Cisco AIR-WLC2006-K9 - Wireless LAN Controller 2006 Podręcznik Użytkownika Pobierz pdf (Strona 34)

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Cisco Wireless LAN Solution Product Guide

OL-7955-01

Chapter 1 Overview

Client Roaming

Inter-Subnet (Layer 3) Roaming

In multiple-controller deployments, the Cisco Wireless LAN Solution supports client roaming across

access points managed by controllers in the same mobility group on different subnets. This roaming is

transparent to the client, because the session is sustained and a tunnel between the controllers allows the

client to continue 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

operator-set session timeout is exceeded.

Note that the Cisco 1030 remote edge lightweight access points at a remote location must be on the same

subnet to support 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 Cisco Wireless LAN

Solution, which has an average handover latency of nine or fewer milliseconds.

This short latency period is controlled by Cisco Wireless LAN Controllers, rather than allowing

independent access points to negotiate roaming handovers.

The Cisco Wireless LAN Solution supports 802.11 VoIP telephone roaming across Cisco 1000 series

lightweight access points managed by Cisco Wireless LAN Controllers on different subnets, as long as

the controllers are in the same mobility group. This roaming is transparent to the VoIP telephone,

because the session is sustained and a tunnel between controllers 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.

Client Location

The Cisco Wireless LAN Solution periodically determines client, rogue access point, rogue access point

client, radio frequency ID (RFID) tag location and stores the locations in the Cisco WCS database. To

view the client location history, browse to the Cisco WCS Monitor Client client – vendor-MAC-address

page and select Recent Map (High Resolution) or Present Map (High Resolution). Cisco WCS Base

supports location to the nearest access point. Cisco WCS Location supports location to within 10 meters.

When Cisco WCS Location is used, Cisco Wireless LAN Solution end users can also deploy Cisco 2700

Series Location Appliances (location appliances), described in the “Cisco 2700 Series Location

Appliances” section on page 1-49. The location appliance enhances the high-accuracy built-in Cisco

WCS Location abilities by computing, collecting and storing historical location data, which can be

displayed in Cisco WCS. In this role, the location appliance acts as a server to one or more Cisco WCS

Servers, collecting, storing, and passing on data from its associated controllers.

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