<s>
A	O
non-broadcast	O
multiple	O
access	O
network	O
(	O
NBMA	B-Protocol
)	O
is	O
a	O
computer	B-Architecture
network	I-Architecture
to	O
which	O
multiple	O
hosts	O
are	O
attached	O
,	O
but	O
data	O
is	O
transmitted	O
only	O
directly	O
from	O
one	O
computer	O
to	O
another	O
single	O
host	O
over	O
a	O
virtual	B-Protocol
circuit	I-Protocol
or	O
across	O
a	O
switched	B-Architecture
fabric	I-Architecture
.	O
</s>
<s>
Some	O
NBMA	B-Protocol
network	O
devices	O
support	O
multicast	O
and	O
broadcast	B-Operating_System
traffic	I-Operating_System
replication	O
(	O
pseudo-broadcasts	O
)	O
.	O
</s>
<s>
This	O
is	O
done	O
by	O
send	O
multiple	O
copies	O
of	O
a	O
broadcast	B-Operating_System
packet	I-Operating_System
,	O
one	O
through	O
virtual	B-Protocol
circuit	I-Protocol
,	O
so	O
that	O
the	O
broadcast	B-Operating_System
gets	O
to	O
all	O
intended	O
recipients	O
.	O
</s>
<s>
The	O
ITU-T	B-General_Concept
G.hn	I-General_Concept
standard	O
provides	O
a	O
specification	O
for	O
creating	O
a	O
high-speed	O
(	O
up	O
to	O
1	O
Gigabit/s	O
)	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
using	O
existing	O
home	O
power	B-Device
lines	I-Device
,	O
phone	O
lines	O
and	O
coaxial	B-Protocol
cables	I-Protocol
.	O
</s>
<s>
Because	O
of	O
multipath	O
propagation	O
,	O
power	B-Device
lines	I-Device
use	O
frequency-selective	O
channels	O
.	O
</s>
<s>
In	O
NBMA	B-Protocol
networks	O
a	O
special	O
technique	O
called	O
split	B-Protocol
horizon	I-Protocol
route	I-Protocol
advertisement	I-Protocol
must	O
be	O
disabled	O
by	O
distance-vector	B-Protocol
routing	I-Protocol
protocols	I-Protocol
in	O
order	O
to	O
route	O
traffic	O
in	O
a	O
hub	O
and	O
spoke	O
topology	O
.	O
</s>
<s>
The	O
reason	O
being	O
is	O
that	O
split	B-Protocol
horizon	I-Protocol
dictates	O
that	O
a	O
router	O
cannot	O
send	O
a	O
routing	O
table	O
update	O
out	O
of	O
the	O
same	O
interface	O
from	O
which	O
it	O
received	O
it	O
.	O
</s>
<s>
This	O
family	O
of	O
protocols	O
relies	O
on	O
link	B-Protocol
layer	I-Protocol
broadcasting	B-Operating_System
for	O
route	O
advertisement	O
propagation	O
,	O
so	O
when	O
this	O
feature	O
is	O
absent	O
,	O
it	O
has	O
to	O
be	O
emulated	O
with	O
a	O
series	O
of	O
unicast	B-Protocol
transmissions	O
,	O
which	O
may	O
result	O
in	O
a	O
receiver	O
node	O
sending	O
a	O
route	O
advertisement	O
back	O
to	O
the	O
node	O
it	O
has	O
just	O
received	O
it	O
from	O
.	O
</s>
