Presentation on theme: "C ISCO ’ S W IRELESS T ECHNOLOGIES :. Introduction to Wireless Technology Wireless LANs (WLANs) use radio frequencies (RFs) that are radiated into air."— Presentation transcript:
Introduction to Wireless Technology Wireless LANs (WLANs) use radio frequencies (RFs) that are radiated into air from an antenna that creates radio waves. These waves can be absorbed, refracted, or reflected by walls, water, and metal surfaces, resulting in low signal strength.
TABLE Wireless Agencies and Standards AgencyPurposeWeb Site Institute of Electrical and Electronics Engineers (IEEE) Creates and maintains operational standards www.ieee.org Federal Communications Commission (FCC) Regulates the use of wireless devices in the U.S. www.fcc.gov European Telecommunications Standards Institute (ETSi) Charted to produce common standards in Europe www.etsi.org Wi-Fi Alliance Promotes and tests for WLAN interoperability www.wi-fi.com WLAN Association (WLANA)Educates and raises consumer awareness regarding WLANs www.wlana.org
The FCC released three unlicensed bands for public use: 900MHz, 2.4GHz, and 5.7GHz. the 900MHz and 2.4GHz bands are referred to as the Industrial, Scientific, and Medical (ISM) bands, and the 5-GHz band is known as the unlicensed National Information Infrastructure (UNII) band.
If you opt to deploy wireless in a range outside of the three public bands, you need to get a specific license from the FCC FIGURE Unlicensed frequencies
Taking off from what you learned in Chapter 1, “Internetworking,” wireless networking has its own 802 standards group- remember, Ethernet’s committee is 802.3. Wireless starts with 802.11, and there are various other up- and-coming standard groups as well, like 802.16 and 802.20. And there’s no doubt that cellular networks will become huge players in our wireless future. But for now, we’re going to concentrate on the 802.11 standards committee and subcommittees The 802.11 Standards
IEEE 802.11 was the first, original standardized WLAN at 1 and 2Mbps. It runs in the 2.4GHz radio frequency and was ratified in 1997 even though we didn’t see many products pop up until around 1999 when 802.11b was introduced. All the committees listed in Table are amendment to the original 802.11 standard except for 802.11F and 802.11T, which are both stand-alone documents.
CommitteePurpose IEEE 802.11a54Mbps, 5GHz standard IEEE 802.11bEnhancements to 802.11 to support 505 and 11Mbps IEEE 802.11cBridge operation procedures; included in the IEEE 8021D standerd IEEE 802.11dInternational roaming extensions IEEE 802.11eQuality of service IEEE 802.11FInter-Access Point Protocol IEEE 802.11g54Mbps, 2.4GHz standard (backward compatible with 802.11b) IEEE 802.11hDynamic Frequency Selection (DFS) and Transmit Power Control (TPC) at 5GHz IEEE 802.11iEnhanced security IEEE 802.11jExtensions for Japan and U.S. public safety IEEE 802.11kRadio resource measurement enhancements IEEE 802.11mMaintenance of the standards; odds and ends IEEE 802.11nHigher throughput improvements using MIMO (multiple input, multiple output antennas) IEEE 802.11pWireless Access for the Vehicular Environment (WAVE) IEEE 802.11rFast roaming IEEE 802.11sExtended Service Set (ESS) Mesh Networking IEEE 802.11TWireless Performance Prediction (WPP) IEEE 802.11uInternetworking with non-802 networks (cellular, for example) IEEE 802.11vWireless network management IEEE 802.11wProtected management frames IEEE 802.11z3650-3700 operation in U.S. TABLE 802.11 Committees and Subcommittees
2.4GHz (802.11b) It operates in the 2.4GHz unlicensed radio band that delivers a maximum data of 11Mbps. The 802.11b standard has been widely adopted by both vendors and customers. 802.11b used a modulation technique called Direct Sequence Spread Spectrum (DSSS).
2.4GHz (802.11g) The 802.11g standards was ratified in June 2003 and is backward compatible with 802.11b. The 802.11g standard delivers the same 54Mbps maximum data rate 802.11a but runs in the 2.4GHz range-the same as 802.11b. 802.11g and 802.11a use Orthogonal Frequency Division Multiplexing (OFDM) modulation.
5GHz (802.11a) The 802.11a standard delivers a maximum data rate of 54Mbps with 12 non-overlapping frequency channels. The 802.11a products allow the person operating at 54Mbps to shift to 48Mbps, 36Mbps, 24Mbps, 18Mbps, 12Mbps, 9Mbps,and finally still communicate farthest from the AP at 6Mbps.
802.11b802.11g802.11a(h) 2.4GHz 5GHz Most commonHigher throughput Up to 11MbpsUp to 54Mbps*Up to 54Mbps DSSSDSSS/OFDMOFDM 3 non-overlapping channels Up to 23 non- overlapping channels **About 25 users per cell About 20 users per cellAbout 15 users per cell Distance limited by multipath Throughput degraded by 802.11b clients Lower market penetrations *Runs Direct Sequence Spread Spectrum when also running the802.11b at speeds of 11Mbps and below. ** This happens to be Cisco’s rule of thumb. Know that the actual number of users per cell varies based on many factors. Comparing 802.11
Wireless Security Open Access All Wi-Fi Certified wireless LAN products are shipped in “open-access mode, with their security features turned off. Security needs to be enabled on wireless devices during their installation in enterprise environments.
SSIDs, WEP, and MAC Address Authentication Basic security was include the use of Service Set Identifiers(SSIDs), open or shared-key authentication, static Wired Equivalency Protocol (WEP), and optional Media Access Control (MAC) authentication. SSID is a common network name for the devices in a WLAN system that create the wireless LAN. An SSID prevents access by any client device that doesn’t have the SSID. The thing is, by default, an access point broadcasts its SSID in its beacon many times a second. And even if SSID broadcasting is turned off, a bad guy can discover the SSID by monitoring the network and just waiting for a client response to the access point.
Two types of authentication were specified y the IEEE 802.11 committee: open authentication: Involves little more than supplying the correct SSID. Shared –key authentication: The access point sends the client device challenge-text packet that the client must encrypt with the correct Wired Equivalency Protocol (WEP) key return to the access point. With out correct key, authentication will fail and the client won’t be allowed to associate with the access point. Client MAC addresses can be statically typed into each access point, and any of them that show up without that MAC addresses in the filter table would be denied access.
WPA or WPA 2 Pre- Shared Key WPA or WPA 2 Pre- Shared Key (PSK) is a better from of wireless security than any other basic wireless security method. The PSK verifies users via a password or identifying code ( also called a passphrase) on the client machine and the access point. A client only access to the network if its password matches to access point’s password. The PSK also provides keying material TKIP or AES uses to generate an encryption key for each packet of transmitted data.