User's Manual

hwc_intro.fm
Overview of the Controller, Access Points and Convergence Software solution
Controller, Access Points and Convergence Software and your network
A31003-W1050-U100-2-7619,
March 2008
HiPath Wireless Controller, Access Points and Convergence Software V5 R1 , C20/C2400 User Guide 29
specific filter is returned or indicated by the authentication mechanism. The
characteristics and level of access for a filter are controlled and defined by the
system administrator.
2.3.6 Mobility and roaming
In typical configurations that are not HiPath Wireless, APs are setup as bridges
that bridge wireless traffic to the local subnet. In bridging configurations, the user
obtains an IP address from the same subnet as the AP. If the user roams within
APs on the same subnet, it is able to keep using the same IP address. However,
if the user roams to another AP outside of that subnet, its IP address is no longer
valid. The user's client device must recognize that the IP address it has is no
longer valid and re-negotiate a new one on the new subnet. The protocol does
not mandate any action on the user. The recovery procedure is entirely client
dependent. Some clients automatically attempt to obtain a new address on roam
(which affects roaming latency), while others will hold on to their IP address. This
loss of IP address continuity seriously affects the client's experience in the
network, because in some cases it can take minutes for a new address to be
negotiated.
The Controller, Access Points and Convergence Software solution centralizes the
user's network point of presence, therefore abstracting and decoupling the user's
IP address assignment from that of the APs location subnet. That means that the
user is able to roam across any AP without loosing its own IP address, regardless
of the subnet on which the serving APs are deployed.
In addition, a HiPath Wireless Controller can learn about other HiPath Wireless
Controllers on the network and then exchange client session information. This
enables a wireless device user to roam seamlessly between different Wireless
APs on different HiPath Wireless Controllers.
2.3.7 Network availability
The Controller, Access Points and Convergence Software provides availability
against Wireless AP outages, HiPath Wireless Controller outages, and even
network outages. The HiPath Wireless Controller (C20/C2400 platforms)in a
VLAN bridged VNS can potentially allow the user to retain the IP address in a
failover scenario, if the VNS/VLAN is common to both controllers. For example,
availability is provided by defining a paired controller configuration by which each
peer can act as the backup controller for the other's APs. APs in one controller
are allowed to failover and register with the alternate controller.
If a HiPath Wireless Controller fails, all of its associated Wireless APs can
automatically switch over to another HiPath Wireless Controller that has been
defined as the secondary or backup HiPath Wireless Controller. If the AP reboots,
the original HiPath Wireless Controller is restored. The original HiPath Wireless