Alcatel OmniAccess Wireless System 2.1 Product Manual page 56

using the same DHCP-assigned or client-assigned IP Address as long as the session remains active.
Note that the tunnel is torn down and the client must reauthenticate when the client sends a DHCP
Discover with a 0.0.0.0 client IP Address or a 169.254.*.* client auto-IP Address, or when the oper-
ator-set session timeout is exceeded.
Note that the OmniAccess 1200R APs at a remote location must be on the same subnet to support
roaming. Also note that the Standalone WPS Alcatel OmniAccess Wireless System described in About
the Alcatel OmniAccess Wireless System does not support Third-Party APs.
Special Case: Voice Over IP Telephone Roaming
Special Case: Voice Over IP Telephone Roaming
802.11 VoIP telephones actively seek out associations with the strongest RF signal to ensure best
Quality of Service (QoS) and maximum throughput. The minimum VoIP telephone requirement of
20 millisecond or shorter latency time for the roaming handover is easily met by the Alcatel Omni-
Access Wireless System, which has an average handover latency of nine or fewer milliseconds.
This short latency period is controlled by Alcatel OmniAccess Switches and Appliances, rather than
allowing independent APs to negotiate roaming handovers.
The Alcatel OmniAccess Wireless System supports 802.11 VoIP telephone roaming across OmniAccess
AP Access Points, OmniAccess 1200R APs, and Third-Party APs managed by Alcatel OmniAccess
Switches and Appliances on different subnets, as long as the Alcatel OmniAccess Switches and Appli-
ances are in the same mobility group. This roaming is transparent to the VoIP telephone, because the
session is sustained and a tunnel between Alcatel OmniAccess Switches and Appliances allows the VoIP
telephone to continue using the same DHCP-assigned IP Address as long as the session remains active.
Note that the tunnel is torn down and the VoIP client must reauthenticate when the VoIP telephone
sends a DHCP Discover with a 0.0.0.0 VoIP telephone IP Address or a 169.254.*.* VoIP telephone
auto-IP Address, or when the operator-set session timeout is exceeded.
Note that the Standalone WPS Alcatel OmniAccess Wireless System described in About the Alcatel
OmniAccess Wireless System does not support Third-Party APs.
About Client Location
Client Location
The Alcatel OmniAccess Wireless System periodically determines client location and stores the locations
in the ACS database. To view the client location history, display the ACS Monitor Client <client> -
<vendor:MACaddr> page and select Recent Map (High Resolution) or Present Map (High Resolution).
About External DHCP Servers
External DHCP Servers
The Alcatel OmniAccess Operating System is designed to appear as a DHCP Relay to the network and as
a DHCP Server to clients with industry-standard external DHCP Servers that support DHCP Relay. This
means that each Alcatel OmniAccess Switch or Appliance appears as a DHCP Relay agent to the DHCP
Server. This also means that the Alcatel OmniAccess Switch or Appliance appears as a DHCP Server at
the virtual IP Address to wireless clients.
Because the Alcatel OmniAccess Switch or Appliance captures the client IP Address obtained from a
DHCP Server, it maintains the same IP Address for that client during same-Alcatel OmniAccess Switch
or Appliance, inter-Alcatel OmniAccess Switch and Appliance, and inter-subnet Client Roaming.
Per-WLAN Assignment
Per-WLAN Assignment
All Alcatel WLANs can be configured to use the same or different DHCP Servers, or no DHCP Server.
This allows operators considerable flexibility in configuring their Wireless LANs, as further described in
the Alcatel WLANs section.
Note that Alcatel WLANs that support Management over Wireless must allow the management (device
servicing) clients to obtain an IP Address from a DHCP Server.
11/5/04 Client Location
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