<s>
The	O
media	B-Protocol
gateway	I-Protocol
control	I-Protocol
protocol	I-Protocol
architecture	O
is	O
a	O
methodology	O
of	O
providing	O
telecommunication	O
services	O
using	O
decomposed	O
multimedia	O
gateways	O
for	O
transmitting	O
telephone	O
calls	O
between	O
an	O
Internet	B-Protocol
Protocol	I-Protocol
network	O
and	O
traditional	O
analog	O
facilities	O
of	O
the	O
public	O
switched	O
telephone	O
network	O
(	O
PSTN	O
)	O
.	O
</s>
<s>
The	O
architecture	O
was	O
originally	O
defined	O
in	O
RFC	O
2805	O
and	O
has	O
been	O
used	O
in	O
several	O
prominent	O
voice	B-Application
over	I-Application
IP	I-Application
(	O
VoIP	B-Application
)	O
protocol	O
implementations	O
,	O
such	O
as	O
the	O
Media	B-Protocol
Gateway	I-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
MGCP	B-Protocol
)	O
and	O
Megaco	O
(	O
H.248	O
)	O
,	O
both	O
successors	O
to	O
the	O
obsolete	O
Simple	B-Protocol
Gateway	I-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
SGCP	B-Protocol
)	O
.	O
</s>
<s>
The	O
architecture	O
divides	O
the	O
functions	O
required	O
for	O
the	O
integration	O
of	O
traditional	O
telecommunication	O
networks	O
and	O
modern	O
packet	B-Protocol
networks	I-Protocol
into	O
several	O
physical	O
and	O
logical	O
components	O
,	O
notably	O
the	O
media	O
gateway	O
,	O
the	O
media	B-Protocol
gateway	I-Protocol
controller	I-Protocol
,	O
and	O
signaling	O
gateways	O
.	O
</s>
<s>
The	O
interaction	O
between	O
the	O
media	O
gateway	O
and	O
its	O
controller	O
is	O
defined	O
in	O
the	O
media	B-Protocol
gateway	I-Protocol
control	I-Protocol
protocol	I-Protocol
.	O
</s>
<s>
Media	O
gateway	O
protocols	O
were	O
developed	O
based	O
on	O
the	O
Internet	B-Protocol
model	I-Protocol
of	O
networking	O
,	O
the	O
Internet	B-Protocol
Protocol	I-Protocol
Suite	I-Protocol
,	O
and	O
are	O
referred	O
to	O
as	O
device	O
control	O
protocols	O
.	O
</s>
<s>
Depending	O
on	O
the	O
size	O
and	O
purpose	O
of	O
the	O
gateway	O
,	O
it	O
may	O
allow	O
IP-originated	O
calls	O
to	O
terminate	O
to	O
the	O
PSTN	O
or	O
vice	O
versa	O
,	O
or	O
may	O
simply	O
provide	O
a	O
means	O
to	O
connect	O
a	O
telephone	O
to	O
a	O
telecommunication	O
system	O
via	O
an	O
IP	B-Protocol
network	I-Protocol
.	O
</s>
<s>
Originally	O
,	O
gateways	O
were	O
viewed	O
as	O
monolithic	O
devices	O
that	O
had	O
call	O
control	O
,	O
using	O
protocols	O
such	O
as	O
H.323	B-Protocol
and	O
the	O
Session	B-Application
Initiation	I-Application
Protocol	I-Application
,	O
and	O
hardware	O
required	O
to	O
control	O
the	O
PSTN	O
interface	O
.	O
</s>
<s>
In	O
1998	O
,	O
the	O
idea	O
of	O
splitting	O
the	O
gateway	O
into	O
two	O
logical	O
parts	O
was	O
proposed	O
:	O
one	O
part	O
,	O
which	O
contains	O
the	O
call	O
control	O
logic	O
,	O
is	O
called	O
the	O
media	B-Protocol
gateway	I-Protocol
controller	I-Protocol
(	O
MGC	O
)	O
or	O
call	O
agent	O
(	O
CA	O
)	O
,	O
and	O
the	O
other	O
part	O
,	O
which	O
interfaces	O
with	O
the	O
PSTN	O
,	O
is	O
called	O
the	O
media	O
gateway	O
(	O
MG	O
)	O
.	O
</s>
<s>
With	O
this	O
functional	O
split	O
,	O
a	O
new	O
interface	O
existed	O
between	O
the	O
MGC	O
and	O
the	O
MG	O
,	O
requiring	O
a	O
framework	O
for	O
communication	O
between	O
the	O
elements	O
,	O
resulting	O
in	O
the	O
media	B-Protocol
gateway	I-Protocol
control	I-Protocol
protocol	I-Protocol
architecture	O
.	O
</s>
<s>
SIP	O
and	O
H.323	B-Protocol
are	O
signaling	O
protocols	O
,	O
while	O
media	B-Protocol
gateway	I-Protocol
control	I-Protocol
protocols	I-Protocol
are	O
device	O
control	O
protocols	O
.	O
</s>
<s>
The	O
architectural	O
difference	O
between	O
SIP	O
and	O
H.323	B-Protocol
,	O
and	O
the	O
media	B-Protocol
gateway	I-Protocol
control	I-Protocol
protocols	I-Protocol
is	O
that	O
the	O
relationships	O
between	O
entities	O
in	O
SIP	O
and	O
H.323	B-Protocol
are	O
peer-to-peer	O
,	O
while	O
the	O
relationships	O
between	O
entities	O
in	O
media	B-Protocol
gateway	I-Protocol
control	I-Protocol
protocols	I-Protocol
use	O
the	O
master/slave	B-Operating_System
(	O
technology	O
)	O
model	O
.	O
</s>
<s>
SIP	O
and	O
H.323	B-Protocol
handle	O
call	O
setup	O
,	O
connection	O
,	O
management	O
,	O
and	O
tear-down	O
of	O
calls	O
between	O
like	O
interfaces	O
,	O
whereas	O
media	B-Protocol
gateway	I-Protocol
control	I-Protocol
protocols	I-Protocol
define	O
the	O
mechanisms	O
of	O
setup	O
of	O
media	O
paths	O
and	O
streams	O
between	O
IP	O
and	O
other	O
networks	O
.	O
</s>
<s>
Several	O
implementations	O
of	O
the	O
media	B-Protocol
gateway	I-Protocol
control	I-Protocol
protocol	I-Protocol
are	O
in	O
common	O
use	O
.	O
</s>
<s>
The	O
Media	B-Protocol
Gateway	I-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
MGCP	B-Protocol
)	O
was	O
first	O
described	O
in	O
RFC	O
2705	O
,	O
and	O
revised	O
in	O
RFC	O
3435	O
.	O
</s>
<s>
Although	O
similar	O
in	O
architecture	O
,	O
MGCP	B-Protocol
and	O
H.248/Megaco	O
are	O
distinctly	O
different	O
protocols	O
and	O
are	O
not	O
interoperable	O
.	O
</s>
<s>
H.248/Megaco	O
and	O
MGCP	B-Protocol
protocols	O
are	O
complementary	O
to	O
H.323	B-Protocol
and	O
SIP	O
,	O
which	O
both	O
may	O
be	O
referred	O
to	O
as	O
intelligent	O
endpoint	O
protocols	O
.	O
</s>
<s>
H.248/Megaco	O
and	O
MGCP	B-Protocol
may	O
be	O
referred	O
to	O
as	O
device	O
control	O
protocols	O
.	O
</s>
<s>
Other	O
media	B-Protocol
gateway	I-Protocol
control	I-Protocol
protocols	I-Protocol
include	O
the	O
predecessors	O
of	O
MGCP	B-Protocol
,	O
namely	O
the	O
Simple	B-Protocol
Gateway	I-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
SGCP	B-Protocol
)	O
and	O
the	O
Internet	B-Protocol
Protocol	I-Protocol
Device	I-Protocol
Control	I-Protocol
(	O
IPDC	O
)	O
.	O
</s>
<s>
A	O
proprietary	O
protocol	O
using	O
a	O
similar	O
architecture	O
is	O
the	O
Cisco	O
Skinny	B-Protocol
Client	I-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
SCCP	O
)	O
.	O
</s>
<s>
One	O
of	O
the	O
technologies	O
usually	O
is	O
a	O
packet	B-Protocol
,	O
frame	O
,	O
or	O
cell	O
network	O
.	O
</s>
<s>
For	O
example	O
,	O
it	O
may	O
convert	O
voice	O
telephone	O
calls	O
between	O
a	O
traditional	O
analog	O
telephone	O
to	O
a	O
digital	O
format	O
for	O
transmission	O
over	O
an	O
Internet	B-Protocol
Protocol	I-Protocol
(	O
IP	O
)	O
network	O
,	O
to	O
facilitate	O
voice	B-Application
over	I-Application
IP	I-Application
communications	O
.	O
</s>
<s>
A	O
media	B-Protocol
gateway	I-Protocol
controller	I-Protocol
(	O
MGC	O
)	O
,	O
also	O
known	O
as	O
a	O
call	O
agent	O
,	O
controls	O
the	O
media	O
gateways	O
.	O
</s>
<s>
The	O
Simple	B-Protocol
Gateway	I-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
SGCP	B-Protocol
)	O
and	O
the	O
Internet	B-Protocol
Protocol	I-Protocol
Device	I-Protocol
Control	I-Protocol
(	O
IPDC	O
)	O
have	O
been	O
replaced	O
by	O
the	O
Media	B-Protocol
Gateway	I-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
MGCP	B-Protocol
)	O
and	O
Megaco	O
,	O
which	O
is	O
also	O
known	O
as	O
H.248	O
.	O
</s>
<s>
7	O
(	O
SS7	O
)	O
,	O
for	O
interconnection	O
with	O
the	O
traditional	O
telephone	O
system	O
,	O
H.323	B-Protocol
,	O
and	O
the	O
Session	B-Application
Initiation	I-Application
Protocol	I-Application
(	O
SIP	O
)	O
.	O
</s>
<s>
MGCP	B-Protocol
emerged	O
from	O
a	O
group	O
now	O
called	O
the	O
International	O
SoftSwitch	B-Device
Consortium	O
.	O
</s>
<s>
In	O
July	O
1998	O
,	O
Telcordia	O
(	O
Bellcore	O
)	O
and	O
Cisco	O
Systems	O
created	O
a	O
protocol	O
called	O
Simple	B-Protocol
Gateway	I-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
SGCP	B-Protocol
)	O
for	O
controlling	O
Telephony	O
Gateways	O
from	O
external	O
call	O
control	O
elements	O
.	O
</s>
<s>
The	O
TAC	O
proposed	O
a	O
device	O
protocol	O
called	O
Internet	B-Protocol
Protocol	I-Protocol
Device	I-Protocol
Control	I-Protocol
(	O
IPDC	O
)	O
in	O
August	O
1998	O
.	O
</s>
<s>
IPDC	O
was	O
intended	O
to	O
be	O
used	O
between	O
a	O
media	O
gateway	O
and	O
a	O
media	B-Protocol
gateway	I-Protocol
controller	I-Protocol
.	O
</s>
<s>
Media	O
gateway	O
were	O
capable	O
of	O
acting	O
as	O
a	O
voice	B-Application
over	I-Application
IP	I-Application
gateway	O
,	O
voice	O
over	O
ATM	O
gateway	O
,	O
dialup	O
modem	O
media	O
gateway	O
,	O
circuit	O
switch	O
,	O
or	O
cross	O
-	O
connect	O
.	O
</s>
<s>
In	O
October	O
1998	O
,	O
Simple	B-Protocol
Gateway	I-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
SGCP	B-Protocol
)	O
was	O
combined	O
with	O
Internet	B-Protocol
Protocol	I-Protocol
Device	I-Protocol
Control	I-Protocol
(	O
IPDC	O
)	O
,	O
resulting	O
in	O
MGCP	B-Protocol
.	O
</s>
<s>
MGCP	B-Protocol
was	O
submitted	O
to	O
the	O
IETF	O
’s	O
MeGaCo	O
working	O
group	O
in	O
October	O
1998	O
.	O
</s>
<s>
IETF	O
merged	O
MGCP	B-Protocol
and	O
MDCP	O
and	O
proposed	O
a	O
new	O
and	O
improved	O
protocol	O
named	O
MeGaCo	O
protocol	O
(	O
also	O
known	O
as	O
H.248	O
)	O
in	O
April	O
1999	O
.	O
</s>
<s>
The	O
first	O
"	O
official	O
"	O
version	O
of	O
MGCP	B-Protocol
is	O
defined	O
in	O
RFC	O
2705	O
as	O
informational	O
.	O
</s>
<s>
MGCP	B-Protocol
currently	O
is	O
purely	O
informational	O
rather	O
than	O
a	O
standard-track	O
protocol	O
,	O
although	O
it	O
includes	O
protocol	O
specification	O
.	O
</s>
<s>
Even	O
while	O
MGCP	B-Protocol
was	O
still	O
an	O
Internet	O
Draft	O
,	O
many	O
companies	O
developed	O
included	O
MGCP	B-Protocol
with	O
their	O
own	O
development	O
rather	O
than	O
wait	O
for	O
a	O
standardized	O
protocol	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
decision	O
was	O
made	O
to	O
release	O
MGCP	B-Protocol
as	O
an	O
informational	O
RFC	O
in	O
October	O
1999	O
.	O
</s>
<s>
IETF	O
development	O
of	O
MGCP	B-Protocol
has	O
stopped	O
,	O
although	O
companies	O
continue	O
to	O
implement	O
MGCP	B-Protocol
,	O
driven	O
by	O
the	O
efforts	O
of	O
the	O
PacketCable	B-Device
development	O
of	O
Network-based	B-Protocol
Call	I-Protocol
Signaling	I-Protocol
.	O
</s>
<s>
Further	O
standardization	O
of	O
MGCP	B-Protocol
effort	O
was	O
pursued	O
in	O
the	O
IETF	O
,	O
in	O
the	O
MEGACO	O
working	O
group	O
,	O
and	O
also	O
in	O
the	O
ITU-T/SG16	O
,	O
under	O
the	O
code	O
name	O
H.GCP	O
.	O
</s>
<s>
The	O
motivation	O
of	O
Megaco	O
was	O
the	O
need	O
to	O
satisfy	O
various	O
requirements	O
that	O
were	O
not	O
addressed	O
properly	O
by	O
MGCP	B-Protocol
.	O
</s>
<s>
Megaco	O
is	O
an	O
evolution	O
of	O
MGCP	B-Protocol
.	O
</s>
<s>
It	O
is	O
a	O
combination	O
of	O
MGCP	B-Protocol
and	O
MDCP	O
,	O
and	O
was	O
published	O
as	O
Standard	O
in	O
RFC	O
3015	O
in	O
November	O
2000	O
.	O
</s>
<s>
Megaco	O
and	O
MGCP	B-Protocol
are	O
different	O
and	O
not	O
interoperable	O
.	O
</s>
<s>
Both	O
H.248	O
and	O
MGCP	B-Protocol
are	O
protocol	O
for	O
controlling	O
media	O
gateways	O
using	O
a	O
media	B-Protocol
gateway	I-Protocol
controller	I-Protocol
or	O
call	O
agent	O
.	O
</s>
<s>
In	O
a	O
VoIP	B-Application
system	O
,	O
H.248	O
and	O
MGCP	B-Protocol
are	O
used	O
with	O
SIP	O
or	O
H.323	B-Protocol
.	O
</s>
<s>
SIP	O
or	O
H.323	B-Protocol
provide	O
intercommunication	O
between	O
gateway	O
controllers	O
and	O
MGCP	B-Protocol
is	O
used	O
to	O
manage	O
media	O
establishment	O
in	O
the	O
media	O
gateways	O
.	O
</s>
