Note
Chapter 4 Wireless Technology
163
Basic Service Set
(BSS)
an IEEE term
used to describe a
group of wireless
devices connected
as an infrastructure
network or an SSID.
Independent Basic
Service Set (IBSS)
a network that does
not use an access
point and usually is
a direct connection
between two wire-
less devices.
Extended Service Set
Identifi er (ESSID)
two or more Wireless
Access Points or
wireless devices
using the same SSID.
The IEEE 802.11 wireless network standard does not use the terms ad hoc,
SSID, or ESSID when describing the technical aspects of a wireless network.
These terms are encountered when reviewing product information provided
by wireless manufacturers. The IEEE uses the terms Basic Service Set (BSS) and
Independent Basic Service Set (IBSS). A Basic Service Set (BSS) is a group of
wireless devices connected as a network, which is described by manufacturers
as an infrastructure network or an SSID. An Independent Basic Service Set
(IBSS) is similar to an ad hoc network. The IBSS does not use an access point and
usually is a direct connection between two wireless devices.
You will see the term Enhanced Service Set Identifi er (ESSID) listed in the
CompTIA Network+ 2009 objectives and acronyms list. The more commonly
accepted translation of the acronym ESSID is Extended Service Set Identifi er.
An Extended Service Set Identifi er (ESSID) refers to two or more Wireless
Access Points or wireless devices using the same SSID. In other words, the network
has been “extended” by using the same SSID for more than one access point. When
multiple access points use the same SSID, a portable wireless device can maintain a
constant connection with the network as the user moves around the location.
The exact meaning of networking terminology can be confusing because device
manufacturers often present the terminology at a novice level rather than at a technical
level. For example, some manufacturers use the term enhanced to indicate a feature that
has been added by that particular manufacturer.
IEEE 802.11 Standard
Radio wave-based networks adhere to the 802.11 standard. The 802.11 standard
consists of four classifi cations of wireless networks: 802.11a, 802.11b, 802.11g, and
802.11n. See Figure 4-17 for a chart of the 802.11 standards and their characteristics.
802.11a
The 802.11a standard operates at the 5-GHz frequency and has a maximum data
rate of 54 Mbps. An 802.11a device may use lower data rates of 48 Mbps, 36 Mbps,
Figure 4-16.
A wireless network
in ad hoc mode.
Ad Hoc Mode