<s>
Dynamic	B-Device
Source	I-Device
Routing	I-Device
(	O
DSR	O
)	O
is	O
a	O
routing	B-Protocol
protocol	O
for	O
wireless	O
mesh	O
networks	O
.	O
</s>
<s>
It	O
is	O
similar	O
to	O
AODV	B-Device
in	O
that	O
it	O
forms	O
a	O
route	O
on-demand	O
when	O
a	O
transmitting	O
node	O
requests	O
one	O
.	O
</s>
<s>
However	O
,	O
it	O
uses	O
source	B-Protocol
routing	I-Protocol
instead	O
of	O
relying	O
on	O
the	O
routing	B-Protocol
table	O
at	O
each	O
intermediate	O
device	O
.	O
</s>
<s>
The	O
accumulated	O
path	O
information	O
is	O
cached	O
by	O
nodes	O
processing	O
the	O
route	O
discovery	O
packets	B-Protocol
.	O
</s>
<s>
The	O
learned	O
paths	O
are	O
used	O
to	O
route	O
packets	B-Protocol
.	O
</s>
<s>
To	O
accomplish	O
source	B-Protocol
routing	I-Protocol
,	O
the	O
routed	B-Protocol
packets	B-Protocol
contain	O
the	O
address	O
of	O
each	O
device	O
the	O
packet	B-Protocol
will	O
traverse	O
.	O
</s>
<s>
This	O
may	O
result	O
in	O
high	O
overhead	O
for	O
long	O
paths	O
or	O
large	O
addresses	O
,	O
like	O
IPv6	B-Protocol
.	O
</s>
<s>
To	O
avoid	O
using	O
source	B-Protocol
routing	I-Protocol
,	O
DSR	O
optionally	O
defines	O
a	O
flow	O
id	O
option	O
that	O
allows	O
packets	B-Protocol
to	O
be	O
forwarded	O
on	O
a	O
hop-by-hop	O
basis	O
.	O
</s>
<s>
This	O
protocol	O
is	O
truly	O
based	O
on	O
source	B-Protocol
routing	I-Protocol
whereby	O
all	O
the	O
routing	B-Protocol
information	I-Protocol
is	O
maintained	O
(	O
continually	O
updated	O
)	O
at	O
mobile	O
nodes	O
.	O
</s>
<s>
If	O
the	O
route	O
is	O
in	O
the	O
Destination	O
Node	O
's	O
route	O
cache	B-General_Concept
,	O
the	O
route	O
would	O
be	O
used	O
.	O
</s>
<s>
In	O
the	O
event	O
of	O
fatal	O
transmission	O
,	O
the	O
Route	O
Maintenance	O
Phase	O
is	O
initiated	O
whereby	O
the	O
Route	O
Error	O
packets	B-Protocol
are	O
generated	O
at	O
a	O
node	O
.	O
</s>
<s>
The	O
erroneous	O
hop	O
will	O
be	O
removed	O
from	O
the	O
node	O
's	O
route	O
cache	B-General_Concept
;	O
all	O
routes	O
containing	O
the	O
hop	O
are	O
truncated	O
at	O
that	O
point	O
.	O
</s>
<s>
For	O
information	O
on	O
other	O
similar	O
protocols	O
,	O
see	O
the	O
list	B-Protocol
of	I-Protocol
ad	I-Protocol
hoc	I-Protocol
routing	I-Protocol
protocols	I-Protocol
.	O
</s>
<s>
Dynamic	B-Device
source	I-Device
routing	I-Device
protocol	O
(	O
DSR	O
)	O
is	O
an	O
on-demand	O
protocol	O
designed	O
to	O
restrict	O
the	O
bandwidth	O
consumed	O
by	O
control	O
packets	B-Protocol
in	O
ad	O
hoc	O
wireless	O
networks	O
by	O
eliminating	O
the	O
periodic	O
table-update	O
messages	O
required	O
in	O
the	O
table-driven	O
approach	O
.	O
</s>
<s>
The	O
major	O
difference	O
between	O
this	O
and	O
the	O
other	O
on-demand	O
routing	B-Protocol
protocols	O
is	O
that	O
it	O
is	O
beacon-less	O
and	O
hence	O
does	O
not	O
require	O
periodic	O
hello	O
packet	B-Protocol
(	O
beacon	O
)	O
transmissions	O
,	O
which	O
are	O
used	O
by	O
a	O
node	O
to	O
inform	O
its	O
neighbors	O
of	O
its	O
presence	O
.	O
</s>
<s>
The	O
basic	O
approach	O
of	O
this	O
protocol	O
(	O
and	O
all	O
other	O
on-demand	O
routing	B-Protocol
protocols	O
)	O
during	O
the	O
route	O
construction	O
phase	O
is	O
to	O
establish	O
a	O
route	O
by	O
flooding	O
RouteRequest	O
packets	B-Protocol
in	O
the	O
network	O
.	O
</s>
<s>
The	O
destination	O
node	O
,	O
on	O
receiving	O
a	O
RouteRequest	O
packet	B-Protocol
,	O
responds	O
by	O
sending	O
a	O
RouteReply	O
packet	B-Protocol
back	O
to	O
the	O
source	O
,	O
which	O
carries	O
the	O
route	O
traversed	O
by	O
the	O
RouteRequest	O
packet	B-Protocol
received	O
.	O
</s>
<s>
When	O
it	O
has	O
data	B-Protocol
packets	I-Protocol
to	O
be	O
sent	O
to	O
that	O
destination	O
,	O
it	O
initiates	O
a	O
RouteRequest	O
packet	B-Protocol
.	O
</s>
<s>
Each	O
node	O
,	O
upon	O
receiving	O
a	O
RouteRequest	O
packet	B-Protocol
,	O
rebroadcasts	O
the	O
packet	B-Protocol
to	O
its	O
neighbors	O
if	O
it	O
has	O
not	O
forwarded	O
it	O
already	O
,	O
provided	O
that	O
the	O
node	O
is	O
not	O
the	O
destination	O
node	O
and	O
that	O
the	O
packet	B-Protocol
’s	O
time	B-Protocol
to	I-Protocol
live	I-Protocol
(	O
TTL	O
)	O
counter	O
has	O
not	O
been	O
exceeded	O
.	O
</s>
<s>
A	O
node	O
,	O
upon	O
receiving	O
a	O
RouteRequest	O
packet	B-Protocol
,	O
checks	O
the	O
sequence	O
number	O
on	O
the	O
packet	B-Protocol
before	O
forwarding	O
it	O
.	O
</s>
<s>
The	O
packet	B-Protocol
is	O
forwarded	O
only	O
if	O
it	O
is	O
not	O
a	O
duplicate	O
RouteRequest	O
.	O
</s>
<s>
The	O
sequence	O
number	O
on	O
the	O
packet	B-Protocol
is	O
used	O
to	O
prevent	O
loop	O
formations	O
and	O
to	O
avoid	O
multiple	O
transmissions	O
of	O
the	O
same	O
RouteRequest	O
by	O
an	O
intermediate	O
node	O
that	O
receives	O
it	O
through	O
multiple	O
paths	O
.	O
</s>
<s>
Thus	O
,	O
all	O
nodes	O
except	O
the	O
destination	O
forward	O
a	O
RouteRequest	O
packet	B-Protocol
during	O
the	O
route	O
construction	O
phase	O
.	O
</s>
<s>
A	O
destination	O
node	O
,	O
after	O
receiving	O
the	O
first	O
RouteRequest	O
packet	B-Protocol
,	O
replies	O
to	O
the	O
source	O
node	O
through	O
the	O
reverse	O
path	O
the	O
RouteRequest	O
packet	B-Protocol
had	O
traversed	O
.	O
</s>
<s>
Nodes	O
can	O
also	O
learn	O
about	O
the	O
neighboring	O
routes	O
traversed	O
by	O
data	B-Protocol
packets	I-Protocol
if	O
operated	O
in	O
the	O
promiscuous	O
mode	O
(	O
the	O
mode	O
of	O
operation	O
in	O
which	O
a	O
node	O
can	O
receive	O
the	O
packets	B-Protocol
that	O
are	O
neither	O
broadcast	O
nor	O
addressed	O
to	O
itself	O
)	O
.	O
</s>
<s>
This	O
route	O
cache	B-General_Concept
is	O
also	O
used	O
during	O
the	O
route	O
construction	O
phase	O
.	O
</s>
<s>
The	O
intermediate	O
nodes	O
also	O
utilize	O
the	O
route	O
cache	B-General_Concept
information	O
efficiently	O
to	O
reduce	O
the	O
control	O
overhead	O
.	O
</s>
<s>
Stale	O
route	O
cache	B-General_Concept
information	O
could	O
also	O
result	O
in	O
inconsistencies	O
during	O
the	O
route	O
reconstruction	O
phase	O
.	O
</s>
<s>
Also	O
,	O
considerable	O
routing	B-Protocol
overhead	O
is	O
involved	O
due	O
to	O
the	O
source-routing	O
mechanism	O
employed	O
in	O
DSR	O
.	O
</s>
<s>
This	O
routing	B-Protocol
overhead	O
is	O
directly	O
proportional	O
to	O
the	O
path	O
length	O
.	O
</s>
