Moby Dick Consolidated System Integration Plan

D0103v1.doc Version 1 6.7.2003
• Third case: the layer two connectivity has been lost unexpectedly as explained in the Network
Environment Info sub-block, and the Automatic Handover sub-block requests an attach
procedure.
NCP
Set
Network
Preferences
Set
Handover
Preference
Manual
Handover
Network
Environment
Infos
Explicit
Connectivity
Request
MTNM
Set
Network
Preferences
Set
Handover
Preference
Network
Environment
Infos
Attach
Procedure
Registration module
Network device drivers
TDCDMA WLAN Ethernet
Figure 7: Attach Procedure block
In the first case, an initial step will be to wait until the Network Environment Info block has received
information from the different device drivers. Then to select a network technology, using the information
stored in the Set Network preferences block. The technology associated to each preference (from the first
to the third) will be analysed, based on the information from the Network Environment Info block, and
selected or rejected according to the following rules: Ethernet is selected if present, WLAN and TD-
CDMA are selected if present and signal to noise ratio for WLAN, signal level for TD-CDMA, is higher
than a predefined threshold (respectively WLAN_threshold and TD-CDMA_threshold).
For example, if network preferences are first WLAN, second TD-CDMA and third Ethernet; and if
WLAN signal to noise ratio is lower than WLAN_threshold, but TD-CDMA signal level higher than TD-
CDMA_threshold and Ethernet is present: WLAN is examined first and rejected, TD-CDMA is examined
second and selected.
In the two other cases, the target network technology will already have been chosen, by the manual or
automatic handover block.
The next step is to assure the L2 connectivity via the device driver of the selected technology. This step
will be detailed in section ‘Handover Execution’, for each of the 3 available technologies. One can refer
to this section for the detailed procedure.
Then link the IP stack to the device driver of the selected Network technology.
The final step is to send the appropriate message to the Registration module, to trigger the AAAC
mechanisms involved in the Attach Procedure:
the message START_REGISTRATION will be used, with parameters: Home Address and CoA of MT,
Access Router IP address, user login and user password. An acknowledgement message will be sent from
the Registration module to the MTNM, REGISTRATION_ACK, to give the status of the attachment.
If it is negative, the global procedure can be restarted after a certain timeout.
The “attach procedure” block can also be triggered to end a user session, when the message
TERMINATE_NETWORK_CONNECTION has been received from the Explicit Connectivity Request
block of the NCP, with no parameter.
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