Cabletron Systems 3Com manual Theory of Operation

Page 23

Theory of Operation 23

Enabling the extended roaming feature is like giving an individual a local post office forwarding address when leaving home for an extended period. When mail arrives for the individual home address, it is forwarded by the local post office to the current care-of-address. Using this method, only the local post office requires notification of the individual current address. While this example represents the general concept of extended roaming operation and functionality, it does not represent the implementation of extended roaming used.

If you wish to use extended roaming, set your wireless clients for extended roaming as specified in the AirConnect Wireless PC Card User Guide.

The following terms describe elements of the extended roaming feature:

■A tunnel is the path taken by the original packet encapsulated within the payload portion of a second packet to some destination on the network.

■A Home Agent is an AP acting as a router on the wireless client home network. The home agent intercepts packets sent to the wireless client home address and tunnels the message to the wireless client at its current location. This happens as long as the wireless client keeps its home agent informed of its current location on some foreign link.

■A Foreign Agent is an AP acting as a router at the wireless client location on a foreign link. The foreign agent serves as the default router for packets sent out by the wireless client connected on the same foreign link.

■A care-of-addressis the IP address used by the wireless client visiting a foreign link. This address changes each time the wireless client moves to another foreign link. It can also be viewed as an exit point of a tunnel between the wireless client home agent and the wireless client itself.

Security Security involves two distinct areas: authentication and privacy. Authentication ensures that only authorized users access the wireless network. Privacy ensures that communication between authenticated users and the network cannot be intercepted or overheard. The Access Control List provides authentication using the wireless LAN service area and a system administrator-supplied list of all the wireless client MAC addresses authorized to access the Home Service Area. Privacy is ensured by enabling the 40-bit WEP encryption option.

Supporting CAM and Continuously Aware Mode (CAM) stations leave their radios on continuously to PSP Stations hear every beacon and message transmitted. These systems operate without any

adjustments by the AP.

A beacon is a uniframe system packet broadcast by the AP to keep the network synchronized. A beacon includes the wireless LAN service area, the AP address, the Broadcast destination addresses, a time stamp, Delivery Traffic Indicator Maps, and the Traffic Indicator Message (TIM).

Power Save Polling (PSP) stations power off their radios for long periods. When a wireless client in PSP mode associates with an AP, it notifies the AP of its activity status. The AP responds by buffering packets received for the wireless client. The PSP-mode wireless client wakes up to listen to the AP beacon every nth Beacon Interval where n is a PSP-mode value from the 1 to 5-range; the Beacon Interval is set on the wireless client. When the wireless client wakes up and sees its bit set in the TIM, it issues a poll request to the AP for packets stored for it. The AP sends

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Contents Version AirConnect 11 Mbps Wireless LAN Access Point User Guide95052-8145 3Com CorporationBayfront Plaza Santa Clara, CaliforniaContents Installing Access Point Hardware Monitoring Wireless Clients Access Point Installation Configuring the AP Access Point Specifications Technical Support Page Topologies Overview of Digital Wireless NetworkingIntroduction AirConnect NetworkOverview of Digital Wireless Networking AirConnect Network Topologies To the Ethernet LAN AirConnect AccessWireless clients PointAirConnect Access Point Results in the original digital data PowerBASE-TWireless clients and APs Radio BasicsRadio Basics 802.1d Spanning Tree Support Wireless LAN Service AreaSite Surveys Filtering and Access Control Network Control Protocol NCP as described PPP Connection Data Rate Requirement Overview of Digital Wireless Networking Theory of Operation Simple Network Management Protocol Snmp Increased MIB Support Using SnmpProgrammable Snmp Trap Support Management protocol MIBMethod Description Using the User InterfaceRequirements Installing Access Point HardwarePrecautions Package ContentsUS line cord Part Number Power OptionsStandard power supply 115/230VAC, 50/60Hz, 24V/14 Remote power distribution system, Part Number AP-PS-11Wall Mount To mount an AP on a wall Mounting the APBelow Ceiling Mount To mount an AP on a ceiling Mounting the AP PowerBASE-T can be used to power the AP UsingPowerBASE-T Condition, and other activity LED IndicatorsOff Blinking Power No power Power on During boot sequence Electrical Management System EMS operating outlet Troubleshooting3Com Support Center Verify AP OperationNetwork connection verification Verify Network Wiring TopologyPage Forwarding Counts Monitoring StatisticsSystem Properties Interface StatisticsStatistics Ethernet StatisticsRadio Frequency Type Name Definition MiscellaneousStatistics window, select Main Menu→Misc Statistics Press Esc or Previous F4 to exitSelect Clear All Statistics Clearing StatisticsKnown APs Setup Network Web Server Help File Access Gaining Access to the User Interface UI Using a Web BrowserGaining access to the User Interface UI Help File AccessSelect System Configuration Accessing the Web Browser UISelect Virtual Directory Select Close/ExitSelect Save F1 to save the configuration Select Special Functions Select Reset APType the case sensitive AP name Under Configuration, select Security Select System PasswordParameter Description Select Easy Setup--Easy SetupSelect Easy Setup--Easy Setup Click Add/Delete Gateways Adding or Deleting Disallowed Wireless Clients Adding Allowed Wireless ClientsAdding or Deleting a Range of Allowed Wireless Clients Select Configuration--Security For the Short RF Preamble setting, click DisabledConsiderations Enabling or Disabling EncryptionFrequency No. of Channels Country Enable or disable interfaces on the APInterface Description Default Condition Enter the Multicast Mask data and voice values Snmp Trap Description Default Value Select Enabled or Disable All for All Snmp TrapsConfiguring the Originating Modem Filtering to Discard Packets Configuring the Answering ModemFiltering to Forward Packets Under Configuration, select Firmware Removing Filtered Packet Types Networking ProtocolsClick Delete Filter Disabling Type FilteringSpecial Function Description Active. Clear the wireless client association table forSelect Regular at the Wireless Clients prompt Monitoring Wireless ClientsWireless Clients Indicates a 3Com voice-enabled device Versions Ascii InterfaceLatest version. Refer to Manually Updating AP Firmware on Arrow/Function Key Control Character Enable serial portConfigure the AP for the following Prompt Description To exit from submenus, press EscConfiguring The Serial Port Select Telnet LoginsPress Tab to select System Password To enable and configure the serial port connection on the APSelect Modem Hangup Setting DescriptionConfiguring the Dial-Up System Hanging UpWindow InstallationConfiguring the AP That can associate with this AP. The default is Disabled Wsaid PPP with Modems PPP DirectEstablishing a Connection From the answering APs UI Set the Connect Mode to AnswerOriginating AP Answering APFor automatic dial-out, reset the AP Press up/down arrows to toggle between range and individual Range of Wireless ClientsRemoving All Allowed Wireless Clients Removing Allowed Wireless ClientsEnable/Disable the ACL Address Filtering Load ACL from Wireless Client ListAdding Disallowed Wireless Clients Removing Disallowed Wireless ClientsOptions Clearing WirelessSetting Logging Clients from the APPrevious version of AP firmware Manually UpdatingAP Firmware Type the firmware file name in the Download Filename field Remainder of this procedure uses Windows 98 as an exampleSelect Alter Filenames/HELP URL/TFTP and press Enter Select Send File Open the Special Functions windowSelect Transfer from the emulation program menu bar Select Alter Filenames/HELP URL/TFTP Server and press Enter Download is complete when the UI displaysExtended Roaming Using MD5Authentication Performing PingsHex-digit sequence Wireless client and the access pointEncryption Restoring Configurations Press the Tab key to highlight .Short RF Preamble EnabledSelect Restore Factory Configuration Output Characteristics Access Point SpecificationsPhysical Characteristics Radio Characteristics Frequency No. of Channels CountryNetwork Characteristics World Wide Web Site ServicesTechnical Support Online TechnicalNorth America Latin AmericaTo obtain an RMA number, call or fax Page Ascii IndexSnmp agent 3Com AirConnect Access Point 3Com Corporation Limited WarrantyObtaining Warranty Radio Frequency Interference Requirements Canada Regulatory Compliance Information3Com End User Software License Agreement Important Read Before Using This Product
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