<s>
Constrained	B-Protocol
Shortest	I-Protocol
Path	I-Protocol
First	I-Protocol
(	O
CSPF	B-Protocol
)	O
is	O
an	O
extension	O
of	O
shortest	O
path	O
algorithms	O
.	O
</s>
<s>
The	O
path	O
computed	O
using	O
CSPF	B-Protocol
is	O
a	O
shortest	O
path	O
fulfilling	O
a	O
set	O
of	O
constraints	O
.	O
</s>
<s>
CSPF	B-Protocol
is	O
widely	O
used	O
in	O
MPLS	B-Protocol
Traffic	O
Engineering	O
.	O
</s>
<s>
The	O
routing	O
using	O
CSPF	B-Protocol
is	O
known	O
as	O
Constraint	B-Protocol
Based	I-Protocol
Routing	I-Protocol
(	O
CBR	O
)	O
.	O
</s>
<s>
The	O
path	O
computed	O
using	O
CSPF	B-Protocol
could	O
be	O
exactly	O
same	O
as	O
that	O
of	O
computed	O
from	O
OSPF	B-Protocol
and	O
IS-IS	B-Protocol
,	O
or	O
it	O
could	O
be	O
completely	O
different	O
depending	O
on	O
the	O
set	O
of	O
constraints	O
to	O
be	O
met	O
.	O
</s>
<s>
If	O
x	O
=	O
50	O
units	O
then	O
CSPF	B-Protocol
will	O
give	O
path	O
A	O
→	O
B	O
→	O
C	O
.	O
</s>
<s>
If	O
x	O
=	O
55	O
units	O
then	O
CSPF	B-Protocol
will	O
give	O
path	O
A	O
→	O
D	O
→	O
E	O
→	O
C	O
.	O
</s>
<s>
If	O
x	O
=	O
90	O
units	O
then	O
CSPF	B-Protocol
will	O
give	O
path	O
A	O
→	O
D	O
→	O
E	O
→	O
F	O
→	O
C	O
.	O
</s>
<s>
In	O
all	O
of	O
these	O
cases	O
OSPF	B-Protocol
and	O
IS-IS	B-Protocol
will	O
result	O
in	O
path	O
A	O
→	O
B	O
→	O
C	O
.	O
</s>
<s>
However	O
,	O
if	O
the	O
link	O
costs	O
in	O
this	O
topology	O
are	O
different	O
,	O
CSPF	B-Protocol
may	O
accordingly	O
determine	O
a	O
different	O
path	O
.	O
</s>
<s>
If	O
x	O
=	O
50	O
units	O
then	O
CSPF	B-Protocol
will	O
give	O
path	O
A	O
→	O
D	O
→	O
E	O
→	O
C	O
.	O
</s>
<s>
If	O
x	O
=	O
55	O
units	O
then	O
CSPF	B-Protocol
will	O
give	O
path	O
A	O
→	O
D	O
→	O
E	O
→	O
C	O
.	O
</s>
<s>
If	O
x	O
=	O
90	O
units	O
then	O
CSPF	B-Protocol
will	O
give	O
path	O
A	O
→	O
D	O
→	O
E	O
→	O
F	O
→	O
C	O
.	O
</s>
