User's Manual
Check Value Algorithm
Installation and User Guide: Airgo Access Point 271
Station Forced Disconnect
The web server can directly signal the AP to disconnect a station. Figure 3 illustrates the signal
flow for this scenario.
Figure 191: Web server initiated forced disconnect of user
The construction of the disconnect URL is identical to the URL for the user initiated station
disconnect. The only difference is that the HTTP request is initiated from the web server to the AP
rather than from the station.
Check Value Algorithm
The check value carried in the Xcv field is calculated using the SHA-1 algorithm (FIPS 180-1
standard). The server must create the appropriate time stamp and check value in server side active
web pages. The check value will typically be created using active pages on the web server (asp,
cgi,.net, etc.). This check value is produced using the following procedure:
1 Create a timestamp of the form yymmddhhMM, where yy=year, mm=month, dd=day,
hh=hours, MM=minutes. For example, the string '0407041355' corresponds to 2004 July 7
1:55pm. This string must always be 10 characters long and all fields must be zero filled.
2 Obtain the parameters from the original redirect URL sent to the server. These are most easily
retained as a cookie. The following parameters are required:
a The STAs MAC address (e.g. '00:0A:F5:00:09:99')
Xdata This should have a value of 8 for a successful disconnect.
Xts A time stamp of the form yymmddhhMM, where yy=year, mm=month,
dd=day, hh=hours, MM=minutes. To be valid, the time value (in UTC)
must be within plus or minus 5 minutes of the AP's time.
Xcv A SHA1 hash using the shared password.
Table 22: Fields in the STA-AP-to-ELPS Disconnect Response
Field Description
(ELPS)
(Captive Portal)