<s>
Terminating	B-Operating_System
Reliable	I-Operating_System
Broadcast	I-Operating_System
(	O
TRB	O
)	O
is	O
a	O
problem	O
in	O
distributed	B-Architecture
computing	I-Architecture
that	O
encapsulates	O
the	O
task	O
of	O
broadcasting	O
a	O
message	O
to	O
a	O
set	O
of	O
receiving	O
processes	B-Operating_System
in	O
the	O
presence	O
of	O
faults	O
.	O
</s>
<s>
A	O
TRB	O
protocol	O
typically	O
organizes	O
the	O
system	O
into	O
a	O
sending	O
process	O
and	O
a	O
set	O
of	O
receiving	O
processes	B-Operating_System
,	O
which	O
may	O
include	O
the	O
sender	O
itself	O
.	O
</s>
<s>
The	O
goal	O
of	O
the	O
protocol	O
is	O
to	O
transfer	O
data	O
(	O
the	O
"	O
message	O
"	O
)	O
from	O
the	O
sender	O
to	O
the	O
set	O
of	O
receiving	O
processes	B-Operating_System
.	O
</s>
<s>
A	O
process	O
may	O
perform	O
many	O
I/O	B-General_Concept
operations	I-General_Concept
during	O
protocol	O
execution	O
,	O
but	O
eventually	O
"	O
delivers	O
"	O
a	O
message	O
by	O
passing	O
it	O
to	O
the	O
application	O
on	O
that	O
process	O
that	O
invoked	O
the	O
TRB	O
protocol	O
.	O
</s>
<s>
The	O
protocol	O
must	O
provide	O
important	O
guarantees	O
to	O
the	O
receiving	O
processes	B-Operating_System
.	O
</s>
<s>
All	O
correct	O
receiving	O
processes	B-Operating_System
,	O
for	O
example	O
,	O
must	O
deliver	O
the	O
sender	O
's	O
message	O
if	O
the	O
sender	O
is	O
also	O
correct	O
.	O
</s>
<s>
A	O
receiving	O
process	O
may	O
deliver	O
a	O
special	O
message	O
,	O
(	O
"	O
sender	O
faulty	O
"	O
)	O
,	O
if	O
the	O
sender	O
failed	O
,	O
but	O
either	O
all	O
correct	O
processes	B-Operating_System
will	O
deliver	O
or	O
none	O
will	O
.	O
</s>
<s>
A	O
correct	O
process	O
is	O
therefore	O
guaranteed	O
that	O
data	O
delivered	O
to	O
it	O
was	O
also	O
delivered	O
to	O
all	O
other	O
correct	O
processes	B-Operating_System
.	O
</s>
<s>
Agreement	O
:	O
if	O
a	O
correct	O
process	O
delivers	O
a	O
message	O
,	O
then	O
all	O
correct	O
processes	B-Operating_System
deliver	O
.	O
</s>
<s>
A	O
simple	O
but	O
invalid	O
TRB	O
protocol	O
might	O
have	O
the	O
sender	O
broadcast	O
the	O
message	O
to	O
all	O
processes	B-Operating_System
,	O
and	O
have	O
receiving	O
processes	B-Operating_System
deliver	O
the	O
message	O
as	O
soon	O
as	O
it	O
is	O
received	O
.	O
</s>
<s>
This	O
protocol	O
,	O
however	O
,	O
does	O
not	O
satisfy	O
agreement	O
if	O
faults	O
can	O
occur	O
:	O
if	O
the	O
sender	O
crashes	O
after	O
sending	O
the	O
message	O
to	O
some	O
processes	B-Operating_System
,	O
but	O
before	O
sending	O
it	O
to	O
others	O
,	O
then	O
the	O
first	O
set	O
of	O
processes	B-Operating_System
may	O
deliver	O
the	O
message	O
while	O
the	O
second	O
set	O
delivers	O
.	O
</s>
<s>
TRB	O
is	O
closely	O
related	O
,	O
but	O
not	O
identical	O
,	O
to	O
the	O
fundamental	O
distributed	B-Architecture
computing	I-Architecture
problem	O
of	O
consensus	B-Operating_System
.	O
</s>
