Hi, everyone! Today I’m going to introduce 802.11r fast roaming.
The 802.11r protocol uses the Fast BSS Transition (FT) function to reduce the number of information exchanges between users in the same mobile domain (MD) and does not require 802.1X authentication or key negotiation during STA roaming. Users are unaware of service interruption and experience low-latency data services during roaming, so their online experience is improved.
Intra-AC 802.11r Fast Roaming
The intra-AC 802.11r fast roaming process is as follows.
Intra-AC 802.11r fast roaming (Over-the-Air)
802.11r fast roaming includes the following two modes:
Over-the-Air: STAs communicate directly with the FAP (AP_2) for FT authentication.
Over-the-DS: STAs communicate with the FAP (AP_2) for FT authentication through the HAP (AP_1).
Currently, Huawei ACs support only the over-the-Air mode.
1. When an STA is connected to the Internet through AP_1 for the first time, the STA is authenticated by AC and a PMK is generated.
a. The AC generates PMK-R0 (calculated based on the SSID, MDID, AC MAC address, and STA MAC address) and PMK-R1 of each AP based on the PMK (calculated based on the PMK-R0, AP MAC address, and STA MAC address), and delivers the PMK-R1 to AP_1.
b. The STA and AC generate and install the pairwise transient key (PTK) and the group temporal key (GTK) by performing the 4-way and 2-way handshakes.
If open system authentication is used, no PMK is generated.
2. The STA initiates an 802.11 FT authentication request to AP_2 during roaming and delivers the PMK-R1 to AP_2.
3. After receiving the request, AP_2 generates and installs a PTK according to PMK-R1 and information contained in the request frame. At the same time, AP_2 starts the re-association timer and sends an 802.11 FT authentication response to the STA.
If 802.1X authentication is used and the AP does not cache PMK information about the STA during FT authentication, the AP reports authentication information to the AC for processing. If the AP caches PMK information about the STA that matches the information carried in the authentication request sent by the STA, the AP does not report authentication information to the AC.
If the open system or PSK authentication is used, the AP does not report authentication information to the AC.
4. After receiving the response, the STA generates and installs a PTK based on the information contained in the response frame. The STA sends AP_2 a re-association request.
5. After receiving the re-association request, AP_2 disables the re-association timer, and then sends a re-association response to the STA.
If an STA blacklist or whitelist is configured on the AC, the AP reports re-association responses to the STA during FT re-association and then reports the STA's re-association request to the AC for processing.
6. After the STA receives the response frame, the roaming is complete.
Inter-AC 802.11r Fast Roaming
The inter-AC 802.11r fast roaming process.
Inter-AC 802.11r fast roaming (Over-the-Air)
802.11r fast roaming includes the following two modes:
Over-the-Air: STAs communicate directly with the FAP (AP_2) for FT authentication.
Over-the-DS: STAs communicate with the FAP (AP_2) for FT authentication through the HAP (AP_1).
Currently, Huawei ACs support only the over-the-Air mode.
1. When an STA is connected to the Internet through AP_1 for the first time, the STA is authenticated by AC_1 and a PMK is generated.
AC_1 generates PMK-R0 (calculated based on the SSID, MDID, AC MAC address, and STA MAC address) and PMK-R1 of each AP based on the PMK (calculated based on the PMK-R0, AP MAC address, and STA MAC address), and delivers the PMK-R1 to AP_1.
a. The STA and AC generate and install the pairwise transient key (PTK) and the group temporal key (GTK) by performing the 4-way and 2-way handshakes.
b. The AC_1 synchronizes the PMK information to the AC_2 through the inter-AC tunnel.
AC_2 generates PMK-R0 and PMK-R1 of AP_2 based on the PMK and delivers PMK-R1 to AP_2.
If open system authentication is used, no PMK is generated.
2. The STA initiates an 802.11 FT authentication request to AP_2 during roaming.
3. After receiving the request, AP_2 generates and installs a PTK according to PMK-R1 and information contained in the request frame. At the same time, AP_2 starts the re-association timer and sends an 802.11 FT authentication response to the STA.
If 802.1X authentication is used and the AP does not cache PMK information about the STA during FT authentication, the AP reports authentication information to the AC for processing. If the AP caches PMK information about the STA that matches the information carried in the authentication request sent by the STA, the AP does not report authentication information to the AC.
If the open system or PSK authentication is used, the AP does not report authentication information to the AC.
4. After receiving the response, the STA generates and installs a PTK based on the information contained in the response frame. The STA sends AP_2 a re-association request.
5. After receiving the re-association request, AP_2 disables the re-association timer, and then sends a re-association response to the STA.
6. If an STA blacklist or whitelist is configured on the AC, the AP reports re-association responses to the STA during FT re-association and then reports the STA's re-association request to the AC for processing.
After the STA receives the response frame of AP_2, the roaming is complete.
This is what I want to talk about/share with you today, thank you!
