<s>
In	O
audio	O
and	O
broadcast	B-Operating_System
engineering	O
,	O
Audio	B-Protocol
over	I-Protocol
Ethernet	I-Protocol
(	O
sometimes	O
AoE	O
—	O
not	O
to	O
be	O
confused	O
with	O
ATA	B-Protocol
over	I-Protocol
Ethernet	I-Protocol
)	O
is	O
the	O
use	O
of	O
an	O
Ethernet-based	O
network	B-Architecture
to	O
distribute	O
real-time	O
digital	O
audio	O
.	O
</s>
<s>
AoE	O
replaces	O
bulky	O
snake	O
cables	O
or	O
audio-specific	O
installed	O
low-voltage	O
wiring	O
with	O
standard	O
network	B-Architecture
structured	O
cabling	O
in	O
a	O
facility	O
.	O
</s>
<s>
AoE	O
provides	O
a	O
reliable	O
backbone	B-General_Concept
for	O
any	O
audio	O
application	O
,	O
such	O
as	O
for	O
large-scale	O
sound	O
reinforcement	O
in	O
stadiums	O
,	O
airports	O
and	O
convention	O
centers	O
,	O
multiple	O
studios	O
or	O
stages	O
.	O
</s>
<s>
While	O
AoE	O
bears	O
a	O
resemblance	O
to	O
voice	B-Application
over	I-Application
IP	I-Application
(	O
VoIP	B-Application
)	O
and	O
audio	O
over	O
IP	O
(	O
AoIP	O
)	O
,	O
AoE	O
is	O
intended	O
for	O
high-fidelity	O
,	O
low-latency	O
professional	O
audio	O
.	O
</s>
<s>
AoE	O
systems	O
use	O
a	O
much	O
higher	O
bit	O
rate	O
(	O
typically	O
1Mbit/s	O
per	O
channel	O
)	O
and	O
much	O
lower	O
latency	O
(	O
typically	O
less	O
than	O
10	O
milliseconds	O
)	O
than	O
VoIP	B-Application
.	O
</s>
<s>
AoE	O
requires	O
a	O
high-performance	O
network	B-Architecture
.	O
</s>
<s>
Performance	O
requirements	O
may	O
be	O
met	O
through	O
use	O
of	O
a	O
dedicated	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
(	O
LAN	B-General_Concept
)	O
or	O
virtual	B-General_Concept
LAN	I-General_Concept
(	O
VLAN	B-General_Concept
)	O
,	O
overprovisioning	O
or	O
quality	O
of	O
service	O
features	O
.	O
</s>
<s>
Some	O
AoE	O
systems	O
use	O
proprietary	O
protocols	O
(	O
at	O
the	O
lower	O
OSI	O
layers	O
)	O
which	O
create	O
Ethernet	B-Protocol
frames	I-Protocol
that	O
are	O
transmitted	O
directly	O
onto	O
the	O
Ethernet	O
(	O
layer	B-Protocol
2	I-Protocol
)	O
for	O
efficiency	B-General_Concept
and	O
reduced	O
overhead	O
.	O
</s>
<s>
The	O
word	O
clock	O
may	O
be	O
provided	O
by	O
broadcast	B-Operating_System
packets	I-Operating_System
.	O
</s>
<s>
There	O
are	O
several	O
different	O
and	O
incompatible	O
protocols	O
for	O
audio	B-Protocol
over	I-Protocol
Ethernet	I-Protocol
.	O
</s>
<s>
Protocols	O
can	O
be	O
broadly	O
categorized	O
into	O
layer-1	B-Application
,	O
layer-2	B-Protocol
and	O
layer-3	B-Application
systems	O
based	O
on	O
the	O
layer	O
in	O
the	O
OSI	O
model	O
where	O
the	O
protocol	O
exists	O
.	O
</s>
<s>
Layer-1	B-Application
protocols	O
use	O
Ethernet	O
wiring	O
and	O
signaling	O
components	O
but	O
do	O
not	O
use	O
the	O
Ethernet	B-Protocol
frame	I-Protocol
structure	O
.	O
</s>
<s>
Layer-1	B-Application
protocols	O
often	O
use	O
their	O
own	O
media	B-Protocol
access	I-Protocol
control	I-Protocol
(	O
MAC	O
)	O
rather	O
than	O
the	O
one	O
native	O
to	O
Ethernet	O
,	O
which	O
generally	O
creates	O
compatibility	O
issues	O
and	O
thus	O
requires	O
a	O
dedicated	O
network	B-Architecture
for	O
the	O
protocol	O
.	O
</s>
<s>
Layer-2	B-Protocol
protocols	O
encapsulate	O
audio	O
data	O
in	O
standard	O
Ethernet	O
packets	O
.	O
</s>
<s>
Most	O
can	O
make	O
use	O
of	O
standard	O
Ethernet	O
hubs	O
and	O
switches	O
though	O
some	O
require	O
that	O
the	O
network	B-Architecture
(	O
or	O
at	O
least	O
a	O
VLAN	B-General_Concept
)	O
be	O
dedicated	O
to	O
the	O
audio	O
distribution	O
application	O
.	O
</s>
<s>
Layer-3	B-Application
protocols	O
encapsulate	O
audio	O
data	O
in	O
OSI	O
model	O
layer	B-Application
3	I-Application
(	O
network	B-Application
layer	I-Application
)	O
packets	O
.	O
</s>
<s>
By	O
definition	O
it	O
does	O
not	O
limit	O
the	O
choice	O
of	O
protocol	O
to	O
be	O
the	O
most	O
popular	O
layer-3	B-Application
protocol	O
,	O
the	O
Internet	B-Protocol
Protocol	I-Protocol
(	O
IP	O
)	O
.	O
</s>
<s>
In	O
some	O
implementations	O
,	O
the	O
layer-3	B-Application
audio	O
data	O
packets	O
are	O
further	O
packaged	O
inside	O
OSI	O
model	O
layer-4	O
(	O
transport	B-Architecture
layer	I-Architecture
)	O
packets	O
,	O
most	O
commonly	O
User	B-Protocol
Datagram	I-Protocol
Protocol	I-Protocol
(	O
UDP	O
)	O
or	O
Real-time	B-Protocol
Transport	I-Protocol
Protocol	I-Protocol
(	O
RTP	B-Protocol
)	O
.	O
</s>
<s>
Use	O
of	O
UDP	O
or	O
RTP	B-Protocol
to	O
carry	O
audio	O
data	O
enables	O
them	O
to	O
be	O
distributed	O
through	O
standard	O
computer	O
routers	B-Protocol
,	O
thus	O
a	O
large	O
distribution	O
audio	O
network	B-Architecture
can	O
be	O
built	O
economically	O
using	O
commercial	O
off-the-shelf	O
equipment	O
.	O
</s>
<s>
Although	O
IP	O
packets	O
can	O
traverse	O
the	O
Internet	O
,	O
most	O
layer-3	B-Application
protocols	O
cannot	O
provide	O
reliable	O
transmission	O
over	O
the	O
Internet	O
due	O
to	O
the	O
limited	O
bandwidth	O
,	O
significant	O
End-to-end	B-Protocol
delay	I-Protocol
and	O
packet	B-Protocol
loss	I-Protocol
that	O
can	O
be	O
encountered	O
by	O
data	O
flow	O
over	O
the	O
Internet	O
.	O
</s>
<s>
For	O
similar	O
reasons	O
,	O
transmission	O
of	O
layer-3	B-Application
audio	O
over	O
wireless	B-Architecture
LAN	I-Architecture
are	O
also	O
not	O
supported	O
by	O
most	O
implementations	O
.	O
</s>
<s>
Hydra2	O
by	O
Calrec	O
uses	O
Cat-5e	O
cabling	O
or	O
fiber	O
through	O
SFP	B-Protocol
transceivers	I-Protocol
.	O
</s>
<s>
MADI	O
uses	O
75-ohm	O
coaxial	O
cable	O
with	O
BNC	B-Protocol
connectors	I-Protocol
or	O
optical	B-Architecture
fibre	I-Architecture
to	O
carry	O
up	O
to	O
64	O
channels	O
of	O
digital	O
audio	O
in	O
a	O
point-to-point	O
connection	O
.	O
</s>
<s>
AES47	O
provides	O
audio	O
networking	O
by	O
passing	O
AES3	O
audio	O
transport	O
over	O
an	O
ATM	O
network	B-Architecture
using	O
structured	O
network	B-Architecture
cabling	O
(	O
both	O
copper	O
and	O
fibre	O
)	O
.	O
</s>
<s>
Audio	O
over	O
IP	O
differs	O
in	O
that	O
it	O
works	O
at	O
a	O
higher	O
layer	O
,	O
encapsulated	B-Protocol
within	O
Internet	B-Protocol
Protocol	I-Protocol
.	O
</s>
<s>
Some	O
of	O
these	O
systems	O
are	O
usable	O
on	O
the	O
Internet	O
,	O
but	O
may	O
not	O
be	O
as	O
instantaneous	O
,	O
and	O
are	O
only	O
as	O
reliable	O
as	O
the	O
network	B-Architecture
route	O
such	O
as	O
the	O
path	O
from	O
a	O
remote	O
broadcast	B-Operating_System
back	O
to	O
the	O
main	O
studio	O
,	O
or	O
the	O
studio/transmitter	O
link	O
(	O
STL	O
)	O
,	O
the	O
most	O
critical	O
part	O
of	O
the	O
airchain	O
.	O
</s>
<s>
This	O
is	O
similar	O
to	O
VoIP	B-Application
,	O
however	O
AoIP	O
is	O
comparable	O
to	O
AoE	O
for	O
a	O
small	O
number	O
of	O
channels	O
,	O
which	O
are	O
usually	O
also	O
data-compressed	O
.	O
</s>
<s>
Reliability	O
for	O
permanent	O
STL	O
uses	O
comes	O
from	O
the	O
use	O
of	O
a	O
virtual	B-Protocol
circuit	I-Protocol
,	O
usually	O
on	O
a	O
leased	B-Architecture
line	I-Architecture
such	O
as	O
T1/E1	B-Protocol
,	O
or	O
at	O
minimum	O
ISDN	B-Protocol
or	O
DSL	O
.	O
</s>
<s>
In	O
broadcasting	B-Operating_System
,	O
and	O
to	O
some	O
extent	O
in	O
studio	O
and	O
even	O
live	O
production	O
,	O
many	O
manufacturers	O
equip	O
their	O
own	O
audio	O
engines	O
to	O
be	O
tied	O
together	O
.	O
</s>
<s>
This	O
may	O
also	O
be	O
done	O
with	O
gigabit	O
Ethernet	O
and	O
optical	B-Architecture
fibre	I-Architecture
rather	O
than	O
wire	O
.	O
</s>
<s>
AoE	O
is	O
not	O
necessarily	O
intended	O
for	O
wireless	B-General_Concept
networks	I-General_Concept
,	O
thus	O
the	O
use	O
of	O
various	O
802.11	O
devices	O
may	O
or	O
may	O
not	O
work	O
with	O
various	O
(	O
or	O
any	O
)	O
AoE	O
protocols	O
.	O
</s>
