<s>
The	O
Time-Triggered	O
Ethernet	O
(	O
SAE	O
AS6802	O
)	O
(	O
also	O
known	O
as	O
TTEthernet	B-Protocol
or	O
TTE	O
)	O
standard	O
defines	O
a	O
fault-tolerant	O
synchronization	O
strategy	O
for	O
building	O
and	O
maintaining	O
synchronized	O
time	O
in	O
Ethernet	O
networks	O
,	O
and	O
outlines	O
mechanisms	O
required	O
for	O
synchronous	O
time-triggered	O
packet	O
switching	O
for	O
critical	O
integrated	O
applications	O
and	O
integrated	O
modular	O
avionics	O
(	O
IMA	O
)	O
architectures	O
.	O
</s>
<s>
TTEthernet	B-Protocol
network	O
devices	O
are	O
standard	O
Ethernet	O
devices	O
with	O
additional	O
capability	O
to	O
configure	O
and	O
establish	O
robust	O
synchronization	O
,	O
synchronous	O
packet	O
switching	O
,	O
traffic	O
scheduling	O
and	O
bandwidth	O
partitioning	O
,	O
as	O
described	O
in	O
SAE	O
AS6802	O
.	O
</s>
<s>
Therefore	O
,	O
TTEthernet	B-Protocol
networks	O
are	O
designed	O
to	O
host	O
different	O
Ethernet	O
traffic	O
classes	O
without	O
interference	O
.	O
</s>
<s>
TTEthernet	B-Protocol
device	O
implementation	O
expands	O
standard	O
Ethernet	O
with	O
services	O
to	O
meet	O
time-critical	O
,	O
deterministic	O
or	O
safety-relevant	O
requirements	O
in	O
double	O
-	O
and	O
triple-redundant	O
configurations	O
for	O
advanced	O
integrated	O
systems	O
.	O
</s>
<s>
TTEthernet	B-Protocol
switching	O
devices	O
are	O
used	O
for	O
integrated	O
systems	O
and	O
safety-related	O
applications	O
primarily	O
in	O
the	O
aerospace	O
,	O
industrial	O
controls	O
and	O
automotive	O
applications	O
.	O
</s>
<s>
TTEthernet	B-Protocol
has	O
been	O
selected	O
by	O
NASA	O
and	O
ESA	O
as	O
the	O
technology	O
for	O
communications	O
between	O
the	O
Orion	O
MPCV	O
and	O
the	O
European	O
Service	O
Module	O
,	O
and	O
is	O
described	O
by	O
the	O
ESA	O
as	O
being	O
"	O
prime	O
choice	O
for	O
future	O
launchers	O
allowing	O
them	O
to	O
deploy	O
distributed	O
modular	O
avionics	O
concepts	O
"	O
.	O
</s>
<s>
TTEthernet	B-Protocol
network	O
devices	O
implement	O
OSI	O
Layer	O
2	O
services	O
,	O
and	O
therefore	O
it	O
claims	O
to	O
be	O
compatible	O
with	O
IEEE	O
802.3	O
standards	O
and	O
coexist	O
with	O
other	O
Ethernet	O
networks	O
and	O
services	O
or	O
traffic	O
classes	O
,	O
such	O
as	O
IEEE	O
802.1Q	O
,	O
on	O
the	O
same	O
device	O
.	O
</s>
<s>
Three	O
traffic	O
classes	O
and	O
message	O
types	O
are	O
provided	O
in	O
current	O
TTEthernet	B-Protocol
switch	O
implementations	O
:	O
</s>
<s>
TTEthernet	B-Protocol
(	O
i.e.	O
</s>
<s>
TTEthernet	B-Protocol
switch	O
can	O
implement	O
a	O
reliable	O
redundancy	O
management	O
and	O
dataflow	O
(	O
datastream	O
)	O
integration	O
to	O
assure	O
message	O
transmission	O
even	O
in	O
case	O
of	O
a	O
switch	O
failure	O
.	O
</s>
<s>
Self-stabilization	O
means	O
that	O
synchronization	O
can	O
reestablish	O
itself	O
,	O
even	O
after	O
a	O
transient	O
upset	O
in	O
a	O
multitude	O
of	O
devices	O
in	O
the	O
distributed	O
computer	B-Architecture
network	I-Architecture
.	O
</s>
<s>
In	O
L-TTA	O
(	O
Loosely	O
TTA	O
)	O
architectures	O
with	O
synchronous	O
TTEthernet	B-Protocol
network	O
,	O
but	O
with	O
local	O
computer	O
clocks	O
decoupled	O
from	O
system/network	O
time	O
the	O
performance	O
of	O
control	O
loops	O
may	O
be	O
limited	O
.	O
</s>
<s>
In	O
this	O
case	O
,	O
time-triggered	O
transmissions	O
are	O
necessarily	O
cyclically	B-Operating_System
scheduled	I-Operating_System
and	O
thus	O
delays	O
between	O
processes	O
in	O
the	O
application	O
layer	O
can	O
be	O
large	O
,	O
e.g.	O
</s>
<s>
with	O
plesiochronous	B-Architecture
processes	O
operating	O
on	O
their	O
own	O
local	O
clock	O
and	O
execution	O
cycle	O
,	O
as	O
is	O
observed	O
in	O
systems	O
using	O
cyclic	O
MIL-STD-1553B	O
buses	O
,	O
up	O
to	O
twice	O
the	O
transmission	O
interval	O
due	O
to	O
released	O
packets	O
waiting	O
for	O
scheduled	O
transmission	O
at	O
the	O
source	O
and	O
for	O
the	O
receiving	O
process	O
to	O
run	O
at	O
the	O
destination	O
.	O
</s>
<s>
In	O
TTEthernet	B-Protocol
devices	O
,	O
this	O
traffic	O
class	O
cannot	O
interfere	O
with	O
deterministic	O
traffic	O
,	O
as	O
it	O
resides	O
in	O
its	O
own	O
separate	O
buffer	O
memory	O
.	O
</s>
<s>
In	O
2010	O
a	O
switch-based	O
implementation	O
was	O
shown	O
to	O
perform	O
better	O
than	O
shared	O
bus	O
systems	O
such	O
as	O
FlexRay	B-Protocol
for	O
use	O
in	O
automobiles	O
.	O
</s>
