A
Glossary of Terms
196
UMA
Unlicensed
Mobile
Access.
UNC
UMA
Network
Controller.
VPN
Virtual
Private
Network.
Secure
communication
between
multiple
networks
or
network
devices
using
insecure
public
networks,
such
as
the
Internet.
VPN
tunnel
A
connection
over
the
Internet
between
a
user
connected
on
a
remote
site
and
a
security
gateway.
A
VPN
provides
privacy
only
so
to
ensure
security
all
IP
packets
are
encrypted
and
sometimes
encapsulated
into
another
IP
packet.
VLink
Virtual
Link.
X.500
The
family
of
joint
ITU
‐
T/ISO
standards
defining
the
X.500
Directory.
The
directory
can
be
used
for
many
applications,
such
as
storing
certificates,
or
information
about
people.
LDAP
is
often
used
to
access
the
X.500
Directory.
X.509
The
ITU
‐
T
X.509
recommendation
defines
the
formats
for
X.509
certificates
and
X.509
CRLs.
Different
X.509
applications
are
further
defined
by
the
PKIX
Working
Group
of
the
IETF.
These
include
X.509
version
3
public
‐
key
certificates
and
X.509
version
2
CRLs.
XCBC
EXtended
Ciphertext
Block
Chaining.