Design Guide for the Alcatel
OmniPCX
Enterprise – Mobile IP Touch
2.1.2.
Appliance/Overlay Mode
In Appliance Mode operation, Access Points are not directly attached to Alcatel OmniAccess Wireless
Switches. In this type of operational mode, the Alcatel 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 or third party supplier.) These Access Points can be configured to automatically
connect to one or multiple OmniAccess Wireless Switch(s) 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.
We can also mix both modes (Direct and Appliance) but for backup purpose the best solution remains the
Appliance mode.
ESD/ Central Pre Sales / DF/ JM
12/34
June 2005 – Ed 01
