<s>
Round-robin	O
(	O
RR	O
)	O
is	O
one	O
of	O
the	O
algorithms	O
employed	O
by	O
process	O
and	O
network	B-Application
schedulers	I-Application
in	O
computing	O
.	O
</s>
<s>
As	O
the	O
term	O
is	O
generally	O
used	O
,	O
time	O
slices	O
(	O
also	O
known	O
as	O
time	O
quanta	O
)	O
are	O
assigned	O
to	O
each	O
process	O
in	O
equal	O
portions	O
and	O
in	O
circular	O
order	O
,	O
handling	O
all	O
processes	O
without	O
priority	O
(	O
also	O
known	O
as	O
cyclic	B-Operating_System
executive	I-Operating_System
)	O
.	O
</s>
<s>
Round-robin	B-Algorithm
scheduling	I-Algorithm
is	O
simple	O
,	O
easy	O
to	O
implement	O
,	O
and	O
starvation-free	O
.	O
</s>
<s>
Round-robin	B-Algorithm
scheduling	I-Algorithm
can	O
be	O
applied	O
to	O
other	O
scheduling	O
problems	O
,	O
such	O
as	O
data	O
packet	O
scheduling	O
in	O
computer	O
networks	O
.	O
</s>
<s>
It	O
is	O
an	O
operating	B-General_Concept
system	I-General_Concept
concept	O
.	O
</s>
<s>
To	O
schedule	O
processes	O
fairly	O
,	O
a	O
round-robin	O
scheduler	O
generally	O
employs	O
time-sharing	B-General_Concept
,	O
giving	O
each	O
job	O
a	O
time	O
slot	O
or	O
quantum	O
(	O
its	O
allowance	O
of	O
CPU	B-Device
time	O
)	O
,	O
and	O
interrupting	O
the	O
job	O
if	O
it	O
is	O
not	O
completed	O
by	O
then	O
.	O
</s>
<s>
In	O
the	O
absence	O
of	O
time-sharing	B-General_Concept
,	O
or	O
if	O
the	O
quanta	O
were	O
large	O
relative	O
to	O
the	O
sizes	O
of	O
the	O
jobs	O
,	O
a	O
process	O
that	O
produced	O
large	O
jobs	O
would	O
be	O
favored	O
over	O
other	O
processes	O
.	O
</s>
<s>
Round-robin	O
algorithm	O
is	O
a	O
pre-emptive	O
algorithm	O
as	O
the	O
scheduler	O
forces	O
the	O
process	O
out	O
of	O
the	O
CPU	B-Device
once	O
the	O
time	O
quota	O
expires	O
.	O
</s>
<s>
For	O
example	O
,	O
if	O
the	O
time	O
slot	O
is	O
100	O
milliseconds	O
,	O
and	O
job1	O
takes	O
a	O
total	O
time	O
of	O
250	O
ms	O
to	O
complete	O
,	O
the	O
round-robin	O
scheduler	O
will	O
suspend	O
the	O
job	O
after	O
100	O
ms	O
and	O
give	O
other	O
jobs	O
their	O
time	O
on	O
the	O
CPU	B-Device
.	O
</s>
<s>
Once	O
the	O
other	O
jobs	O
have	O
had	O
their	O
equal	O
share	O
(	O
100	O
ms	O
each	O
)	O
,	O
job1	O
will	O
get	O
another	O
allocation	O
of	O
CPU	B-Device
time	O
and	O
the	O
cycle	O
will	O
repeat	O
.	O
</s>
<s>
This	O
process	O
continues	O
until	O
the	O
job	O
finishes	O
and	O
needs	O
no	O
more	O
time	O
on	O
the	O
CPU	B-Device
.	O
</s>
<s>
Consider	O
the	O
following	O
table	O
with	O
the	O
arrival	O
time	O
and	O
execute	O
time	O
of	O
the	O
process	O
with	O
the	O
quantum	O
time	O
of	O
100	O
ms	O
to	O
understand	O
the	O
round-robin	B-Algorithm
scheduling	I-Algorithm
:	O
</s>
<s>
In	O
best-effort	O
packet	B-Protocol
switching	I-Protocol
and	O
other	O
statistical	B-Algorithm
multiplexing	I-Algorithm
,	O
round-robin	B-Algorithm
scheduling	I-Algorithm
can	O
be	O
used	O
as	O
an	O
alternative	O
to	O
first-come	O
first-served	O
queuing	O
.	O
</s>
<s>
A	O
multiplexer	O
,	O
switch	O
,	O
or	O
router	O
that	O
provides	O
round-robin	B-Algorithm
scheduling	I-Algorithm
has	O
a	O
separate	O
queue	O
for	O
every	O
data	O
flow	O
,	O
where	O
a	O
data	O
flow	O
may	O
be	O
identified	O
by	O
its	O
source	O
and	O
destination	O
address	O
.	O
</s>
<s>
Round-robin	B-Algorithm
scheduling	I-Algorithm
results	O
in	O
max-min	B-Algorithm
fairness	I-Algorithm
if	O
the	O
data	O
packets	O
are	O
equally	O
sized	O
,	O
since	O
the	O
data	O
flow	O
that	O
has	O
waited	O
the	O
longest	O
time	O
is	O
given	O
scheduling	O
priority	O
.	O
</s>
<s>
In	O
that	O
case	O
fair	B-Algorithm
queuing	I-Algorithm
would	O
be	O
preferable	O
.	O
</s>
<s>
If	O
guaranteed	O
or	O
differentiated	O
quality	O
of	O
service	O
is	O
offered	O
,	O
and	O
not	O
only	O
best-effort	O
communication	O
,	O
deficit	B-Algorithm
round-robin	I-Algorithm
(	O
DRR	O
)	O
scheduling	O
,	O
weighted	B-Algorithm
round-robin	I-Algorithm
(	O
WRR	O
)	O
scheduling	O
,	O
or	O
weighted	B-Algorithm
fair	I-Algorithm
queuing	I-Algorithm
(	O
WFQ	B-Algorithm
)	O
may	O
be	O
considered	O
.	O
</s>
<s>
In	O
multiple-access	O
networks	O
,	O
where	O
several	O
terminals	O
are	O
connected	O
to	O
a	O
shared	O
physical	O
medium	O
,	O
round-robin	B-Algorithm
scheduling	I-Algorithm
may	O
be	O
provided	O
by	O
token	B-Protocol
passing	I-Protocol
channel	O
access	O
schemes	O
such	O
as	O
Token	B-Device
Ring	I-Device
,	O
or	O
by	O
polling	B-General_Concept
or	O
resource	O
reservation	O
from	O
a	O
central	O
control	O
station	O
.	O
</s>
<s>
However	O
,	O
if	O
link	B-Protocol
adaptation	I-Protocol
is	O
used	O
,	O
it	O
will	O
take	O
a	O
much	O
longer	O
time	O
to	O
transmit	O
a	O
certain	O
amount	O
of	O
data	O
to	O
"	O
expensive	O
"	O
users	O
than	O
to	O
others	O
since	O
the	O
channel	O
conditions	O
differ	O
.	O
</s>
<s>
Round-robin	B-Algorithm
scheduling	I-Algorithm
does	O
not	O
utilize	O
this	O
.	O
</s>
<s>
Higher	O
throughput	O
and	O
system	B-Protocol
spectrum	I-Protocol
efficiency	I-Protocol
may	O
be	O
achieved	O
by	O
channel-dependent	O
scheduling	O
,	O
for	O
example	O
a	O
proportionally	B-Algorithm
fair	I-Algorithm
algorithm	O
,	O
or	O
maximum	B-Algorithm
throughput	I-Algorithm
scheduling	I-Algorithm
.	O
</s>
<s>
Note	O
that	O
the	O
latter	O
is	O
characterized	O
by	O
undesirable	O
scheduling	B-Operating_System
starvation	I-Operating_System
.	O
</s>
<s>
This	O
type	O
of	O
scheduling	O
is	O
one	O
of	O
the	O
very	O
basic	O
algorithms	O
for	O
Operating	B-General_Concept
Systems	I-General_Concept
in	O
computers	O
which	O
can	O
be	O
implemented	O
through	O
a	O
circular	O
queue	O
data	O
structure	O
.	O
</s>
