<s>
Delay-tolerant	B-Protocol
networking	I-Protocol
(	O
DTN	O
)	O
is	O
an	O
approach	O
to	O
computer	B-Architecture
network	I-Architecture
architecture	O
that	O
seeks	O
to	O
address	O
the	O
technical	O
issues	O
in	O
heterogeneous	B-Protocol
networks	I-Protocol
that	O
may	O
lack	O
continuous	O
network	O
connectivity	O
.	O
</s>
<s>
Recently	O
,	O
the	O
term	O
disruption-tolerant	B-Protocol
networking	I-Protocol
has	O
gained	O
currency	O
in	O
the	O
United	O
States	O
due	O
to	O
support	O
from	O
DARPA	O
,	O
which	O
has	O
funded	O
many	O
DTN	O
projects	O
.	O
</s>
<s>
Disruption	O
may	O
occur	O
because	O
of	O
the	O
limits	O
of	O
wireless	O
radio	O
range	O
,	O
sparsity	O
of	O
mobile	O
nodes	B-Protocol
,	O
energy	O
resources	O
,	O
attack	O
,	O
and	O
noise	O
.	O
</s>
<s>
In	O
the	O
1970s	O
,	O
spurred	O
by	O
the	O
decreasing	O
size	O
of	O
computers	O
,	O
researchers	O
began	O
developing	O
technology	O
for	O
routing	B-Protocol
between	O
non-fixed	O
locations	O
of	O
computers	O
.	O
</s>
<s>
While	O
the	O
field	O
of	O
ad	O
hoc	O
routing	B-Protocol
was	O
inactive	O
throughout	O
the	O
1980s	O
,	O
the	O
widespread	O
use	O
of	O
wireless	O
protocols	O
reinvigorated	O
the	O
field	O
in	O
the	O
1990s	O
as	O
mobile	B-General_Concept
ad	I-General_Concept
hoc	I-General_Concept
networking	I-General_Concept
(	O
MANET	B-General_Concept
)	O
and	O
vehicular	B-Device
ad	I-Device
hoc	I-Device
networking	I-Device
became	O
areas	O
of	O
increasing	O
interest	O
.	O
</s>
<s>
Concurrently	O
with	O
(	O
but	O
separate	O
from	O
)	O
the	O
MANET	B-General_Concept
activities	O
,	O
DARPA	O
had	O
funded	O
NASA	O
,	O
MITRE	O
and	O
others	O
to	O
develop	O
a	O
proposal	O
for	O
the	O
Interplanetary	O
Internet	O
(	O
IPN	O
)	O
.	O
</s>
<s>
In	O
2002	O
,	O
Kevin	O
Fall	O
started	O
to	O
adapt	O
some	O
of	O
the	O
ideas	O
in	O
the	O
IPN	O
design	O
to	O
terrestrial	O
networks	O
and	O
coined	O
the	O
term	O
delay-tolerant	B-Protocol
networking	I-Protocol
and	O
the	O
DTN	O
acronym	O
.	O
</s>
<s>
The	O
mid-2000s	O
brought	O
about	O
increased	O
interest	O
in	O
DTNs	O
,	O
including	O
a	O
growing	O
number	O
of	O
academic	O
conferences	O
on	O
delay	O
and	O
disruption-tolerant	B-Protocol
networking	I-Protocol
,	O
and	O
growing	O
interest	O
in	O
combining	O
work	O
from	O
sensor	O
networks	O
and	O
MANETs	B-General_Concept
with	O
the	O
work	O
on	O
DTN	O
.	O
</s>
<s>
This	O
field	O
saw	O
many	O
optimizations	O
on	O
classic	O
ad	O
hoc	O
and	O
delay-tolerant	B-Protocol
networking	I-Protocol
algorithms	O
and	O
began	O
to	O
examine	O
factors	O
such	O
as	O
security	O
,	O
reliability	O
,	O
verifiability	O
,	O
and	O
other	O
areas	O
of	O
research	O
that	O
are	O
well	O
understood	O
in	O
traditional	O
computer	B-Architecture
networking	I-Architecture
.	O
</s>
<s>
In	O
these	O
challenging	O
environments	O
,	O
popular	O
ad	O
hoc	O
routing	B-Protocol
protocols	O
such	O
as	O
AODV	B-Device
and	O
DSR	B-Device
fail	O
to	O
establish	O
routes	O
.	O
</s>
<s>
However	O
,	O
when	O
instantaneous	O
end-to-end	O
paths	O
are	O
difficult	O
or	O
impossible	O
to	O
establish	O
,	O
routing	B-Protocol
protocols	O
must	O
take	O
to	O
a	O
"	O
store	B-Protocol
and	I-Protocol
forward	I-Protocol
"	O
approach	O
,	O
where	O
data	O
is	O
incrementally	O
moved	O
and	O
stored	O
throughout	O
the	O
network	O
in	O
hopes	O
that	O
it	O
will	O
eventually	O
reach	O
its	O
destination	O
.	O
</s>
<s>
Commonly	O
known	O
as	O
the	O
Bundle	B-Protocol
Protocol	I-Protocol
,	O
this	O
protocol	O
defines	O
a	O
series	O
of	O
contiguous	O
data	O
blocks	O
as	O
a	O
bundle	O
—	O
where	O
each	O
bundle	O
contains	O
enough	O
semantic	O
information	O
to	O
allow	O
the	O
application	O
to	O
make	O
progress	O
where	O
an	O
individual	O
block	O
may	O
not	O
.	O
</s>
<s>
Bundles	O
are	O
routed	B-Protocol
in	O
a	O
store	B-Protocol
and	I-Protocol
forward	I-Protocol
manner	O
between	O
participating	O
nodes	B-Protocol
over	O
varied	O
network	O
transport	O
technologies	O
(	O
including	O
both	O
IP	B-Protocol
and	O
non-IP	O
based	O
transports	O
)	O
.	O
</s>
<s>
The	O
bundle	O
architecture	O
therefore	O
operates	O
as	O
an	O
overlay	B-Architecture
network	I-Architecture
,	O
providing	O
a	O
new	O
naming	O
architecture	O
based	O
on	O
Endpoint	O
Identifiers	O
(	O
EIDs	O
)	O
and	O
coarse-grained	O
class	B-Device
of	I-Device
service	I-Device
offerings	O
.	O
</s>
<s>
Due	O
to	O
the	O
store	B-Protocol
and	I-Protocol
forward	I-Protocol
nature	O
of	O
delay-tolerant	O
protocols	O
,	O
routing	B-Protocol
solutions	O
for	O
delay-tolerant	B-Protocol
networks	I-Protocol
can	O
benefit	O
from	O
exposure	O
to	O
application-layer	O
information	O
.	O
</s>
<s>
Bundle	B-Protocol
protocols	I-Protocol
collect	O
application	O
data	O
into	O
bundles	O
that	O
can	O
be	O
sent	O
across	O
heterogeneous	B-Protocol
network	I-Protocol
configurations	O
with	O
high-level	O
service	O
guarantees	O
.	O
</s>
<s>
The	O
service	O
guarantees	O
are	O
generally	O
set	O
by	O
the	O
application	O
level	O
,	O
and	O
the	O
RFC	O
5050	O
Bundle	B-Protocol
Protocol	I-Protocol
specification	O
includes	O
"	O
bulk	O
"	O
,	O
"	O
normal	O
"	O
,	O
and	O
"	O
expedited	O
"	O
markings	O
.	O
</s>
<s>
The	O
Bundle	B-Protocol
Protocol	I-Protocol
for	O
CCSDS	O
is	O
a	O
profile	O
of	O
RFC5050	O
specifically	O
addressing	O
the	O
Bundle	B-Protocol
Protocol	I-Protocol
's	O
utility	O
for	O
data	O
communication	O
in	O
space	O
missions	O
.	O
</s>
<s>
Addressing	O
security	O
issues	O
has	O
been	O
a	O
major	O
focus	O
of	O
the	O
bundle	B-Protocol
protocol	I-Protocol
.	O
</s>
<s>
Possible	O
attacks	O
take	O
the	O
form	O
of	O
nodes	B-Protocol
behaving	O
as	O
a	O
"	O
black	O
hole	O
"	O
or	O
a	O
"	O
flooder	O
"	O
.	O
</s>
<s>
Security	O
concerns	O
for	O
delay-tolerant	B-Protocol
networks	I-Protocol
vary	O
depending	O
on	O
the	O
environment	O
and	O
application	O
,	O
though	O
authentication	O
and	O
privacy	O
are	O
often	O
critical	O
.	O
</s>
<s>
Solutions	O
have	O
typically	O
been	O
modified	O
from	O
mobile	B-Protocol
ad	I-Protocol
hoc	I-Protocol
network	I-Protocol
and	O
distributed	O
security	O
research	O
,	O
such	O
as	O
the	O
use	O
of	O
distributed	O
certificate	O
authorities	O
and	O
PKI	B-Architecture
schemes	O
.	O
</s>
<s>
information	O
encrypted	O
with	O
their	O
public	O
identifier	O
;	O
and	O
2	O
)	O
the	O
use	O
of	O
tamper-evident	O
tables	O
with	O
a	O
gossiping	B-Operating_System
protocol	I-Operating_System
;	O
</s>
<s>
There	O
are	O
a	O
number	O
of	O
implementations	O
of	O
the	O
Bundle	B-Protocol
Protocol	I-Protocol
:	O
</s>
<s>
NASA	O
Interplanetary	O
Overlay	B-Architecture
Network	I-Architecture
(	O
ION	O
)	O
—	O
Written	O
in	O
C	O
;	O
designed	O
to	O
run	O
on	O
a	O
wide	O
variety	O
of	O
platforms	O
;	O
conforms	O
to	O
restrictions	O
for	O
space	O
flight	O
software	O
(	O
e.g.	O
</s>
<s>
—	O
C++	O
-	O
based	O
;	O
designed	O
to	O
be	O
a	O
reference	O
/	O
learning	O
/	O
teaching	O
implementation	O
of	O
the	O
Bundle	B-Protocol
Protocol	I-Protocol
.	O
</s>
<s>
Currently	O
used	O
in	O
ISS	B-Device
operations	O
.	O
</s>
<s>
NASA	O
Interplanetary	O
Overlay	B-Architecture
Network	I-Architecture
(	O
ION	O
)	O
—	O
C	O
;	O
intended	O
to	O
be	O
usable	O
in	O
embedded	O
environments	O
including	O
spacecraft	O
flight	O
computers	O
.	O
</s>
<s>
Currently	O
used	O
in	O
ISS	B-Device
operations	O
.	O
</s>
<s>
-	O
C	O
;	O
A	O
Bundle	B-Protocol
Protocol	I-Protocol
library	O
and	O
associated	O
applications	O
by	O
Goddard	O
Space	O
Flight	O
Center	O
.	O
</s>
<s>
Intended	O
for	O
general	O
use	O
,	O
particularly	O
in	O
space	O
flight	O
applications	O
,	O
integration	O
with	O
(	O
core	O
Flight	O
System	O
)	O
,	O
and	O
other	O
applications	O
where	O
store-and-forward	B-Protocol
capabilities	O
are	O
needed	O
.	O
</s>
<s>
Some	O
research	O
efforts	O
look	O
at	O
DTN	O
for	O
the	O
Interplanetary	O
Internet	O
by	O
examining	O
use	O
of	O
the	O
Bundle	B-Protocol
Protocol	I-Protocol
in	O
space	O
:	O
</s>
<s>
The	O
project	O
at	O
the	O
University	O
of	O
Surrey	O
,	O
which	O
was	O
the	O
first	O
to	O
test	O
the	O
bundle	B-Protocol
protocol	I-Protocol
in	O
space	O
on	O
the	O
UK-DMC	O
Disaster	O
Monitoring	O
Constellation	O
satellite	O
in	O
2008	O
.	O
</s>
<s>
BioServe	O
Space	O
Technologies	O
,	O
one	O
of	O
the	O
first	O
payload	O
developers	O
to	O
adopt	O
the	O
DTN	O
technology	O
,	O
has	O
utilized	O
their	O
CGBA	O
(	O
Commercial	O
Generic	O
Bioprocessing	O
Apparatus	O
)	O
payloads	O
on	O
board	O
the	O
ISS	B-Device
,	O
which	O
provide	O
computational/communications	O
platforms	O
,	O
to	O
implement	O
the	O
DTN	O
protocol	O
.	O
</s>
