<s>
Core-based	B-Architecture
trees	I-Architecture
(	O
CBT	O
)	O
is	O
a	O
proposal	O
for	O
making	O
IP	O
Multicast	O
scalable	B-Architecture
by	O
constructing	O
a	O
tree	B-Data_Structure
of	O
routers	B-Protocol
.	O
</s>
<s>
What	O
differentiates	O
it	O
from	O
other	O
schemes	O
for	O
multicasting	O
is	O
that	O
the	O
routing	O
tree	B-Data_Structure
comprises	O
multiple	O
"	O
cores	O
"	O
(	O
also	O
known	O
as	O
"	O
centres	O
"	O
)	O
.	O
</s>
<s>
The	O
locations	O
of	O
the	O
core	O
routers	B-Protocol
are	O
statically	O
configured	O
.	O
</s>
<s>
Other	O
routers	B-Protocol
are	O
added	O
by	O
growing	O
"	O
branches	O
"	O
of	O
a	O
tree	B-Data_Structure
,	O
comprising	O
a	O
chain	O
of	O
routers	B-Protocol
,	O
from	O
the	O
core	O
routers	B-Protocol
out	O
towards	O
the	O
routers	B-Protocol
directly	O
adjacent	O
to	O
the	O
multicast	O
group	O
members	O
.	O
</s>
