Moby Dick Consolidated System Integration Plan

D0103v1.doc Version 1 6.7.2003
• If WLA N is the currently used Network technology and we receive from the WLAN device
driver an update with a different identification, we compare it to the best candidate for handover
and keep the one with the highest signal to noise ratio.
• If WLAN is not the currently used Network technology and we receive from the WLAN device
driver an update, we compare it to the best candidate for handover and keep the one with the
highest signal to noise ratio. In this case, when all candidate will have been considered, we will
send an update message NETWORK_ENVIRONMENT_INFOS to the NCP, with the new signal
level.
For TD-CDMA, the message TD-CDMA_INFO will contain the following information: a list of [signal
level, cell Id and IPv6 address of the corresponding Access Router]. We also keep up to two entries
locally: current TD-CDMA “access point” if this technology is in use, and best candidate for handover.
And the same algorithm as for WLAN applies.
By construction, the TD-CDMA driver will have the capability to produce the information needed (cell id
/ signal level / Access Router IPv6 address) and transmit them to the MTNM.
An extension will be required for the WLAN driver, to retrieve the information needed (IPv6 address of
Access Router - signal to noise ratio – IPv6 subnet prefix) and transmit them to the MTNM. This
extension has been implemented on the Prism2 driver for the SMC WLAN cards.
For Ethernet, an extension to the driver will also be needed, to monitor the Router Advertisements
received on this interface (even when it is not connected to the IP stack). Here, we have two possible
solutions. First one: use a specific tool to discover availability / unavailability of the Ethernet link, and
retrieve router advertisements, although this facility might not be offered by all cards.
Second one: connect to Ethernet driver from user space with a raw socket every N seconds, and wait until
a Router Advertisement is received (with a timeout to declare the link unavailable).
The specific tool proposed for the first solution has been evaluated and works fine. Therefore the first
solution is implemented.
The Network Environment Info block will also be aware of the current technology in use, and will warn
the NCP when a change occurs (Attach Procedure, Manual Handover, and Automatic Handover), via the
message NETWORK_TECHNOLOGY_IN_USE (this message will also contain the IPv6 subnet prefix of
the currently used Access Router).
This block will also have the responsibility, when possible, to detect that the layer two connectivity has
been lost “unexpectedly”, for the network technology currently in use, or about to be used during a fast
handover.
• For TD-CMDA, it means receiving the message LOST_TD-CDMA_CONN from the RCM,
indicating that the radio connection has been lost; or receiving a message TD-CDMA_INFO
from the RCM, with a signal level lower than TD-CDMA_lower value.
• For WLAN, it means receiving a message WLAN_INFO from the monitoring extension of the
WLAN driver, with a signal level lower than WLAN_lower value.
• For Ethernet, it means receiving the message ETHERNET_INFO, with information “Ethernet not
present”.
If the layer two connectivity has been lost for the currently in use network technology, the Automatic
Handover procedure should be triggered to select a new Network Technology among those available (the
current one will be marked as unavailable). But as we have lost connectivity with current Access Router,
the Fast Handover procedure cannot be used. A “regular Handover” will have to be triggered, that is to
say a registration procedure in a first implementation approach (see Handover Execution block for more
details).
If the layer 2 connectivity has been lost for the target technology during a Fast Handover procedure, this
procedure should be aborted via a message ABORT_HANDOVER, sent to the Fast Handover module (see
Handover Execution block for more details). This will not be implemented, because it complicates the
whole process, and we expect the Fast Handover to be fast enough for the target technology to stay in
acceptable L2 conditions.
4.1.2.2.4 Attach Procedure block
The “attach procedure” block can be triggered in these three first cases:
• First case: the message START_NETWORK_CONNECTION has been received from the Explicit
Connectivity Request block of the NCP, with parameters user login and user password. In this
case, the message START_NETWORK_CONNECTION_ACK should be sent back to the NCP,
after the attach procedure has been executed, with the status as parameter. This first case is the
initial registration procedure, for a user that has not been authenticated and authorized yet.
• Second case: a handover has been decided by the Manual or Automatic Handover sub-block, but
it cannot be fast (inter domain handover), so an attach procedure is requested.
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