Modbus
Cellular
Gateway
Index
skipping
is
used
to
reserve
slots
for
new
function
insertion,
when
required.
370
7.5
Captive
Portal
A
captive
portal
is
a
portal
web
page
that
is
displayed
before
a
user
can
browse
Internet.
The
portal
is
often
used
to
present
a
login
page.
This
is
done
by
intercepting
most
packets,
regardless
of
address
or
port,
until
the
user
opens
a
browser
and
tries
to
access
the
web.
At
that
time
the
browser
is
redirected
to
a
web
page
which
may
require
authentication
and/or
payment,
or
simply
display
an
acceptable
use
policy
and
require
the
user
to
agree.
Captive
portals
are
used
at
many
Wi
‐
Fi
hotspot
services,
and
can
be
used
to
control
wired
access
(e.g.
apartment
houses,
hotel
rooms,
business
centers,
"open"
Ethernet
jacks)
as
well.
15
Since
the
login
page
itself
must
be
presented
to
the
client,
either
that
login
page
is
locally
stored
in
the
gateway,
or
the
web
server
hosting
that
page
must
be
"whitelisted"
via
a
walled
garden
to
bypass
the
authentication
process.
Depending
on
the
feature
set
of
the
gateway,
multiple
web
servers
can
be
whitelisted
(say
for
iframes
or
links
within
the
login
page).
In
addition
to
whitelisting
the
URLs
of
web
hosts,
some
gateways
can
whitelist
TCP
ports.
The
MAC
address
of
attached
clients
can
also
be
set
to
bypass
the
login
process.
This
technique
has
occasionally
been
referred
to
as
UAM
(Universal
Access
Method)
in
implementations
and
standards
forums.
1
The
gateway
supports
the
Captive
Portal
function
to
ask
guests
or
passengers
to
pass
the
authentication
process
before
they
can
surf
the
Internet
via
the
gateway.
There
are
two
approaches,
including
internal
captive
portal
and
external
captive
portal.
For
external
captive
portal,
you
must
specify
external
RADIUS
(Remote
Authentication
Dial
In
User
Service)
server
and
external
UAM
(Universal
Access
Method)
server.
In
contrast,
for
internal
captive
portal,
you
will
only
select
“Internal
RADIUS
Server”
option
for
user
authentication.
The
user
account
database
can
be
an
embedded
database,
an
external
AD
database
or
an
external
LDAP
database.
However,
the
UAM
server
is
not
necessary
for
this
case
and
that
the
captive
portal
Web
site
is
embedded
in
the
device.
7.5.1
Configuration
Administrator
of
gateway
can
enable
the
Captive
Portal
function
and
configure
the
device
to
be
the
internal
captive
portable
or
the
external
captive
portal
for
the
function.
But
please
be
noted
that
there
is
only
selected
AMIT
gateway
models
support
external
captive
portal
function.
15
http://en.wikipedia.org/wiki/Captive_portal
