<s>
In	O
the	O
seven-layer	O
OSI	O
model	O
of	O
computer	B-Architecture
networking	I-Architecture
,	O
the	O
network	B-Application
layer	I-Application
is	O
layer	B-Application
3	I-Application
.	O
</s>
<s>
The	O
network	B-Application
layer	I-Application
is	O
responsible	O
for	O
packet	B-Protocol
forwarding	I-Protocol
including	O
routing	B-Protocol
through	O
intermediate	O
routers	B-Protocol
.	O
</s>
<s>
The	O
network	B-Application
layer	I-Application
provides	O
the	O
means	O
of	O
transferring	O
variable-length	O
network	B-Protocol
packets	I-Protocol
from	O
a	O
source	O
to	O
a	O
destination	O
host	B-Device
via	O
one	O
or	O
more	O
networks	O
.	O
</s>
<s>
Within	O
the	O
service	O
layering	O
semantics	O
of	O
the	O
OSI	O
network	O
architecture	O
,	O
the	O
network	B-Application
layer	I-Application
responds	O
to	O
service	O
requests	O
from	O
the	O
transport	B-Architecture
layer	I-Architecture
and	O
issues	O
service	O
requests	O
to	O
the	O
data	B-Protocol
link	I-Protocol
layer	I-Protocol
.	O
</s>
<s>
Functions	O
of	O
the	O
network	B-Application
layer	I-Application
include	O
:	O
</s>
<s>
For	O
example	O
,	O
IP	B-Protocol
is	O
connectionless	B-Protocol
,	O
in	O
that	O
a	O
data	B-Protocol
packet	I-Protocol
can	O
travel	O
from	O
a	O
sender	O
to	O
a	O
recipient	O
without	O
the	O
recipient	O
having	O
to	O
send	O
an	O
acknowledgement	O
.	O
</s>
<s>
Every	O
host	B-Device
in	O
the	O
network	O
must	O
have	O
a	O
unique	O
address	O
that	O
determines	O
where	O
it	O
is	O
.	O
</s>
<s>
On	O
the	O
Internet	O
,	O
addresses	O
are	O
known	O
as	O
IP	B-Protocol
addresses	O
(	O
Internet	B-Protocol
Protocol	I-Protocol
)	O
.	O
</s>
<s>
Since	O
many	O
networks	O
are	O
partitioned	O
into	O
subnetworks	O
and	O
connect	O
to	O
other	O
networks	O
for	O
wide-area	O
communications	O
,	O
networks	O
use	O
specialized	O
hosts	O
,	O
called	O
gateways	O
or	O
routers	B-Protocol
,	O
to	O
forward	O
packets	B-Protocol
between	O
networks	O
.	O
</s>
<s>
The	O
TCP/IP	B-Protocol
model	I-Protocol
describes	O
the	O
protocols	O
used	O
by	O
the	O
Internet	O
.	O
</s>
<s>
The	O
TCP/IP	B-Protocol
model	I-Protocol
has	O
a	O
layer	O
called	O
the	O
Internet	B-Protocol
layer	I-Protocol
,	O
located	O
above	O
the	O
link	B-Protocol
layer	I-Protocol
.	O
</s>
<s>
In	O
many	O
textbooks	O
and	O
other	O
secondary	O
references	O
,	O
the	O
TCP/IP	B-Protocol
Internet	B-Protocol
layer	I-Protocol
is	O
equated	O
with	O
the	O
OSI	O
network	B-Application
layer	I-Application
.	O
</s>
<s>
However	O
,	O
this	O
comparison	O
is	O
misleading	O
,	O
as	O
the	O
allowed	O
characteristics	O
of	O
protocols	O
(	O
e.g.	O
,	O
whether	O
they	O
are	O
connection-oriented	O
or	O
connection-less	B-Protocol
)	O
placed	O
into	O
these	O
layers	O
are	O
different	O
in	O
the	O
two	O
models	O
.	O
</s>
<s>
The	O
TCP/IP	B-Protocol
Internet	B-Protocol
layer	I-Protocol
is	O
in	O
fact	O
only	O
a	O
subset	O
of	O
functionality	O
of	O
the	O
network	B-Application
layer	I-Application
.	O
</s>
<s>
The	O
following	O
are	O
examples	O
of	O
protocols	O
operating	O
at	O
the	O
network	B-Application
layer	I-Application
.	O
</s>
