Modbus
Cellular
Gateway
Index
skipping
is
used
to
reserve
slots
for
new
function
insertion,
when
required.
299
Scenario
Application
Timing
When
one
client
host
in
the
Intranet
wants
to
run
peer
‐
to
‐
peer
applications,
like
multiplayer
gaming,
the
NAT
gateway
needs
the
UPnP
function
to
automatically
setup
or
remove
port
mapping
rules
in
the
gateway.
Scenario
Description
Usually,
the
active
port
service
attempt
to
access
the
gateway
from
the
Internet
will
be
ignored
by
the
gateway
for
security.
Normal
NAT
mechanism
has
the
connection
tracking
feature
to
direct
the
response
packets
from
the
Internet
back
to
the
source
end
of
request
packets
in
the
Intranet.
Once
one
application
in
the
Intranet
host
needs
an
additional
service
port
to
be
activated
at
the
WAN
interface
of
the
gateway,
it
will
ask
the
gateway
to
do
that
by
using
UPnP
protocol.
Then
the
Internet
server
can
use
the
service
port
to
contact
the
application
for
data
communication.
Parameter
Setup
Example
Following
table
lists
the
parameter
configuration
as
an
example
for
the
NAT
Gateway
in
above
diagram.
Use
default
value
for
those
parameters
that
are
not
mentioned
in
the
table.
Configuration
Path
[UPnP]
‐
[Configuration]
UPnP
■
Enable
Scenario
Operation
Procedure
In
above
diagram,
the
"NAT
Gateway"
is
the
gateway
of
Network
‐
A
and
the
subnet
of
its
Intranet
is
10.0.75.0/24.
It
has
the
IP
address
of
10.0.75.2
for
LAN
interface
and
118.18.81.33
for
WAN
‐
1
interface.
There
is
one
gaming
station
in
the
Intranet
and
a
game
server
in
the
Internet.
A
gaming
application
is
executed
and
data
is
communicated
between
the
gaming
station
and
server.
The
gaming
application
needs
more
service
ports
to
be
activated
in
the
gateway,
so
that
the
gaming
server
can
send
data
to
the
station
actively
via
those
service
ports.
At
first
stage,
the
gaming
server
sends
an
active
accessing
for
service
port
1000
to
the
NAT
Gateway,
the
gateway
ignores
it
since
the
service
port
1000
is
deactivated
at
current
stage.
When
the
gaming
has
not
be
executed
yet,
the
NAT
mechanism
in
the
gateway
has
its
connection
tracking
feature
to
direct
the
response
packets
from
the
Internet
back
to
the
source
end
of
request
packets
in
the
Intranet.
Once
the
gaming
application
in
the
Intranet
host
is
executed
and
it
needs
an
additional
service
port,
like
1300,
to
be
activated
at
the
WAN
interface
of
the
gateway,
it
will
ask
the
gateway
to
do
that
by
using
UPnP
protocol.
Finally,
the
gaming
server
can
use
the
service
port
to
actively
contact
the
application
in
the
gaming
station
for
data
communication.
