<s>
Dynamic	B-Protocol
Packet	I-Protocol
Transport	I-Protocol
(	O
DPT	O
)	O
is	O
a	O
Cisco	O
transport	B-Architecture
protocol	I-Architecture
designed	O
for	O
use	O
in	O
optical	B-Architecture
fiber	I-Architecture
ring	B-Architecture
networks	I-Architecture
.	O
</s>
<s>
In	O
overview	O
,	O
it	O
is	O
quite	O
similar	O
to	O
POS	B-Protocol
and	O
DTM	B-Protocol
.	O
</s>
<s>
It	O
was	O
one	O
of	O
the	O
major	O
influences	O
on	O
the	O
Resilient	O
Packet	B-Protocol
Ring/802.17	O
standard	O
.	O
</s>
<s>
DPT	O
as	O
opposed	O
to	O
POS	B-Protocol
or	O
normal	O
SONET/SDH	B-Protocol
is	O
able	O
to	O
use	O
both	O
rings	O
at	O
the	O
same	O
time	O
whereas	O
POS	B-Protocol
only	O
uses	O
one	O
ring	O
under	O
normal	O
circumstances	O
but	O
switches	O
to	O
the	O
second	O
upon	O
failure	O
of	O
the	O
first	O
.	O
</s>
<s>
Cisco	O
claims	O
that	O
DPT	O
can	O
run	O
with	O
double	O
the	O
bit-rate	O
of	O
POS	B-Protocol
due	O
to	O
this	O
characteristic	O
.	O
</s>
<s>
DPT	O
is	O
not	O
a	O
PPP	B-Protocol
whereas	O
POS	B-Protocol
is	O
,	O
this	O
means	O
that	O
traffic	O
between	O
two	O
nodes	O
of	O
a	O
DPT	O
ring	O
does	O
not	O
affect	O
intermediate	O
nodes	O
.	O
</s>
<s>
With	O
the	O
introduction	O
of	O
DPT	O
came	O
the	O
introduction	O
of	O
another	O
Cisco	O
developed	O
MAC	O
layer	O
protocol	O
,	O
Spatial	B-Protocol
Reuse	I-Protocol
Protocol	I-Protocol
or	O
SRP	O
.	O
</s>
<s>
Both	O
control	O
packets	B-Protocol
,	O
and	O
data	B-Protocol
packets	I-Protocol
are	O
transmitted	O
on	O
both	O
rings	O
in	O
order	O
to	O
maintain	O
connectivity	O
and	O
full	O
bandwidth	O
utilization	O
in	O
normal	O
situations	O
;	O
but	O
once	O
a	O
failure	O
occurs	O
,	O
the	O
control	O
data	O
will	O
notify	O
the	O
applicable	O
routers	O
of	O
the	O
failure	O
and	O
all	O
the	O
routers	O
will	O
switch	O
to	O
using	O
only	O
their	O
active	O
interfaces	O
for	O
data	O
and	O
control	O
packets	B-Protocol
.	O
</s>
<s>
The	O
structure	O
of	O
a	O
DPT	O
Packet	B-Protocol
is	O
quite	O
similar	O
to	O
that	O
of	O
Ethernet	O
.	O
</s>
<s>
It	O
contains	O
a	O
source	O
and	O
destination	O
MAC	O
address	O
(	O
both	O
48-bits	O
long	O
)	O
,	O
a	O
protocol	O
type	O
identifier	O
(	O
used	O
for	O
identifying	O
the	O
upper	O
layer	O
protocol	O
contained	O
in	O
the	O
payload	O
)	O
,	O
and	O
a	O
frame	B-Protocol
check	I-Protocol
sequence	I-Protocol
used	O
to	O
validate	O
the	O
data	O
.	O
</s>
<s>
This	O
means	O
that	O
the	O
DPT	O
protocol	O
can	O
operate	O
above	O
several	O
physical	O
mediums	O
such	O
as	O
SONET/SDH	B-Protocol
,	O
Gigabit	O
Ethernet	O
,	O
and	O
others	O
.	O
</s>
