Lancom 821 ADSL/ISDN Manual page 13

LANCOM 821 ADSL/ISDN – LANCOM 1621 ADSL/ISDN – LANCOM 1711 VPN
Conventional network infrastructure
First, let's have a look at a typical network structure that can be found in this
form or similar forms in many companies:
Head Office
LAN
Subsidiary
The corporate network is based on the internal network (LAN) in the head-
quarters. This LAN is connected to the outside world in three ways:
A subsidiary is connected to the LAN, typically using a leased line.
PCs dial into the central network via modem or ISDN connections (Remote
Access Service – RAS).
The central LAN has a connection to the Internet so that its users can
access the Web, and send and receive e-mail.
All connections to the outside world are based on dedicated lines, i.e.
switched or leased lines. Dedicated lines are very reliable and secure. On the
other hand, they involve high costs. In general, the costs for dedicated lines
are dependent on the distance. Especially in the case of long-distance con-
nections, keeping an eye out of cost-effective alternatives can be worthwhile.
The appropriate hardware must be available in the headquarters for every
type of required connection (analog dial-up, ISDN, leased lines). In addition
Workstation in remote
access, e.g. homework
Internet
Chapter 1: Introduction
LAN
13