802.11 standard and wireless network operation mode

802.11 standard

802.11 standard Introduction:

IEEE 802.11 is a common standard for today's wireless LANs and is the standard for wireless network communications defined by the International Institute of Electrical Engineering (IEEE).
It defines the media access control layer (MAC layer) and the physical layer. The physical layer defines two types of spread-spectrum modulation and an infrared transmission on the 2.4GHz ISM band, and the total data transfer rate is designed to be 2mbit/s. Both devices can build their own ad hoc networks, or they can communicate under the coordination of the base station (base stations, BS) or access point (Access Point,ap). In order to achieve good communication quality in different communication environment, using CSMA/CA (Carrier sense multiple access/collision avoidance) hardware communication method

Note: Wi-Fi standard is just one of the 8.02.11 standards here, Wi-Fi standards are based on the 802.11 standard

802.11 evolution process of protocol standards:

802.11

Posted on 1997

Rate 1Mbps or 2Mbps
Infrared transmission Media (not implemented)
Radio frequency Signal Coding (modulation) (radio frequencies)
-direct-sequence Spread-spectrum (DSSS)-----Direct Sequence spread spectrum
-frequency hopping Spread-spectrum (FHSS)-----frequency hopping spread spectrum
Media Access-----csma/ca c=b+log2 (1+s/n) (carrier-listening multi-access conflict avoidance)
-Listen for a timed length based on the algorithm
-Send the data before the contract statement
Request to Send/clear to Send (rts/cts)

802.11b

Complementary code keying (CCK)-----Supplemental Codes Key
5.5 and one Mbit/s
2.4GHz Band (2.4ghz-2.485ghz)
14 Overlapping channel channels
22MHz Broadband per channel
Only three completely non-overlapping channels
United States -1 to one (2.412 GHz-2.462 GHz)
Europe-1 to (2.412 GHz-2.472 GHz)

Japan -1 to (2.412 GHz-2.482 GHz)
Note: The channels of the adjacent two wireless devices do not overlap, so as not to cause impact

802.11a
Almost simultaneous release with 802.11b
-because the price of equipment has not been widely used?

Using 5GHz Broadband
-2.4ghz wideband interference sources (microwave, Bluetooth, cordless phones)
-5hgz frequency has more broadband space, can accommodate more non-overlapping channels
-orthogonal frequency-division multiplexing (OFDM) signal modulation method
-Orthogonal Frequency Division multiplexing technology
Higher rate 54Mbps, 20MHz broadband per channel
Frequency
-5.15-5.35ghz Indoor
-5.7-5.8ghz Outdoor

802.11G

2.4GHz
Orthogonal frequency-division multiplexing (OFDM) signal modulation method?

Same as 802.11a rate
Global spin down, backwards compatible with 802.11b, and switch to CCK signal modulation method
20/22mhz Broadband per signal

802.11N

2.4 or 5 GHz frequency
300Mbps up to 600Mbps
Multiple-input Multiple-output (MIMO) multi-input and multi-out communication technology
Multi-antenna, multi-radio, independent transceiver signal
40MHz channel bandwidth can be used to double the data transfer rate
In a full 802.11n device network, the new message format can be used, which is the highest rate

20/40mhz Broadband per channel

802.11 protocol families:

802 committee under the 11th Group is responsible for the development of wireless LAN standards
IEEE 802.1 1 The Original WLAN Standard-1 Mbit/s and 2 Mbit/w,2.4ghz RF Andir

IEEE 802.11 a mbit/s,5 GHz

IEEE 802.11 b 802.11 enhancements to support 5.5 Mbit/s and one Mbit/s
IEEE 802.11 c Bridge Operation Procedure

IEEE 802.11 d International (country to country) Roaming Extensions
IEEE 802.11 e Quality of Service (Qos), including Packet bursting

IEEE 802.11 F inter-access point Protocol

IEEE 802.11 g mbit/s,2.4 GHz

IEEE 802.11 h Spectrum Managed 802.11 a (5 GHz) for European compatibility

IEEE 802.11 i enhanced Security
IEEE 802.11 j Extensions for Japan
IEEE 802.11 k Radio Resource Measurement enhancements

IEEE 802.11 n Higher throughput Using multiple input,multiple ouput (MIMO) Antennas

IEEE 802.11 p Wireless Access for the Vehicular environment (WAVE)

IEEE 802.11 r Fast BSS Transition (FT)

IEEE 802.11 s Mesh networking,extended Service Set (ESS)
IEEE 802.11 T Wireless performance prediction (WPP)

IEEE 802.11 u internetworking with Non-802 Networks (i.e.:cellular)

IEEE 802.11 v wrieless Network Management
IEEE 802.11 v wrieless Network Management
IEEE 802.11 w Protected Management Frames

IEEE 802.11 y 3650-3700 MHz operation in the US
IEEE 802.11 z Direct Link Setup (DLS) Extensions

IEEE 802.11 ZM maintenance of the standard

IEEE 802.11 aa Robust streatming of Audio Video Transport Streams
IEEE 802.11 ac Very high Troughput < 6 GHz

IEEE 802.11 ad Very high troughput, GHz

IEEE 802.11 ae Qos Management

IEEE 802.11 af TV whitespace

IEEE 802.11 ah SUb 1 GHz

IEEE 802.11 ai Fast Initial Link Setip

Daily use

IEEE 802.11-the Original WLAN Standard
IEEE 802.11 a-up to si Mbit/s on 5 GHz
IEEE 802.11 b-5.5 Mbit/s and one Mbit/s? On 2.4 GHz

IEEE 802.11 g-up to si Mbit/s on 2.4 Ghz.backward compatible with 802.11B
IEEE 802.11 i-provides Enhanced security
IEEE 802.11 n-provides higher throughput with multiple input/multiple Output (MIMO)

802.11 frame type description:

The 802.11 standard defines three types of frames:
Data frame
Control frame
Manage Frames (Management frame)

Frame types are identified by the header frame control, the 2-byte Type field and the 4-bit subtype (subtyep) field in the field, indicating that each of the three frames contains multiple subtypes that implement different functions

Data frame:
The purpose of data packets is to carry higher level data (such as IP packets, ISO7 layer protocol)
The data sent to the customer service or the client sends out is in the data frame. Data frames can contain up to 4 address segments that identify the sending, receiving, BSSID, and wireless routes that forward the changed data frame

Control frame:
The function of the control frame is to gain control of the channel and help the device to transmit data through the channel. The control frame contains only the frame header information and no data payload. (Management frames are supervised, primarily used to join or exit wireless networks, and to handle transfers between access points)

Control: The control packet gets its name from the term "media access Control (MAC)", which is used to control access to shared media (i.e. physical media, such as optical cables)

1 Request to Send,rts Packet
2 clearing the Send (clear to send,cts) packet

3 ack Acknowledgement (rts/cts)
4 Ps-poll: When a mobile workstation wakes up from power-down mode, a ps-poll frame is sent to the base station to obtain any staging frame
The control frame is usually used in conjunction with the data frame, which is responsible for the emptying of the area, the acquisition of the channel and the maintenance of the carrier monitoring, and the positive response when the data is received, thereby promoting the reliability of data transmission between workstations.

Manage frames: Manage frames for monitoring, primarily for joining or exiting wireless networks, and for handling transfer of connections between access points

Beacon: The AP announces the data rate allowed by BBS and BBS by means of broadcast. Beacons send all devices in the BSA at frequencies of 10 times per second.

Probing: A wireless device can send probe request frames to all APS or designated APS within its range to require the AP to provide their BBS information. The process of detecting BBS information is called active scanning.

Unblock and certify frames: wireless devices If you want to join a BBS, you must first send an authentication request frame to the AP. If the wireless device wants to leave the authentication state, then it can send the de-authentication frame to the AP

IMPORTANT: The AP can also send a cancellation authentication frame to the wireless device to force the device to leave the authentication state!

Management: Manage the management of the Packet control network

1 Beacon Frame (Beacons): In a wireless device, regular wireless signals (similar to heartbeat packets) are sent periodically and sequentially at specified intervals, primarily for locating and synchronizing use

2 release authentication (deauthentication) packets

3 Probe (Request and response)

4 Authenticate (Request and response)

5 Associate (Request and response)

6 reassociate (Request and response)

7 Dissassociate (notify)

The WLAN has the following three network topologies:

1 Independent basic Service Set (independent BSS, IBSS) network (also called Ad-hoc Network)
2 basic services Set (basic service Set, BSS) network
3 Extended Services Set (Extent Service Set, ESS) network

Ad-hoc

Also known as independent Basic Service Set (IBSS)

There are at least 2 direct communication components of Stas
Also known as peer to peer mode

One of the STA is responsible for the AP's work
-Broadcast SSID via Beacon
-Authentication of other Stas
For example: Win7 comes with the Ad-hoc set up function, can let us very convenient in a small area of rapid formation of "LAN", network playing games what is very convenient

ad-hoc Network model:

BSS Network:

Contains at least one AP and one station, forming a basic Service Set (BSS)

For personal PCs, the most used "wireless Wi-Fi" refers to the BSS network mode

BSS Network Model:

ESS Network:

APS connected to a limited network, called Distribution System (DS)
Multiple APS connected to the same DS form a extend Service Set (ESS)

WIRELESS distribution SYSTEM (WDS)

Similar to Wired DS, just a network of multiple APS connected wirelessly
Bridging------Only the APS communicate with each other
Repeating-----allows all APS and STA to communicate

MONITOR MODR

Monitor is not a true wireless mode
But it's important for wireless penetration.
Allow wireless card without any filtering (802.11 header)
The promiscuous mode with wired networks can be analogous
The appropriate network card and driver can not only monitor, but also injection

802.11 standard and wireless network operation mode