<s>
Time-Sensitive	B-Protocol
Networking	I-Protocol
(	O
TSN	O
)	O
is	O
a	O
set	O
of	O
standards	O
under	O
development	O
by	O
the	O
Time-Sensitive	B-Protocol
Networking	I-Protocol
task	O
group	O
of	O
the	O
IEEE	O
802.1	O
working	O
group	O
.	O
</s>
<s>
The	O
TSN	O
task	O
group	O
was	O
formed	O
in	O
November	O
2012	O
by	O
renaming	O
the	O
existing	O
Audio	B-Protocol
Video	I-Protocol
Bridging	I-Protocol
Task	I-Protocol
Group	I-Protocol
and	O
continuing	O
its	O
work	O
.	O
</s>
<s>
The	O
majority	O
of	O
projects	O
define	O
extensions	O
to	O
the	O
IEEE	O
802.1Q	O
Bridges	O
and	O
Bridged	O
Networks	O
,	O
which	O
describes	O
virtual	B-General_Concept
LANs	I-General_Concept
and	O
network	B-Protocol
switches	I-Protocol
.	O
</s>
<s>
Applications	O
include	O
converged	O
networks	O
with	O
real-time	B-General_Concept
audio/video	O
streaming	O
and	O
real-time	B-General_Concept
control	I-General_Concept
streams	O
which	O
are	O
used	O
in	O
automotive	O
or	O
industrial	O
control	O
facilities	O
.	O
</s>
<s>
Standard	O
Information	B-General_Concept
technology	I-General_Concept
network	O
equipment	O
has	O
no	O
concept	O
of	O
"	O
time	O
"	O
and	O
cannot	O
provide	O
synchronization	O
and	O
precision	O
timing	O
.	O
</s>
<s>
Even	O
if	O
the	O
average	O
hop	B-Protocol
delay	O
is	O
very	O
low	O
,	O
individual	O
delays	O
can	O
be	O
unacceptably	O
high	O
.	O
</s>
<s>
The	O
different	O
AVB/TSN	B-Protocol
standards	O
documents	O
specified	O
by	O
IEEE	O
802.1	O
can	O
be	O
grouped	O
into	O
three	O
basic	O
key	O
component	O
categories	O
that	O
are	O
required	O
for	O
a	O
complete	O
real-time	B-General_Concept
communication	O
solution	O
based	O
on	O
switched	B-Protocol
Ethernet	I-Protocol
networks	O
with	O
deterministic	O
quality	O
of	O
service	O
(	O
QoS	O
)	O
for	O
point-to-point	O
connections	O
.	O
</s>
<s>
Applications	O
which	O
need	O
a	O
deterministic	B-Protocol
network	I-Protocol
that	O
behaves	O
in	O
a	O
predictable	O
fashion	O
include	O
audio	O
and	O
video	O
,	O
initially	O
defined	O
in	O
Audio	B-Protocol
Video	I-Protocol
Bridging	I-Protocol
(	O
AVB	O
)	O
;	O
control	O
networks	O
that	O
accept	O
inputs	O
from	O
sensors	O
,	O
perform	O
control	O
loop	O
processing	O
,	O
and	O
initiate	O
actions	O
;	O
safety-critical	O
networks	O
that	O
implement	O
packet	O
and	O
link	O
redundancy	O
;	O
and	O
mixed	O
media	O
networks	O
that	O
handle	O
data	O
with	O
varying	O
levels	O
of	O
timing	O
sensitivity	O
and	O
priority	O
,	O
such	O
as	O
vehicle	O
networks	O
that	O
support	O
climate	O
control	O
,	O
infotainment	O
,	O
body	O
electronics	O
,	O
and	O
driver	O
assistance	O
.	O
</s>
<s>
The	O
IEEE	O
AVB/TSN	B-Protocol
suite	O
serves	O
as	O
the	O
foundation	O
for	O
deterministic	B-Protocol
networking	I-Protocol
to	O
satisfy	O
the	O
common	O
requirements	O
of	O
these	O
applications	O
.	O
</s>
<s>
AVB/TSN	B-Protocol
can	O
handle	O
rate-constrained	O
traffic	O
,	O
where	O
each	O
stream	O
has	O
a	O
bandwidth	O
limit	O
defined	O
by	O
minimum	O
inter-frame	O
intervals	O
and	O
maximal	O
frame	O
size	O
,	O
and	O
time-trigger	O
traffic	O
with	O
an	O
exact	O
accurate	O
time	O
to	O
be	O
sent	O
.	O
</s>
<s>
For	O
real-time	B-General_Concept
communication	O
with	O
hard	O
,	O
non-negotiable	O
time	O
boundaries	O
for	O
end-to-end	O
transmission	O
latencies	O
,	O
all	O
devices	O
in	O
this	O
network	O
need	O
to	O
have	O
a	O
common	O
time	O
reference	O
and	O
therefore	O
,	O
need	O
to	O
synchronize	O
their	O
clocks	O
among	O
each	O
other	O
.	O
</s>
<s>
This	O
is	O
not	O
only	O
true	O
for	O
the	O
end	O
devices	O
of	O
a	O
communication	O
stream	O
,	O
such	O
as	O
an	O
industrial	O
controller	O
and	O
a	O
manufacturing	O
robot	O
,	O
but	O
also	O
true	O
for	O
network	O
components	O
,	O
such	O
as	O
Ethernet	B-Protocol
switches	I-Protocol
.	O
</s>
<s>
Due	O
to	O
these	O
constraints	O
,	O
time	O
in	O
TSN	O
networks	O
is	O
usually	O
distributed	O
from	O
one	O
central	O
time	O
source	O
directly	O
through	O
the	O
network	O
itself	O
using	O
the	O
IEEE	B-Protocol
1588	I-Protocol
Precision	I-Protocol
Time	I-Protocol
Protocol	I-Protocol
,	O
which	O
utilizes	O
Ethernet	B-Protocol
frames	I-Protocol
to	O
distribute	O
time	O
synchronization	O
information	O
.	O
</s>
<s>
IEEE	B-Protocol
802.1AS	I-Protocol
is	O
a	O
tightly	O
constrained	O
subset	O
of	O
IEEE	B-Protocol
1588	I-Protocol
with	O
sub-microsecond	O
precision	O
and	O
extensions	O
to	O
support	O
synchronisation	O
over	O
WiFi	O
radio	O
(	O
IEEE	O
802.11	O
)	O
.	O
</s>
<s>
The	O
idea	O
behind	O
this	O
profile	O
is	O
to	O
narrow	O
the	O
huge	O
list	O
of	O
different	O
IEEE	B-Protocol
1588	I-Protocol
options	O
down	O
to	O
a	O
manageable	O
few	O
critical	O
options	O
that	O
are	O
applicable	O
to	O
home	O
networks	O
or	O
networks	O
in	O
automotive	O
or	O
industrial	O
automation	O
environments	O
.	O
</s>
<s>
IEEE	O
802.1AS-2011	O
defines	O
the	O
Generalized	O
Precision	B-Protocol
Time	I-Protocol
Protocol	I-Protocol
(	O
gPTP	B-Protocol
)	O
profile	O
which	O
,	O
like	O
all	O
profiles	O
of	O
IEEE	B-Protocol
1588	I-Protocol
,	O
selects	O
among	O
the	O
options	O
of	O
1588	O
,	O
but	O
also	O
generalizes	O
the	O
architecture	O
to	O
allow	O
PTP	O
to	O
apply	O
beyond	O
wired	O
Ethernet	O
networks	O
.	O
</s>
<s>
To	O
account	O
for	O
data	O
path	O
delays	O
,	O
the	O
gPTP	B-Protocol
protocol	O
measures	O
the	O
frame	O
residence	O
time	O
within	O
each	O
bridge	O
(	O
the	O
time	O
required	O
for	O
receiving	O
,	O
processing	O
,	O
queuing	O
and	O
transmission	O
of	O
timing	O
information	O
from	O
the	O
ingress	O
to	O
egress	O
ports	O
)	O
,	O
and	O
the	O
link	O
latency	O
of	O
each	O
hop	B-Protocol
(	O
a	O
propagation	O
delay	O
between	O
two	O
adjacent	O
bridges	O
)	O
.	O
</s>
<s>
On	O
the	O
protocol	O
level	O
,	O
these	O
priorities	O
are	O
visible	O
in	O
the	O
Priority	O
Code	O
Point	O
(	O
PCP	O
)	O
field	O
in	O
the	O
802.1Q	O
VLAN	B-General_Concept
tag	O
of	O
a	O
standard	O
Ethernet	B-Protocol
frame	I-Protocol
.	O
</s>
<s>
The	O
reason	O
for	O
this	O
is	O
buffering	O
effects	O
inside	O
the	O
Ethernet	B-Protocol
switches	I-Protocol
.	O
</s>
<s>
If	O
a	O
switch	O
has	O
started	O
the	O
transmission	O
of	O
an	O
Ethernet	B-Protocol
frame	I-Protocol
on	O
one	O
of	O
its	O
ports	O
,	O
even	O
the	O
highest	O
priority	O
frame	O
has	O
to	O
wait	O
inside	O
the	O
switch	O
buffer	O
for	O
this	O
transmission	O
to	O
finish	O
.	O
</s>
<s>
This	O
is	O
not	O
an	O
issue	O
in	O
environments	O
where	O
applications	O
do	O
not	O
depend	O
on	O
the	O
timely	O
delivery	O
of	O
single	O
Ethernet	B-Protocol
frames	I-Protocol
-	O
such	O
as	O
office	O
IT	O
infrastructures	O
.	O
</s>
<s>
In	O
these	O
environments	O
,	O
file	O
transfers	O
,	O
emails	O
or	O
other	O
business	O
applications	O
have	O
limited	O
time	O
sensitivity	O
themselves	O
and	O
are	O
usually	O
protected	O
by	O
other	O
mechanisms	O
further	O
up	O
the	O
protocol	O
stack	O
,	O
such	O
as	O
the	O
Transmission	B-Protocol
Control	I-Protocol
Protocol	I-Protocol
.	O
</s>
<s>
In	O
industrial	O
automation	O
(	O
Programmable	B-Architecture
Logic	I-Architecture
Controller	I-Architecture
(	O
PLC	B-Architecture
)	O
with	O
an	O
industrial	O
robot	O
)	O
and	O
automotive	O
car	O
environments	O
,	O
where	O
closed	O
loop	O
control	O
or	O
safety	O
applications	O
are	O
using	O
the	O
Ethernet	O
network	O
,	O
reliable	O
and	O
timely	O
delivery	O
is	O
of	O
utmost	O
importance	O
.	O
</s>
<s>
AVB/TSN	B-Protocol
enhances	O
standard	O
Ethernet	O
communication	O
by	O
adding	O
mechanisms	O
to	O
provide	O
different	O
time	O
slices	O
for	O
different	O
traffic	O
classes	O
and	O
ensure	O
timely	O
delivery	O
with	O
soft	O
and	O
hard	O
real-time	B-General_Concept
requirements	O
of	O
control	O
system	O
applications	O
.	O
</s>
<s>
The	O
mechanism	O
of	O
utilizing	O
the	O
eight	O
distinct	O
VLAN	B-General_Concept
priorities	O
is	O
retained	O
,	O
to	O
ensure	O
complete	O
backward	O
compatibility	O
to	O
non-TSN	O
Ethernet	O
.	O
</s>
<s>
The	O
maximum	O
number	O
of	O
hops	B-Protocol
is	O
7	O
.	O
</s>
<s>
The	O
per-port	O
peer	O
delay	O
provided	O
by	O
gPTP	B-Protocol
and	O
the	O
network	O
bridge	O
residence	O
delay	O
are	O
added	O
to	O
calculate	O
the	O
accumulated	O
delays	O
and	O
ensure	O
the	O
latency	O
requirement	O
is	O
met	O
.	O
</s>
<s>
Control	O
traffic	O
has	O
the	O
third-highest	O
priority	O
and	O
includes	O
gPTP	B-Protocol
and	O
SRP	O
traffic	O
.	O
</s>
<s>
Time-aware	O
scheduler	O
802.1Qbv	O
introduces	O
Class	O
CDT	O
for	O
realtime	O
control	O
data	O
from	O
sensors	O
and	O
command	O
streams	O
to	O
actuators	O
,	O
with	O
worst-case	O
latency	O
of	O
100μs	O
over	O
5	O
hops	B-Protocol
,	O
and	O
a	O
maximum	O
transmission	O
period	O
of	O
0.5	O
ms.	O
Class	O
CDT	O
takes	O
the	O
highest	O
priority	O
over	O
classes	O
A	O
,	O
B	O
,	O
and	O
control	O
traffic	O
.	O
</s>
<s>
IEEE	O
802.1Qav	O
Forwarding	O
and	O
Queuing	O
Enhancements	O
for	O
Time-Sensitive	O
Streams	O
defines	O
traffic	O
shaping	O
using	O
priority	O
classes	O
,	O
which	O
is	O
based	O
on	O
a	O
simple	O
form	O
of	O
"	O
leaky	O
bucket	O
"	O
credit-based	B-Algorithm
fair	I-Algorithm
queuing	I-Algorithm
.	O
</s>
<s>
Though	O
credit-based	O
shaper	O
provides	O
fair	O
scheduling	O
for	O
low-priority	O
packets	O
and	O
smooths	O
out	O
traffic	O
to	O
eliminate	O
congestion	O
,	O
unfortunately	O
,	O
average	O
delay	O
increases	O
up	O
to	O
250	O
μs	O
per	O
hop	B-Protocol
,	O
which	O
is	O
too	O
high	O
for	O
control	O
applications	O
,	O
whereas	O
a	O
time-aware	O
shaper	O
(	O
IEEE	O
802.1Qbv	O
)	O
has	O
a	O
fixed	O
cycle	O
delay	O
from	O
30μs	O
to	O
several	O
milliseconds	O
,	O
and	O
typical	O
delay	O
of	O
125μs	O
.	O
</s>
<s>
SRP	O
employs	O
variants	O
of	O
Multiple	O
Registration	O
Protocol	O
(	O
MRP	O
)	O
to	O
register	O
and	O
de-register	O
attribute	O
values	O
on	O
switches/bridges/devices	O
-	O
the	O
Multiple	O
MAC	O
Registration	O
Protocol	O
(	O
MMRP	O
)	O
,	O
the	O
Multiple	O
VLAN	B-General_Concept
Registration	O
Protocol	O
(	O
MVRP	O
)	O
,	O
and	O
the	O
Multiple	O
Stream	O
Registration	O
Protocol	O
(	O
MSRP	O
)	O
.	O
</s>
<s>
To	O
improve	O
TSN	O
administration	O
on	O
large	O
scale	O
networks	O
,	O
each	O
User	O
Network	O
Interface	O
(	O
UNI	O
)	O
provides	O
methods	O
for	O
requesting	O
Layer	B-Protocol
2	I-Protocol
services	O
,	O
supplemented	O
by	O
Centralized	O
Network	O
Configuration	O
(	O
CNC	O
)	O
to	O
provide	O
centralized	O
reservation	O
and	O
scheduling	O
,	O
and	O
remote	O
management	O
using	O
NETCONF/RESTCONF	O
protocols	O
and	O
IETF	O
YANG/NETCONF	O
data	O
modeling	O
.	O
</s>
<s>
Seamless	O
interop	O
with	O
Resource	B-Protocol
Reservation	I-Protocol
Protocol	I-Protocol
(	O
RSVP	B-Protocol
)	O
transport	O
is	O
provided	O
.	O
</s>
<s>
While	O
the	O
802.1Qav	O
FQTSS/CBS	O
works	O
very	O
well	O
with	O
soft	O
real-time	B-General_Concept
traffic	O
,	O
worst-case	O
delays	O
are	O
both	O
hop	B-Protocol
count	I-Protocol
and	O
network	O
topology	O
dependent	O
.	O
</s>
<s>
IEEE	O
802.1Qch	O
Cyclic	O
Queuing	O
and	O
Forwarding	O
(	O
CQF	O
)	O
,	O
also	O
known	O
as	O
the	O
Peristaltic	O
Shaper	O
(	O
PS	O
)	O
,	O
introduces	O
double	O
buffering	O
which	O
allows	O
bridges	O
to	O
synchronize	O
transmission	O
(	O
frame	O
enqueue/dequeue	O
operations	O
)	O
in	O
a	O
cyclic	O
manner	O
,	O
with	O
bounded	O
latency	O
depending	O
only	O
on	O
the	O
number	O
of	O
hops	B-Protocol
and	O
the	O
cycle	O
time	O
,	O
completely	O
independent	O
of	O
the	O
network	O
topology	O
.	O
</s>
<s>
Time-aware	O
scheduler	O
introduces	O
Stream	O
Reservation	O
Class	O
CDT	O
for	O
time-critical	O
control	O
data	O
,	O
with	O
worst-case	O
latency	O
of	O
100	O
μs	O
over	O
5	O
hops	B-Protocol
,	O
and	O
maximum	O
transmission	O
period	O
of	O
0.5ms	O
,	O
in	O
addition	O
to	O
classes	O
A	O
and	O
B	O
defined	O
for	O
IEEE	O
802.1Qav	O
credit-based	O
traffic	O
shaper	O
.	O
</s>
<s>
By	O
granting	O
exclusive	O
access	O
to	O
the	O
transmission	O
medium	O
and	O
devices	O
to	O
time-critical	O
traffic	O
classes	O
,	O
the	O
buffering	O
effects	O
in	O
the	O
Ethernet	B-Protocol
switch	I-Protocol
transmission	O
buffers	O
can	O
be	O
avoided	O
and	O
time-critical	O
traffic	O
can	O
be	O
transmitted	O
without	O
non-deterministic	O
interruptions	O
.	O
</s>
<s>
Time	O
slice	O
1	O
only	O
allows	O
the	O
transmission	O
of	O
traffic	O
tagged	O
with	O
VLAN	B-General_Concept
priority	O
3	O
,	O
and	O
time	O
slice	O
2	O
in	O
each	O
cycle	O
allows	O
for	O
the	O
rest	O
of	O
the	O
priorities	O
to	O
be	O
sent	O
.	O
</s>
<s>
Since	O
the	O
IEEE	O
802.1Qbv	O
scheduler	O
requires	O
all	O
clocks	O
on	O
all	O
network	O
devices	O
(	O
Ethernet	B-Protocol
switches	I-Protocol
and	O
end	O
devices	O
)	O
to	O
be	O
synchronized	O
and	O
the	O
identical	O
schedule	O
to	O
be	O
configured	O
,	O
all	O
devices	O
understand	O
which	O
priority	O
can	O
be	O
sent	O
to	O
the	O
network	O
at	O
any	O
given	O
point	O
in	O
time	O
.	O
</s>
<s>
IEEE	O
802.1Qav	O
supports	O
soft	O
real-time	B-General_Concept
.	O
</s>
<s>
The	O
Time-Sensitive	B-Protocol
Networking	I-Protocol
Task	O
Group	O
specifies	O
a	O
number	O
of	O
different	O
schedulers	O
and	O
traffic	O
shapers	O
that	O
can	O
be	O
combined	O
to	O
achieve	O
the	O
nonreactive	O
coexistence	O
of	O
hard	O
real-time	B-General_Concept
,	O
soft	O
real-time	B-General_Concept
and	O
background	O
traffic	O
on	O
the	O
same	O
Ethernet	O
infrastructure	O
.	O
</s>
<s>
By	O
partially	O
or	O
completely	O
blocking	O
a	O
time-critical	O
time	O
slice	O
,	O
real-time	B-General_Concept
frames	O
can	O
be	O
delayed	O
up	O
to	O
the	O
point	O
where	O
they	O
cannot	O
meet	O
the	O
application	O
requirements	O
any	O
longer	O
.	O
</s>
<s>
This	O
is	O
very	O
similar	O
to	O
the	O
actual	O
buffering	O
effects	O
that	O
happen	O
in	O
non-TSN	O
Ethernet	B-Protocol
switches	I-Protocol
,	O
so	O
TSN	O
has	O
to	O
specify	O
a	O
mechanism	O
to	O
prevent	O
this	O
from	O
happening	O
.	O
</s>
<s>
During	O
this	O
guard	O
band	O
time	O
,	O
no	O
new	O
Ethernet	B-Protocol
frame	I-Protocol
transmission	O
may	O
be	O
started	O
,	O
only	O
already	O
ongoing	O
transmissions	O
may	O
be	O
finished	O
.	O
</s>
<s>
For	O
an	O
Ethernet	B-Protocol
frame	I-Protocol
according	O
to	O
IEEE	O
802.3	O
with	O
a	O
single	O
IEEE	O
802.1Q	O
VLAN	B-General_Concept
tag	O
and	O
including	O
interframe	B-Protocol
spacing	I-Protocol
,	O
the	O
total	O
length	O
is	O
:	O
1500	O
byte	O
(	O
frame	O
payload	O
)	O
+	O
18	O
byte	O
(	O
ethernet	O
addresses	O
,	O
EtherType	B-Protocol
and	O
CRC	O
)	O
+	O
4	O
byte	O
(	O
VLAN	B-General_Concept
Tag	O
)	O
+	O
12	O
byte	O
(	O
Interframe	B-Protocol
spacing	I-Protocol
)	O
+	O
8	O
byte	O
(	O
preamble	O
and	O
SFD	O
)	O
=	O
1542	O
byte	O
.	O
</s>
<s>
This	O
mechanism	O
is	O
used	O
when	O
store-and-forward	B-Protocol
switching	I-Protocol
is	O
utilized	O
:	O
after	O
the	O
full	O
reception	O
of	O
an	O
Ethernet	B-Protocol
frame	I-Protocol
that	O
needs	O
to	O
be	O
transmitted	O
on	O
a	O
port	O
where	O
the	O
guard	O
band	O
is	O
in	O
effect	O
,	O
the	O
scheduler	O
checks	O
the	O
overall	O
length	O
of	O
the	O
frame	O
.	O
</s>
<s>
This	O
mechanism	O
,	O
however	O
,	O
cannot	O
be	O
used	O
when	O
cut-through	B-Protocol
switching	I-Protocol
is	O
enabled	O
,	O
since	O
the	O
total	O
length	O
of	O
the	O
Ethernet	B-Protocol
frame	I-Protocol
needs	O
to	O
be	O
known	O
a	O
priori	O
.	O
</s>
<s>
Therefore	O
,	O
when	O
cut-through	B-Protocol
switching	I-Protocol
is	O
used	O
to	O
minimize	O
end-to-end	O
latency	O
,	O
the	O
waste	O
of	O
bandwidth	O
will	O
still	O
occur	O
.	O
</s>
<s>
The	O
two	O
working	O
groups	O
collaborated	O
in	O
this	O
endeavour	O
since	O
the	O
technology	O
required	O
both	O
changes	O
in	O
the	O
Ethernet	O
Media	B-Protocol
Access	I-Protocol
Control	I-Protocol
(	O
MAC	O
)	O
scheme	O
that	O
is	O
under	O
the	O
control	O
of	O
IEEE	O
802.3	O
,	O
as	O
well	O
as	O
changes	O
in	O
the	O
management	O
mechanisms	O
that	O
are	O
under	O
the	O
control	O
of	O
IEEE	O
802.1	O
.	O
</s>
<s>
During	O
the	O
process	O
of	O
sending	O
a	O
best	O
effort	O
Ethernet	B-Protocol
frame	I-Protocol
,	O
the	O
MAC	O
interrupts	O
the	O
frame	O
transmission	O
just	O
before	O
the	O
start	O
of	O
the	O
guard	O
band	O
.	O
</s>
<s>
Frame	O
pre-emption	O
always	O
operates	O
on	O
a	O
pure	O
link-by-link	O
basis	O
and	O
only	O
fragments	O
from	O
one	O
Ethernet	B-Protocol
switch	I-Protocol
to	O
the	O
next	O
Ethernet	B-Protocol
switch	I-Protocol
,	O
where	O
the	O
frame	O
is	O
reassembled	O
.	O
</s>
<s>
In	O
contrast	O
to	O
fragmentation	O
with	O
the	O
Internet	B-Protocol
Protocol	I-Protocol
(	O
IP	B-Protocol
)	O
,	O
no	O
end-to-end	O
fragmentation	O
is	O
supported	O
.	O
</s>
<s>
In	O
contrast	O
to	O
the	O
regular	O
Ethernet	O
CRC32	O
,	O
the	O
last	O
16	O
bits	O
are	O
inverted	O
to	O
make	O
a	O
partial	O
frame	O
distinguishable	O
from	O
a	O
regular	O
Ethernet	B-Protocol
frame	I-Protocol
.	O
</s>
<s>
To	O
signal	O
the	O
capability	O
for	O
frame	O
pre-emption	O
on	O
a	O
link	O
,	O
an	O
Ethernet	B-Protocol
switch	I-Protocol
announces	O
this	O
capability	O
through	O
the	O
LLDP	B-Protocol
(	O
Link	B-Protocol
Layer	I-Protocol
Discovery	I-Protocol
Protocol	I-Protocol
)	O
.	O
</s>
<s>
When	O
a	O
device	O
receives	O
such	O
an	O
LLDP	B-Protocol
announcement	O
on	O
a	O
network	O
port	O
and	O
supports	O
frame	O
pre-emption	O
itself	O
,	O
it	O
may	O
activate	O
the	O
capability	O
.	O
</s>
<s>
Any	O
device	O
that	O
receives	O
the	O
LLDP	B-Protocol
pre-emption	O
announcement	O
assumes	O
that	O
on	O
the	O
other	O
end	O
of	O
the	O
link	O
,	O
a	O
device	O
is	O
present	O
that	O
can	O
understand	O
the	O
changes	O
in	O
the	O
frame	O
format	O
(	O
changed	O
CRC32	O
and	O
SFD	O
)	O
.	O
</s>
<s>
IEEE	O
802.3br	O
specifies	O
the	O
best	O
accuracy	O
for	O
this	O
mechanism	O
at	O
64	O
byte	O
-	O
due	O
to	O
the	O
fact	O
that	O
this	O
is	O
the	O
minimum	O
size	O
of	O
a	O
still	O
valid	O
Ethernet	B-Protocol
frame	I-Protocol
.	O
</s>
<s>
Since	O
the	O
pre-emption	O
takes	O
place	O
in	O
hardware	O
in	O
the	O
MAC	O
,	O
as	O
the	O
frame	O
passes	O
through	O
,	O
cut-through	B-Protocol
switching	I-Protocol
can	O
be	O
supported	O
as	O
well	O
,	O
since	O
the	O
overall	O
frame	O
size	O
is	O
not	O
needed	O
a	O
priori	O
.	O
</s>
<s>
Asynchronicity	O
is	O
achieved	O
by	O
interleaved	O
shaping	O
with	O
traffic	O
characterization	O
based	O
on	O
Token	B-Algorithm
Bucket	I-Algorithm
Emulation	O
,	O
a	O
token	B-Algorithm
bucket	I-Algorithm
emulation	O
model	O
,	O
to	O
eliminate	O
the	O
burstiness	O
cascade	O
effects	O
of	O
per-class	O
shaping	O
.	O
</s>
<s>
The	O
UBS	O
is	O
an	O
improvement	O
on	O
Rate-Controlled	O
Service	O
Disciplines	O
(	O
RCSDs	O
)	O
to	O
control	O
selection	O
and	O
transmission	O
of	O
each	O
individual	O
frame	O
at	O
each	O
hop	B-Protocol
,	O
decoupling	O
stream	O
bandwidth	O
from	O
the	O
delay	O
bound	O
by	O
separation	O
of	O
rate	O
control	O
and	O
packet	O
scheduling	O
,	O
and	O
using	O
static	O
priorities	O
and	O
First	O
Come	O
-	O
First	O
Serve	O
and	O
Earliest	B-Algorithm
Due	I-Algorithm
-	I-Algorithm
Date	I-Algorithm
First	I-Algorithm
queuing	O
.	O
</s>
<s>
IEEE	O
802.1Qca	O
Path	O
Control	O
and	O
Reservation	O
(	O
PCR	O
)	O
specifies	O
extensions	O
to	O
the	O
Intermediate	B-Protocol
Station	I-Protocol
to	I-Protocol
Intermediate	I-Protocol
Station	I-Protocol
(	O
IS-IS	B-Protocol
)	O
protocol	O
to	O
configure	O
multiple	O
paths	O
in	O
bridged	O
networks	O
.	O
</s>
<s>
The	O
IEEE	O
802.1Qca	O
standard	O
uses	O
Shortest	B-Protocol
Path	I-Protocol
Bridging	I-Protocol
(	O
SPB	O
)	O
with	O
a	O
software-defined	O
networking	O
(	O
SDN	O
)	O
hybrid	O
mode	O
-	O
the	O
IS-IS	B-Protocol
protocol	O
handles	O
basic	O
functions	O
,	O
while	O
the	O
SDN	O
controller	O
manages	O
explicit	O
paths	O
using	O
Path	B-Protocol
Computation	I-Protocol
Elements	I-Protocol
(	O
PCEs	O
)	O
at	O
dedicated	O
server	O
nodes	O
.	O
</s>
<s>
These	O
are	O
derived	O
from	O
Equal	B-Protocol
Cost	I-Protocol
Tree	I-Protocol
(	O
ECT	O
)	O
,	O
Multiple	B-Protocol
Spanning	I-Protocol
Tree	I-Protocol
Instance	I-Protocol
(	O
MSTI	O
)	O
and	O
Internal	O
Spanning	O
Tree	O
(	O
IST	O
)	O
,	O
and	O
Explicit	O
Tree	O
(	O
ET	O
)	O
protocols	O
.	O
</s>
<s>
Industrial	O
fault-tolerance	O
HSR	B-Protocol
and	O
PRP	B-Protocol
specified	O
in	O
IEC	O
62439-3	O
are	O
supported	O
.	O
</s>
<s>
RAP	O
supports	O
the	O
'	O
topology-independent	O
per-hop	O
latency	O
calculation	O
 '	O
capability	O
of	O
TSN	O
shapers	O
such	O
as	O
802.1Qch	O
Cyclic	O
Queuing	O
and	O
Forwarding	O
(	O
CQF	O
)	O
and	O
P802.1Qcr	O
Asynchronous	O
Traffic	O
Shaping	O
(	O
ATS	O
)	O
.	O
</s>
<s>
IEEE	O
P802.1ABdh	O
Station	O
and	O
Media	B-Protocol
Access	I-Protocol
Control	I-Protocol
Connectivity	O
Discovery	O
-	O
Support	O
for	O
Multiframe	O
Protocol	O
Data	O
Units	O
(	O
LLDPv2	O
)	O
updates	O
LLDP	B-Protocol
to	O
support	O
IETF	O
Link	O
State	O
Vector	O
Routing	O
protocol	O
and	O
improve	O
efficiency	O
of	O
protocol	O
messages	O
.	O
</s>
<s>
The	O
IEEE	O
802.1Qcp	O
standard	O
implements	O
the	O
YANG	O
data	O
model	O
to	O
provide	O
a	O
Universal	B-Application
Plug-and-Play	I-Application
(	O
uPnP	B-Application
)	O
framework	O
for	O
status	O
reporting	O
and	O
configuration	O
of	O
equipment	O
such	O
as	O
Media	B-Protocol
Access	I-Protocol
Control	I-Protocol
(	O
MAC	O
)	O
Bridges	O
,	O
Two-Port	O
MAC	O
Relays	O
(	O
TPMRs	O
)	O
,	O
Customer	O
Virtual	B-General_Concept
Local	I-General_Concept
Area	I-General_Concept
Network	I-General_Concept
(	O
VLAN	B-General_Concept
)	O
Bridges	O
,	O
and	O
Provider	O
Bridges	O
,	O
and	O
to	O
support	O
the	O
802.1X	O
Security	O
and	O
802.1AX	O
Datacenter	O
Bridging	O
standards	O
.	O
</s>
<s>
The	O
IETF	O
Deterministic	B-Protocol
Networking	I-Protocol
(	O
DetNet	O
)	O
Working	O
Group	O
is	O
focusing	O
to	O
define	O
deterministic	O
data	O
paths	O
with	O
high	O
reliability	O
and	O
bounds	O
on	O
latency	O
,	O
loss	O
,	O
and	O
packet	O
delay	O
variation	O
(	O
jitter	O
)	O
,	O
such	O
as	O
audio	O
and	O
video	O
streaming	O
,	O
industrial	O
automation	O
,	O
and	O
vehicle	O
control	O
.	O
</s>
<s>
The	O
goals	O
of	O
Deterministic	B-Protocol
Networking	I-Protocol
are	O
to	O
migrate	O
time-critical	O
,	O
high-reliability	O
industrial	O
and	O
audio-video	O
applications	O
from	O
special-purpose	O
Fieldbus	O
networks	O
to	O
IP	B-Protocol
packet	O
networks	O
.	O
</s>
<s>
DetNet	O
operates	O
at	O
the	O
IP	B-Protocol
Layer	B-Application
3	I-Application
routed	O
segments	O
using	O
a	O
Software-Defined	O
Networking	O
layer	O
to	O
provide	O
IntServ	O
and	O
DiffServ	O
integration	O
,	O
and	O
delivers	O
services	O
over	O
lower	O
Layer	B-Protocol
2	I-Protocol
bridged	O
segments	O
using	O
technologies	O
such	O
as	O
MPLS	B-Protocol
and	O
IEEE	O
802.1	O
AVB/TSN	B-Protocol
.	O
</s>
<s>
Traffic	O
Engineering	O
(	O
TE	O
)	O
routing	O
protocols	O
translate	O
DetNet	O
flow	O
specification	O
to	O
AVB/TSN	B-Protocol
controls	O
for	O
queuing	O
,	O
shaping	O
,	O
and	O
scheduling	O
algorithms	O
,	O
such	O
as	O
IEEE	O
802.1Qav	O
credit-based	O
shaper	O
,	O
IEEE802.1Qbv	O
time-triggered	O
shaper	O
with	O
a	O
rotating	O
time	O
scheduler	O
,	O
IEEE802.1Qch	O
synchronized	O
double	O
buffering	O
,	O
802.1Qbu/802.3br	O
Ethernet	O
packet	O
pre-emption	O
,	O
and	O
802.1CB	O
frame	O
replication	O
and	O
elimination	O
for	O
reliability	O
.	O
</s>
<s>
Also	O
protocol	O
interworking	O
defined	O
by	O
IEEE	O
802.1CB	O
is	O
used	O
to	O
advertise	O
TSN	O
sub-network	O
capabilities	O
to	O
DetNet	O
flows	O
via	O
the	O
Active	O
Destination	O
MAC	O
and	O
VLAN	B-General_Concept
Stream	O
identification	O
functions	O
.	O
</s>
<s>
DetNet	O
flows	O
are	O
matched	O
by	O
destination	O
MAC	O
address	O
,	O
VLAN	B-General_Concept
ID	O
and	O
priority	O
parameters	O
to	O
Stream	O
ID	O
and	O
QoS	O
requirements	O
for	O
talkers	O
and	O
listeners	O
in	O
the	O
AVB/TSN	B-Protocol
sub-network	O
.	O
</s>
