Linksys WRT51AB What Ieee 802.11b features are supported?, What is ad-hoc mode?, What is roaming?

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Instant Wireless® Series

What IEEE 802.11b features are supported?

The product supports the following IEEE 802.11b functions:

CSMA/CA plus Acknowledge protocol

Multi-Channel Roaming

Automatic Rate Selection

RTS/CTS feature

Fragmentation

Power Management

What is ad-hoc mode?

When a wireless network is set to ad-hoc mode, the wireless-equipped com- puters are configured to communicate directly with each other. The ad-hoc wireless network will not communicate with any wired network.

What is infrastructure mode?

When a wireless network is set to infrastructure mode, the wireless network is configured to communicate with a wired network through a wireless access point.

What is roaming?

Roaming is the ability of a portable computer user to communicate continu- ously while moving freely throughout an area greater than that covered by a sin- gle access point. Before using the roaming function, the workstation must make sure that it is the same channel number with the access point of dedicated cov- erage area.

To achieve true seamless connectivity, the wireless LAN must incorporate a number of different functions. Each node and access point, for example, must always acknowledge receipt of each message. Each node must maintain contact with the wireless network even when not actually transmitting data. Achieving these functions simultaneously requires a dynamic RF networking technology that links access points and nodes. In such a system, the user’s end node under- takes a search for the best possible access to the system. First, it evaluates such factors as signal strength and quality, as well as the message load currently being carried by each access point and the distance of each access point to the wired backbone. Based on that information, the node next selects the right access point and registers its address. Communications between end node and host computer can then be transmitted up and down the backbone.

As the user moves on, the end node’s RF transmitter regularly checks the sys- tem to determine whether it is in touch with the original access point or whether it should seek a new one. When a node no longer receives acknowledgment

Dual-Band Wireless A+B Broadband Router

from its original access point, it undertakes a new search. Upon finding a new access point, it then re-registers, and the communication process continues.

What is ISM band?

The FCC and their counterparts outside of the U.S. have set aside bandwidth for unlicensed use in the ISM (Industrial, Scientific and Medical) band. Spectrum in the vicinity of 2.4 GHz, in particular, is being made available worldwide. This presents a truly revolutionary opportunity to place convenient high-speed wireless capabilities in the hands of users around the globe.

What is Spread Spectrum?

Spread Spectrum technology is a wideband radio frequency technique devel- oped by the military for use in reliable, secure, mission-critical communica- tions systems. It is designed to trade off bandwidth efficiency for reliability, integrity, and security. In other words, more bandwidth is consumed than in the case of narrowband transmission, but the trade-off produces a signal that is, in effect, louder and thus easier to detect, provided that the receiver knows the parameters of the spread-spectrum signal being broadcast. If a receiver is not tuned to the right frequency, a spread-spectrum signal looks like background noise. There are two main alternatives, Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS).

What is DSSS? What is FHSS? And what are their differences? Frequency-HoppingSpread-Spectrum (FHSS) uses a narrowband carrier that changes frequency in a pattern that is known to both transmitter and receiver. Properly synchronized, the net effect is to maintain a single logical channel. To an unintended receiver, FHSS appears to be short-duration impulse noise. Direct-SequenceSpread-Spectrum (DSSS) generates a redundant bit pattern for each bit to be transmitted. This bit pattern is called a chip (or chipping code). The longer the chip, the greater the probability that the original data can be recovered. Even if one or more bits in the chip are damaged during trans- mission, statistical techniques embedded in the radio can recover the original data without the need for retransmission. To an unintended receiver, DSSS appears as low power wideband noise and is rejected (ignored) by most nar- rowband receivers.

Will the information be intercepted while it is being transmitted through the air? WLAN features two-fold protection in security. On the hardware side, as with Direct Sequence Spread Spectrum technology, it has the inherent security fea- ture of scrambling. On the software side, WLAN offers the encryption function (WEP) to enhance security and access control.

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Contents Dual-Band Wireless A+B Broadband Router Copyright & Trademarks Table of Contents Common Problems and Solutions Frequently Asked Questions IntroductionEnvironmental 127 Router’s Functions FeaturesIP Addresses What’s an IP Address?Dhcp Dynamic Host Configuration Protocol Servers Router Setup OverviewDynamic IP Addresses Getting to Know the Dual-Band Wireless A+B Broadband Router Router’s Back PanelRouter’s Front Panel LEDs LAN Indicators Internet IndicatorsProceed to Connect the Router Wired Connection to a PC Connect the RouterOverview Wireless Connection to a PC Configure the PCsGo to Configure the Router’s Basic Settings Configuring Windows 98 and Millennium PCsConfiguring Windows 2000 PCs Configuring Windows XP PCs Configure the Router’s Basic Settings Enter the Default Gateway Automatic Configuration DhcpStatic or Fixed IP Address Enter the Internet IP AddressRouter’s Web-based Utility How to Access the Web-based UtilitySetup Automatic Configuration DhcpStatic IP Pptp 5GHz, 802.11a 5GHz, 802.11a WEP 4GHz, 802.11b WEP Status PasswordLAN Dhcp Help LogAdvanced Tabs 5GHz, 802.11a Advanced Wireless802.1x Configuration Radius Server Filters Private MAC Filter To set up a filter Private IP Filter11-20 , 21-30 , 31-40 , or 41-50 from Port Forwarding Applications External Port TCP Protocol UDP ProtocolClick the Delete This Entry button RoutingDMZ Host MAC Address Clone Common Problems and Solutions Appendix a TroubleshootingNeed to set a static IP address on a PC For Windows NTFor Windows XP Want to test my Internet connectionFor Windows 98, Me, 2000, and XP TCP UDP Need to set up a server behind my RouterCan’t get the Internet game, server, or application to work Need to upgrade the firmware To start over, I need to set the Router to factory defaultFirmware upgrade failed, and/or the Diag LED is flashing My DSL service’s PPPoE is always disconnectingClick the Advanced = Filters tab Frequently Asked QuestionsHow can I block corrupted FTP downloads? Does the Router support ICQ send file?What are the advanced features of the Router? What is DMZ Hosting?What is the Ieee 802.11a standard? What is the Ieee 802.11b standard?What is ad-hoc mode? What Ieee 802.11b features are supported?What is infrastructure mode? What is roaming?What is a MAC Address? What is WEP?How do I reset the Router? How do I resolve issues with signal loss?Step One Pinging an IP Address Appendix B How to Ping Your ISP’s E-mail & Web AddressesAppendix C Configuring Wireless Security Step Two Pinging for a Web AddressBackground WEP Encryption 802.1x AuthenticationFigure C-2 MD5 Authentication for Windows XPFigure C-5 Figure C-9 Digital Certificate InstallationFigure C-13 Click Install this certificateFigure C-18 TLS Authentication for Windows XPFigure C-21 For Windows 95, 98, and Me Figure C-25For Windows NT, 2000, and XP Figure D-3Appendix E Glossary 111 113 115 117 119 121 123 125 One 10/100 RJ-45 Port for Cable/DSL Modem Appendix F SpecificationsCategory 5 Ethernet Network Cable or better EnvironmentalSales Information Technical Support RMA Issues Fax Appendix G Warranty InformationAppendix H Contact Information Web site FTP siteCopyright 2002 Linksys, All Rights Reserved