LANCOM Wireless DSL – LANCOM Wireless ADSL
Chapter 1: Introduction
12
EN
ADSL- over-ISDN or ADSL-over- POTS?
ADSL can operate over modern ISDN telephone service as well as conven-
tional analog service (POTS –
P
lain
O
ld
T
elephone
S
ervice).
There are, however, different technical specifications for the two telephone
systems. For this reason, devices in the LANCOM Wireless DSL series are
offered in two different versions: A version for ADSL-over-POTS and a version
for ADSL-over-ISDN.
You can determine which telephone system a device supports by looking at
the model description on the bottom of the device. The label containing the
device name also contains an additional code which stands for the telephone
system the device supports:
An 'Annex A' type LANCOM Wireless DSL can only be used with ADSL-over-
POTS service. Similarly, an 'Annex B' device can only be used with ADSL-over-
ISDN service. Retrofitting a device to function with a different telephone sys-
tem is not possible.
ADSL-over-ISDN connections also exist that do not operate in conjunction
with ISDN, but which use a conventional analog telephone connection. A
prominent example would be Deutsche Telekom’s T-DSL service.
1.2
Which use does VPN offer?
For LANCOM 1811
Wireless DSL and
LANCOM 1821
Wireless ADSL only
A VPN (
V
irtual
P
rivate
N
etwork) can be used to set up cost-effective, public
IP networks, for example via the ultimate network: the Internet.
The models LANCOM 1811 Wireless DSL and LANCOM 1821 Wireless
ADSL are equipped with 5 active channels by default. The LANCOM
VPN Option. The additional VPN-25 Option can extend VPN support
to 25 tunnels (including hardware acceleration).
While this may sound unspectacular at first, in practice it has profound effects.
To illustrate this, let's first look at a typical corporate network without VPN
Code
Supported telephone system
'Annex A'
ADSL-over-POTS
'Annex B'
ADSL-over-ISDN
