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Industrial Ethernet Wireless LAN RLM Manager, CP 1515 Manager
C79000-G8976-C171-01 185
transmission. The key values are shown by capital letters to indicate a real
key or by zero to indicate a non-configured index.
The column “Keys 1-2-3-4” shows an equal sign (=) when the value does not
change from the previous period. This is particularly relevant when it
concerns the stations keys, since it is envisaged that knowledge of the key
values is typically not transferred to the end users, so they have to return
their station equipment to an IT department to get the key values changed. It
is envisaged that changing the Txkey Index is an action that can be done by
end users, since it does not reveal secret information.
Three key roll-over strategies are distinguished:
•Single Key – No Transition (page 185),
•Single Key – Transition Period (page 187), and
•Alternative Schemes (page 188).
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Table 4Single Key - No Transition shows a system, where at each point in
time only one single key is used. The key to be used is dictated by the AP
settings, showing only one valid key at each period. This requires a change
over of keys at all stations more or less synchronous with the Radio Link
Module configuration changes. This is not practical and hence there are four
keys.