Wi-Fi IEEE 802.11 Standards 802.11a 802.11b 802.11g 802.11n 802.11ac Note: This slide is a simple overview of the 802.11 standards described in this section.

802.11 Standards define how devices communicate Some define how to secure communications Each sub-standard by a IEEE subcommittee

Hardware Adapters Wireless Ethernet NICS PCI, PC Card, external USB

Wireless access point (WAP) Basic WAP operates like a hub at Layer 1 Often multiple devices in one box High-speed hub or switch Bridge Router

Figure 16.4 Wireless client configuration utility

Wireless Network Modes Ad hoc mode Also called peer-to-peer mode Uses a mesh topology Independent Basic Service Set (IBBS) Teaching Tip Remind the students of the mesh topology they studied in Chapter 3.

Wireless Network Modes Infrastructure mode Uses one or more access points Similar to a wired star topology Basic service set (BSS) Serviced by a single WAP Extended service set (ESS) Serviced by two or more WAPs Teaching Tip Point out that Infrastructure mode Requires more planning Is suited for business networks Is suitable for networks sharing dedicated resources

Speed Dependent on a few factors Standard used by wireless devices Distance Interference Dead spots Teaching Tip Please mention that the “chicken wire” in stucco buildings can degrade, if not entirely block, wireless signals. We experience this every day with a WAP in the house and a wireless host in the office—and both buildings swathed in stucco. The distance from the WAP to the wireless NIC is no more than 25 feet, but we did a great deal of tweaking and changing of the equipment and settings before achieving desired speeds.

Basic Service Set Identifier (BSSID) Most basic infrastructure mode network BSS is one WAP and one or more nodes BSSID same as the MAC address of WAP IBSS nodes (ad hoc mode) 48-bit string BSSID in every packet

Service Set Identifier (SSID) Another level of naming Standard name applied to BSS or IBSS Sometimes called a network name

Extended Service Set Identifier (ESSID) Wi-Fi network with multiple WAPs (ESS) Most Wi-Fi devices use term SSID

Broadcasting Frequency Potential for interference from other wireless devices Tech must know frequencies of other wireless devices Original 802.11 standards use 2.4-GHz frequency

Broadcast Methods Original IEEE 802.11 standard used spread-spectrum radio waves Broadcasts data in small, discrete chunks Used different frequencies within a range Note: See the spread-spectrum methods in the next three slides.

Three different spread-spectrum broadcasting methods DSSS Direct Sequence Spread Spectrum (faster but uses more bandwidth) FHSS Frequency Hopping Spread Spectrum (slower but uses less bandwidth) OFDM Orthogonal Frequency Division Multiplexing (latest and most commonly used)

Orthogonal frequency-division multiplexing (OFDM) Latest method Combines multiple frequencies of DSSS with FHSS’s hopping capability Later 802.11 standards use this

Channels (2.4Ghz band) A portion of the spectrum 802.11 standard defined 14 channels Different countries may limit channels Note: It may be necessary to move WAPs to other channels to avoid overlap.

Channels (2.4Ghz band) In U.S. WAP may use channels 1 – 11 There is overlap Most WAPs default to channel 1, 6, or 11 Channels (5Ghz band) Non issue Over 40 channels Automatic channel switching Note: It may be necessary to move WAPs to other channels to avoid overlap.

CSMA/CA Carrier sense multiple access/collision avoidance Access method Allows multiple devices to share network media Wireless devices cannot detect collisions Two collision avoidance methods Distributed coordination function (DCF) Point coordination Function (PCF) Note: Review how CSMA/CD works for wired networks, then compare with wireless networks. Only DCF is currently implemented.

802.11b Data throughput up to 11 Mbps Range up to 300 feet Popular 2.4-GHz frequency is crowded More likely to have interference from other wireless devices

802.11a Device on market after 802.11b Different from all other 802.11 standards 5-GHz frequency range Up to 54 Mbps Short range (~150 feet) Never as popular as 802.11b Incompatible with 802.11b

802.11g Up to 54 Mbps Range of 802.11b (~300 feet) Backward compatible with 802.11b WAP can service both 802.11b and 802.11g All 802.11g network runs in native mode Add 802.11b devices Mixed mode All communications drop to 11 Mbps max

802.11n Multiple in/multiple out (MIMO) Four at 150Mbps = 600 Mbps Many WAPs use transmit beamforming Dual-band WAPs run at 5 GHz and 2.4 GHz Some WAPs support 802.11a devices Teaching Tip Point out the interesting Tech Tip on the 802.16 standard on page 436. This standard is not explicitly listed in the CompTIA Network+ Exam Objectives, but it is included in the Key Terms list for this chapter, and is an important protocol to watch as new devices appear.

802.11ac Upgrade of 802.11n Operates exclusively in 5GHz range Increased channel bonding Faster data transfers Eight MIMO streams (2x 802.11n) Up to 7 Gbps Teaching Tip Point out the interesting Tech Tip on the 802.16 standard on page 436. This standard is not explicitly listed in the CompTIA Network+ Exam Objectives, but it is included in the Key Terms list for this chapter, and is an important protocol to watch as new devices appear.

Wireless Networking Security Problem Easy-to-install devices have no default security Network data packets are in radio waves Three wireless security methods MAC address filtering Wireless authentication Data Encryption Note: Details on the three wireless security methods are on the following slides.

MAC address filtering Allow or Deny specific MAC addresses Problem: hackers can spoof MAC addresses MAC address must be updated for changes

Wireless Authentication Users with proper credentials get access Can use a centralized security database 802.1X standard RADIUS Server Extensible Authentication Protocol (EAP) password encryption Note: Wireless authentication can use Active Directory accounts. More on RADIUS Servers in following slide.

Wireless Authentication RADIUS server Provides authentication for network access Client computer is called a supplicant WAP is the Network Access Server (NAS) NAS contacts RADIUS server RADIUS server checks security database User given access if credentials are correct

Figure 16.7 Authenticating using RADIUS

Wireless authentication problem areas Connection must be secure PPP between supplicant and WAP/NAS IPSec between WAP/NAS and RADIUS server RADIUS server uses an authentication protocol EAP-TLS EAP-TTLS PEAP WAP and wireless NICs must use same authentication protocol

Figure 16.8 Authentication using RADIUS with protocols in place

Figure 16.9 Setting EAP authentication scheme

Data Encryption Wired Equivalent Privacy (WEP) 64- or 128-bit encryption algorithm Problems Easily cracked Key is static and shared No user authentication

Data Encryption Wi-Fi Protected Access (WPA) Dynamic encryption key generation Issued per-user and per-session Temporal Key Integrity Protocol (TKIP) 128-bit encryption key Problem: key can be broken

Data Encryption Wi-Fi Protected Access 2 (WPA2) Amendment of 802.11 standard by 802.11i Issued per-user and per-session Uses Advanced Encryption Standard (AES) 128-bit block cipher Not completely hack proof Deters casual hackers Longer is better!

Power over Ethernet (PoE) Power and Ethernet signals via Ethernet ports Good for WAPs far from power outlets Both WAP and switch must comply with PoE

Implementing Wi-Fi

Site Survey What wireless devices are already there? Radio bands in use Existing SSIDs and channels Unique SSIDs Separate channels within same radio band Locate Interference Sources Create sketch and identify interference sources High-interference area may require 802.11n May need multiple WAPs to avoid dead zones Teaching Tip Because setting up a wireless network is very basic and easy to do, consider doing a demonstration of the setup of both a WAP and a client. Bring in a wireless access point, a laptop (if you cannot do this on a classroom computer), and a wireless network adapter (USB), and walk students through this part of the chapter. Discuss the SSID, the default router address, and so on. If you can do this, it will go a long way toward helping students understand the concept. If this is not feasible, slides showing screenshots from the set up work well, too.

Figure 16.10 Site survey with interference sources noted

Figure 16.12 Selecting ad hoc mode in wireless configuration utility

Setting up an Infrastructure Network Placing Access Points Omni-directional and centered Radio waves flow outward Standard straight-wire dipole antennae Off-center position Gaining gain Focusing the wave with directional antenna

Figure 16.13 Room layout with WAP in the center

Figure 16.14 Replacement antenna on WAP

Setting up an Infrastructure Network Access Point Configuration Configure the SSID (ESSID) and beacon Configure MAC address filtering Configure encryption Configure channel and frequency Configure the client

Figure 16.17 Setting the beacon interval

Figure 16. 18 MAC address filtering configuration Figure 16.18 MAC address filtering configuration screen for a Linksys WAP

Figure 16.19 Encryption key configuration screen on Linksys WAP

Figure 16. 20 Encryption screen on client wireless Figure 16.20 Encryption screen on client wireless network adapter configuration utility

Figure 16.21 Encryption screen with RADIUS option

Figure 16.22 Changing the channel

Figure 16.23 Selecting frequency

Extending the Network Adding a WAP Wireless Bridge Repeating bridges Point-to-point Point-to-multipoint Repeating bridges Bridges with access point and router functions

Verify the Installation Move traffic between computers Always verify installation before leaving

Figure 16.25 Linksys wireless bridge device