<s>
Hop-by-hop	B-Protocol
transport	I-Protocol
is	O
a	O
principle	O
of	O
controlling	O
the	O
flow	O
of	O
data	O
in	O
a	O
network	O
.	O
</s>
<s>
With	O
hop-by-hop	B-Protocol
transport	I-Protocol
,	O
chunks	O
of	O
data	O
are	O
forwarded	O
from	O
node	O
to	O
node	O
in	O
a	O
store-and-forward	B-Protocol
manner	O
.	O
</s>
<s>
As	O
hop-by-hop	B-Protocol
transport	I-Protocol
involves	O
not	O
only	O
the	O
source	O
and	O
destination	O
node	O
,	O
but	O
rather	O
some	O
or	O
all	O
of	O
the	O
intermediate	O
nodes	O
as	O
well	O
,	O
it	O
allows	O
data	O
to	O
be	O
forwarded	O
even	O
if	O
the	O
path	O
between	O
source	O
and	O
destination	O
is	O
not	O
permanently	O
connected	O
during	O
communication	O
.	O
</s>
<s>
However	O
,	O
the	O
End-to-end	B-Application
principle	I-Application
claims	O
that	O
transport	O
control	O
should	O
be	O
implemented	O
end-to-end	O
unless	O
implementing	O
hop-by-hop	B-Protocol
transport	I-Protocol
achieves	O
considerably	O
better	O
performance	O
.	O
</s>
<s>
Moreover	O
,	O
hop-by-hop	B-Protocol
transport	I-Protocol
requires	O
per-flow	O
state	O
information	O
at	O
intermediate	O
nodes	O
,	O
which	O
limits	O
its	O
scalability	O
.	O
</s>
<s>
This	O
is	O
one	O
of	O
the	O
reasons	O
why	O
almost	O
all	O
communication	O
today	O
is	O
controlled	O
by	O
end-to-end	O
transport	O
protocols	O
such	O
as	O
TCP	B-Protocol
.	O
</s>
<s>
Current	O
research	O
in	O
the	O
area	O
of	O
sparse	O
mobile	O
networks	O
is	O
considering	O
hop-by-hop	B-Protocol
transport	I-Protocol
for	O
application	O
scenarios	O
where	O
end-to-end	B-Application
connectivity	I-Application
is	O
only	O
available	O
intermittently	O
,	O
as	O
under	O
such	O
conditions	O
,	O
hop-by-hop	B-Protocol
transport	I-Protocol
can	O
achieve	O
substantial	O
performance	O
gains	O
.	O
</s>
