1. Chapter 6: Connecting Through a Wireless Network

2. Current Wireless Networking Technologies
Two drawbacks of wire-based networking
Tangle of wires connecting computer and peripherals
Cost of pulling wires through walls, ceilings, floors
Wireless technology resolves many wire-based issues
Wireless media are forms of electromagnetic radiation
Three major current wireless networking technologies
Radio wave technologies (short range and a popular option)
Infrared technologies (short range)
Terrestrial and satellite microwave technologies (long range)
Hands-on Networking Fundamentals

3. A Short History of Wireless Networks
Wireless standards develop in parallel with ham radio
Telecommunications Act of 1996
IEEE standard set in 1997
A few of the entities influencing standards
IEEE (Institute of Electrical and Electronics Engineers)
IETF (International Engineering Task Force)
ISO (International Organization for Standardization)
Hands-on Networking Fundamentals

4. Wireless Network Support Organizations
Wi-Fi Alliance
Offers a certification program to vendors
Tests wireless devices so they can be certified to meet IEEE standards
Devices that pass the testing can display the Wi-Fi CERTIFIED insignia
Hands-on Networking Fundamentals

5. Radio Wave Technologies
Frequency ranges of various transmission types
Network signals are transmitted over higher frequencies than local radio station broadcasts
AM: 535–1605 kilohertz (kHz)
FM: 88–108 megahertz (MHz)
Network: MHz, GHz, GHz
Directional signal transmitted between buildings
Transmission involves sending and receiving antennas
Wave is short in length and low-power (1-10 watts)
Suitable for line-of-sight transmission
Signal goes from point to point on earth's surface
Limitations due to interruptions, such as hills
Data capacity range: 1 Mbps to over 300 Mbps
Hands-on Networking Fundamentals

6. Spread Spectrum Spread spectrum technology for packet transmissions
Spreads transmission over adjoining frequencies (allows for greater bandwidth use)
Frequency range: 902–928 MHz range
Data transfer range: 1–600 Mbps
Hands-on Networking Fundamentals

7. Radio Wave Technologies
Disadvantages to radio wave communications
Wireless networks are more susceptible to interference (such as interference caused by certain building materials and by surrounding electrical devices)
Some wireless frequencies are shared by amateur radio operators, the US military, and cell phone companies – can cause interference
Interference from natural obstacles
Inadequate security
Other radio wave technologies include Bluetooth, HiperLAN, Infrared, WiMAX, HiperMAN, and cellular phone
Hands-on Networking Fundamentals

8. IEEE 802.11 Radio Wave Networking
IEEE group: most influential wireless standards
Includes a, b, g, and n
Communication with devices is non-proprietary
Features of standards
Encompass either fixed or mobile wireless stations
Involve two kinds of communications
Asynchronous: discrete units with a start and stop bit
Synchronous: signal has timing restrictions
Support SNMP protocol and network authentication
Operate at two lower OSI layers: Data Link and Physical
Recognize indoor and outdoor wireless communication
Hands-on Networking Fundamentals

9. Wireless Components
Three components: transceiver, access point, antenna
Wireless NIC (WNIC): transceiver card
Functions as transmitter and receiver
Operates at Physical and Data Link layers of OSI model
May be internal (PCI card), a removable CardBus, or external (USB key fob)
Most are compatible with the Microsoft Network Driver Interface Specification (NDIS)
Enables support for multiple protocols
Essential to the function of WNICs
Hands-on Networking Fundamentals

10. Wireless Components
Access point: interfaces WNICs and a cabled network (allows wireless devices to communicate with non-wireless devices)
May support the following types of network interfaces: AUI, 10Base2, 10BaseT, 100Base technologies, 1000Base technologies, 40 GB Ethernet technologies, 100 GB Ethernet technologies, FDDI, Cable modem port, or DSL telecommunications port
Antenna: device that radiates and receives radio waves
Both WNICs and access points employ antennas
Most are either directional or omnidirectional
Hands-on Networking Fundamentals

11. Directional Antenna Sends radio waves in one main direction
Amplifies signal better than omnidirectional antenna
Gain: amplification of radiated signal
Application: transmitting signals between buildings
Each building has an antenna
Antennas connected to access points
Signal has more gain in one direction
Small portion of signal is radiated outward
Hands-on Networking Fundamentals

12. Figure 6-2 Directional antenna
Hands-on Networking Fundamentals
Figure 6-2 Directional antenna

13. Omnidirectional Antenna
Radiates radio waves in all directions
Diffused signal likely has less gain than directional type
Most often used on an indoor network
Mobile users need to send and receive in all directions
Signals moving over shorter distances require less gain
Omnidirectional antenna deployed varies with device
WNIC on portable devices use a snap-on antenna
Access point for indoor network
May have a snap-on antenna
May connect to antenna using cable
Outdoor access point connects to antenna via a cable
Hands-on Networking Fundamentals

14. Figure 6-3 Omnidirectional antennas
Hands-on Networking Fundamentals
Figure 6-3 Omnidirectional antennas

15. Wireless Networking Access Methods
Two access methods: priority-based and CSMA/CA
Priority-based access
Access point device functions as a point coordinator
Point coordinator establishes contention-free period during which it polls stations to see which devices need to transmit
Intended for time sensitive communications
Voice, video, and videoconferencing are examples
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)
Also called the distributed coordination function
CSMA/CA works to avoid collisions
Coordinate nodes using DIFS delay and backoff time
Hands-on Networking Fundamentals

16. Interference Interference may corrupt data transmission
Many sources of interference
Natural: weather, solar flares, mountains
Artificial: other wireless communications, buildings
Hands-on Networking Fundamentals

17. Transmission Speeds
Transmission speeds are defined through four standards: a, b, g, n
Correspond to the Physical layer of the OSI model
There are two newer very-high-speed wireless LAN standards under development:
802.11ac
802.11ad
Hands-on Networking Fundamentals

18. 802.11g Supports three transmission methods on the 2.4 GHz band
OFDM (native mode)
Similar to OFDM under a (different bands)
Minimum speed: 6 Mbps
Maximum speed: 54 Mbps
Complementary Code Keying (CCK)
Used with DSSS for backward compatibility with b
Minimum speed: 1 Mbps
Maximum speed: 11 Mbps
Packet Binary Convolution Code (PBCC)
Unofficial extension used with b
Offers speeds of 22 Mbps and 33 Mbps
Hands-on Networking Fundamentals

19. 802.11g Restrictions and considerations using 802.11g
Devices must support minimum speeds by standard
Speed values: 1, 2, 5.5, 6, 11, 12, and 24 Mbps
Slightly shorter range than b
More access points may be needed
Smaller bandwidth (90 MHz) than a or b
No more than three access points in given area
Devices combine with b devices on one LAN
Advantage: retain earlier investment in b
Disadvantage: lowers network performance
Hands-on Networking Fundamentals

20. 802.11n
Uses a technology called multiple-input multiple-output (MIMO) with spatial multiplexing
Uses multiple antennas at the transmitting and receiving devices
Spatial multiplexing – means a device can transmit and receive two or more data streams over one channel within a frequency
Multiple frames can be aggregated together in one transmission
802.11n uses smaller sized ACK frames (8 bytes) and one ACK can be used to verify receipt of multiple frames (called a block ACK)
Hands-on Networking Fundamentals

21. 802.11n
Number of times a channel must be acquired and released is significantly reduced due to frame aggregation, making it more efficient than other technologies
Can use 20 and 40 MHz channels within the 2.4 and 5 GHz bands
Can be up to four simultaneous data streams per 20 or 40 MHz channel for a top speed of 600 Mbps
At this writing, most n devices have a top speed of 300+ Mbps
Factors such as distance, obstacles, and electrical interference can affect actual throughput
Hands-on Networking Fundamentals

22. 802.11ac Currently under development at this writing
Designed around the technologies used by n
MIMO is expanded into multiuser MIMO or MU-MIMO
Frames sent to and from multiple users can be sent simultaneously on the same channel
Expands transmission capabilities to use the 80 MHz channel for even wider bandwidth
Hands-on Networking Fundamentals

23. 802.11ad Also under development at this writing
Targeted at accomplishing transmission speeds of roughly 7 Gbps
Operates using the 60 MHz channel
Designed for shorter transmission distances (likely to be restricted by walls
Manufacturers are looking at ad for Wi-Fi based phone communications and HD movies on big-screen wireless TVs
Hands-on Networking Fundamentals

24. 802.11a, b, g and n Compared
802.11a, 80211g, and n standards offer greater speed
Range varies per standard
802.11a devices transmit up to 18 meters
802.11b devices reach over 91 meters
802.11g devices transmit between 30 and 100 meters
802.11n devices can reach up to 200 meters
Hands-on Networking Fundamentals

25. 802.11a, b, g and n Compared
Uses for a, g and n devices
Applications requiring high bandwidth (voice and video)
In small areas with high concentration of users (lab)
802.11b devices are used when bandwidth is not critical
802.11n is a much better and more versatile alternative than a, b, or g
Hands-on Networking Fundamentals

26. Deployment Tips
Do not place an access point against a wall or floor
If possible, place the access point in a main or central location
If the access point cannot be centrally located, consider extending the signal by using a wireless repeater or by replacing an omnidirectional antenna with a directional antenna
Avoid placing the access point on or inside a metal cabinet or shelf
Remove sources of interference such as microwave ovens, cordless phones, etc…
Hands-on Networking Fundamentals

27. Deployment Tips
Consider replacing internal WNICs that do not have external antennas with WNICs that have them
Replace any a, b and g devices with n devices (or with ac as these become available
Use the 5 GHz band and 40 MHz channels for n access points
Purchase devices with multiple antennas for more data streaming capability
Hands-on Networking Fundamentals

28. 802.11 Security Techniques Methods attackers can use to infiltrate:
Identify wireless network targets by using:
Antenna: vary by directionality and gain
Wireless NIC: connects to antenna
Global positioning system (GPS): locates target
War-driving software: passes data from antenna to GPS
Use network sniffer to capture packets
Purpose: capture ids or passwords, conduct espionage
Man-in-the-middle attack: interception of message
standards offers several security approaches
Hands-on Networking Fundamentals

29. Open System Authentication
Allows any two stations to authenticate each other
Simple method
Sender requests authentication from destination
Authentication is complete when receiver verifies request
Provides very little security
Used by default by many vendor devices
Hands-on Networking Fundamentals

30. Shared Key Authentication and Wired Equivalent Privacy (WEP)
Two stations use the same WEP encryption key
Consists of key, checksum, initialization information
Total key length is 64- or 128-bits
128-bit key supports superior 128-bit encryption
Up to four WEP keys can be stored in key index
Authenticating using shared key and WEP
Sender requests authentication from another station
Contacted station sends back challenge text
Sender encrypts challenge text, returns to challenger
If returned text properly decoded, verification sent
Hands-on Networking Fundamentals

31. Wi-Fi Protected Access (WPA)
Uses WEP-like features, but encrypted keys change
Key changes make WPA more secure than WEP
WPA2 is latest version
Uses Advanced Encryption Standard (AES)
Considered “government grade security”
The private key can be either 128, 192, or 256 bits in length
Preshared key (PSK) is a WPA enhancement
Targeted for home and small networks that do not have additional enterprise network security measures
Hands-on Networking Fundamentals

32. Wi-Fi Protected Access (WPA)
Setting up PSK network security
Enter a password or passphrase (master key when installing access point)
After the password is entered, WPA is automatically activated
All wireless devices must use the same passphrase
When configuring WPA or WPA2 there can be two options:
Personal – typically used on home or small networks
Enterprise – coordinates security through an enterprise-wide Remote Authentication Dial-Up User Service (RADIUS) server
Hands-on Networking Fundamentals

33. Service Set Identifier
SSID: identification value up to 32 characters in length
Value defines logical network for all member devices
Examples of SSIDs
Series of random characters
String identifying network purpose, such as "Atmospheric Research"
SSID often configured by default
Ensure that vendor default is replaced
Use SSID value difficult to guess
Hands-on Networking Fundamentals

34. 802.1X and i Security
802.1X: wireless and wired authentication approach
Port-based form of authentication
Ports over which connection is made act in two roles
Uncontrolled: allows unauthenticated communications
Controlled: allows only authenticated communications
Node roles: supplicant and authenticator
Disadvantage: authentication process not encrypted
802.11i adds three features to enhance 802.1x
Temporal Key Integrity Protocol (TKIP)
Advanced Encryption Standard (AES)
Robust Secure Network (RSN)
Hands-on Networking Fundamentals

35. Using Authentication to Disconnect
Two stations disconnect when:
Either sends a deauthentication notice
Deauthentication notice results in instant termination
Two communicating stations cannot be inadvertently disconnected by another nonauthenticated station
Hands-on Networking Fundamentals

36. Network Topologies
Independent basic service set (IBSS) topology
Consist of two or more stations in direct communication
Peer-to-peer communication between WNICs on nodes
Stations are often added on impromptu basis
Extended service set (ESS) topology
Deploys one or more access points
Enables more extensive area of service than the IBSS
Network sizes range from small to large
IBSS network is easy to expand into an ESS network
Avoid combining both networks in same proximity
Hands-on Networking Fundamentals

37. Figure 6-14 ESS wireless topology
Hands-on Networking Fundamentals
Figure ESS wireless topology

38. Multiple Cell Wireless LANs
Occur when an ESS topology employs two or more access points
Cell: broadcast area around single access point
Roaming: ability to move wireless device across cells
Cells must be configured with same frequency, speed, security
Inter-Access Point Protocol (IAPP)
Enables a mobile station to move among cells
Encapsulates UDP and IP for roaming communications
Enables existing access points to be notified and exchange information when a new access point is attached to a network
Hands-on Networking Fundamentals

39. Alternative Radio Wave Technologies
Popular alternatives to group
Bluetooth
HiperLAN
Each of these is a wireless specification developed and supported by specific vendors
Hands-on Networking Fundamentals

40. Bluetooth Defined through the Bluetooth Special Interest Group
Characteristics
Uses Frequency Hopping Spread Spectrum (FHSS)
Frequency hopping: transmissions hop among 79 frequencies
Occurs in 2.4 GHz range (2.4– GHz)
Uses high wattage transmissions that can reach up to 100 meters
Can use asynchronous or synchronous communication
Bluetooth v. 3 offers the optional high speed specification which can transmit up to 24 Mbps
Hands-on Networking Fundamentals

41. Bluetooth Bluetooth v. 4 offers three operating environments:
High-speed: implements Bluetooth version 3+HS
Low-energy: used for sensors such as in-home glucose monitors, pedometers, watches, and remote control devices
Can transmit at up to 1 Mbps at a range of about 100 meters
Classic: encompasses the older versions of Bluetooth from 1.1 – 3.0 (excluding 3.0+HS) with a maximum data rate of approximately 1 Mbps
Hands-on Networking Fundamentals

42. Bluetooth
Bluetooth devices are divided into three classes based on range:
Class 1: up to about 100 meters
Typically used for network-type applications such as wireless access points
Class 2: up to about 10 meters
Typically used for wireless devices such as keyboards, mice, microphones, and audio devices
Class 3: up to about 1 meter
Typically used for close range transmissions such as medical monitoring devices, watches, and exercise monitoring
Hands-on Networking Fundamentals

43. Bluetooth Bluetooth uses time division duplexing (TDD)
Packets are sent in alternating directions using time slots
One of three encryption modes can be configured:
Mode 1: no encryption is used
Mode 2: communications that are addressed are encrypted but broadcasts are not encrypted
Mode 3: all communications are encrypted used a 128-bit encryption master key
Stream cipher encryption is used for Bluetooth
Hands-on Networking Fundamentals

44. HiperLAN High-Performance Radio Local Area Network
Features of second version, HiperLAN2
Transmits at up to 54 Mbps in the 5 GHz range
Compatible with Ethernet
Supports Data Encryption Standard (DES)
Supports Quality of Service (QoS)
HiperLAN2 operates in two modes
Direct: peer-to-peer similar to IBSS topology
Centralized: certain access points centralize control
Both HiperLAN2 modes use TDD
Hands-on Networking Fundamentals

45. Infrared Technologies
Broadcasts in single direction or all directions
Advantages of infrared medium
Inexpensive
Difficult to intercept
Not susceptible to RFI or EMI
Disadvantages of infrared medium
Slow data transmissions (between 1 and 16 Mbps)
Does not penetrate walls
Experiences interference from strong visible light
Diffused infrared: reflects infrared light from ceiling
Defined by IEEE R standard
Communication with pulse position modulation (PPM)
Hands-on Networking Fundamentals

46. Figure 6-15 Diffused infrared wireless communications
Hands-on Networking Fundamentals
Figure Diffused infrared wireless communications

47. Wireless MANs Based on IEEE 802.16 standard (WiMAX)
Provides connectivity up to 75 Mbps
Has a reach of up to 30 miles
WiMAX called connection for "last mile"
Connects home or office to wired network provider
Implementing WiMAX for rural office
Install wireless communication at network provider
Include a directional or omnidirectional antenna
Connect directional antenna to wireless router in office
Point office antenna to provider's antenna
Hands-on Networking Fundamentals

48. Wireless MANs WiMAX operates in the 2 to 66 GHz range
In the US most WiMAX networks at the 2.3, 2.5, 3.5, 3.65, and 5.8 GHz frequencies
The IEEE standard provides connectivity up to 75 Mbps with a reach of up to 48 kilometers (30 miles)
In many installations the actual distance is 8-16 kilometers (5-10 miles)
WiMAX can be a cost-effective way to create a network over several miles
Hands-on Networking Fundamentals

49. Microwave Technologies
Work in one of two ways: terrestrial and satellite
Have theoretical bandwidth up to 720 Mbps and beyond
Hands-on Networking Fundamentals

50. Terrestrial Microwave
Characteristics of transmission
Between two directional parabolic antennas (dishes)
Performed in ranges of 4–6 GHz and 21–23 GHz
Require the operator to obtain an FCC license
Uses of terrestrial microwave transmission
Where cabling costs are too high
Where cabling and wireless options not possible
Example: between two large buildings in a city
Hands-on Networking Fundamentals

51. Satellite Microwave Transmits signal between three antennas
One antenna on a satellite in space
Connection speeds are currently at 2-3 Mbps with newer systems providing up to 12 Mbps
May be "throttled" down for uploading large files
Also vary due to weather, signal strength, usage
User equipment needed for satellite communication
Satellite dish about 2 or 3 feet in diameter
Digital modems to transmit and receive signals
Coaxial (TV-like) cables from the modems to dish
USB cable from modems to a USB port on computer
Software from provider to enable computer setup
Hands-on Networking Fundamentals

52. Figure 6-20 Satellite communications setup
Hands-on Networking Fundamentals
Figure Satellite communications setup

53. Satellite Microwave Geosynchronous satellites
Orbit at 22,300 miles above the Earth
Orbital position stationary with respect to earth
Extreme distance can cause transmission delays
Low Earth orbiting (LEO) satellites
Orbit between 435 and 1000 miles above the Earth
Facilitate faster transmission of two-way signals
Uses of satellite networks
Broadband (high-speed) Internet communications
Satellite phone communications
Worldwide video conferencing
Classroom and educational communications
Other communications involving voice, video, data
Hands-on Networking Fundamentals