Handover
There is no standardised handover procedure between one access point and another. If a mobile terminal wishes to maintain its Internet access as it leaves one access point and comes in to range of another, then it must generally manage the registration procedures itself.
(This will be an issue for the future commercial success of Wireless LANs.)
F
igure 2 below shows the typical arrangement of a centrally controlled access service. A backhaul network connects a number of geographically dispersed access points to a central location. At that location the AAA functions and Internet connectivity are provided. So that control may be provided over subscriber access, the arrangements do not allow direct access to the Internet from an access point. Instead, traffic is sent through the backhaul via the backhaul network. Such a network typically uses L2TP tunnels established through the (public) Internet, one tunnel set up per active user.
Figure 2: The elements of a centrally controlled 802.11 access service.
The observant reader will realise that LI is, in principle, easy to achieve at the central location where account information, activity information and the associated traffic are all readily available.
This arrangement may support the free access and paid access business models. If paid access is offered from federated networks, then the arrangement described above could be used with some extra complication relating to AAA, but with all traffic being backhauled to the central location.
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