<s>
The	O
wireless	O
data	O
exchange	O
standard	O
Bluetooth	B-Protocol
uses	O
a	O
variety	O
of	O
protocols	O
.	O
</s>
<s>
Core	O
protocols	O
are	O
defined	O
by	O
the	O
trade	O
organization	O
Bluetooth	B-Protocol
SIG	O
.	O
</s>
<s>
The	O
Bluetooth	B-General_Concept
protocol	I-General_Concept
stack	O
is	O
split	O
in	O
two	O
parts	O
:	O
a	O
"	O
controller	O
stack	O
"	O
containing	O
the	O
timing	O
critical	O
radio	O
interface	O
,	O
and	O
a	O
"	O
host	O
stack	O
"	O
dealing	O
with	O
high	O
level	O
data	O
.	O
</s>
<s>
The	O
controller	O
stack	O
is	O
generally	O
implemented	O
in	O
a	O
low	O
cost	O
silicon	O
device	O
containing	O
the	O
Bluetooth	B-Protocol
radio	O
and	O
a	O
microprocessor	O
.	O
</s>
<s>
For	O
integrated	O
devices	O
such	O
as	O
Bluetooth	B-Protocol
headsets	O
,	O
the	O
host	O
stack	O
and	O
controller	O
stack	O
can	O
be	O
run	O
on	O
the	O
same	O
microprocessor	O
to	O
reduce	O
mass	O
production	O
costs	O
;	O
this	O
is	O
known	O
as	O
a	O
hostless	O
system	O
.	O
</s>
<s>
There	O
are	O
no	O
retransmissions	O
,	O
but	O
forward	B-Error_Name
error	I-Error_Name
correction	I-Error_Name
can	O
be	O
optionally	O
applied	O
.	O
</s>
<s>
Standardized	O
communication	O
between	O
the	O
host	O
stack	O
(	O
e.g.	O
,	O
a	O
PC	O
or	O
mobile	O
phone	O
OS	O
)	O
and	O
the	O
controller	O
(	O
the	O
Bluetooth	B-Protocol
integrated	O
circuit	O
(	O
IC	O
)	O
)	O
.	O
</s>
<s>
The	O
most	O
commonly	O
used	O
are	O
USB	B-Protocol
(	O
in	O
PCs	O
)	O
and	O
UART	O
(	O
in	O
mobile	O
phones	O
and	O
PDAs	O
)	O
.	O
</s>
<s>
In	O
Bluetooth	B-Protocol
devices	O
with	O
simple	O
functionality	O
(	O
e.g.	O
,	O
headsets	O
)	O
,	O
the	O
host	O
stack	O
and	O
controller	O
can	O
be	O
implemented	O
on	O
the	O
same	O
microprocessor	O
.	O
</s>
<s>
This	O
is	O
the	O
LMP	O
equivalent	O
for	O
Bluetooth	B-General_Concept
Low	I-General_Concept
Energy	I-General_Concept
(	O
LE	O
)	O
,	O
but	O
is	O
simpler	O
.	O
</s>
<s>
It	O
is	O
implemented	O
on	O
the	O
controller	O
and	O
manages	O
advertisement	O
,	O
scanning	O
,	O
connection	O
and	O
security	O
from	O
a	O
low-level	O
,	O
close	O
to	O
the	O
hardware	O
point	O
of	O
view	O
from	O
Bluetooth	B-Protocol
perspective	O
.	O
</s>
<s>
L2CAP	B-General_Concept
is	O
used	O
within	O
the	O
Bluetooth	B-General_Concept
protocol	I-General_Concept
stack	O
.	O
</s>
<s>
L2CAP	B-General_Concept
's	O
functions	O
include	O
:	O
</s>
<s>
Providing	O
one-way	O
transmission	O
management	O
of	O
multicast	O
data	O
to	O
a	O
group	O
of	O
other	O
Bluetooth	B-Protocol
devices	O
.	O
</s>
<s>
L2CAP	B-General_Concept
is	O
used	O
to	O
communicate	O
over	O
the	O
host	O
ACL	O
link	O
.	O
</s>
<s>
In	O
basic	O
mode	O
,	O
L2CAP	B-General_Concept
provides	O
packets	O
with	O
a	O
payload	O
configurable	O
up	O
to	O
64kB	O
,	O
with	O
672	O
bytes	O
as	O
the	O
default	O
MTU	O
,	O
and	O
48	O
bytes	O
as	O
the	O
minimum	O
mandatory	O
supported	O
MTU	O
.	O
</s>
<s>
In	O
retransmission	O
and	O
flow	O
control	O
modes	O
,	O
L2CAP	B-General_Concept
can	O
be	O
configured	O
for	O
reliable	O
or	O
asynchronous	O
data	O
per	O
channel	O
by	O
performing	O
retransmissions	O
and	O
CRC	O
checks	O
.	O
</s>
<s>
Reliability	O
in	O
either	O
of	O
these	O
modes	O
is	O
optionally	O
and/or	O
additionally	O
guaranteed	O
by	O
the	O
lower	O
layer	O
Bluetooth	B-Protocol
BDR/EDR	O
air	O
interface	O
by	O
configuring	O
the	O
number	O
of	O
retransmissions	O
and	O
flush	O
timeout	O
(	O
time	O
after	O
which	O
the	O
radio	O
will	O
flush	O
packets	O
)	O
.	O
</s>
<s>
BNEP	O
is	O
used	O
for	O
delivering	O
network	O
packets	O
on	O
top	O
of	O
L2CAP	B-General_Concept
.	O
</s>
<s>
BNEP	O
performs	O
a	O
similar	O
function	O
to	O
Subnetwork	B-Protocol
Access	I-Protocol
Protocol	I-Protocol
(	O
SNAP	O
)	O
in	O
Wireless	O
LAN	O
.	O
</s>
<s>
In	O
the	O
protocol	O
stack	O
,	O
BNEP	O
is	O
bound	O
to	O
L2CAP	B-General_Concept
.	O
</s>
<s>
The	O
Bluetooth	B-General_Concept
protocol	I-General_Concept
RFCOMM	O
is	O
a	O
simple	O
set	O
of	O
transport	O
protocols	O
,	O
made	O
on	O
top	O
of	O
the	O
L2CAP	B-General_Concept
protocol	O
,	O
providing	O
emulated	O
RS-232	O
serial	B-Protocol
ports	I-Protocol
(	O
up	O
to	O
sixty	O
simultaneous	O
connections	O
to	O
a	O
Bluetooth	B-Protocol
device	O
at	O
a	O
time	O
)	O
.	O
</s>
<s>
RFCOMM	O
is	O
sometimes	O
called	O
serial	B-Protocol
port	I-Protocol
emulation	O
.	O
</s>
<s>
The	O
Bluetooth	B-Protocol
serial	B-Protocol
port	I-Protocol
profile	O
(	O
SPP	O
)	O
is	O
based	O
on	O
this	O
protocol	O
.	O
</s>
<s>
It	O
is	O
used	O
directly	O
by	O
many	O
telephony	O
related	O
profiles	O
as	O
a	O
carrier	O
for	O
AT	O
commands	O
,	O
as	O
well	O
as	O
being	O
a	O
transport	O
layer	O
for	O
OBEX	O
over	O
Bluetooth	B-Protocol
.	O
</s>
<s>
Many	O
Bluetooth	B-Protocol
applications	O
use	O
RFCOMM	O
because	O
of	O
its	O
widespread	O
support	O
and	O
publicly	O
available	O
API	O
on	O
most	O
operating	O
systems	O
.	O
</s>
<s>
Additionally	O
,	O
applications	O
that	O
used	O
a	O
serial	B-Protocol
port	I-Protocol
to	O
communicate	O
can	O
be	O
quickly	O
ported	O
to	O
use	O
RFCOMM	O
.	O
</s>
<s>
In	O
the	O
protocol	O
stack	O
,	O
RFCOMM	O
is	O
bound	O
to	O
L2CAP	B-General_Concept
.	O
</s>
<s>
For	O
example	O
,	O
when	O
connecting	O
a	O
mobile	O
phone	O
to	O
a	O
Bluetooth	B-Protocol
headset	O
,	O
SDP	O
will	O
be	O
used	O
to	O
determine	O
which	O
Bluetooth	B-General_Concept
profiles	I-General_Concept
are	O
supported	O
by	O
the	O
headset	O
(	O
headset	O
profile	O
,	O
hands	O
free	O
profile	O
,	O
advanced	O
audio	O
distribution	O
profile	O
,	O
etc	O
.	O
)	O
</s>
<s>
Each	O
service	O
is	O
identified	O
by	O
a	O
Universally	O
Unique	O
Identifier	O
(	O
UUID	O
)	O
,	O
with	O
official	O
services	O
(	O
Bluetooth	B-General_Concept
profiles	I-General_Concept
)	O
assigned	O
a	O
short	O
form	O
UUID	O
(	O
16	O
bits	O
rather	O
than	O
the	O
full	O
128	O
)	O
.	O
</s>
<s>
In	O
the	O
protocol	O
stack	O
,	O
SDP	O
is	O
bound	O
to	O
L2CAP	B-General_Concept
.	O
</s>
<s>
Used	O
to	O
set	O
up	O
and	O
control	O
speech	O
and	O
data	O
calls	O
between	O
Bluetooth	B-Protocol
devices	O
.	O
</s>
<s>
The	O
protocol	O
is	O
based	O
on	O
the	O
ITU-T	O
standard	O
Q.931	O
,	O
with	O
the	O
provisions	O
of	O
Annex	O
D	O
applied	O
,	O
making	O
only	O
the	O
minimum	O
changes	O
necessary	O
for	O
Bluetooth	B-Protocol
.	O
</s>
<s>
Used	O
by	O
the	O
remote	O
control	O
profile	O
to	O
transfer	O
AV/C	O
commands	O
over	O
an	O
L2CAP	B-General_Concept
channel	O
.	O
</s>
<s>
In	O
the	O
protocol	O
stack	O
,	O
AVCTP	O
is	O
bound	O
to	O
L2CAP	B-General_Concept
.	O
</s>
<s>
Used	O
by	O
the	O
advanced	O
audio	O
distribution	O
profile	O
to	O
stream	O
music	O
to	O
stereo	O
headsets	O
over	O
an	O
L2CAP	B-General_Concept
channel	O
.	O
</s>
<s>
In	O
the	O
protocol	O
stack	O
,	O
AVDTP	O
is	O
bound	O
to	O
L2CAP	B-General_Concept
.	O
</s>
<s>
It	O
is	O
maintained	O
by	O
the	O
Infrared	O
Data	O
Association	O
but	O
has	O
also	O
been	O
adopted	O
by	O
the	O
Bluetooth	B-Protocol
Special	O
Interest	O
Group	O
and	O
the	O
SyncML	B-General_Concept
wing	O
of	O
the	O
Open	O
Mobile	O
Alliance	O
(	O
OMA	O
)	O
.	O
</s>
<s>
In	O
Bluetooth	B-Protocol
,	O
OBEX	O
is	O
used	O
for	O
many	O
profiles	O
that	O
require	O
simple	O
data	O
exchange	O
(	O
e.g.	O
,	O
object	O
push	O
,	O
file	O
transfer	O
,	O
basic	O
imaging	O
,	O
basic	O
printing	O
,	O
phonebook	O
access	O
,	O
etc	O
.	O
</s>
<s>
Similar	O
in	O
scope	O
to	O
SDP	O
but	O
specially	O
adapted	O
and	O
simplified	O
for	O
Low	O
Energy	O
Bluetooth	B-Protocol
.	O
</s>
<s>
In	O
the	O
protocol	O
stack	O
,	O
ATT	O
is	O
bound	O
to	O
L2CAP	B-General_Concept
.	O
</s>
<s>
This	O
is	O
used	O
by	O
Bluetooth	B-General_Concept
Low	I-General_Concept
Energy	I-General_Concept
implementations	O
for	O
pairing	O
and	O
transport	O
specific	O
key	O
distribution	O
.	O
</s>
<s>
In	O
the	O
protocol	O
stack	O
,	O
SMP	O
is	O
bound	O
to	O
L2CAP	B-General_Concept
.	O
</s>
