12.3_WLAN Operation Flashcards
The 802.11 standard identifies two main wireless topology modes:
Ad hoc mode and Infrastructure mode
802.11 Wireless Topology Modes
This is when two devices connect wirelessly in a peer-to-peer (P2P) manner without using APs or wireless routers. The IEEE 802.11 standard refers to an ** network as an ___.
Ad hoc mode
independent basic service set (IBSS)
Examples include wireless clients connecting directly to each other using Bluetooth or Wi-Fi Direct.
802.11 Wireless Topology Modes
This is when wireless clients interconnect via a wireless router or AP, such as in WLANs. APs connect to the network infrastructure using the wired distribution system, such as Ethernet.
Infrastructure mode
802.11 Wireless Topology Modes
A variation of the ad hoc topology is when a smart phone or tablet with cellular data access is enabled to create a personal hotspot.
Tethering
Infrastructure mode defines two topology building blocks:
Basic Service Set (BSS)
Extended Service Set (ESS)
INFRASTRUCTURE MODE TOPOLOGY BUILDING BLOCKS
___consists of a single AP interconnecting all associated wireless clients
Basic Service Set
INFRASTRUCTURE MODE TOPOLOGY BUILDING BLOCKS
Two BSSs are shown in the figure. The circles depict the coverage area for the BSS, which is called the ____.
Basic Service Area (BSA)
INFRASTRUCTURE MODE TOPOLOGY BUILDING BLOCKS
The Layer 2 MAC address of the AP is used to uniquely identify each BSS, which is called the ___
Basic Service Set Identifier (BSSID)
The___is the formal name of the BSS and is always associated with only one AP.
BSSID or Basic Service Set Identifier
802.11 Frame Structure
This identifies the type of wireless frame and contains subfields for protocol version, frame type, address type, power management, and security settings.
Frame Control
802.11 Frame Structure
This is typically used to indicate the remaining duration needed to receive the next frame transmission.
Duration
802.11 Frame Structure
This is typically used to indicate the remaining duration needed to receive the next frame transmission.
Duration
802.11 Frame Structure
From a wireless device:
___: MAC address of the AP.
Address 1 Receiver Address
802.11 Frame Structure
From a wireless device:
___: MAC address of the sender.
Address 2 Transmitter Address
802.11 Frame Structure
From a wireless device:
__: MAC address of the destination which could be a wireless device or wired device.
Address 3 SA/DA/BSSID
802.11 Frame Structure
From the AP:
___: MAC address of the sender.
Address 1 Receiver Address
802.11 Frame Structure
From the AP:
__: MAC address of the AP.
Address 2 Transmitter Address
802.11 Frame Structure
From the AP:
__: MAC address of the wireless destination.
Address 3 SA/DA/BSSID
802.11 Frame Structure
From the AP:
__: This contains information to control sequencing and fragmented frames.
Sequence Control
802.11 Frame Structure
From the AP:
__: This usually missing because it is used only in ad hoc mode.
Address4
802.11 Frame Structure
From the AP:
___: This contains the data for transmission.
Payload
802.11 Frame Structure
From the AP:
__: This is used for Layer 2 error control.
FCS
802.11 Frame Structure
From the AP:
__: This is used for Layer 2 error control.
FCS
WLANs are ____(full-duplex/ half-duplex), shared media configurations
Half-duplex
WLANs use ____ as the method to determine how and when to send data on the network.
carrier sense multiple access with collision avoidance (CSMA/CA)
An important part of the 802.11 process is discovering a WLAN and subsequently connecting to it. Wireless devices complete the following three stage process, as shown in the figure:
Discover a wireless AP
Authenticate with AP
Associate with AP
Wireless Client and AP Association
___ name appears in the list of available wireless networks on a client. In larger organizations that use multiple VLANs to segment traffic, each ** is mapped to one VLAN. Depending on the network configuration, several APs on a network can share a common
SSID
Wireless Client and AP Association
__: This is required from the wireless client to authenticate to the AP.
Password
Wireless Client and AP Association
__: This refers to the 802.11a/b/g/n/ac/ad WLAN standards. APs and wireless routers can operate in a Mixed mode meaning that they can simultaneously support clients connecting via multiple standards.
Network mode
Wireless Client and AP Association
__: This refers to the security parameter settings, such as WEP, WPA, or WPA2. Always enable the highest security level supported.
Security mode
Wireless Client and AP Association
__: This refers to the frequency bands used to transmit wireless data. Wireless routers and APs can scan the radio frequency channels and automatically select an appropriate channel setting. The channel can also be set manually if there is interference with another AP or wireless device.
Channel settings
Wireless clients connect to the AP using a scanning (probing) process. This process can be __or __.
passive
active
In __mode, the AP openly advertises its service by periodically sending broadcast beacon frames containing the SSID, supported standards, and security settings
passive
__ mode allows the wireless clients to choose which network and AP to use.
passive
In ___ mode, wireless clients must know the name of the SSID. The wireless client initiates the process by broadcasting a probe request frame on multiple channels. The probe request includes the SSID name and standards supported. APs configured with the SSID will send a probe response that includes the SSID, supported standards, and security settings
active
