MAD00558_jv - презентация

1 © 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Wireless LANs Introducing WLANs

2 © 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Wireless Data Technologies

3 © 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Wireless Data Technologies (Cont.)

4 © 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Wireless Data Technologies (Cont.) PAN (Personal Area Network) LAN (Local Area Network) WAN (Wide Area Network) MAN (Metropolitan Area Network) PANLANMANWAN Standards Bluetooth IEEE a, b, g MMDS, LMDS GSM, GPRS, CDMA, 2.5–3G Speed

5 © 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Wireless LAN (WLAN) A WLAN is a shared network. An access point is a shared device and functions like a shared Ethernet hub. Data is transmitted over radio waves. Two-way radio communications (half-duplex) are used. The same radio frequency is used for sending and receiving (transceiver).

6 © 2006 Cisco Systems, Inc. All rights reserved. BCMSN v WLAN Evolution Warehousing Retail Health care Education Businesses Home

7 © 2006 Cisco Systems, Inc. All rights reserved. BCMSN v What Are WLANs? They are: Local In building or campus for mobile users Radio or infrared Not required to have RF licenses in most countries Using equipment owned by customers They are not: WAN or MAN networks Cellular phones networks Packet data transmission via celluar phone networks –Cellular digital packet data (CDPD) –General packet radio service (GPRS) –2.5G to 3G services

8 © 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Similarities Between WLAN and LAN A WLAN is an 802 LAN. –Transmits data over the air vs. data over the wire –Looks like a wired network to the user –Defines physical and data link layer –Uses MAC addresses The same protocols/applications run over both WLANs and LANs. –IP (network layer) –IPSec VPNs (IP-based) –Web, FTP, SNMP (applications)

9 © 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Differences Between WLAN and LAN WLANs use radio waves as the physical layer. –WLANs use CSMA/CA instead of CSMA/CD to access the network. Radio waves have problems that are not found on wires. –Connectivity issues. Coverage problems Multipath issues Interference, noise –Privacy issues. WLANs use mobile clients. –No physical connection. –Battery-powered. WLANs must meet country-specific RF regulations.

10 © 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Summary Different wireless data technologies with different characteristics are available. WLANs were introduced to provide local connectivity with higher data rates. WLANs use half-duplex transmission. WLANs have similarities and differences compared to wired LANS.

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