Symbol Technologies AP-5131 - Manual (Page 36)

AP-5131 Access Point Product Reference Guide 1-20
different AP-5131. The roam occurs when the MU analyzes the reception quality at a location and
determines a different AP-5131 provides better signal strength and lower MU load distribution.
If the MU does not find an AP-5131 with a workable signal, it can perform a scan to find any AP. As
MUs switch APs, the AP updates its association statistics.
The user can configure the ESSID to correspond to up to 16 WLANs on each 802.11a or 802.11b/g
radio. A Wireless Local Area Network (WLAN) is a data-communications system that flexibly extends
the functionalities of a wired LAN. A WLAN does not require lining up devices for line-of-sight
transmission, and are thus, desirable. Within the WLAN, roaming users can be handed off from one
AP-5131 to another like a cellular phone system. WLANs can therefore be configured around the
needs of specific groups of users, even when they are not in physical proximity.
1.3.2 MAC Layer Bridging
The AP-5131 provides MAC layer bridging between its interfaces. The AP-5131 monitors traffic from
its interfaces and, based on frame address, forwards the frames to the proper destination. The
AP-5131 tracks source and destination addresses to provide intelligent bridging as MUs roam or
network topologies change. The AP-5131 also handles broadcast and multicast messages and
responds to MU association requests.
The AP-5131 listens to all packets on its LAN and WAN interfaces and builds an address database
using MAC addresses. An address in the database includes the interface media that the device uses
to associate with the AP-5131. The AP-5131 uses the database to forward packets from one interface
to another. The bridge forwards packets addressed to unknown systems to the Default Interface
(Ethernet).
The AP-5131 internal stack interface handles all messages directed to the AP-5131. Each AP-5131
stores information on destinations and their interfaces to facilitate forwarding. When a user sends
an ARP (Address Resolution Protocol) request packet, the AP-5131 forwards it over all enabled
interfaces except over the interface the ARP request packet was received.
On receiving the ARP response packet, the AP-5131 database keeps a record of the destination
address along with the receiving interface. With this information, the AP-5131 forwards any directed
packet to the correct destination. Transmitted ARP request packets echo back to other MUs. The
AP-5131 removes from its database the destination or interface information that is not used for a
specified time. The AP refreshes its database when it transmits or receives data from these
destinations and interfaces.