<s>
IP	B-Protocol
exchange	I-Protocol
or	O
(	O
IPX	B-Protocol
)	O
is	O
a	O
telecommunications	O
interconnection	B-Architecture
model	O
for	O
the	O
exchange	O
of	O
IP	B-Protocol
based	O
traffic	O
between	O
customers	O
of	O
separate	O
mobile	O
and	O
fixed	O
operators	O
as	O
well	O
as	O
other	O
types	O
of	O
service	O
provider	O
(	O
such	O
as	O
ISP	O
)	O
,	O
via	O
IP	B-Protocol
based	O
Network-to-Network	B-Protocol
Interface	I-Protocol
.	O
</s>
<s>
IPX	B-Protocol
is	O
developed	O
by	O
the	O
GSM	O
Association	O
.	O
</s>
<s>
IPX	B-Protocol
is	O
not	O
intended	O
to	O
replace	O
or	O
compete	O
with	O
the	O
Internet	O
but	O
it	O
does	O
offer	O
an	O
alternative	O
option	O
for	O
service	O
providers	O
.	O
</s>
<s>
The	O
intent	O
of	O
IPX	B-Protocol
is	O
to	O
provide	O
interoperability	O
of	O
IP-based	O
services	O
between	O
all	O
service	O
provider	O
types	O
within	O
a	O
commercial	O
framework	O
that	O
enables	O
all	O
parties	O
in	O
the	O
value	O
chain	O
to	O
receive	O
a	O
commercial	O
return	O
.	O
</s>
<s>
It	O
may	O
not	O
be	O
evident	O
to	O
end-users	O
whether	O
their	O
service	O
provider	O
utilises	O
the	O
IPX	B-Protocol
model	O
or	O
not	O
,	O
however	O
,	O
the	O
ability	O
for	O
service	O
providers	O
to	O
differentiate	O
services	O
using	O
the	O
flexibility	O
provided	O
by	O
the	O
IPX	B-Protocol
model	O
,	O
ultimately	O
provides	O
for	O
end-user	O
choice	O
.	O
</s>
<s>
Traditionally	O
,	O
voice	O
traffic	O
interconnection	B-Architecture
between	O
different	O
operators	O
has	O
utilized	O
the	O
international	O
SS7/TDM	O
networks	O
.	O
</s>
<s>
However	O
,	O
lately	O
the	O
all-IP	O
paradigm	O
with	O
VoIP	B-Application
is	O
being	O
rapidly	O
introduced	O
by	O
different	O
operators	O
in	O
various	O
forms	O
,	O
such	O
as	O
IMS	B-Protocol
.	O
</s>
<s>
In	O
order	O
to	O
minimize	O
the	O
number	O
of	O
conversions	O
between	O
packet-switched	B-Protocol
voice	O
and	O
circuit-switched	B-Protocol
voice	O
there	O
is	O
a	O
clear	O
need	O
to	O
deploy	O
an	O
IP	B-Protocol
based	O
NNI	B-Protocol
(	O
Network-to-Network	B-Protocol
Interface	I-Protocol
)	O
and	O
therefore	O
an	O
IP	B-Protocol
based	O
interconnection	B-Architecture
network	O
.	O
</s>
<s>
It	O
is	O
also	O
evident	O
that	O
a	O
large	O
number	O
of	O
IP	B-Protocol
based	O
services	O
(	O
such	O
as	O
Presence	B-Protocol
or	O
IM	B-Application
)	O
simply	O
cannot	O
be	O
interconnected	O
using	O
a	O
SS7/TDM	O
network	O
,	O
further	O
increasing	O
the	O
need	O
for	O
evolution	O
into	O
an	O
IP	B-Protocol
based	O
interconnection	B-Architecture
network	O
.	O
</s>
<s>
Since	O
the	O
year	O
2000	O
GSM	O
operators	O
have	O
been	O
using	O
GRX	O
(	O
GPRS	O
Roaming	O
Exchange	O
)	O
network	O
for	O
routing	O
the	O
IP	B-Protocol
based	O
commercial	O
roaming	O
traffic	O
between	O
visited	O
and	O
home	O
operators	O
.	O
</s>
<s>
Mainly	O
2.5G	O
and	O
3G	B-Architecture
data	O
roaming	O
has	O
been	O
using	O
GRX	O
.	O
</s>
<s>
GRX	O
is	O
a	O
private	O
IP	B-Protocol
network	O
(	O
separated	O
from	O
the	O
internet	O
)	O
consisting	O
of	O
multiple	O
different	O
GRX	O
carriers	O
that	O
are	O
connected	O
to	O
each	O
other	O
via	O
peering	B-Protocol
points	I-Protocol
.	O
</s>
<s>
Even	O
though	O
the	O
GRX	O
environment	O
is	O
not	O
entirely	O
suitable	O
as	O
a	O
common	O
IP	B-Protocol
network	O
for	O
interconnection	B-Architecture
and	O
roaming	O
,	O
it	O
offers	O
a	O
good	O
starting	O
point	O
for	O
the	O
development	O
of	O
IPX	B-Protocol
.	O
</s>
<s>
IPX	B-Protocol
development	O
has	O
been	O
done	O
in	O
various	O
GSM	O
Association	O
projects	O
and	O
working	O
groups	O
since	O
2004	O
.	O
</s>
<s>
IP	B-Protocol
based	O
interconnection	B-Architecture
could	O
be	O
handled	O
with	O
Internet	O
,	O
since	O
Internet	O
natively	O
supports	O
the	O
IP	B-Protocol
protocol	I-Protocol
and	O
offers	O
the	O
required	O
global	O
connectivity	O
.	O
</s>
<s>
Naturally	O
operators	O
and	O
other	O
service	O
providers	O
are	O
free	O
to	O
choose	O
which	O
interconnection	B-Architecture
option	O
to	O
use	O
.	O
</s>
<s>
IPX	B-Protocol
architecture	O
consists	O
of	O
different	O
IPX	B-Protocol
Providers	O
connecting	O
together	O
via	O
an	O
IPX	B-Protocol
peering	B-Protocol
point	I-Protocol
for	O
traffic	O
exchange	O
.	O
</s>
<s>
Both	O
signaling	O
(	O
such	O
as	O
SIP	B-Application
)	O
and	O
media	O
(	O
such	O
as	O
RTP	B-Protocol
)	O
is	O
transported	O
end-to-end	O
in	O
accordance	O
with	O
IPX	B-Protocol
specifications	O
.	O
</s>
<s>
A	O
typical	O
end-to-end	O
path	O
of	O
traffic	O
in	O
a	O
fixed	O
to	O
mobile	O
interconnection	B-Architecture
scenario	O
is	O
illustrated	O
below	O
:	O
</s>
<s>
IPX	B-Protocol
offers	O
both	O
bilateral	O
and	O
multilateral	O
interconnection	B-Architecture
.	O
</s>
<s>
Bilateral	O
means	O
the	O
traditional	O
model	O
of	O
two	O
operators	O
bilaterally	O
writing	O
an	O
interconnection	B-Architecture
contract	O
prior	O
to	O
setting	O
up	O
a	O
connection	O
to	O
each	O
other	O
themselves	O
.	O
</s>
<s>
Multilateral	O
on	O
the	O
other	O
hand	O
means	O
that	O
the	O
IPX	B-Protocol
provider	O
to	O
some	O
extent	O
takes	O
care	O
of	O
both	O
handling	O
the	O
contract	O
and	O
connectivity	O
set-up	O
on	O
behalf	O
of	O
the	O
operators	O
.	O
</s>
<s>
Setting	O
up	O
bilateral	O
interconnection	B-Architecture
contracts	O
&	O
connections	O
with	O
tens/hundreds	O
of	O
other	O
operators	O
can	O
be	O
a	O
major	O
burden	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
multilateral	O
option	O
,	O
which	O
allows	O
an	O
operator	O
to	O
open	O
multiple	O
connections	O
by	O
making	O
a	O
single	O
contract	O
and	O
single	O
technical	O
connection	O
with	O
the	O
IPX	B-Protocol
provider	O
,	O
makes	O
interconnection	B-Architecture
deployment	O
easier	O
and	O
faster	O
.	O
</s>
<s>
Cascading	O
payments	O
–	O
the	O
cascading	O
responsibility	O
in	O
IPX	B-Protocol
means	O
each	O
party	O
is	O
responsible	O
for	O
the	O
performance	O
of	O
the	O
next	O
party	O
in	O
the	O
transit	O
chain	O
.	O
</s>
<s>
All	O
IP	B-Protocol
-	O
supporting	O
natively	O
IP	B-Protocol
based	O
protocols	O
(	O
such	O
as	O
SIP	B-Application
,	O
RTP	B-Protocol
,	O
GTP	B-Protocol
,	O
SMTP	B-Protocol
,	O
SCTP	B-Protocol
etc	O
.	O
)	O
</s>
<s>
Backwards	O
compatible	O
-	O
IPX	B-Protocol
specifications	O
are	O
compliant	O
with	O
the	O
existing	O
specifications	O
and	O
recommendations	O
.	O
</s>
<s>
NNI	B-Protocol
only	O
-	O
IPX	B-Protocol
requirements	O
address	O
NNI	B-Protocol
only	O
.	O
</s>
<s>
Principles	O
of	O
IPX	B-Protocol
have	O
been	O
successively	O
tested	O
and	O
validated	O
by	O
GSMA	O
.	O
</s>
<s>
From	O
2004	O
onwards	O
,	O
GSMA	O
SIP	B-Application
Trials	O
tested	O
IP-based	O
NNI	B-Protocol
with	O
numerous	O
IMS	B-Protocol
based	O
services	O
.	O
</s>
<s>
IPX	B-Protocol
Pre-commercial	O
Implementation	O
trials	O
have	O
been	O
ongoing	O
since	O
April	O
2007	O
focusing	O
especially	O
on	O
packet	B-Protocol
switched	I-Protocol
voice	O
service	O
.	O
</s>
<s>
GSMA	O
press	O
release	O
in	O
February	O
2008	O
explains	O
that	O
IPX	B-Protocol
trials	O
have	O
been	O
completed	O
successfully	O
.	O
</s>
<s>
A	O
number	O
of	O
international	O
carriers	O
are	O
preparing	O
to	O
roll	O
out	O
IPX	B-Protocol
services	O
,	O
such	O
as	O
IPX	B-Protocol
Voice	O
,	O
Belgacom	O
International	O
Carrier	O
Services	O
,	O
BT	O
,	O
CITIC	O
1616	O
,	O
Deutsche	O
Telekom	O
ICSS	O
,	O
iBasis	O
,	O
Reach	O
,	O
SAP	O
Mobile	O
Services	O
,	O
Syniverse	O
,	O
Tata	O
Communications	O
,	O
Telecom	O
Italia	O
Sparkle	O
,	O
Telecom	O
New	O
Zealand	O
International	O
,	O
Telefónica	O
International	O
Wholesale	O
Services	O
,	O
Telekom	O
Austria	O
,	O
Telenor	O
Global	O
Services	O
,	O
TeliaSonera	O
International	O
Carrier	O
,	O
Comfone	O
AG	O
Switzerland	O
.	O
</s>
<s>
These	O
companies	O
will	O
function	O
as	O
IPX	B-Protocol
Providers	O
towards	O
fixed	O
and	O
mobile	O
operators	O
and	O
other	O
service	O
provider	O
types	O
.	O
</s>
