<s>
NAT	B-Protocol
Port	I-Protocol
Mapping	I-Protocol
Protocol	I-Protocol
(	O
NAT-PMP	B-Protocol
)	O
is	O
a	O
network	O
protocol	O
for	O
establishing	O
network	B-Protocol
address	I-Protocol
translation	I-Protocol
(	O
NAT	O
)	O
settings	O
and	O
port	B-Protocol
forwarding	I-Protocol
configurations	O
automatically	O
without	O
user	O
effort	O
.	O
</s>
<s>
The	O
protocol	O
automatically	O
determines	O
the	O
external	O
IPv4	B-Protocol
address	O
of	O
a	O
NAT	O
gateway	O
,	O
and	O
provides	O
means	O
for	O
an	O
application	O
to	O
communicate	O
the	O
parameters	O
for	O
communication	O
to	O
peers	O
.	O
</s>
<s>
Apple	O
introduced	O
NAT-PMP	B-Protocol
in	O
2005	O
by	O
as	O
part	O
of	O
the	O
Bonjour	B-Application
specification	O
,	O
as	O
an	O
alternative	O
to	O
the	O
more	O
common	O
ISO	O
Standard	O
Internet	B-Protocol
Gateway	I-Protocol
Device	I-Protocol
Protocol	I-Protocol
implemented	O
in	O
many	O
NAT	O
routers	B-Protocol
.	O
</s>
<s>
NAT-PMP	B-Protocol
runs	O
over	O
the	O
User	B-Protocol
Datagram	I-Protocol
Protocol	I-Protocol
(	O
UDP	O
)	O
and	O
uses	O
port	B-Protocol
number	I-Protocol
5351	O
.	O
</s>
<s>
It	O
has	O
no	O
built-in	O
authentication	O
mechanisms	O
because	O
forwarding	O
a	O
port	O
typically	O
does	O
not	O
allow	O
any	O
activity	O
that	O
could	O
not	O
also	O
be	O
achieved	O
using	O
STUN	B-Protocol
methods	O
.	O
</s>
<s>
The	O
benefit	O
of	O
NAT-PMP	B-Protocol
over	O
STUN	B-Protocol
is	O
that	O
it	O
does	O
not	O
require	O
a	O
STUN	B-Protocol
server	O
and	O
a	O
NAT-PMP	B-Protocol
mapping	O
has	O
a	O
known	O
expiration	O
time	O
,	O
allowing	O
the	O
application	O
to	O
avoid	O
sending	O
inefficient	O
keep-alive	O
packets	O
.	O
</s>
<s>
NAT-PMP	B-Protocol
is	O
the	O
predecessor	O
to	O
the	O
Port	B-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
PCP	O
)	O
.	O
</s>
