CEH

352 Chapter 15 ■ Wireless Networking

TA B LE 15.1 Wireless standards

Type Frequency (Ghz) Speed (Mbps) Range (ft)

8 0 2.11a 5 54 75

8 0 2.11b 2.4 11 150

8 0 2.11g 2.4 11 150

8 0 2.11n 2.4/5 54 ~10 0

8 0 2.16 ( W iM A X ) 10 – 66 70–1000 30 (miles)

Bluetooth 2.4 1–3 (first gen) 33

The IEEE 802.11 family of standards evolved from a base standard that

originally debuted in 1997. Initially the speeds were very slow—around 1

to 2 Mbps—and not very popular outside of specific implementations and

deployments. Since that time, wireless networks have gotten faster and

more widespread and they use wider frequency bands than before.

So why all the different letters in the 802.11 family? Well, the short answer is that the

additional letters correspond to the working groups that came up with the modifications

to 802.11. For example, 802.11a refers to the standard that defines changes to the physical

network layer required to support the various frequency and modulation requirements.

Service Set Identifier

Once a wireless access point or wireless network is established, the next step involves

getting clients to attach to it in order to transmit data. This is the job of the service set

identifier (SSID). An access point will broadcast an SSID, which will be used by clients to

identify and attach to the network. The SSID is typically viewed as the text string that end

users see when they are searching for a wireless network. The SSID can be made up of most

combinations of characters, but it can only ever be a maximum of 32 bytes in size.

When you install and set up your device, be sure to change the SSID name

that is configured by default with most access points. Leaving the default

name as “Linksys” or “dlink,” for example, can tip off an attacker that

perhaps you have left other default settings in place.

The SSID is continually broadcast by the access point or points to allow clients to identify

the network. A client is configured with the name of an access point in order to join the given

network. It is possible to think of the SSID configured on a client as a token used to access the