<s>
Byte	B-Protocol
serving	I-Protocol
(	O
other	O
names	O
:	O
Range	O
Requests	O
;	O
Byte	O
Range	O
Serving	O
;	O
Page	O
on	O
demand	O
)	O
is	O
the	O
process	O
introduced	O
in	O
HTTP	B-Protocol
protocol	I-Protocol
1.1	O
of	O
sending	O
only	O
a	O
portion	O
of	O
a	O
message	O
from	O
a	O
server	O
to	O
a	O
client	O
.	O
</s>
<s>
Byte	B-Protocol
serving	I-Protocol
begins	O
when	O
an	O
HTTP	B-Protocol
server	O
advertises	O
its	O
willingness	O
to	O
serve	O
partial	O
requests	O
using	O
the	O
Accept-Ranges	O
response	O
header	O
.	O
</s>
<s>
If	O
the	O
range	O
is	O
valid	O
,	O
the	O
server	O
sends	O
it	O
to	O
the	O
client	O
with	O
a	O
206	B-Protocol
Partial	I-Protocol
Content	I-Protocol
status	B-Protocol
code	I-Protocol
and	O
a	O
Content-Range	O
header	O
listing	O
the	O
range	O
sent	O
.	O
</s>
<s>
If	O
the	O
range	O
is	O
invalid	O
,	O
the	O
server	O
responds	O
with	O
a	O
416	B-Protocol
Requested	I-Protocol
Range	I-Protocol
Not	I-Protocol
Satisfiable	I-Protocol
status	B-Protocol
code	I-Protocol
.	O
</s>
<s>
Byte	B-Protocol
Serving	I-Protocol
is	O
therefore	O
a	O
method	O
of	O
bandwidth	O
optimization	O
.	O
</s>
<s>
In	O
the	O
HTTP/1.0	B-Protocol
standard	O
,	O
clients	O
were	O
only	O
able	O
to	O
request	O
an	O
entire	O
document	O
.	O
</s>
<s>
Similarly	O
PDF	B-Application
files	I-Application
can	O
be	O
optimized	O
for	O
byte	B-Protocol
serving	I-Protocol
to	O
allow	O
multi-gigabyte	O
files	O
to	O
be	O
instantly	O
viewable	O
in	O
the	O
browser	O
by	O
only	O
requesting	O
the	O
data	O
required	O
to	O
render	O
the	O
current	O
page	O
.	O
</s>
<s>
Byte	B-Protocol
serving	I-Protocol
can	O
also	O
be	O
used	O
by	O
multihomed	B-Protocol
clients	O
to	O
simultaneously	O
download	O
a	O
resource	O
over	O
multiple	O
network	O
interfaces	O
.	O
</s>
<s>
To	O
achieve	O
this	O
type	O
of	O
application-layer	O
link	B-Architecture
aggregation	I-Architecture
,	O
multiple	O
HTTP	B-Protocol
sessions	O
are	O
established	O
and	O
logical	O
file	O
segments	O
are	O
collaboratively	O
downloaded	O
from	O
the	O
server	O
and	O
reassembled	O
at	O
the	O
client	O
.	O
</s>
<s>
The	O
use	O
of	O
the	O
Chunked	O
Transfer-Encoding	O
is	O
not	O
byte-serving	O
,	O
but	O
is	O
instead	O
a	O
method	O
in	O
which	O
an	O
HTTP/1.1	B-Protocol
server	O
sends	O
the	O
entire	O
resource	O
,	O
but	O
in	O
several	O
separate	O
portions	O
(	O
or	O
chunks	O
)	O
of	O
data	O
.	O
</s>
<s>
Byte	B-Protocol
serving	I-Protocol
and	O
chunking	O
are	O
compatible	O
and	O
can	O
be	O
used	O
with	O
or	O
without	O
the	O
other	O
.	O
</s>
<s>
Later	O
versions	O
of	O
the	O
HTTP	B-Protocol
protocol	I-Protocol
continue	O
to	O
support	O
byte	B-Protocol
serving	I-Protocol
,	O
though	O
the	O
use	O
of	O
chunked	O
transfer	O
encoding	O
is	O
superseded	O
by	O
alternative	O
methods	O
.	O
</s>
