5.5 Wireless Networking Flashcards
WIRELESS NETWORKING
Wireless networking is a way to network without wires.
IEEE 802.1
The most common specifications for how wireless networking devices should communicate are defined by the IEEE 802.11 standards.
This set of specifications, also called the 802.11 family make-up the set of technologies we call Wi-Fi.
The most common specifications you might run into are:
802.11b
802.11a
802.11g
802.11n
802.11ac.
In terms of our networking model, you should think of 802.11 protocols as defining how we operate at both the physical and the data link layers.
FREQUENCY BAND
A frequency band is a certain section of the radio spectrum that’s been agreed upon to be used for certain communications.
Wi-Fi networks operate on a few different frequency bands, most commonly the 2.4 gigahertz and 5 gigahertz bands.
802.11 FRAME
An 802.11 frame has a number of fields:
1 FRAME CONTROL FIELD
2 DURATION FIELD
3 SOURCE ADDRESS FIELD
4 INTENDED DESTINATION FIELD
5 RECEIVER ADDRESS
6 SEQUENCE CONTROL FIELD
7 TRANSMITTER ADDRESS
8 DATA PAYLOAD
9 FRAME CHECK SEQUENCE
1 FRAME CONTROL FIELD
Is 16 bits long and contains a number of sub-fields that are used to describe how the frame itself should be processed.
2 DURATION FIELD
It specifies how long the total frame is. The receiver knows how long it should expect to have to listen to the transmission.
3 SOURCE ADDRESS FIELD
Represents the MAC address of the sending device.
WIRELESS ACCESS POINT
Is a device that bridges the wireless and wired portions of a network.
4 INTENDED DESTINATION FIELD
5 RECEIVER ADDRESS
The MAC address of the access point that should receive the frame.
7 TRANSMITTER ADDRESS
The MAC address of whatever has just transmitted the frame.
6 SEQUENCE CONTROL FIELD
Is 16 bits long and mainly contains a sequence number used to keep track of ordering the frames
8 DATA PAYLOAD
Has all of the data of the protocols further up the stack.
9 FRAME CHECK SEQUENCE
Contains a checksum used for a cyclical redundancy check.
AD-HOC NETWORKS
Nodes all speak directly to each other.
In an ad-hoc network, there isn’t really any supporting network infrastructure.
WIRELESS LANS or WLANS
One or more access points act as a bridge between a wireless and a wired network.
The wired LAN contains the outbound Internet link. In order to access resources outside of the WLAN, wireless devices would communicate with access points. They then forward traffic along to the gateway router where everything proceeds like normal.
MESH NETWORKS
Are a hybrid of the two.
This network lets you deploy more access points to the mesh without having to run a cable to each of them. With this setup, you can really increase the performance and range of a wireless network.
CHANNELS
Channels are individual, smaller sections of the overall frequency band used by a wireless network.
WEP
WEP stands for Wired Equivalent Privacy and it’s an encryption technology that provides a very low level of privacy.
WEP only uses 40 bits for its encryption key.
WPA
WPA or Wifi Protected Access.
WPA by default uses a 128-bit key, making it a whole lot more difficult to crack than WEP.
WPA2
An update to the original WPA.
WPA2 uses a 256 bit key.
MAC FILTERING
With MAC filtering, you configure your access points to only allow for connections from a specific set of MAC addresses belonging to devices you trust.
CELLULAR NETWORKING
Cellular networking operates over radio waves and there are specific frequency bands specifically reserved for cellular transmissions.
Cellular networks are built around the concept of cells. Each cell is assigned a specific frequency band for use. Neighboring cells are set up to use bands that don’t overlap.
