WESM zl Management and Configuration Guide WT.01.28 and greater

9-2

Fast Layer 2 Roaming and Layer 3 Mobility

Overview

The type of roaming that your ProCurve Wireless Edge Services zl Modules support

depends on your network topology and module configurations, as well as on other

factors.

This overview has three main purposes:

■ explaining when you can and should configure fast Layer 2 roaming

■ explaining when Layer 3 mobility is required

■ summarizing the configurations required to implement the best possible roaming

behavior in various circumstances

The sections that follow the overview explain how to enable fast Layer 2 roaming

and Layer 3 mobility.

Layer 2 Roaming on a Single Wireless Edge Services

zl Module

The Wireless LAN System, with its coordinated AP design, facilitates fast and

seamless roaming between wireless cells. A central device, the Wireless Edge

Services zl Module, controls all security settings and associations with wireless

stations. The module generates and encrypts 802.11 frames. In other words, the

module functions much like a single, high-capability AP with many remote radios

(the RPs). Therefore, when a station disassociates from one RP and reassociates with

another RP adopted by the same module, the module already has in place the

association, authentication, and encryption keys.

No matter which security options you have enabled on a wireless LAN (WLAN), a

station can quickly roam (under 50 milliseconds) between two RPs adopted by the

same module.

The Wireless Edge Services zl Module also supports 802.11i mechanisms for

speeding roaming in a WLAN that requires Wi-Fi Protected Access (WPA)/WPA2

with 802.1X. These mechanisms help to speed roaming both between RPs adopted

by the same module and by different modules.