Information Technology Reference
In-Depth Information
one can plug into an Ethernet jack and gain access to the Physical layer of the net-
work. However, higher layers are not necessarily open, either through the limited
station isolation provided through an Ethernet switch, or through virtual LAN
(VLAN) network privacy.
Private networks simply implement a crude method of VLAN through a net-
work “name” and associated password. This can be a significant advantage, as the
casual user cannot simply jump onto a wireless LAN and perhaps use sniffer tech-
nology to penetrate further.
Encryption methods may also be an enhanced feature that is important to a
network administrator. While conventional wired networks do indeed emit tiny sig-
nals that can be picked up by an intruder, at least they do not intentionally broad-
cast network traffic. But your sensitive data, from correspondence to personnel
information, passes along any network, and now can be broadcast to the nearby
world through the wonder of WLANs.
The only way to deal with this real or perceived threat is to encrypt all data
passing over the WLAN. Many encryption standards are available, and this fact can
lead to incompatible “enhancements” between manufacturers.
Before we get into planning the wireless network, let's look at the types of wireless
links. Regardless of the type of WLAN technology, there are basically three types of
links, of which two are closely related (Fig. 13.7).
Indoor Point-to-Multipoint LANs
The majority of WLAN implementations are made within a building (Fig. 13.7a).
Invariably, these are multipoint connections, although rarely a point-to-point link
is made to span a large distance in an industrial plant or an aircraft hanger. These
indoor point-to-point links are sometimes best accomplished with infrared links, as
none of the disadvantages normally associated with outdoor infrared links are
present.
The typical indoor LAN serves to link wireless workstations to a corporate
LAN backbone. Access points (APs) are distributed throughout the building to pro-
vide wireless coverage at all the needed locations. Often, the APs are mounted above
the ceiling tiles and out of view, except for an unobtrusive antenna.
Multipoint LANs may also be implemented without APs, but this is normally
limited to a small number of devices within a particular room, as there is no
straightforward method to distribute the signal to other areas.
