<s>
Audio	B-Protocol
Video	I-Protocol
Bridging	I-Protocol
(	O
AVB	O
)	O
is	O
a	O
common	O
name	O
for	O
the	O
set	O
of	O
technical	O
standards	O
which	O
provide	O
improved	O
synchronization	O
,	O
low-latency	O
,	O
and	O
reliability	O
for	O
switched	B-Protocol
Ethernet	I-Protocol
networks	O
.	O
</s>
<s>
IEEE	O
802.1AS-2011	O
:	O
Timing	O
and	O
Synchronization	O
for	O
Time-Sensitive	O
Applications	O
(	O
gPTP	B-Protocol
)	O
;	O
</s>
<s>
IEEE	O
802.1BA-2011	O
:	O
Audio	B-Protocol
Video	I-Protocol
Bridging	I-Protocol
(	O
AVB	O
)	O
Systems	O
;	O
</s>
<s>
IEEE	O
802.1Qat	O
and	O
802.1Qav	O
amendments	O
have	O
been	O
incorporated	O
to	O
the	O
base	O
IEEE	O
802.1Q-2011	O
document	O
,	O
which	O
specifies	O
the	O
operation	O
of	O
Media	O
Access	O
Control	O
(	O
MAC	O
)	O
Bridges	O
and	O
Virtual	B-General_Concept
Bridged	I-General_Concept
Local	I-General_Concept
Area	I-General_Concept
Networks	I-General_Concept
.	O
</s>
<s>
AVB	O
was	O
initially	O
developed	O
by	O
the	O
Institute	O
of	O
Electrical	O
and	O
Electronics	O
Engineers	O
(	O
IEEE	O
)	O
Audio	B-Protocol
Video	I-Protocol
Bridging	I-Protocol
task	O
group	O
of	O
the	O
IEEE	O
802.1	O
standards	O
committee	O
.	O
</s>
<s>
In	O
November	O
2012	O
,	O
Audio	B-Protocol
Video	I-Protocol
Bridging	I-Protocol
task	O
group	O
was	O
renamed	O
to	O
Time-Sensitive	B-Protocol
Networking	I-Protocol
task	O
group	O
to	O
reflect	O
the	O
expanded	O
scope	O
of	O
its	O
work	O
,	O
which	O
is	O
to	O
"	O
provide	O
the	O
specifications	O
that	O
will	O
allow	O
time-synchronized	O
low	O
latency	O
streaming	O
services	O
through	O
IEEE	O
802	O
networks	O
"	O
.	O
</s>
<s>
Even	O
digital	O
AV	O
standards	O
,	O
such	O
as	O
S/PDIF	O
for	O
audio	O
and	O
the	O
serial	B-Protocol
digital	I-Protocol
interface	I-Protocol
(	O
SDI	O
)	O
for	O
video	O
,	O
retain	O
these	O
properties	O
.	O
</s>
<s>
Attempts	O
to	O
solve	O
these	O
problems	O
were	O
based	O
on	O
multi-point	O
network	O
topologies	O
,	O
such	O
as	O
IEEE	B-Protocol
1394	I-Protocol
(	O
FireWire	B-Protocol
)	O
,	O
and	O
included	O
adaptation	O
of	O
standard	O
switched	B-Protocol
computer	B-Architecture
network	I-Architecture
technologies	O
such	O
as	O
Audio	B-Protocol
over	I-Protocol
Ethernet	I-Protocol
and	O
Audio	O
over	O
IP	O
.	O
</s>
<s>
Unfortunately	O
professional	O
,	O
home	O
,	O
and	O
automotive	O
AV	O
solutions	O
came	O
to	O
use	O
specialized	O
protocols	O
that	O
do	O
not	O
interoperate	O
between	O
each	O
other	O
or	O
standard	O
IT	O
protocols	O
,	O
while	O
standard	O
computer	B-Architecture
networks	I-Architecture
did	O
not	O
provide	O
tight	O
quality	O
of	O
service	O
with	O
strict	O
timing	O
and	O
predictable	O
or	O
bounded	O
latency	O
.	O
</s>
<s>
To	O
overcome	O
these	O
limitations	O
,	O
Audio	B-Protocol
Video	I-Protocol
Bridging	I-Protocol
networks	O
transmit	O
multiple	O
audiovisual	O
streams	O
through	O
standard	O
Ethernet	B-Protocol
switches	I-Protocol
(	O
i.e.	O
</s>
<s>
MAC	B-Protocol
bridges	I-Protocol
)	O
connected	O
in	O
a	O
hierarchical	B-Data_Structure
tree	I-Data_Structure
topology	I-Data_Structure
.	O
</s>
<s>
AVB	O
includes	O
layer	B-Protocol
2	I-Protocol
protocols	O
to	O
reserve	O
connection	O
bandwidth	O
and	O
prioritise	O
network	O
traffic	O
,	O
which	O
guarantee	O
precise	O
sync	O
clock	O
and	O
low	O
transmission	O
latency	O
for	O
each	O
stream	O
.	O
</s>
<s>
Audio	B-Protocol
Video	I-Protocol
Bridging	I-Protocol
is	O
implemented	O
as	O
a	O
switched	B-Protocol
Ethernet	I-Protocol
network	O
which	O
works	O
by	O
reserving	O
a	O
fraction	O
of	O
the	O
available	O
Ethernet	O
for	O
AV	O
traffic	O
.	O
</s>
<s>
Precise	O
synchronization	O
using	O
Generalized	O
Precision	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
(	O
gPTP	B-Protocol
)	O
profile	O
(	O
IEEE	B-Protocol
802.1AS	I-Protocol
)	O
,	O
</s>
<s>
The	O
IEEE	O
802.1BA	B-Protocol
is	O
an	O
umbrella	O
standard	O
for	O
these	O
three	O
principal	O
technologies	O
,	O
which	O
defines	O
application-specific	O
configurations	O
and	O
operation	O
procedures	O
for	O
devices	O
in	O
switched	B-Protocol
audio	O
video	O
networks	O
.	O
</s>
<s>
The	O
new	O
layer-2	B-Protocol
configuration	O
protocols	O
work	O
with	O
backward-compatible	O
extensions	O
to	O
the	O
Ethernet	O
802.1	O
frame	O
format	O
;	O
such	O
minimal	O
changes	O
allow	O
AVB	O
devices	O
to	O
coexist	O
and	O
communicate	O
in	O
standard	O
IT	O
networks	O
,	O
however	O
,	O
only	O
AVB-capable	O
switches	O
and	O
endpoint	O
can	O
reserve	O
network	O
resources	O
with	O
admission	O
control	O
and	O
synchronize	O
local	O
time	O
to	O
a	O
master	O
clock	O
,	O
which	O
is	O
required	O
for	O
low	O
latency	O
time-sensitive	O
traffic	O
.	O
</s>
<s>
An	O
IEEE	B-Protocol
802.1AS	I-Protocol
network	O
timing	O
domain	O
includes	O
all	O
devices	O
that	O
communicate	O
using	O
the	O
gPTP	B-Protocol
protocol	O
.	O
</s>
<s>
The	O
grandmaster	O
is	O
a	O
device	O
chosen	O
as	O
the	O
reference	O
clock	O
;	O
the	O
802.1BA	B-Protocol
specification	O
requires	O
every	O
talker	O
and	O
network	B-Protocol
bridge	I-Protocol
to	O
be	O
grandmaster	O
capable	O
.	O
</s>
<s>
IEEE	O
Std	O
1722-2011	O
for	O
a	O
Layer	B-Protocol
2	I-Protocol
Audio	O
Video	O
Transport	O
Protocol	O
(	O
AVTP	O
)	O
defines	O
details	O
for	O
transmitting	O
IEEE	O
1394/IEC	O
61883	O
streams	O
and	O
other	O
AV	O
formats	O
,	O
setting	O
the	O
presentation	O
time	O
for	O
each	O
AV	O
stream	O
,	O
and	O
manage	O
latencies	O
from	O
worst	O
case	O
delay	O
calculated	O
by	O
the	O
gPTP	B-Protocol
protocol	O
.	O
</s>
<s>
Higher	O
layer	O
services	O
can	O
improve	O
synchronisation	O
and	O
latency	O
of	O
media	O
transmission	O
by	O
mapping	O
the	O
AVB	O
Stream	O
ID	O
to	O
internal	O
stream	O
identifiers	O
to	O
and	O
basing	O
internal	O
timestamps	O
on	O
gPTP	B-Protocol
master	O
clock	O
.	O
</s>
<s>
IEEE	O
Std	O
1733-2011	O
defines	O
a	O
Layer	B-Application
3	I-Application
protocol	O
profile	O
for	O
Real-time	B-Protocol
Transport	I-Protocol
Protocol	I-Protocol
(	O
RTP	O
)	O
applications	O
with	O
a	O
RTCP	B-Protocol
payload	O
format	O
,	O
which	O
assigns	O
the	O
Stream	O
ID	O
from	O
SRP	O
to	O
the	O
RTP	O
's	O
Synchronization	O
source	O
identifier	O
(	O
SSRC	O
)	O
,	O
and	O
correlates	O
RTP	O
timestamps	O
for	O
presentation	O
time	O
with	O
802.1AS	O
gPTP	B-Protocol
master	O
clock	O
.	O
</s>
<s>
AES67	O
is	O
based	O
on	O
standard	O
RTP	O
over	O
UDP/IP	B-Protocol
and	O
IEEE	B-Protocol
1588	I-Protocol
Precision	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
(	O
PTPv2	O
)	O
for	O
timing	O
;	O
interoperability	O
with	O
AVB/TSN	B-Protocol
can	O
be	O
achieved	O
by	O
linking	O
IEEE	B-Protocol
802.1AS	I-Protocol
timing	O
information	O
to	O
AES67	O
PTPv2	O
payload	O
data	O
.	O
</s>
<s>
The	O
IETF	O
Deterministic	B-Protocol
Networking	I-Protocol
(	O
DetNet	O
)	O
Working	O
Group	O
is	O
working	O
to	O
define	O
deterministic	O
data	O
paths	O
with	O
bounds	O
on	O
latency	O
,	O
loss	O
,	O
and	O
packet	O
delay	O
variation	O
(	O
jitter	O
)	O
,	O
and	O
high	O
reliability	O
.	O
</s>
<s>
DetNet	O
shall	O
operate	O
over	O
both	O
Layer	B-Protocol
2	I-Protocol
bridged	O
segments	O
and	O
Layer	B-Application
3	I-Application
routed	O
segments	O
,	O
relying	O
on	O
interoperability	O
with	O
AVB/TSN	B-Protocol
switches	O
when	O
possible	O
.	O
</s>
<s>
The	O
stated	O
goal	O
is	O
to	O
enable	O
geographically	O
distributed	O
,	O
campus/enterprise	O
-wide	O
Intranet	B-General_Concept
for	O
content	O
delivery	O
with	O
bounded	O
low	O
latency	O
(	O
10-15	O
ms	O
)	O
.	O
</s>
<s>
A	O
single	O
network	O
shall	O
handle	O
both	O
A/V	O
and	O
IT	O
traffic	O
,	O
with	O
Layer	B-Application
3	I-Application
routing	O
on	O
top	O
of	O
AVB	O
QoS	O
networks	O
to	O
enable	O
sharing	O
content	O
between	O
Layer	B-Protocol
2	I-Protocol
AVB	O
segments	O
,	O
and	O
provide	O
IntServ	O
and	O
DiffServ	O
integration	O
with	O
AVB	O
where	O
possible	O
.	O
</s>
<s>
In	O
November	O
2005	O
,	O
it	O
was	O
moved	O
to	O
the	O
IEEE	O
802.1	O
committee	O
responsible	O
for	O
cross-network	B-Protocol
bridging	I-Protocol
standards	O
.	O
</s>
