Users may be on the move within the coverage area of the wireless network. However, because the signal coverage of a single AP (wireless access point) device is limited, users often cross the coverage from one AP to another during the movement. In order to avoid the interruption of network communication when the mobile user switches between different APs, the wireless roaming technology is used here.
Basic concept:
Diffuse AC: or HA (Home-AC); a wireless terminal (STA) controls a wireless in the roaming group for the first time The wireless controller is the diffused AC of the wireless terminal (STA).
Incoming AC: or FA (Foreign-AC); it is connecting with the wireless terminal (STA), and it is not the wireless controller of the HA, the wireless controller is the wireless controller of the wireless terminal (STA). Diffuse into AC.
Intra-AC roaming: A wireless terminal (STA) roams from one AP of a wireless controller to another AP in the same wireless controller, which is called intra-AC roaming.
Inter-AC roaming: A wireless terminal (STA) roams from an AP in a wireless controller to an AP in another wireless controller, which is called inter-AC roaming.
Intra-AC roaming:
(1) A terminal associates with AP 1 through fast roaming, which connects to the AC.
(2) The terminal disconnects the association with AP 1 and roams to AP 2 connected to the same wireless controller AC.
(3) The process of connecting the terminal to AP 2 is intra-AC roaming.
Roaming between ACs:
(1) A terminal associates with AP 1 through fast roaming, which connects to AC 1.
(2) The terminal disconnects from AP 1 and roams to AP 2, which is connected to another WLC member AC 2.
(3) The process in which the terminal associates with AP 2 is inter-AC roaming. Before roaming between ACs, AC 1 and AC 2 need to synchronize the information of the pre-roaming terminal through the IACTP tunnel.
Intra-FA roaming:
(1) A terminal associates with AP 1 in a fast roaming mode, which connects to AC 1.
(2) The terminal disconnects from AP 1 and roams to AP 2, which is connected to another WLC member AC 2. At this time, AC 2 is the FA of the terminal.
(3) The terminal associates with AP 2 through inter-AC roaming. Before roaming between ACs, AC 1 and AC 2 need to synchronize the information of the pre-roaming terminal through the IACTP tunnel.
(4) The terminal disconnects from AP 2 and roams to AP 3, where it and AP 2 are connected to the same wireless controller AC 2. The process in which the terminal associates with AP 3 is intra-FA roaming.
Inter-FA roaming:
(1) A terminal associates with AP 1 in a fast roaming mode, which connects to AC 1.
(2) The terminal disconnects from AP 1 and roams to AP 2 connected to another WLC member AC 2. At this time, AC 2 is the FA of the terminal.
(3) The process in which the terminal associates with AP 2 is inter-AC roaming.
(4) The terminal disconnects the association with AP 2 and roams to AP 3 connected to another wireless controller member AC 3. At this time AC 3 is the FA of the terminal. The process of associating the terminal with AP3 is inter-FA roaming. Before roaming between ACs, AC 1 needs to synchronize the information of pre-roaming terminals with AC 2 and AC 3 through the IACTP tunnel.
WLAN roaming strategy mainly solves the following problems:
1. Avoid packet loss or even service interruption due to long authentication time during roaming
802.1x authentication, The number and time of packet exchanges in authentication processes such as Portal authentication is greater than that in the WLAN connection process. Therefore, roaming needs to avoid re-authentication and authorization and key negotiation processes.
2. Ensure that the user authorization information remains unchanged
The user's authentication and authorization information is the pass for the user to access the network. If the service is not interrupted after roaming, it must be ensured that the user is on the AC The authentication and authorization information remains unchanged.
3. Ensure that the user's IP address remains unchanged
The application layer protocols all use the IP address and TCP/UDP Session as the user's service bearer. After roaming, the user must be able to keep the original IP address unchanged. Change, the corresponding TCP/UDP Session can not be interrupted, and the application layer data can be forwarded normally.
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