LAN Switching and Wireless: Ch7 - Basic Wireless Concepts and Configuration

LAN Switching and Wireless

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Abdelkhalik Mosa

Suez Canal University

Faculty of Computers and Informatics - Ismailia - Egypt

Note …

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Introduction

• Wireless technologies use electromagnetic waves to carry information between devices.

• WLANs use radio frequencies (RF) instead of cables at the Physical layer and MAC sub-layer of the Data Link layer.

Wireless LAN Vs. Ethernet LAN

Wireless PAN, LAN, MAN and WAN

PAN : Personal Area NetworksLAN : Local Area NetworksWLAN : Wireless Local Area NetworksMAN : Metropolitan Area NetworksWAN : Wide Area Networks

Introduction: Infrared

• Infrared (IR) is relatively low energy and cannot penetrate through walls or other obstacles.

• A specialized communication port known as an Infrared Direct Access (IrDA) port uses IR to exchange information between devices.

• IR only allows a one-to-one type of connection.

• IR is also used for remote control devices, wireless mice, and wireless keyboards.

• IR generally used for short-range, line-of-sight, communications.

Introduction: Radio Frequency (RF)

• RF waves can penetrate through walls and other obstacles, allowing a much greater range than IR.

• Certain areas of the RF bands have been set aside for use by unlicensed devices such as WLANs, and computer peripherals.

– This includes the 900 MHz, 2.4 GHz, and the 5 GHz frequency ranges. These ranges are known as the ISM bands.

Benefits of Wireless Technology

Limitations of Wireless Technology

Wireless LANs (WLANs)

• 802.11 wireless LANs extend the 802.3 Ethernet LAN infrastructures to provide additional connectivity options.

Wireless LAN Standards

• The governmental agencies in countries, license some frequency bands, leaving some frequency bands unlicensed.

• Licensed bands:

– The most common are AM and FM radio, shortwave radio (for police department communications), and mobile phones.

• Unlicensed frequencies:

– Can be used by all kinds of devices; however, the devices must still conform to the rules set up by the regulatory agency.

• A device using an unlicensed band must use power levels at or below a particular setting so as not to interfere too much with other devices sharing that unlicensed band.

Wireless LAN Standards

• OFDM have faster data rates than DSSS.

• DSSS is simpler and less expensive to implement than OFDM.

Wireless Fidelity (Wi-Fi) Certification

• Wi-Fi Alliance, a global, nonprofit, industry trade association devoted to promoting the growth and acceptance of WLANs.

• The Wi-Fi Alliance is an association of vendors whose objective is to improve the interoperability of products that are based on the 802.11 standard.

• The Wi-Fi logo on a device means it meets standards and should interoperate with other devices of the same standard.

• The three key organizations influencing WLAN standards are:

ITU-R regulates allocation of RF bands.

IEEE specifies how RF is modulated to carry info.

Wi-Fi ensures that vendors make devices that are interoperable.

Wireless Infrastructure Components: Wireless NIC

Wireless NIC encodes a data stream onto an RF signal.

Wireless Infrastructure Components: Wireless Access Points

• An access point is a Layer 2 device that functions like a 802.3 Ethernet hub.

• An access point connects wireless clients to the wired LAN.

• Association is the process by which a client joins an 802.11 network.

• RF signals attenuate as they move away from their point of origin, causing the Hidden node problem.

• One means of resolving the hidden node problem is a CSMA/CAfeature called request to send/clear to send (RTS/CTS).

Wireless Infrastructure Components: Wireless Access Points

• The hidden node problem

Wireless Infrastructure Components: Wireless Routers

• Wireless routers perform the role of access point, Ethernet switch, and router.

Configurable Parameters for Wireless Endpoints

Network Modes

Channels

SSID

802.11 Topologies: Ad Hoc (IBSS)

Independent Basic Service Set (IBSS)

802.11 Topologies: BSS

Basic Service Set (BSS)

802.11 Topologies: ESS

Extended Basic Service Set (ESS)

Client and Access Point Association: Beacons

• Beacons: Frames used by the WLAN network to advertise its presence.

Client and Access Point Association: Probes

• Probes: Frames used by WLAN clients to find their networks.

Client and Access Point Association: Authentication

Client and Access Point Association: Association

• Association: The process for establishing the data link between an access point and a WLAN client.

Threats to Wireless Security: Unauthorized Access

• Major categories of threats that lead to unauthorized access:

1. War Drivers:• Find open networks and use them to gain free internet

access.2. Hackers:

• Exploit weak privacy measures to view sensitive WLAN information and even break into WLANs.

3. Employees:• Plug consumer-grade APIs/gateways into company

Ethernet ports to create their own WLANs.

Threats to Wireless Security: Man-in-the-Middle Attacks

Threats to Wireless Security: Denial of Service

Wireless Security Protocol Overview

• Open Authentication: no authentication.

• WEP authentication: was supposed to provide privacy to a link.

Static, crackable, and not scalable.

Cloaking SSIDs and filtering MAC addresses were used.

Authenticating to the Wireless LAN

Authenticating to the Wireless LAN

• EAP is a framework for authenticating network access.

Encryption – TKIP and AES

• TKIP is the encryption method certified as WPA.

It encrypts the Layer 2 payload.

It carries out a message integrity check (MIC) in the encrypted packet which ensures against a message being tampered with.

• AES is the encryption method certified as WPA2.

• PSK or PSK2 with TKIP is the same as WPA.

• PSK or PSK2 with AES is the same as WPA2.

• PSK2, without an encryption method, is the same as WPA2.

Controlling Access to the Wireless LAN

• The concept of depth means having multiple solutions available.

• Implement this three-step approach:

1. SSID cloaking: Disable SSID broadcasts from access points

2. MAC address filtering: Permit or deny clients based on their MAC address

3. WLAN security implementation: WPA or WPA2.

• Neither SSID cloaking nor MAC address filtering are considered a valid means of securing a WLAN for the following reasons:

1. MAC addresses are easily spoofed.

2. SSIDs are easily discovered even they aren’t broadcasted.

Configuring the Wireless Access Point

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Configuring the Wireless Access Point

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Configuring Basic Wireless Settings

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Configuring Security

• "Personal“ means no AAA server is used.

• "Enterprise“ means a AAA server and EAP authentication is used.

Configuring Security

Configuring a wireless NIC

Scan for SSIDsSelecting the Wireless

Security Protocol

WLAN Troubleshooting: Incorrect Channel Settings

WLAN Troubleshooting: Solving RF Interference

WLAN Troubleshooting: Access Point Misplacement

WLAN Troubleshooting: Authentication and Encryption

LAN Switching and Wireless: Ch7 - Basic Wireless Concepts and Configuration

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