
to	O
exceed	O
50%	O
penetration	O
in	O
many	O
markets	O
.	O
</s>
<s>
Broadband	B-General_Concept
connections	O
are	O
always	O
active	O
,	O
as	O
the	O
gateway	O
devices	O
(	O
routers	B-Protocol
,	O
broadband	B-General_Concept
modems	I-General_Concept
)	O
are	O
rarely	O
turned	O
off	O
,	O
so	O
that	O
the	O
address	O
uptake	O
by	O
Internet	O
service	O
providers	O
continued	O
at	O
an	O
accelerating	O
pace	O
.	O
</s>
<s>
Just	O
15	O
years	O
later	O
,	O
almost	O
half	O
of	O
them	O
had	O
persistent	O
broadband	B-General_Concept
connections	O
.	O
</s>
<s>
Inefficient	O
address	O
use	O
Organizations	O
that	O
obtained	O
IP	B-Protocol
addresses	I-Protocol
in	O
the	O
1980s	O
were	O
often	O
allocated	O
far	O
more	O
addresses	O
than	O
they	O
actually	O
required	O
,	O
because	O
the	O
initial	O
classful	B-Protocol
network	I-Protocol
allocation	O
method	O
was	O
inadequate	O
to	O
reflect	O
reasonable	O
usage	O
.	O
</s>
<s>
Many	O
organizations	O
continue	O
to	O
utilize	O
public	O
IP	B-Protocol
addresses	I-Protocol
for	O
devices	O
not	O
accessible	O
outside	O
their	O
local	O
network	O
.	O
</s>
<s>
Due	O
to	O
inefficiencies	O
caused	O
by	O
subnetting	B-Protocol
,	O
it	O
is	O
difficult	O
to	O
use	O
all	O
addresses	O
in	O
a	O
block	O
.	O
</s>
<s>
The	O
host-density	O
ratio	O
,	O
as	O
defined	O
in	O
RFC	O
3194	O
,	O
is	O
a	O
metric	O
for	O
utilization	O
of	O
IP	B-Protocol
address	I-Protocol
blocks	O
,	O
that	O
is	O
used	O
in	O
allocation	O
policies	O
.	O
</s>
<s>
Efforts	O
to	O
delay	O
address	O
space	O
exhaustion	O
started	O
with	O
the	O
recognition	O
of	O
the	O
problem	O
in	O
the	O
early	O
1990s	O
,	O
and	O
the	O
introduction	O
of	O
a	O
number	O
of	O
stop-gap	O
refinements	O
to	O
make	O
the	O
existing	O
structure	O
operate	O
more	O
efficiently	O
,	O
such	O
as	O
CIDR	B-Protocol
methods	O
and	O
strict	O
usage-based	O
allocation	O
policies	O
.	O
</s>
<s>
The	O
Internet	O
Engineering	O
Task	O
Force	O
(	O
IETF	O
)	O
created	O
the	O
Routing	O
and	O
Addressing	O
Group	O
(	O
ROAD	O
)	O
in	O
November	O
1991	O
to	O
respond	O
to	O
the	O
scalability	O
problem	O
caused	O
by	O
the	O
classful	B-Protocol
network	I-Protocol
allocation	O
system	O
in	O
place	O
at	O
the	O
time	O
.	O
</s>
<s>
IPv6	B-Protocol
,	O
the	O
successor	O
technology	O
to	O
IPv4	O
,	O
was	O
designed	O
to	O
address	O
this	O
problem	O
.	O
</s>
<s>
Although	O
the	O
predicted	O
depletion	O
was	O
already	O
approaching	O
its	O
final	O
stages	O
,	O
most	O
providers	O
of	O
Internet	O
services	O
and	O
software	O
vendors	O
were	O
just	O
beginning	O
IPv6	B-Architecture
deployment	I-Architecture
at	O
that	O
time	O
.	O
</s>
<s>
use	O
of	O
network	B-Protocol
address	I-Protocol
translation	I-Protocol
(	O
NAT	O
)	O
which	O
allows	O
a	O
private	B-Protocol
network	I-Protocol
to	O
use	O
one	O
public	O
IP	B-Protocol
address	I-Protocol
and	O
permitting	O
private	O
addresses	O
in	O
the	O
private	B-Protocol
network	I-Protocol
;	O
</s>
<s>
use	O
of	O
private	B-Protocol
network	I-Protocol
addressing	O
;	O
</s>
<s>
network	O
renumbering	O
and	O
subnetting	B-Protocol
to	O
reclaim	O
large	O
blocks	O
of	O
address	O
space	O
allocated	O
in	O
the	O
early	O
days	O
of	O
the	O
Internet	O
,	O
when	O
the	O
Internet	O
used	O
inefficient	O
classful	B-Protocol
network	I-Protocol
addressing	O
.	O
</s>
<s>
In	O
accord	O
with	O
ICANN	B-Application
policies	O
,	O
IANA	O
proceeded	O
to	O
allocate	O
one	O
of	O
those	O
five	O
s	O
to	O
each	O
RIR	O
,	O
exhausting	O
the	O
IANA	O
pool	O
,	O
at	O
a	O
ceremony	O
and	O
press	O
conference	O
on	O
3	O
February	O
2011	O
.	O
</s>
<s>
This	O
date	O
marked	O
the	O
point	O
where	O
not	O
everyone	O
who	O
needed	O
an	O
IPv4	B-Protocol
address	I-Protocol
could	O
be	O
allocated	O
one	O
.	O
</s>
<s>
As	O
a	O
consequence	O
of	O
this	O
exhaustion	O
,	O
end-to-end	B-Application
connectivity	I-Application
as	O
required	O
by	O
specific	O
applications	O
will	O
not	O
be	O
universally	O
available	O
on	O
the	O
Internet	O
until	O
IPv6	B-Protocol
is	O
fully	O
implemented	O
.	O
</s>
<s>
However	O
,	O
IPv6	B-Protocol
hosts	O
cannot	O
directly	O
communicate	O
with	O
IPv4	O
hosts	O
,	O
and	O
have	O
to	O
communicate	O
using	O
special	O
gateway	O
services	O
.	O
</s>
<s>
This	O
means	O
that	O
general-purpose	O
computers	O
must	O
still	O
have	O
IPv4	O
access	O
,	O
for	O
example	O
through	O
NAT64	B-Protocol
,	O
in	O
addition	O
to	O
the	O
new	O
IPv6	B-Protocol
address	O
,	O
which	O
is	O
more	O
effort	O
than	O
just	O
supporting	O
IPv4	O
or	O
IPv6	B-Protocol
.	O
</s>
<s>
The	O
demand	O
for	O
IPv6	B-Protocol
is	O
expected	O
to	O
become	O
pervasive	O
over	O
three	O
to	O
four	O
years	O
.	O
</s>
<s>
In	O
early	O
2011	O
,	O
only	O
16	O
–	O
26%	O
of	O
computers	O
were	O
IPv6	B-Protocol
capable	O
,	O
while	O
only	O
0.2	O
%	O
preferred	O
IPv6	B-Protocol
addressing	O
with	O
many	O
using	O
transition	O
methods	O
such	O
as	O
Teredo	B-Protocol
tunneling	I-Protocol
.	O
</s>
<s>
About	O
0.15	O
%	O
of	O
the	O
top	O
million	O
websites	O
were	O
IPv6	B-Protocol
accessible	O
in	O
2011	O
.	O
</s>
<s>
IPv4	B-Protocol
exhaustion	I-Protocol
mitigation	O
technologies	O
include	O
IPv4	B-Protocol
address	I-Protocol
sharing	O
to	O
access	O
IPv4	O
content	O
,	O
IPv6	B-Protocol
dual-stack	O
implementation	O
,	O
protocol	O
translation	O
to	O
access	O
IPv4	O
and	O
IPv6-addressed	O
content	O
,	O
and	O
bridging	O
and	O
tunneling	O
to	O
bypass	O
single	O
protocol	O
routers	B-Protocol
.	O
</s>
<s>
Early	O
signs	O
of	O
accelerated	O
IPv6	B-Architecture
adoption	I-Architecture
after	O
IANA	O
exhaustion	O
are	O
evident	O
.	O
</s>
<s>
All	O
the	O
RIRs	O
have	O
set	O
aside	O
a	O
small	O
pool	O
of	O
IP	B-Protocol
addresses	I-Protocol
for	O
the	O
transition	O
to	O
IPv6	B-Protocol
(	O
for	O
example	O
carrier-grade	B-Protocol
NAT	I-Protocol
)	O
,	O
from	O
which	O
each	O
LIR	O
can	O
typically	O
get	O
at	O
most	O
1024	O
in	O
total	O
.	O
</s>
<s>
ARIN	O
and	O
LACNIC	O
reserves	O
the	O
last	O
for	O
IPv6	B-Protocol
transition	I-Protocol
.	O
</s>
<s>
APNIC	O
,	O
and	O
RIPE	O
NCC	O
have	O
reserved	O
the	O
last	O
obtained	O
block	O
for	O
IPv6	B-Protocol
transition	I-Protocol
.	O
</s>
<s>
After	O
IANA	O
exhaustion	O
,	O
IPv4	B-Protocol
address	I-Protocol
space	O
requests	O
became	O
subject	O
to	O
additional	O
restrictions	O
at	O
ARIN	O
,	O
and	O
became	O
even	O
more	O
restrictive	O
after	O
reaching	O
the	O
last	O
in	O
April	O
2014	O
.	O
</s>
<s>
On	O
31	O
March	O
2017	O
,	O
AFRINIC	O
became	O
the	O
last	O
regional	O
Internet	O
registry	O
to	O
run	O
down	O
to	O
its	O
last	O
block	O
of	O
IPv4	O
addresses	O
(	O
102/8	O
)	O
,	O
thus	O
triggering	O
the	O
first	O
phase	O
of	O
its	O
IPv4	B-Protocol
exhaustion	I-Protocol
policy	O
.	O
</s>
<s>
"	O
On	O
13	O
January	O
2020	O
,	O
AFRINIC	O
approved	O
an	O
IPv4	O
prefix	O
that	O
resulted	O
in	O
no	O
more	O
than	O
a	O
/11	O
of	O
non-reserved	O
space	O
to	O
be	O
available	O
in	O
the	O
Final	O
/8	B-Protocol
,	O
"	O
which	O
triggered	O
its	O
IPv4	B-Protocol
Exhaustion	I-Protocol
Phase	O
2	O
.	O
</s>
<s>
These	O
addresses	O
will	O
be	O
allocated	O
to	O
our	O
members	O
(	O
LIRs	O
)	O
according	O
to	O
their	O
position	O
on	O
a	O
new	O
waiting	O
list	O
…	O
"	O
The	O
announcement	O
also	O
called	O
for	O
support	O
for	O
the	O
implementation	O
of	O
the	O
IPv6	B-Protocol
roll-out	O
.	O
</s>
<s>
As	O
the	O
slope	O
of	O
the	O
APNIC	O
pool	O
line	O
on	O
the	O
"	O
Geoff	O
Huston	O
's	O
projection	O
of	O
the	O
evolution	O
of	O
the	O
IP	B-Protocol
pool	I-Protocol
for	O
each	O
RIR	O
"	O
chart	O
to	O
the	O
right	O
shows	O
,	O
the	O
last	O
block	O
would	O
have	O
been	O
emptied	O
within	O
one	O
month	O
without	O
this	O
policy	O
.	O
</s>
<s>
The	O
1,024	O
addresses	O
in	O
the	O
block	O
can	O
be	O
used	O
by	O
APNIC	O
members	O
to	O
supply	O
NAT44	B-Protocol
or	O
NAT64	B-Protocol
as	O
a	O
service	O
on	O
an	O
IPv6	B-Protocol
network	O
.	O
</s>
<s>
However	O
at	O
a	O
new	O
large	O
ISP	O
,	O
1,024	O
IPv4	O
addresses	O
might	O
not	O
be	O
enough	O
to	O
provide	O
IPv4	O
connectivity	O
to	O
all	O
the	O
customers	O
due	O
to	O
the	O
limited	O
number	O
of	O
ports	B-Protocol
available	O
per	O
IPv4	B-Protocol
address	I-Protocol
.	O
</s>
<s>
The	O
regional	O
Internet	O
registries	O
(	O
RIRs	O
)	O
for	O
Asia	O
(	O
APNIC	O
)	O
and	O
North	O
America	O
have	O
a	O
policy	O
called	O
the	O
Inter-RIR	O
IPv4	B-Protocol
Address	I-Protocol
Transfer	O
Policy	O
,	O
which	O
allows	O
IPv4	O
addresses	O
to	O
be	O
transferred	O
from	O
North	O
America	O
to	O
Asia	O
.	O
</s>
<s>
Estimates	O
of	O
the	O
time	O
of	O
complete	O
IPv4	B-Protocol
address	I-Protocol
exhaustion	I-Protocol
varied	O
widely	O
in	O
the	O
early	O
2000s	O
.	O
</s>
<s>
On	O
21	O
May	O
2007	O
,	O
the	O
American	O
Registry	O
for	O
Internet	O
Numbers	O
(	O
ARIN	O
)	O
,	O
the	O
RIR	O
for	O
the	O
US	O
,	O
Canada	O
and	O
a	O
number	O
of	O
island	O
states	O
(	O
mostly	O
in	O
the	O
Caribbean	O
)	O
,	O
advised	O
the	O
Internet	O
community	O
that	O
,	O
due	O
to	O
the	O
expected	O
exhaustion	O
in	O
2010	O
,	O
"	O
migration	O
to	O
IPv6	B-Protocol
numbering	O
resources	O
is	O
necessary	O
for	O
any	O
applications	O
which	O
require	O
ongoing	O
availability	O
from	O
ARIN	O
of	O
contiguous	O
IP	O
numbering	O
resources	O
"	O
.	O
</s>
<s>
"	O
Applications	O
"	O
include	O
general	O
connectivity	O
between	O
devices	O
on	O
the	O
Internet	O
,	O
as	O
some	O
devices	O
only	O
have	O
an	O
IPv6	B-Protocol
address	O
allocated	O
.	O
</s>
<s>
On	O
20	O
June	O
2007	O
,	O
the	O
Latin	O
American	O
and	O
Caribbean	O
Internet	O
Addresses	O
Registry	O
(	O
LACNIC	O
)	O
,	O
advised	O
"	O
preparing	O
its	O
regional	O
networks	O
for	O
IPv6	B-Protocol
"	O
by	O
1	O
January	O
2011	O
,	O
for	O
the	O
exhaustion	O
of	O
IPv4	O
addresses	O
"	O
in	O
three	O
years	O
time	O
"	O
.	O
</s>
<s>
On	O
26	O
June	O
2007	O
,	O
the	O
Asia-Pacific	O
Network	O
Information	O
Centre	O
(	O
APNIC	O
)	O
,	O
the	O
RIR	O
for	O
the	O
Pacific	O
and	O
Asia	O
,	O
endorsed	O
a	O
statement	O
by	O
the	O
Japan	O
Network	O
Information	O
Center	O
(	O
JPNIC	O
)	O
that	O
to	O
continue	O
the	O
expansion	O
and	O
development	O
of	O
the	O
Internet	O
a	O
move	O
towards	O
an	O
IPv6-based	O
Internet	O
is	O
advised	O
.	O
</s>
<s>
On	O
26	O
October	O
2007	O
,	O
the	O
Réseaux	O
IP	O
Européens	O
Network	O
Coordination	O
Centre	O
(	O
RIPE	O
NCC	O
)	O
,	O
the	O
RIR	O
for	O
Europe	O
,	O
the	O
Middle	O
East	O
,	O
and	O
parts	O
of	O
Central	O
Asia	O
,	O
endorsed	O
a	O
statement	O
by	O
the	O
RIPE	O
community	O
urging	O
"	O
the	O
widespread	O
deployment	B-Architecture
of	I-Architecture
IPv6	I-Architecture
be	O
made	O
a	O
high	O
priority	O
by	O
all	O
stakeholders	O
"	O
.	O
</s>
<s>
In	O
May	O
2009	O
,	O
the	O
RIPE	O
NCC	O
launched	O
IPv6ActNow.org	O
to	O
help	O
explain	O
"	O
IPv6	B-Protocol
in	O
terms	O
everyone	O
can	O
understand	O
and	O
providing	O
a	O
variety	O
of	O
useful	O
information	O
aimed	O
at	O
promoting	O
the	O
global	O
adoption	O
of	O
IPv6	B-Protocol
"	O
.	O
</s>
<s>
On	O
25	O
August	O
2009	O
,	O
ARIN	O
announced	O
a	O
joint	O
series	O
event	O
in	O
the	O
Caribbean	O
region	O
to	O
push	O
for	O
the	O
implementation	O
of	O
IPv6	B-Protocol
.	O
</s>
<s>
ARIN	O
reported	O
at	O
this	O
time	O
that	O
less	O
than	O
10.9	O
%	O
of	O
IPv4	B-Protocol
address	I-Protocol
space	O
is	O
remaining	O
.	O
</s>
<s>
World	O
IPv6	B-Protocol
Day	O
was	O
an	O
event	O
sponsored	O
and	O
organized	O
by	O
the	O
Internet	O
Society	O
and	O
several	O
large	O
content	O
providers	O
to	O
test	O
public	O
IPv6	B-Architecture
deployment	I-Architecture
.	O
</s>
<s>
The	O
test	O
primarily	O
consisted	O
of	O
websites	O
publishing	O
AAAA	B-Protocol
records	I-Protocol
,	O
allowing	O
IPv6	B-Protocol
capable	O
hosts	O
to	O
connect	O
to	O
these	O
sites	O
using	O
IPv6	B-Protocol
,	O
and	O
for	O
misconfigured	O
networks	O
to	O
be	O
corrected	O
.	O
</s>
<s>
World	O
IPv6	B-Protocol
Launch	O
Day	O
occurred	O
on	O
6	O
June	O
2012	O
,	O
following	O
the	O
success	O
of	O
World	O
IPv6	B-Protocol
Day	O
a	O
year	O
earlier	O
.	O
</s>
<s>
It	O
involved	O
many	O
more	O
participants	O
and	O
had	O
a	O
more	O
ambitious	O
goal	O
of	O
permanently	O
enabling	O
IPv6	B-Protocol
on	O
participant	O
organizations	O
 '	O
networks	O
.	O
</s>
<s>
Before	O
and	O
during	O
the	O
time	O
when	O
classful	B-Protocol
network	I-Protocol
design	O
was	O
still	O
used	O
as	O
allocation	O
model	O
,	O
large	O
blocks	O
of	O
IP	B-Protocol
addresses	I-Protocol
were	B-Protocol
allocated	I-Protocol
to	I-Protocol
some	I-Protocol
organizations	I-Protocol
.	O
</s>
<s>
Since	O
the	O
use	O
of	O
CIDR	B-Protocol
the	O
Internet	O
Assigned	O
Numbers	O
Authority	O
(	O
IANA	O
)	O
could	O
potentially	O
reclaim	O
these	O
ranges	O
and	O
reissue	O
the	O
addresses	O
in	O
smaller	O
blocks	O
.	O
</s>
<s>
Similarly	O
,	O
IP	B-Protocol
address	I-Protocol
blocks	O
have	O
been	O
allocated	O
to	O
entities	O
that	O
no	O
longer	O
exist	O
and	O
some	O
allocated	O
IP	B-Protocol
address	I-Protocol
blocks	O
or	O
large	O
portions	O
of	O
them	O
have	O
never	O
been	O
used	O
.	O
</s>
<s>
No	O
strict	O
accounting	O
of	O
IP	B-Protocol
address	I-Protocol
allocations	O
has	O
been	O
undertaken	O
,	O
and	O
it	O
would	O
take	O
a	O
significant	O
amount	O
of	O
effort	O
to	O
track	O
down	O
which	O
addresses	O
really	O
are	O
unused	O
,	O
as	O
many	O
are	O
in	O
use	O
only	O
on	O
intranets	B-General_Concept
.	O
</s>
<s>
There	O
have	O
been	O
proposals	O
to	O
use	O
the	O
class	B-Protocol
E	I-Protocol
network	I-Protocol
range	O
of	O
IPv4	O
addresses	O
(	O
which	O
would	O
add	O
268.4million	O
IP	B-Protocol
addresses	I-Protocol
to	O
the	O
available	O
pool	O
)	O
but	O
many	O
computer	O
and	O
router	B-Protocol
operating	B-General_Concept
systems	I-General_Concept
and	O
firmware	O
do	O
not	O
allow	O
the	O
use	O
of	O
these	O
addresses	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
the	O
proposals	O
have	O
sought	O
not	O
to	O
designate	O
the	O
class	O
E	O
space	O
for	O
public	O
assignment	O
,	O
but	O
instead	O
propose	O
to	O
permit	O
its	O
private	O
use	O
for	O
networks	O
that	O
require	O
more	O
address	O
space	O
than	O
is	O
currently	O
available	O
through	O
RFC	B-Protocol
1918	I-Protocol
.	O
</s>
<s>
Several	O
organizations	O
have	O
returned	O
large	O
blocks	O
of	O
IP	B-Protocol
addresses	I-Protocol
.	O
</s>
<s>
Notably	O
,	O
Stanford	O
University	O
relinquished	O
their	O
Class	O
A	O
IP	B-Protocol
address	I-Protocol
block	O
in	O
2000	O
,	O
making	O
16million	O
IP	B-Protocol
addresses	I-Protocol
available	O
.	O
</s>
<s>
The	O
primary	O
benefits	O
of	O
an	O
IPv4	B-Protocol
address	I-Protocol
market	O
are	O
that	O
it	O
allows	O
buyers	O
to	O
maintain	O
undisrupted	O
local	O
network	O
functionality	O
.	O
</s>
<s>
IPv6	B-Architecture
adoption	I-Architecture
,	O
while	O
in	O
progress	O
,	O
is	O
currently	O
still	O
in	O
early	O
stages	O
.	O
</s>
<s>
The	O
creation	O
of	O
a	O
market	O
in	O
IPv4	O
addresses	O
would	O
only	O
delay	O
the	O
practical	O
exhaustion	O
of	O
the	O
IPv4	B-Protocol
address	I-Protocol
space	O
for	O
a	O
relatively	O
short	O
time	O
,	O
since	O
the	O
public	O
Internet	O
is	O
still	O
growing	O
.	O
</s>
<s>
The	O
concept	O
of	O
legal	O
ownership	O
of	O
IP	B-Protocol
addresses	I-Protocol
as	O
property	O
is	O
explicitly	O
denied	O
by	O
ARIN	O
and	O
RIPE	O
NCC	O
policy	O
documents	O
and	O
by	O
the	O
ARIN	O
Registration	O
Services	O
Agreement	O
,	O
although	O
ownership	O
rights	O
have	O
been	O
postulated	O
based	O
on	O
a	O
letter	O
from	O
the	O
National	O
Science	O
Foundation	O
General	O
Counsel	O
.	O
</s>
<s>
Ad-hoc	O
trading	O
in	O
addresses	O
could	O
lead	O
to	O
fragmented	O
patterns	O
of	O
routing	O
that	O
could	O
increase	O
the	O
size	O
of	O
the	O
global	B-Protocol
routing	I-Protocol
table	I-Protocol
,	O
potentially	O
causing	O
problems	O
for	O
routers	B-Protocol
with	O
insufficient	O
routing	O
memory	O
resources	O
.	O
</s>
<s>
As	O
the	O
IPv4	B-Protocol
address	I-Protocol
pool	O
depletes	O
,	O
some	O
ISPs	O
will	O
not	O
be	O
able	O
to	O
provide	O
globally	O
routable	O
IPv4	O
addresses	O
to	O
customers	O
.	O
</s>
<s>
Several	O
technologies	O
have	O
been	O
developed	O
for	O
providing	O
IPv4	O
service	O
over	O
an	O
IPv6	B-Protocol
access	O
network	O
.	O
</s>
<s>
In	O
ISP-level	O
IPv4	O
NAT	O
,	O
ISPs	O
may	O
implement	O
IPv4	O
network	B-Protocol
address	I-Protocol
translation	I-Protocol
within	O
their	O
networks	O
and	O
assign	O
private	O
IPv4	O
addresses	O
to	O
customers	O
.	O
</s>
<s>
Furthermore	O
,	O
some	O
ISPs	O
may	O
have	O
to	O
divide	O
their	O
network	O
into	O
subnets	B-Protocol
to	O
allow	O
them	O
to	O
reuse	O
private	O
IPv4	O
addresses	O
,	O
complicating	O
network	O
administration	O
.	O
</s>
<s>
There	O
are	O
also	O
concerns	O
that	O
features	O
of	O
consumer-grade	O
NAT	O
such	O
as	O
DMZs	O
,	O
STUN	B-Protocol
,	O
UPnP	B-Application
and	O
application-level	O
gateways	O
might	O
not	O
be	O
available	O
at	O
the	O
ISP	O
level	O
.	O
</s>
<s>
ISP-level	O
NAT	O
may	O
result	O
in	O
multiple-level	O
address	O
translation	O
which	O
is	O
likely	O
to	O
further	O
complicate	O
the	O
use	O
of	O
technologies	O
such	O
as	O
port	B-Protocol
forwarding	I-Protocol
used	O
to	O
run	O
Internet	O
servers	B-Application
within	O
private	B-Protocol
networks	I-Protocol
.	O
</s>
<s>
NAT64	B-Protocol
translates	O
IPv6	B-Protocol
requests	O
from	O
clients	O
to	O
IPv4	O
requests	O
.	O
</s>
<s>
This	O
avoids	O
the	O
need	O
to	O
provision	O
any	O
IPv4	O
addresses	O
to	O
clients	O
and	O
allows	O
clients	O
that	O
only	O
support	O
IPv6	B-Protocol
to	O
access	O
IPv4	O
resources	O
.	O
</s>
<s>
DS-Lite	O
(	O
Dual-Stack	O
Light	O
)	O
uses	O
tunnels	O
from	O
the	O
customer	O
premises	O
equipment	O
to	O
a	O
network	B-Protocol
address	I-Protocol
translator	I-Protocol
at	O
the	O
ISP	O
.	O
</s>
<s>
The	O
consumer	O
premises	O
equipment	O
encapsulates	O
the	O
IPv4	O
packets	O
in	O
an	O
IPv6	B-Protocol
wrapper	O
and	O
sends	O
them	O
to	O
a	O
host	O
known	O
as	O
the	O
AFTR	B-Protocol
element	O
.	O
</s>
<s>
The	O
AFTR	B-Protocol
element	O
de-encapsulates	O
the	O
packets	O
and	O
performs	O
network	B-Protocol
address	I-Protocol
translation	I-Protocol
before	O
sending	O
them	O
to	O
the	O
public	O
Internet	O
.	O
</s>
<s>
The	O
NAT	O
in	O
the	O
AFTR	B-Protocol
uses	O
the	O
IPv6	B-Protocol
address	O
of	O
the	O
client	O
in	O
its	O
NAT	O
mapping	O
table	O
.	O
</s>
<s>
This	O
means	O
that	O
different	O
clients	O
can	O
use	O
the	O
same	O
private	O
IPv4	O
addresses	O
,	O
therefore	O
avoiding	O
the	O
need	O
for	O
allocating	O
private	O
IPv4	O
IP	B-Protocol
addresses	I-Protocol
to	O
customers	O
or	O
using	O
multiple	O
NATs	O
.	O
</s>
<s>
Address	B-Protocol
plus	I-Protocol
Port	I-Protocol
allows	O
stateless	O
sharing	O
of	O
public	O
IP	B-Protocol
addresses	I-Protocol
based	O
on	O
TCP/UDP	O
port	B-Protocol
numbers	I-Protocol
.	O
</s>
<s>
Each	O
node	B-Protocol
is	O
allocated	O
both	O
an	O
IPv4	B-Protocol
address	I-Protocol
and	O
a	O
range	O
of	O
port	B-Protocol
numbers	I-Protocol
to	O
use	O
.	O
</s>
<s>
Other	O
nodes	O
may	O
be	O
allocated	O
the	O
same	O
IPv4	B-Protocol
address	I-Protocol
but	O
a	O
different	O
range	O
of	O
ports	B-Protocol
.	O
</s>
<s>
Deployment	B-Architecture
of	I-Architecture
IPv6	I-Architecture
is	O
the	O
standards-based	O
solution	O
to	O
the	O
IPv4	B-Protocol
address	I-Protocol
shortage	I-Protocol
.	O
</s>
<s>
IPv6	B-Protocol
is	O
endorsed	O
and	O
implemented	O
by	O
all	O
Internet	O
technical	O
standards	O
bodies	O
and	O
network	O
equipment	O
vendors	O
.	O
</s>
<s>
It	O
encompasses	O
many	O
design	O
improvements	O
,	O
including	O
the	O
replacement	O
of	O
the	O
32-bit	O
IPv4	B-Protocol
address	I-Protocol
format	O
with	O
a	O
128-bit	O
address	O
which	O
provides	O
an	O
addressing	O
space	O
without	O
limitations	O
for	O
the	O
foreseeable	O
future	O
.	O
</s>
<s>
IPv6	B-Protocol
has	O
been	O
in	O
active	O
production	O
deployment	O
since	O
June	O
2006	O
,	O
after	O
organized	O
worldwide	O
testing	O
and	O
evaluation	O
in	O
the	O
6bone	B-Protocol
project	O
ceased	O
.	O
</s>
<s>
Interoperability	O
for	O
hosts	O
using	O
only	O
IPv4	O
protocols	O
is	O
implemented	O
with	O
a	O
variety	O
of	O
IPv6	B-Protocol
transition	I-Protocol
mechanisms	I-Protocol
.	O
</s>
