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Anonymous users2024-02-06When it comes to the historical origins of wireless LANs, everyone may think that they are a relatively recent emerging technology, but they actually appeared earlier than expected. The initial application of wireless LAN can be traced back to 50 years ago during World War II, when the U.S. Army used radio signals for data transmission, and they developed a set of radio transmission technology, and used very high encryption technology. During World War II, the technology was widely used by both the U.S. and Allied forces, and scholars were inspired by it.
In 1971, researchers at the University of Hawaii created the first radio communication network based on packet technology, known as the Alohnet network, which was the first wireless local area network. The WLAN consists of seven computers using a bi-directional star topology across four Hawaiian islands, with the central computer located on Oahu Island. From this point on, wireless LAN can be said to be officially born.
With the birth and initial development of the personal computer, wireless LANs in the true modern sense only began to emerge in the late 80s of the last century, when Motorola developed the first generation of commercial wireless LANs. In 1990, the IEEE launched the project and officially began the standardization of wireless local area networks. In 1997, the IEEE improved the international interoperability standards for protocols; In 1999, the IEEE approved a communication standard with two wireless networks; In 2001, the IEEE made a clear statement on the draft of QoS and wireless LAN security; In 2002, more than 130 participating companies became Standard Voting members.
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Anonymous users2024-02-05The architecture of a wireless LAN is slightly different from that of Ethernet, in that a wireless LAN adds a logical link control (LLC) sublayer to specify the data type.
The specific way to represent the data type is to add a 2-byte Ethernet type field with a fixed prefix aa03000000
The reason for this difference is that Ethernet and Wi-Fi use different standard-defined MAC frame types.
The smallest unit of a wireless LAN is the basic set of services.
Features:
The maximum transmission distance is 100 300 meters.
is a collision domain with a limited number of endpoints.
Created by one endpoint and joined by other endpoints.
Mac Frame Transfer Process:
The source terminal sends data to the destination terminal.
The destination terminal correctly receives the data and replies to the reply frame.
Features:
There is a device called an AP.
Endpoints are interconnected via APs.
BSS can be interconnected with other networks via APs.
Mac Frame Transfer Process:
If the source and destination terminals are in the same BSS, the communication between the terminals is confirmed through AP ** and segmented during transmission.
The geographic extent covered by the basic set of services is calledEssential Service Area (BSA).
Features:
A wireless LAN is equivalent to a network segment.
AP implements MAC frames between Ethernet and Wi-Fi**.
AP converts Ethernet MAC frame formats to and from Wi-Fi MAC frame formats.
Mac Frame Transfer Process:
Features:
Mac frame format
Note: The "To DS" bit is set to 1 when the receiver of the MAC frame is an AP, bridge, or other device
From DS" is set to 1 when the sender of the MAC frame is an AP, bridge, etc
BSSID is an abbreviation for Basic Service Set Identification and is known asBasic service set identifier, is a 48-bit number generated by IBSS when it is created, and is generally the MAC address of the AP, which is used to uniquely identify the IBSS
For APs, you need to configure:
For a terminal that needs to be connected to BSS, you need to configure:
During the synchronization process, the terminal needs to complete the following tasks:
The synchronization process is divided into:Passive synchronization processwithActive synchronization process
Passive synchronization process
Active synchronization process
The process by which an AP authenticates an endpoint
Open system identification
Shared key authentication
The endpoint is associated with the AP
Prerequisites: After the synchronization and authentication process is completed, the AP has the resources required for terminal access, such as the capacity of the association table and the number of terminals that can be associated.
Once the association is established, the AP adds the MAC address of the endpoint to the MAC address list, and only endpoints that have a MAC address in the MAC address list of the AP can pass the AP ** data.
Wireless LAN networking.
A Mac frame for a Wi-Fi network.
The process of connecting a terminal to a wireless LAN.
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The characteristics of the LAN are as follows:
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