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Fat AP and Cloud AP V200R008C00 CLI-based Configuration Guide

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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
STA Access

STA Access

STA access involves the following steps:
  • Scanning
  • Link authentication
  • Association

Scanning

A STA can actively or passively scan wireless networks.

Active Scanning

In active scanning, a STA periodically searches for nearby wireless networks. The STA can send two types of Probe Request frames: probes containing an SSID and probes that do not contain an SSID.
  • Probes containing an SSID: The STA sends a Probe Request frame containing an SSID in each channel to search for the AP with the same SSID. Only the AP with the same SSID will respond to the STA. For example, in Figure 9-6, the STA sends a Probe Request frame containing the SSID huawei to search for an AP with the SSID huawei.

    Figure 9-6  Active scanning by sending a Probe Request frame containing an SSID

    This method applies to the scenario where a STA actively scans wireless networks to access a specified wireless network.

  • Probes that do not contain an SSID: The STA periodically broadcasts a Probe Request frame that does not contain an SSID in the supported channels as shown in Figure 9-7. The APs return Probe Response frames to notify the STA of the wireless services they can provide.

    Figure 9-7  Active scanning by sending a Probe Request frame containing no SSID

    This method applies to the scenario where a STA actively scans wireless networks to determine whether wireless services are available.

Passive Scanning

When passive scanning is enabled, a STA listens on the Beacon frames that an AP periodically sends in each channel to obtain AP information, as shown in Figure 9-8. A Beacon frame contains information including the SSID and supported rate.

Figure 9-8  Passive scanning process

To converse power, enable the STA to passively scan wireless networks. In most cases, VoIP terminals passively scan wireless networks.

Link Authentication

To ensure wireless link security, an AP needs to authenticate STAs that attempt to access the AP. IEEE 802.11 defines two authentication modes: open system authentication and shared key authentication.
  • Open system authentication requires no authentication. STAs that attempt to access the AP are successfully authenticated as long as the AP supports this mode. An illustration of the open system authentication procedure is shown in Figure 9-9.
    Figure 9-9  Open system authentication

  • Shared key authentication requires that the STA and AP have the same shared key preconfigured. The AP checks whether the STA has the same shared key to determine whether the STA can be authenticated. If the STA has the same shared key as the AP, the STA is authenticated. Otherwise, STA authentication fails. Figure 9-10 shows the shared key authentication process.
    Figure 9-10  Shared key authentication

    The shared key authentication process consists of the following steps:
    1. The STA sends an Authentication Request packet to the AP.
    2. The AP generates a challenge and sends it to the STA.
    3. The STA uses the preconfigured key to encrypt the challenge and sends it to the AP.
    4. The AP uses the preconfigured key to decrypt the encrypted challenge and compares the decrypted challenge with the challenge sent to the STA. If the two challenges are the same, the STA is authenticated. Otherwise, STA authentication fails.

Association

Client association is also known as link negotiation. After link authentication is complete, a STA initiates link negotiation using Association packets, as shown in Figure 9-11.

Figure 9-11  STA association

  • STA association consists of the following steps:
    1. The STA sends an Association Request packet to the AP. The Association Request packet carries the STA's parameters and the parameters that the STA selects according to the service configuration, including the transmission rate, channel, QoS capabilities, access authentication algorithm, and encryption algorithm.
    2. The AP determines whether to associate with the STA according to the received Association Request packet and replies with an Association Response packet.
NOTE:
After association, the STA determines whether it needs to be authenticated according to the received Association Response packet:
  • If the STA does not need to be authenticated, the STA can access the wireless network.
  • If the STA needs to be authenticated, the STA initiates user access authentication. After authentication, the STA can access the wireless network.For details about user access authentication, see User Access and Authentication Configuration Guide.
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Updated: 2019-01-11

Document ID: EDOC1000176006

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