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Voice over WLAN Mobile IP Touch Design Guide R2.0
2.1.2. Appliance/Overlay Mode
In Appliance Mode operation, Access Points are not directly attached to Alcatel-Lucent OmniAccess
Wireless Switches. In this type of operational mode, the Alcatel-Lucent OmniAccess Wireless Switch acts
only as an Access Point Controller and does not directly host AP via local 10/100 ports.
This type of operation mode can be highly desirable and advantageous in the following situations:
1. When existing data network elements are present and capable to supporting WLAN Access Points
and traffic.
2. In large and/or multi-floor buildings where cables lengths are commonly in excess of 100m from
the data switching centers and wiring closets to Access Points, thus causing problems for Inline
Power over Ethernet (IEEE 802.3af.)
In cases such as this, localized power options can be proposed to meet or eliminate the distance
limitation and power problems.
3. When system failover/redundancy of the WLAN controller elements is highly desired.
2.1.2.1. Appliance /Overlay Mode Operation
While OmniAccess Wireless Switches can support Direct Mode operation, they can also be used for
Appliance Mode scenarios. In this way, Access Points can be directly connected to an existing LAN
infrastructure Ethernet data switch (from Alcatel-Lucent or third party supplier.) These Access Points can
be configured to automatically connect to multiple OmniAccess Wireless Switch (one at a time) using a
tunnel protocol optimized for lightweight access points management and traffic transport (GRE, IPSec,
and/or L2TP.)
This type of operational mode with OmniAccess Wireless Switches allows for a low cost redundancy
proposal for small configurations, particularly with the OmniAccess 4308 model. By being aware of the IP
addresses of multiple OmniAccess Wireless Switches, Access Points can perform near-immediate transfer
of management responsibilities to backup OmniAccess Wireless Switches and in so doing maintain
operation during periods of partial network outage and/or OmniAccess Wireless Switch maintenance.
Since Access Points are not directly attached to OmniAccess Wireless Switches, network connectivity and
power options must be provided by an Ethernet switch or other source. It is important to ensure that the
desired Ethernet switch is capable of supporting the QoS requirements of the VoIP traffic that it will be
forced to carry. The tunnel path between the Access Point and the Wireless Switch must receive high
priority to ensure a sufficient level of voice quality.
ESD/ Central Pre Sales / DF/ PH
Figure 5: Appliance Mode (WLAN Switch)
17/45
January 2007 – Ed 01
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