<s>
The	O
Neighbor	B-Protocol
Discovery	I-Protocol
Protocol	I-Protocol
(	O
NDP	O
)	O
,	O
or	O
simply	O
Neighbor	B-Protocol
Discovery	I-Protocol
(	O
ND	O
)	O
,	O
is	O
a	O
protocol	O
of	O
the	O
Internet	B-Protocol
protocol	I-Protocol
suite	I-Protocol
used	O
with	O
Internet	B-Protocol
Protocol	I-Protocol
Version	I-Protocol
6	I-Protocol
(	O
IPv6	B-Protocol
)	O
.	O
</s>
<s>
It	O
operates	O
at	O
the	O
link	B-Protocol
layer	I-Protocol
of	O
the	O
Internet	B-Protocol
model	I-Protocol
,	O
and	O
is	O
responsible	O
for	O
gathering	O
various	O
information	O
required	O
for	O
network	O
communication	O
,	O
including	O
the	O
configuration	O
of	O
local	O
connections	O
and	O
the	O
domain	B-Protocol
name	I-Protocol
servers	I-Protocol
and	O
gateways	O
.	O
</s>
<s>
The	O
protocol	O
defines	O
five	O
ICMPv6	B-Protocol
packet	O
types	O
to	O
perform	O
functions	O
for	O
IPv6	B-Protocol
similar	O
to	O
the	O
Address	O
Resolution	O
Protocol	O
(	O
ARP	O
)	O
and	O
Internet	B-Protocol
Control	I-Protocol
Message	I-Protocol
Protocol	I-Protocol
(	O
ICMP	O
)	O
Router	B-Protocol
Discovery	I-Protocol
and	O
Router	O
Redirect	O
protocols	O
for	O
IPv4	B-Protocol
.	O
</s>
<s>
It	O
provides	O
many	O
improvements	O
over	O
its	O
IPv4	B-Protocol
counterparts	O
(	O
RFC	O
4861	O
,	O
section	O
3.1	O
)	O
.	O
</s>
<s>
The	O
Inverse	B-Protocol
Neighbor	I-Protocol
Discovery	I-Protocol
(	O
IND	O
)	O
protocol	O
extension	O
(	O
RFC	O
3122	O
)	O
allows	O
nodes	O
to	O
determine	O
and	O
advertise	O
an	O
IPv6	B-Protocol
address	O
corresponding	O
to	O
a	O
given	O
link-layer	B-Protocol
address	O
,	O
similar	O
to	O
Reverse	B-Protocol
ARP	I-Protocol
for	O
IPv4	B-Protocol
.	O
</s>
<s>
The	O
Secure	B-Protocol
Neighbor	I-Protocol
Discovery	I-Protocol
Protocol	I-Protocol
(	O
SEND	O
)	O
,	O
a	O
security	O
extension	O
of	O
NDP	O
,	O
uses	O
Cryptographically	B-Protocol
Generated	I-Protocol
Addresses	I-Protocol
(	O
CGA	O
)	O
and	O
the	O
Resource	B-Protocol
Public	I-Protocol
Key	I-Protocol
Infrastructure	I-Protocol
(	O
RPKI	B-Protocol
)	O
to	O
provide	O
an	O
alternative	O
mechanism	O
for	O
securing	O
NDP	O
with	O
a	O
cryptographic	O
method	O
that	O
is	O
independent	O
of	O
IPsec	B-Protocol
.	O
</s>
<s>
Neighbor	B-Protocol
Discovery	I-Protocol
Proxy	O
(	O
ND	O
Proxy	O
)	O
(	O
RFC	O
4389	O
)	O
provides	O
a	O
service	O
similar	O
to	O
IPv4	B-Protocol
Proxy	B-Protocol
ARP	I-Protocol
and	O
allows	O
bridging	O
multiple	O
network	O
segments	O
within	O
a	O
single	O
subnet	O
prefix	O
when	O
bridging	O
cannot	O
be	O
done	O
at	O
the	O
link	B-Protocol
layer	I-Protocol
.	O
</s>
<s>
NDP	O
defines	O
five	O
ICMPv6	B-Protocol
packet	O
types	O
for	O
the	O
purpose	O
of	O
router	O
solicitation	O
,	O
router	O
advertisement	O
,	O
neighbor	O
solicitation	O
,	O
neighbor	O
advertisement	O
,	O
and	O
network	O
redirects	O
.	O
</s>
<s>
Neighbor	O
Solicitation	O
(	O
Type	O
135	O
)	O
Neighbor	O
solicitations	O
are	O
used	O
by	O
nodes	O
to	O
determine	O
the	O
link-layer	B-Protocol
address	O
of	O
a	O
neighbor	O
,	O
or	O
to	O
verify	O
that	O
a	O
neighbor	O
is	O
still	O
reachable	O
via	O
a	O
cached	O
link-layer	B-Protocol
address	O
.	O
</s>
<s>
Router	B-Protocol
discovery	I-Protocol
:	O
hosts	O
can	O
locate	O
routers	O
residing	O
on	O
attached	O
links	O
.	O
</s>
<s>
Parameter	O
discovery	O
:	O
hosts	O
can	O
find	O
link	O
parameters	O
(	O
e.g.	O
,	O
MTU	B-Protocol
)	O
.	O
</s>
<s>
Address	O
resolution	O
:	O
mapping	O
between	O
IP	O
addresses	O
and	O
link-layer	B-Protocol
addresses	O
.	O
</s>
<s>
Recursive	O
DNS	B-Protocol
Server	O
(	O
RDNSS	O
)	O
and	O
DNS	B-Protocol
Search	O
List	O
(	O
DNSSL	O
)	O
assignment	O
via	O
a	O
router	O
advertisement	O
(	O
RA	O
)	O
options	O
.	O
</s>
