11
I-WLAN
178
Authentication
of
the
security
gateway
with
certificates
is
done
without
referencing
a
CRL
on
a
CA
server.
The
gateway
sends
the
appropriate
Host
Certificate
to
the
client
which
then
validates
it
against
its
own,
preinstalled
CA
signed
root
certificate.
This
may
require
the
use
of
Intermediate
Certificates
that
are
also
sent
to
the
client
by
the
security
gateway.
The
sequence
of
steps
in
this
process
is
described
later.
I-WLAN components
The
SEG
components
for
I
‐
WLAN
are:
•
An
IPsec
Tunnel
for
remote,
roaming
client
access
to
the
security
gateway.
This
is
tightly
coupled
to
a
GTP
tunnel
using
SEG
Interface
Stitching
.
•
A
GTP
Tunnel
for
access
to
the
GPRS
backbone
network
from
the
security
gateway.
This
is
tightly
coupled
to
an
IPsec
tunnel
using
SEG
Interface
Stitching
.
•
The
SEG
should
have
a
license
installed
that
has
GTP
enabled.
The
current
license
capabilities
can
be
examined
with
the
license
CLI
command.
If
GTP
is
not
enabled,
the
GTP
tunnels,
the
interface
stitching,
and
the
stitched
IPsec
tunnels
will
not
function.
•
At
least
one
DNS
server
IP
address
must
be
configured
in
the
SEG
for
DNS
lookup.
This
may
be
located
in
the
GPRS
backbone
network.
GTP tunnels
The
principal
properties
for
defining
a
GTP
tunnel
are
listed
below.
Not
all
the
available
properties
are
included.
The
ones
that
are
omitted
are
usually
rarely
changed
from
their
defaults
but
can
be
if
required.
General settings
•
LocalEndpoint
The
logical
IP
address
of
the
GTP
interface.
This
is
the
address
that
will
be
used
as
the
source
address
for
GTP
‐
C
and
GTP
‐
U.
The
IP
Address
must
be
unique
amongst
GTP
interfaces
if
there
is
more
than
one.
•
EndUserDNS
If
a
DNS
is
configured
for
the
GTP
interface,
this
IP
address
will
be
passed
back
to
the
client.
If
no
DNS
is
configured
for
the
GTP
interface,
the
configured
DNS
client
for
the
security
gateway
will
be
used
instead.
•
RoundRobinDNS
Round
‐
robin
between
hosts
when
the
DNS
name
contains
multiple
hosts.
The
default
value
is
No
.
This
option
can
be
used
for
load
balancing
between
multiple
GGSNs.
•
MaxRequests
This
parameter
is
a
counter
that
specifies
a
maximum
value
for
the
number
of
retransmissions
for
requests
towards
GTP
peers.
A
path
to
a
GTP
peer
will
be
considered
down
if
the
number
of
retries
is
greater
than
the
maximum
specified.
The
default
value
is
5
.