Symbol Technologies AP-4131 manual Mobile IP

Introduction

An MU can roam within a coverage area by switching APs. Roaming occurs when:

•an unassociated MU attempts to associate or reassociate with an available AP

•the supported rate changes or the MU finds a better transmit rate with another AP

•the RSSI (received signal strength indicator) of a potential AP exceeds the current AP

•the ratio of good-transmitted packets to attempted-transmitted packets falls below a threshold.

An MU selects the best available AP and adjusts itself to the AP direct- sequence channel to begin association. Once associated, the AP begins forwarding any frames it receives addressed to the MU. Each frame contains fields for the current direct-sequence channel. The MU uses these fields to resynchronize to the AP.

The scanning and association process continues for active MUs. This process allows the MUs to find new APs and discard out-of-range or deactivated APs. By testing the airwaves, the MUs can choose the best network connection available.

1.3.7Mobile IP

The Internet Protocol identifies the MU point of attachment to a network through its IP address. The AP routes packets according to the location information contained in the IP header. If the MU roams across routers to another subnet, the following situations occur:

•The MU changes its point of attachment without changing its IP address, causing forthcoming packets to become undeliverable.

•The MU changes its IP address when it moves to a new network, causing it to lose connection.

Mobile IP enables an MU to communicate with other hosts using only its home IP address after changing its point-of-attachment to the internet/intranet.

AP-4131 Access Point Product Reference Guide 21