Call Flow Summary
- PPP Negotiation: A data call is initiated by beginning PPP. Once PPP is successfully established, the system will understand if the call is a mobile IP call or simple IP call. At this point, the system is not aware of the subscriber username and will use settings from the default subscriber template in the source context or the context defined by the "aaa default-domain subscriber" setting in the global configuration.
- FA Agent Advertisement:
Once the system has determined the call is a Mobile IP call, the FA will send a
Router Advertisement message with a Mobility Agent Advertisement extension. The
Mobility Agent Advertisement includes a Registration Lifetime field. The value
of this field will come from one of two places. The FA service has a
configurable setting named "advertise reg-lifetime". The default value for this
setting is 600. A setting in the default subscriber template called "timeout
idle" is also a candidate. The default value for this setting is 0 (null). The
smaller of these two configurable parameters is used as the Registration
Lifetime value. Leaving the settings at the defaults will result in an
advertised lifetime of 600.
Advertise Reg-Lifetime in FA Service Timeout Idle in Subscriber Template Resulting Advertised Registration Lifetime 600 0 600 600 900 600 3600 1200 1200
- AAA Authentication and MIP Registration Request: The next
step in the MIP process will be to authenticate the user at the FA. It is at
this stage where a failure condition can be introduced.
If the Access-Accept message does not return any values related to timers, the subscribers MIP Registration Request is sent on to the HA.
If the Access-Accept message does include an attribute relating to Idle or Absolute timer the FA will evaluate the requested lifetime from the device to the value returned by the AAA. The FA will treat any Idle or Absolute timer value returned by the AAA as a maximum value and as such:
- If the requested MIP lifetime from the device is less-than than the returned radius attribute, the lifetime value is considered valid and the MIP Registration Request is forwarded on to the HA.
- If the requested MIP lifetime from the device is greater-than the returned radius attribute, the requested lifetime value is considered to be too long. The FA will send a MIP Registration Reply to the device with a response code of Error 69 - Requested Lifetime Too Long . In the reply message, the FA will populate the Lifetime value with the maximum acceptable lifetime. The device may send a new MIP request with this new lifetime value.
MIP Lifetime Requested by Device Idle-Timer Value in Access-Accept Resulting MIP Lifetime Request in MIP Request to HA 3600 (Not Returned) 3600 3600 7200 3600 3600 1800 Failure - Error 69
- HA Process MIP Request:
The HA has now received a Mobile IP Registration request forwarded by the FA on
behalf of the device. The MIP request contains the username and the requested
lifetime (as well as other parameters). The HA will take this lifetime request
and compare it to the configurable parameters associated with the HA service
and associated configurations. The HA will use the username to determine which
subscriber template to use for subscriber specific settings.
The parameters the HA uses to determine the MIP lifetime are the requested lifetime, the "reg-lifetime" setting in the HA service and the "timeout idle" setting in the subscriber template. If the requested MIP lifetime is lower it is be sent back to the mobile; if the MIP lifetime is higher the system sends back an RRQ accept with the lifetime set to 5 seconds less than the lower of the idle or absolute timeout for the user.
MIP Lifetime Requested by Device Timeout Idle/Absolute in Subscriber Template Reg-Lifetime Value in HA Service MIP Lifetime Returned to Mobile Device 3600 0(default) 7200 3600 3600 7200 1805 1800 3600 1705 3600 1700 PDSN/FA HA Advertise Reg-Lifetime in FA Service Timeout Idle/Absolute in Subsc. Template (Source Context) Idle-Timer Value in Access-Accept Timeout Idle/Absolute in Subscriber Template(HA Context) Reg-Lifetime Value in HA Service Resulting Lifetime Value sent to Mobile Device 600 0(default) (not returned) 0(default) 7200 600 1800 900 7200 7200 1805 900 3600 1200 3600 1705 3600 1200 1500 3600 1500 0(default) 3600 1500 3600 0(default) (not returned) 0(default) 2405 2400 3600 0(default) (not returned) 2005 3600 2000 65534 0(default) 7200 0(default) 3600 Lifetime Too Long