<s>
Available	B-Protocol
bit	I-Protocol
rate	I-Protocol
(	O
ABR	B-Protocol
)	O
is	O
a	O
service	O
used	O
in	O
ATM	O
networks	O
when	O
source	O
and	O
destination	O
do	O
n't	O
need	O
to	O
be	O
synchronized	O
.	O
</s>
<s>
ABR	B-Protocol
does	O
not	O
guarantee	O
against	O
delay	O
or	O
data	B-General_Concept
loss	I-General_Concept
.	O
</s>
<s>
ABR	B-Protocol
mechanisms	O
allow	O
the	O
network	O
to	O
allocate	O
the	O
available	O
bandwidth	O
fairly	O
over	O
the	O
present	O
ABR	B-Protocol
sources	O
.	O
</s>
<s>
ABR	B-Protocol
is	O
one	O
of	O
five	O
service	O
categories	O
defined	O
by	O
the	O
ATM	O
Forum	O
for	O
use	O
in	O
an	O
ATM	O
Network	O
.	O
</s>
<s>
The	O
network	B-Protocol
switches	I-Protocol
use	O
locally	O
available	O
information	O
to	O
determine	O
the	O
explicit	O
allowable	O
rates	O
or	O
relative	O
rate	O
(	O
increase/decrease	O
)	O
for	O
the	O
source	O
.	O
</s>
<s>
ABR	B-Protocol
sets	O
a	O
minimum	O
cell	O
rate	O
(	O
MCR	O
)	O
and	O
a	O
peak	O
cell	O
rate	O
(	O
PCR	O
)	O
.	O
</s>
<s>
Many	O
implementers	O
consider	O
ABR	B-Protocol
to	O
be	O
overly	O
complex	O
,	O
and	O
its	O
adoption	O
has	O
been	O
modest	O
.	O
</s>
