Brocade Mobility 7131 Access Point Product Reference Guide (Supporting software release 4.4.0.0 and later) - Manual (Page 38)

26 Brocade Mobility 7131 Access Point Product Reference Guide
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Mobility 7131 Access Point access points with the same ESSID define a coverage area. A valid
ESSID is an alphanumeric, case-sensitive identifier up to 32 characters. An MU searches for an
access point Mobility 7131 Access Point with a matching ESSID and synchronizes (associates) to
establish communications. This device association allows MUs within the coverage area to move
about or roam. As the MU roams from cell to cell, it associates with a different access point Mobility
7131 Access Point. The roam occurs when the MU analyzes the reception quality at a location and
determines a different Mobility 7131 Access Point provides better signal strength and lower MU
load distribution.
If the MU does not find an Mobility 7131 Access Point access point 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/n or
802.11b/g/n 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
Mobility 7131 Access Point access point to another like a phone system. WLANs can therefore be
configured around the needs of specific groups of users, even when they are not in physical
proximity.
MAC Layer Bridging
The access point Mobility 7131 Access Point provides MAC layer bridging between its interfaces.
The Mobility 7131 Access Point access point monitors traffic from its interfaces and, based on
frame address, forwards the frames to the proper destination. The access point tracks source and
destination addresses to provide intelligent bridging as MUs roam or network topologies change.
The access point Mobility 7131 Access Point also handles broadcast and multicast messages and
responds to MU association requests.
The access point Mobility 7131 Access Point 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 Mobility 7131 Access Point access point.
The access point Mobility 7131 Access Point 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 access point Mobility 7131 Access Point internal stack interface handles all messages directed
to the access point Mobility 7131 Access Point. Each Mobility 7131 Access Point stores information
on destinations and their interfaces to facilitate forwarding. When a user sends an ARP (Address
Resolution Protocol) request packet, the access point Mobility 7131 Access Point forwards it over
all enabled interfaces except over the interface the ARP request packet was received.
On receiving the ARP response packet, the access point Mobility 7131 Access Point database
keeps a record of the destination address along with the receiving interface. With this information,
the access point Mobility 7131 Access Point forwards any directed packet to the correct
destination. Transmitted ARP request packets echo back to other MUs. The access point removes
from its database the destination or interface information not used for a specified time. The AP
refreshes its database when it transmits or receives data from these destinations and interfaces.