JARINGAN KOMPUTER 2JARINGAN KOMPUTER 2

WIRELESS LANWIRELESS LAN

Muhammad Zen S. Hadi, ST. MSc.

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Course OutlineCourse Outline• Introduction of Wireless Network• IEEE 802.11 Architecture• IEEE 802.11 Physical Layer• Data Encryption Wireless• Site Survey

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Wireless?Wireless?• A wireless LAN or WLAN is a wireless local area

t k th t di it inetwork that uses radio waves as its carrier.• The last link with the users is wireless, to give a

net o k onne tion to ll e in b ilding onetwork connection to all users in a building or campus.

• The backbone network usually uses cables• The backbone network usually uses cables

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How do wireless LANs work?How do wireless LANs work?Wireless LANs operate in almost the same way aswired LANs, using the same networking protocolsand supporting the most of the sameapplications.

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How are WLANs Different?How are WLANs Different?• They use specialized physical and data link

protocolsprotocols• They integrate into existing networks through

access points which provide a bridging f n tionfunction

• They let you stay connected as you roam from one coverage area to anotherg

• They have unique security considerations • They have specific interoperability

i trequirements • They require different hardware• They offer performance that differs from wired• They offer performance that differs from wired

LANs. 5

Physical and Data Link LayersPhysical and Data Link LayersPhysical Layer:

Th i l NIC t k f f d t f• The wireless NIC takes frames of data from the link layer, scrambles the data in a predetermined way, then uses the modified datapredetermined way, then uses the modified data stream to modulate a radio carrier signal.

Data Link Layer:• Uses Carriers-Sense-Multiple-Access with

Collision Avoidance (CSMA/CA).

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Integration With Existing NetworksNetworks• Wireless Access Points (APs) - a small device

th t b id i l t ffi t t kthat bridges wireless traffic to your network. • Most access points bridge wireless LANs into

Ethe net net o kEthernet networks.

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Integration With Existing NetworksNetworks

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IEEE 802.11 Network ArchitectureWireless network architecture :1. Basic Service Set (BSS)( )2. Extended Service Set (ESS)

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Ad Hoc NetworkingAd Hoc Networking• Peer-to-peer network• Set up temporarily to meet some immediate

need• E.g. group of employees, each with laptop or

palmtop, in business or classroom meetingN t k f d ti f ti• Network for duration of meeting

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Add Hoc LANAdd Hoc LAN

• A group of stations using the same radio frequency –Basic Service Set

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Infrastructure Wireless LANInfrastructure Wireless LAN

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Multi-Cell Wireless LAN Configuration (Infrastructure Network)(Infrastructure Network)

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Access Point in “Root Mode”Access Point in Root Mode

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Access Point in “Repeater Mode”Mode

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IEEE 802.11 Protocol ArchitectureArchitecture

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802 11 Physical Layer802.11 Physical Layer• Issued in four stages• First part in 1997• First part in 1997

— IEEE 802.11 — Includes MAC layer and three physical layer specifications

T i 2 4 GH b d d i f d— Two in 2.4-GHz band and one infrared— All operating at 1 and 2 Mbps

• Two additional parts in 1999— IEEE 802.11a

• 5-GHz band up to 54 Mbps— IEEE 802.11b

• 2.4-GHz band at 5.5 and 11 Mbps

• Most recent in 2002— IEEE 802.g extends IEEE 802.11b to higher data ratesg g

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802.11 Physical Layer80 ys ca aye

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Spread SpectrumSpread Spectrum

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Frequency Hopping Spread Spectrum

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Direct Sequencing Spread Spectrum

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Graphical representation of Wi-Fi channels in 2 4 GHz bandFi channels in 2.4 GHz band

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Channel ReuseChannel Reuse

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Current Standards a b gCurrent Standards – a, b, g860 Kbps 1 and 2 Mbps

Proprietary

1 and 2 Mbps 11 Mbps 54 Mbps

Standards-basedNetwork

Speed

900 MHz 2.4 GHz802.11 Ratified

802.11a,b Ratified

2.4 GHz 5 GHzRadio

IEEE 802.11Begins Drafting

802.11g Ratified

• 802.11a— Up to 54 Mbps

1986 1988 1990 1992 1994 1996 1998 2000 2003g

Up to 54 Mbps— 5 GHz— Not compatible with either 802.11b or 802.11g

• 802 11b• 802.11b— Up to 11 Mbps— 2.4 GHz

• 802 11g

802.11g is backwards compatible with 802.11b, but with a drawback (later)• 802.11g

— Up to 54 Mbps— 2.4 GHz

(later)

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802.11 PHY (Physical Layer) TechnologiesTechnologies

860 Kbps 1 and 2 Mbps

Proprietary

1 and 2 Mbps 11 Mbps 54 Mbps

Standards-basedNetwork

Speed

900 MHz 2.4 GHz802.11 Ratified

802.11a,b Ratified

802.11g Ratified

2.4 GHz 5 GHzRadio

IEEE 802.11Begins Drafting

• Three types of radio transmission within the unlicensed 2.4-GHz frequency bands:

1986 1988 1990 1992 1994 1996 1998 2000 2003g

frequency bands: — Frequency hopping spread spectrum (FHSS) 802.11b (not used)— Direct sequence spread spectrum (DSSS) 802.11b

O th l f di i i lti l i (OFDM) 802 11— Orthogonal frequency-division multiplexing (OFDM) 802.11g • One type of radio transmission within the unlicensed 5-GHz frequency

bands: — Orthogonal frequency-division multiplexing (OFDM) 802.11a

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WLAN Devices: Access Points

In-building Infrastructureg• 1200 Series (802.11a and 802.11b)• 1100 Series (802.11b)

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Wireless LAN Devices: Client AdaptersAdapters

Clients (NICs)• 350 Series (802.11b)( )• 5 GHz client adapter (802.11a)

Drivers are supported for all popular operating systems, including Windows 95, 98, NT 4.0, Windows 2000, Windows ME, Windows XP, Mac OS Version 9.x, and Linux.

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Wireless LAN Devices: AntennasAntennasAntenna

•2 4GHz Antennas2.4GHz Antennas•5 GHz AntennasIndoor Vs Outdoor

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AntennasAntennas• Indoor and Outdoor • Outdoor

• 2.4 GHz • 5 GHz

• WLAN and Bridging • Bridging

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Dipole / Omni AntennaDipole / Omni Antenna

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Point to Multipoint LinkPoint to Multipoint Link

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Point-to-point Wireless LinkPoint-to-point Wireless Link

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AntennaAntenna

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Packet AnalysisPacket Analysis

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Data EncryptionData EncryptionSecure Transmission of Information• Physical layer• Physical layer

– Physical security of data transmission is gained by usingspread spectrum technology which makes it less vulnerable tointerference

• MAC (Medium Access Control) layer– Encryption algorithm is called Wired Equivalent Privacy (WEP)g

Use static encryption key. – Wi-Fi Protected Access (WPA)

WPA uses a Temporal Key Integrity Protocol (TKIP)WPA uses a Temporal Key Integrity Protocol (TKIP), which changes keys with every data packet.

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The Site SurveyThe Site Survey• Helps define the coverage areas, data rates, the

i l t f i tprecise placement of access point.• Gather information: diagramming the coverage

e nd me ing the ign l t ength SNRarea and measuring the signal strength, SNR (signal to noise ratio), RF interference levels

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Site SurveySite Survey

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