<s>
In	O
telecommunications	O
,	O
a	O
network-to-network	B-Protocol
interface	I-Protocol
(	O
NNI	O
)	O
is	O
an	O
interface	O
that	O
specifies	O
signaling	O
and	O
management	O
functions	O
between	O
two	O
networks	O
.	O
</s>
<s>
An	O
NNI	O
circuit	O
can	O
be	O
used	O
for	O
interconnection	O
of	O
signalling	O
(	O
e.g.	O
,	O
SS7	O
)	O
,	O
Internet	B-Protocol
Protocol	I-Protocol
(	O
IP	O
)	O
(	O
e.g.	O
,	O
MPLS	B-Protocol
)	O
or	O
ATM	O
networks	O
.	O
</s>
<s>
In	O
networks	O
based	O
on	O
MPLS	B-Protocol
or	O
GMPLS	O
,	O
NNI	O
is	O
used	O
for	O
the	O
interconnection	O
of	O
core	O
provider	B-General_Concept
routers	I-General_Concept
(	O
class	O
4	O
or	O
higher	O
)	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
GMPLS	O
,	O
the	O
type	O
of	O
interconnection	O
can	O
vary	O
across	O
Back-to-Back	O
,	O
EBGP	B-Protocol
or	O
mixed	O
NNI	O
connection	O
scenarios	O
,	O
depending	O
on	O
the	O
type	O
of	O
VRF	B-General_Concept
exchange	O
used	O
for	O
interconnection	O
.	O
</s>
<s>
In	O
case	O
of	O
Back-to-Back	O
,	O
VRF	B-General_Concept
is	O
necessary	O
to	O
create	O
VLANs	B-General_Concept
and	O
subsequently	O
sub-interfaces	O
(	O
VLAN	B-General_Concept
headers	O
and	O
DLCI	O
headers	O
for	O
Ethernet	O
and	O
Frame	B-Protocol
Relay	I-Protocol
network	I-Protocol
packets	O
)	O
on	O
each	O
interface	O
used	O
for	O
the	O
NNI	O
circuit	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
eBGP	B-Protocol
NNI	O
interconnection	O
,	O
IP	O
routers	O
are	O
taught	O
how	O
to	O
dynamically	O
exchange	O
VRF	B-General_Concept
records	O
without	O
VLAN	B-General_Concept
creation	O
.	O
</s>
<s>
NNI	O
also	O
can	O
be	O
used	O
for	O
interconnection	O
of	O
two	O
VoIP	B-Application
nodes	O
.	O
</s>
<s>
NNI	O
interconnection	O
is	O
encapsulation	O
independent	O
,	O
but	O
Ethernet	O
and	O
Frame	B-Protocol
Relay	I-Protocol
are	O
commonly	O
used	O
.	O
</s>
