<s>
6rd	B-Protocol
is	O
a	O
mechanism	O
to	O
facilitate	O
IPv6	B-Protocol
rapid	O
deployment	O
across	O
IPv4	B-Protocol
infrastructures	O
of	O
Internet	O
service	O
providers	O
(	O
ISPs	O
)	O
.	O
</s>
<s>
It	O
is	O
derived	O
from	O
6to4	B-Protocol
,	O
a	O
preexisting	O
mechanism	O
to	O
transfer	O
IPv6	B-Protocol
packets	O
over	O
the	O
IPv4	B-Protocol
network	I-Protocol
,	O
with	O
the	O
significant	O
change	O
that	O
it	O
operates	O
entirely	O
within	O
the	O
end-user	O
'	O
s	O
ISP	O
's	O
network	O
,	O
thus	O
avoiding	O
the	O
major	O
architectural	O
problems	O
inherent	O
in	O
the	O
original	O
design	O
of	O
6to4	B-Protocol
.	O
</s>
<s>
The	O
name	O
6rd	B-Protocol
is	O
a	O
reference	O
to	O
both	O
the	O
rapid	O
deployments	O
of	O
IPv6	B-Protocol
it	O
makes	O
possible	O
and	O
,	O
informally	O
,	O
the	O
initials	O
(	O
RD	O
)	O
of	O
its	O
inventor	O
,	O
Rémi	O
Després	O
.	O
</s>
<s>
A	O
description	O
of	O
6rd	B-Protocol
principles	O
and	O
of	O
how	O
they	O
were	O
first	O
used	O
by	O
Free	O
is	O
published	O
in	O
RFC	O
5569	O
.	O
</s>
<s>
The	O
detailed	O
6rd	B-Protocol
specification	O
prepared	O
for	O
standardization	O
in	O
the	O
IETF	O
is	O
available	O
as	O
RFC	O
5969	O
.	O
</s>
<s>
In	O
November	O
2007	O
,	O
Rémi	O
Després	O
—	O
who	O
was	O
one	O
of	O
the	O
creators	O
of	O
the	O
Transpac	O
data	O
network	O
in	O
France	O
in	O
the	O
1970s	O
—	O
proposed	O
to	O
Free	O
,	O
the	O
second	O
largest	O
ISP	O
in	O
France	O
,	O
to	O
use	O
the	O
6rd	B-Protocol
mechanism	O
he	O
had	O
invented	O
to	O
rapidly	O
deploy	O
IPv6	B-Protocol
.	O
</s>
<s>
While	O
Free	O
had	O
until	O
then	O
no	O
short-term	O
plan	O
to	O
offer	O
IPv6	B-Protocol
service	O
,	O
Rani	O
Assaf	O
,	O
the	O
CTO	O
of	O
Free	O
,	O
immediately	O
decided	O
to	O
implement	O
the	O
solution	O
.	O
</s>
<s>
Five	O
weeks	O
later	O
,	O
with	O
due	O
marketing	O
approval	O
and	O
operational	O
validation	O
,	O
the	O
press	O
release	O
announcing	O
that	O
IPv6	B-Protocol
was	O
available	O
to	O
Free	O
's	O
customers	O
was	O
issued	O
.	O
</s>
<s>
The	O
first	O
draft	O
describing	O
the	O
6rd	B-Protocol
mechanism	O
and	O
Free	O
's	O
deployment	O
was	O
submitted	O
to	O
IETF	O
on	O
9	O
February	O
2008	O
.	O
</s>
<s>
In	O
March	O
2010	O
,	O
a	O
Working	O
Group	O
of	O
the	O
IETF	O
approved	O
that	O
its	O
latest	O
draft	O
on	O
6rd	B-Protocol
should	O
become	O
,	O
after	O
some	O
more	O
modifications	O
,	O
a	O
standards-track	O
RFC	O
.	O
</s>
<s>
In	O
October	O
2010	O
Comcast	O
made	O
6rd	B-Protocol
software	O
for	O
home	O
gateway	O
devices	O
available	O
via	O
open	O
source	O
for	O
free	O
.	O
</s>
<s>
6to4	B-Protocol
works	O
by	O
relaying	O
traffic	O
between	O
native	O
IPv6	B-Protocol
and	O
IPv4	B-Protocol
using	O
relay	O
servers	O
which	O
advertise	O
common	O
IPv4	B-Protocol
and	O
IPv6	B-Protocol
prefixes	O
to	O
networks	O
they	O
are	O
prepared	O
to	O
provide	O
relay	O
services	O
for	O
,	O
but	O
there	O
is	O
no	O
guarantee	O
that	O
all	O
native	O
IPv6	B-Protocol
hosts	O
have	O
a	O
working	O
route	O
toward	O
such	O
a	O
relay	O
.	O
</s>
<s>
Because	O
of	O
this	O
,	O
a	O
6to4	B-Protocol
host	O
is	O
not	O
guaranteed	O
to	O
be	O
reachable	O
by	O
all	O
native	O
IPv6	B-Protocol
hosts	O
.	O
</s>
<s>
6rd	B-Protocol
changes	O
this	O
model	O
by	O
making	O
each	O
ISP	O
use	O
one	O
of	O
its	O
own	O
IPv6	B-Protocol
prefixes	O
instead	O
of	O
the	O
special	O
prefix	O
standardized	O
for	O
6to4	B-Protocol
,	O
so	O
a	O
provider	O
is	O
guaranteed	O
that	O
its	O
6rd	B-Protocol
hosts	O
will	O
be	O
reachable	O
from	O
all	O
native	O
IPv6	B-Protocol
hosts	O
that	O
can	O
reach	O
their	O
IPv6	B-Protocol
network	O
.	O
</s>
<s>
Because	O
6rd	B-Protocol
relays	O
can	O
only	O
be	O
used	O
by	O
a	O
limited	O
set	O
of	O
hosts	O
that	O
are	O
all	O
under	O
the	O
control	O
of	O
the	O
same	O
administrative	O
entity	O
,	O
it	O
also	O
reduces	O
the	O
scope	O
for	O
traffic	O
anonymization	O
attacks	O
such	O
as	O
those	O
possible	O
with	O
6to4	B-Protocol
.	O
</s>
<s>
The	O
simplest	O
6rd	B-Protocol
deployment	O
,	O
which	O
uses	O
32	O
bits	O
of	O
IPv6	B-Protocol
address	O
space	O
to	O
map	O
the	O
entire	O
IPv4	B-Protocol
address	O
space	O
,	O
consumes	O
more	O
address	O
space	O
than	O
typical	O
with	O
IPv6	B-Protocol
natively	O
supported	O
in	O
all	O
ISP	O
routers	O
.	O
</s>
<s>
This	O
can	O
be	O
mitigated	O
by	O
omitting	O
redundant	O
parts	O
of	O
the	O
IPv4	B-Protocol
address	O
space	O
,	O
and	O
in	O
some	O
cases	O
by	O
deploying	O
multiple	O
6rd	B-Protocol
domains	O
.	O
</s>
<s>
The	O
default	O
allocation	O
of	O
IPv6	B-Protocol
space	O
by	O
a	O
regional	O
Internet	O
registry	O
(	O
RIR	O
)	O
is	O
a	O
32-bit	O
prefix	O
.	O
</s>
<s>
Since	O
it	O
takes	O
32	O
bits	O
to	O
map	O
an	O
IPv4	B-Protocol
address	O
with	O
6rd	B-Protocol
,	O
this	O
implies	O
that	O
an	O
ISP	O
would	O
only	O
be	O
able	O
to	O
allocate	O
64-bit	O
IPv6	B-Protocol
prefixes	O
to	O
its	O
customers	O
if	O
it	O
were	O
to	O
use	O
entire	O
IPv4	B-Protocol
addresses	O
.	O
</s>
<s>
6rd	B-Protocol
,	O
however	O
,	O
allows	O
any	O
redundant	O
part	O
of	O
an	O
IPv4	B-Protocol
address	O
to	O
be	O
discarded	O
:	O
For	O
example	O
,	O
if	O
the	O
IPv4	B-Protocol
addresses	O
an	O
ISP	O
issues	O
to	O
its	O
customers	O
all	O
share	O
the	O
same	O
first	O
eighteen	O
bits	O
,	O
a	O
6rd	B-Protocol
prefix	O
only	O
need	O
include	O
the	O
remaining	O
fourteen	O
bits	O
.	O
</s>
<s>
Without	O
this	O
flexibility	O
,	O
Free	O
originally	O
assigned	O
64-bit	O
IPv6	B-Protocol
prefixes	O
to	O
its	O
customers	O
but	O
was	O
able	O
to	O
assign	O
them	O
shorter	O
prefixes	O
once	O
it	O
obtained	O
a	O
larger	O
allocation	O
of	O
IPv6	B-Protocol
space	O
(	O
a	O
26-bit	O
prefix	O
)	O
from	O
the	O
RIPE	O
NCC	O
.	O
</s>
<s>
Free	O
has	O
used	O
6rd	B-Protocol
since	O
December	O
2007	O
.	O
</s>
<s>
In	O
2008	O
,	O
a	O
report	O
from	O
Google	B-Application
on	O
its	O
visibility	O
of	O
IPv6	B-Protocol
use	O
showed	O
France	O
as	O
having	O
the	O
second	O
highest	O
IPv6	B-Protocol
penetration	O
in	O
the	O
world	O
,	O
with	O
95%	O
of	O
its	O
IPv6	B-Protocol
being	O
with	O
"	O
native	O
"	O
IPv6	B-Protocol
addresses	O
,	O
almost	O
all	O
from	O
Free	O
.	O
</s>
<s>
Comcast	O
announced	O
in	O
January	O
2010	O
a	O
trial	O
using	O
6rd	B-Protocol
in	O
the	O
second	O
quarter	O
of	O
2010	O
.	O
</s>
<s>
They	O
began	O
that	O
6RD	B-Protocol
trial	O
on	O
June	O
30	O
,	O
2010	O
,	O
which	O
was	O
expected	O
to	O
ramp	O
up	O
to	O
several	O
hundred	O
users	O
in	O
July	O
2010	O
.	O
</s>
<s>
But	O
6rd	B-Protocol
is	O
not	O
anticipated	O
to	O
be	O
Comcast	O
's	O
primary	O
IPv6	B-Protocol
strategy	O
.	O
</s>
<s>
Comcast	O
has	O
tested	O
2	O
different	O
home	O
gateways	O
with	O
6rd	B-Protocol
,	O
one	O
of	O
which	O
they	O
have	O
made	O
available	O
via	O
open	O
source	O
.	O
</s>
<s>
In	O
addition	O
,	O
they	O
have	O
published	O
6rd	B-Protocol
configuration	O
instructions	O
for	O
any	O
user	O
on	O
their	O
network	O
that	O
wishes	O
to	O
use	O
their	O
6rd	B-Protocol
border	O
relays	O
.	O
</s>
<s>
Comcast	O
planned	O
to	O
deactivate	O
their	O
6rd	B-Protocol
service	O
on	O
June	O
30	O
,	O
2011	O
in	O
anticipation	O
of	O
their	O
wider	O
deployment	O
of	O
native	O
dual	O
stack	O
.	O
</s>
<s>
Charter	O
has	O
announced	O
the	O
planned	O
deployment	O
of	O
6rd	B-Protocol
across	O
their	O
network	O
in	O
2012	O
.	O
</s>
<s>
They	O
host	O
a	O
public	O
6rd	B-Protocol
border	O
relay	O
for	O
their	O
subscribers	O
.	O
</s>
<s>
The	O
Linux	B-Operating_System
kernel	I-Operating_System
added	O
support	O
for	O
6rd	B-Protocol
in	O
version	O
2.6.33	O
.	O
</s>
<s>
The	O
Japanese	O
company	O
SoftBank	O
have	O
announced	O
that	O
they	O
will	O
begin	O
rolling	O
out	O
IPv6	B-Protocol
using	O
6rd	B-Protocol
.	O
</s>
<s>
Swisscom	O
is	O
rolling	O
out	O
6RD	B-Protocol
in	O
2011	O
.	O
</s>
<s>
The	O
Japanese	O
company	O
began	O
its	O
6rd	B-Protocol
trial	O
in	O
March	O
2011	O
.	O
</s>
<s>
Canadian	O
ISP	O
Videotron	O
has	O
deployed	O
6rd	B-Protocol
in	O
beta	O
on	O
June	O
8	O
,	O
2011	O
for	O
customers	O
using	O
a	O
6rd-ready	O
router	O
.	O
</s>
<s>
In	O
December	O
2011	O
,	O
Dutch	O
ISP	O
Telfort	O
announced	O
it	O
was	O
starting	O
an	O
IPv6	B-Protocol
pre-pilot	O
based	O
on	O
6rd	B-Protocol
,	O
inviting	O
customers	O
to	O
participate	O
.	O
</s>
<s>
As	O
of	O
January	O
2013	O
,	O
6rd	B-Protocol
is	O
open	O
as	O
opt-in	O
to	O
all	O
Telfort	O
fixed	O
line	O
(	O
ADSL	O
and	O
VDSL	O
)	O
customers	O
.	O
</s>
<s>
The	O
"	O
opt-in	O
"	O
means	O
the	O
customer	O
has	O
to	O
enable	O
6RD	B-Protocol
in	O
the	O
Telfort	O
Zyxel	O
modem	O
to	O
get	O
IPv6	B-Protocol
connectivity	O
.	O
</s>
<s>
CenturyLink	B-Application
has	O
supported	O
6rd	B-Protocol
since	O
April	O
2012	O
including	O
a	O
list	O
of	O
compatible	O
modems	O
.	O
</s>
<s>
In	O
January	O
2013	O
,	O
Dutch	O
ISP	O
ZeelandNet	O
announced	O
it	O
was	O
starting	O
an	O
IPv6	B-Protocol
pre-pilot	O
based	O
on	O
6rd	B-Protocol
,	O
inviting	O
customers	O
to	O
participate	O
.	O
</s>
<s>
After	O
the	O
trial	O
they	O
expect	O
to	O
have	O
a	O
native/dual	O
-stack	O
solution	O
on	O
their	O
EuroDOCSIS	B-Protocol
consumer	O
network	O
and	O
business	O
fiber	O
network	O
.	O
</s>
<s>
As	O
of	O
June	O
12	O
,	O
2013	O
,	O
Dutch	O
ISP	O
OnsBrabantNet	O
supports	O
6rd	B-Protocol
on	O
their	O
network	O
.	O
</s>
<s>
In	O
October	O
2013	O
,	O
Norwegian	O
ISP	O
Altibox	O
announced	O
that	O
they	O
offer	O
IPv6	B-Protocol
to	O
70,000	O
customers	O
based	O
on	O
6rd	B-Protocol
.	O
</s>
<s>
All	O
customers	O
who	O
bypass	O
the	O
ISP	O
's	O
"	O
home	O
central	O
"	O
were	O
able	O
to	O
use	O
6rd	B-Protocol
in	O
March	O
2013	O
,	O
though	O
it	O
was	O
only	O
announced	O
on	O
a	O
technician	O
's	O
Twitter	O
account	O
.	O
</s>
<s>
In	O
November	O
2014	O
,	O
Sonic.net	O
made	O
6rd	B-Protocol
available	O
for	O
subscribers	O
with	O
compatible	O
equipment	O
to	O
choose	O
to	O
enable	O
it	O
.	O
</s>
<s>
Telia	O
Company	O
is	O
using	O
6rd	B-Protocol
.	O
</s>
<s>
Tweak	O
,	O
a	O
Dutch	O
fiber	O
ISP	O
,	O
is	O
using	O
6rd	B-Protocol
.	O
</s>
