<s>
IP	O
networks	O
are	O
divided	O
logically	O
into	O
subnetworks	B-Protocol
.	O
</s>
<s>
Computers	O
in	O
the	O
same	O
subnetwork	B-Protocol
have	O
the	O
same	O
address	O
prefix	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
a	O
typical	O
home	O
network	O
with	O
legacy	O
Internet	B-Protocol
Protocol	I-Protocol
version	I-Protocol
4	I-Protocol
,	O
the	O
network	O
prefix	O
would	O
be	O
something	O
like	O
192.168.1.0/24	O
,	O
as	O
expressed	O
in	O
CIDR	O
notation	O
.	O
</s>
<s>
With	O
IPv4	B-Protocol
,	O
commonly	O
home	O
networks	O
use	O
private	O
addresses	O
(	O
defined	O
in	O
)	O
that	O
are	O
non-routable	O
on	O
the	O
public	O
Internet	O
and	O
use	O
address	B-Protocol
translation	I-Protocol
to	O
convert	O
to	O
routable	O
addresses	O
when	O
connecting	O
to	O
hosts	O
outside	O
the	O
local	O
network	O
.	O
</s>
<s>
Business	O
networks	O
typically	O
had	O
manually	O
provisioned	O
subnetwork	B-Protocol
prefixes	O
.	O
</s>
<s>
In	O
IPv6	B-Protocol
global	O
addresses	O
are	O
used	O
end-to-end	O
,	O
so	O
even	O
home	O
networks	O
may	O
need	O
to	O
distribute	O
public	O
,	O
routable	O
IP	O
addresses	O
to	O
hosts	O
.	O
</s>
<s>
Since	O
it	O
would	O
not	O
be	O
practical	O
to	O
manually	O
provision	O
networks	O
at	O
scale	O
,	O
in	O
IPv6	B-Protocol
networking	O
,	O
DHCPv6	B-Protocol
prefix	B-Protocol
delegation	I-Protocol
is	O
used	O
to	O
assign	O
a	O
network	B-General_Concept
address	I-General_Concept
prefix	I-General_Concept
and	O
automate	O
configuration	O
and	O
provisioning	O
of	O
the	O
public	O
routable	O
addresses	O
for	O
the	O
network	O
.	O
</s>
<s>
The	O
way	O
this	O
works	O
for	O
example	O
in	O
case	O
of	O
a	O
home	O
network	O
is	O
that	O
the	O
home	O
router	O
uses	O
DHCPv6	B-Protocol
protocol	O
to	O
request	O
a	O
network	O
prefix	O
from	O
the	O
ISP	O
's	O
DHCPv6	B-Protocol
server	O
.	O
</s>
<s>
Once	O
assigned	O
,	O
the	O
ISP	O
routes	O
this	O
network	O
to	O
the	O
customer	O
's	O
home	O
router	O
and	O
the	O
home	O
router	O
starts	O
advertising	O
the	O
new	O
addresses	O
to	O
hosts	O
on	O
the	O
network	O
,	O
either	O
via	O
SLAAC	O
or	O
using	O
DHCPv6	B-Protocol
.	O
</s>
<s>
DHCPv6	B-Protocol
Prefix	B-Protocol
Delegation	I-Protocol
is	O
supported	O
by	O
most	O
ISPs	O
who	O
provide	O
native	O
IPv6	B-Protocol
for	O
consumers	O
on	O
fixed	O
networks	O
.	O
</s>
<s>
Prefix	B-Protocol
delegation	I-Protocol
is	O
generally	O
not	O
supported	O
on	O
cellular	O
networks	O
,	O
for	O
example	O
LTE	O
or	O
5G	O
.	O
</s>
<s>
Personal	O
hotspots	O
may	O
still	O
provide	O
IPv6	B-Protocol
access	O
to	O
hosts	O
on	O
the	O
network	O
by	O
using	O
a	O
different	O
technique	O
called	O
Proxy	O
Neighbor	O
Discovery	O
or	O
using	O
the	O
technique	O
described	O
in	O
.	O
</s>
<s>
One	O
of	O
the	O
reasons	O
why	O
cellular	O
networks	O
may	O
not	O
yet	O
support	O
prefix	B-Protocol
delegation	I-Protocol
is	O
that	O
the	O
operators	O
want	O
to	O
use	O
prefixes	O
they	O
can	O
aggregate	O
to	O
a	O
single	O
route	O
.	O
</s>
<s>
To	O
solve	O
this	O
,	O
defines	O
an	O
optional	O
mechanism	O
and	O
the	O
related	O
DHCPv6	B-Protocol
option	O
to	O
allow	O
exclusion	O
of	O
one	O
specific	O
prefix	O
from	O
a	O
delegated	O
prefix	O
set	O
.	O
</s>
