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Networking

Module Nine

QuestionAnswer
Ad hoc A type of wireless LAN in which stations communicate directly with each other (rather than using an access point)
Infrastructure WLAN A type of WLAN in which stations communicate with an access point and not directly with each other.
Access Point A device used on wireless LANs that transmits and receives wireless signals to and from multiple nodes and restransmits them to the rest of the network segment.
Service Set identifier (SSID) A unique character string used to identify an access point on an 802.11
Association In the context of wireless networking, the communication that occurs between a station and an access point to enable the station to connect to the network via that access point.
Reassociation In the context of wireless networking, the process of a station establishing a connection (or associating) with a different access point.
Carrier Sense Multiple Access with Collision Detection(CSMA/CD) A network access method specified for use by IEEE 802.3 (Ethernet) networks. In CSMA/CD, each node waits its turn before trnasmitting data to avoid interfering with other nodes' transmissions.
Directional Antenna A type of antenna that issues wireless signals along a single direction, or path
Omnidirectional Antenna A type of antenna that issues and receives wireless signals with equal strength and clarity in all directions.
Geosynchronous orbit (GEO) The term used to refer to a satellite that maintains a constant distance from a point on the equator at every point in its orbit.
Low Earth Orbiting (LEO) A type of satellite that orbits the earth with an altitude between 100 and 900 miles, closer to the Earth's poles than the orbits of either GEO or MEO staellites.
Medium Earth Orbiting (MEO) A type of satellite that orbits the earth roughly 60000 to 12000 miles above its surface, positioned between the equator and the poles.
Hot Spots An area covered by a wireless access point that provides visitors with wireless services, including Internet access.
Line-of-sight (LOS) A wireless signal or path that travles directly in a straight line from its transmitter to its intended receiver.
War Driving The act of driving while running a laptop configured to detect and capture wireless data transmissions
Wired Equivalent Privacy (WEP) A key encryption technique for wireless networks that uses keys both to authenticate network clients and to encrypt data in transit.
Wi-Fi Protected Access (WPA) A wireless security method endorsed by the Wi-fi Alliance that is considered a subset of the 802.11 standard.
WPA-2 The name given in the 802.11 security standard by the Wi-fi Alliance. WPA-2 includes support for the older WPA security method.
Wi-fi 802.11; The IEEE standard for wireless networking
Wi-Max 802.16; An IEEE standard for wireless MANs. 802.16 networks may use frequencies between 2 and 66 GHz.
Wireless Broadband `The term used to describe the recently released standards for high-throughput, long-distance digital data exchange over wireless connections.
WLAN Wireless network that uses IR or RF waves to transmit data between nodes in close proximity oIEEE 802.11 (Wi-Fi), Bluetooth, IrDA
Broadband Wireless network that uses RF waves to transmit data between nodes that are not in close proximity oIEEE 802.16 (WiMAX), Satellite
9KHz - 100KHz Frequency Radio navigation, marine, aeronautical
100KHZ - 1 MHz Frequency AM radio
1 MHz - 10MHz Frequency Shortwave radio
10MHz - 100MHz Frequency FM radio
100MHz - 1 GHz Frequency Television, L-band satelite, PCS, C-Band satelitte, Cellular phones, wireless LANs
1GHz - 10 GHz Frequency Ku-Band satelite, Ka-Band satelite
10GHz - 300GHz Frequency Other satelite
Wireless Transmission Basics share many similarities with wire-bound signals protocols and encoding schemes
Wireless Transmission Basics has many differences to wire-bound signals no fixed path, Tx/Rx controlled and corrected differently, uses tuned antennas
Directional issues (concentrates) signals in a single direction
Omnidirectional issues signals in all directions
What type of wireless service uses a directional antenna? Satellite downlink used to receive digital tv signals. Point to Point and Line-of-sight(LOS)
This type of propagation uses the least amount of energy: Line-of-sight (LOS)
Wireless Transmission Basics Affected by three phenomena Reflection, Diffraction, Diffusion
Reflection bouncing of the RF waves, caused by objects larger than the wavelength. Reflected waves continue to propagate
Diffraction splitting of the RF waves, caused by objects with sharp edges. Split waves continue to propagate (sometimes called “bending”)
Diffusion scattering of the RF waves, caused by objects smaller than the wavelength and objects with rough surfaces (direct relationship to roughness)
Phenomena causes multipath signals which has both an upside and downside
What is the downside to multipath signaling? Signal delay causes signal confusion. Because of their various paths, multipath signals travel different distances between their transmitter and receiver
Signal degradation Fading and Attenuation
Fading and Attenuation naturally occurring weakening of the signal, also caused by the effects of reflection, diffraction and diffusion
Identify two sources of wireless LAN interference: Cellular phones, Mobile phones, overhead lights
Signal types Narrowband, broadband, spread spectrum
Signal categories Fixed and Mobile
Fixed transmitter/receiver do not move (point-to-point)
Mobile receivers are free to roam
Infrared Wireless (IrDA) •Designed for applications where devices are in very close proximity •Operates in the 300GHz to 300,000GHz frequency range, depends on line-of-sight •Remains a viable technology for close proximity wireless applications
WLAN (IEEE 802.11) Two common implementations: ad hoc and infrastructure
Ad hoc WLAN without an Access Point (usually consists of only two nodes)
Infrastructure WLAN with at least one Access Point
Access Point (connectivity device) similar to a wire-bound hub, receives signals from multiple devices and retransmits signals to the entire network
Stations should be within 300 feet to an Access Point
LAN connecting Access Points may be up to 1000 feet apart
IEEE 802.11 Data Link and Physical Layer Standards 802.11a, b, g and n
IEEE 802.11 Share many similarities at the data link layer
802.11 networks use MAC addresses, allows high compatibility with 802.3 networks
What type of signaling method is used by 802.11a, b and g WLANs half-duplex signaling
Which wireless station scanning mode causes an access point to send a probe response? active scanning
Data link MAC sub layer is responsible for: Association, physical addressing, network access
Association oProcess of locating/identifying an Access Point, performed by node with “scanning”
Active scanning node sends a probe frame, AP replies
Passive scanning AP sends beacon frame, node receives and decides to associate or not
Access method Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) oSimilar to CSMA/CD, except every transmission is acknowledged
Request to Send/Clear to Send (RTS/CTS) o Optional protocol that allows a station to own the full bandwidth temporarily o Increases efficiency for large data transfers at the cost of more overhead
When multiple Access Points exist, nodes will usually select: oStrongest signal Access Point or the lowest error rate Access Point oNodes may perform reassociation as they roam
7. Fragmentation occurs at the Network layer on 802.3 Ethernet networks. Where does it occur on an 802.11 network? MAC Sublayer
802.11 Frame types: Control, data, management
Control allows for medium access and data delivery control (ACK/RTS/CTS frames)
Data carry the actual data
Management control of association and reassociation
802.11 Error checking and fragmentation Data frames use a “sequence control” field, indicates fragmentation
802.11a Multiple frequency bands in the 5GHz range Theoretical throughput of 54Mbps (11-18 Mbps actual) Average range of 20 meters
802.11b and g Multiple frequency bands in the 2.4GHz range Theoretical throughput of 802.11b – 11Mbps (about 5 Mbps actual) Theoretical throughput of 802.11g – 54Mbps (20-25 Mbps actual)
802.11 n Multiple frequency bands in the 2.4GHz and 5GHz range Theoretical throughput of up to 300 Mbps Average range is higher than previous versions MIMO technology (multiple antennas) Backward compatible with b and g with performance loss
The geographic range of 802.11b and g WLANs is about: 100 meters (approx. 330 feet)
What is the maximum frame size of an 802.11n frame? 64 KB
Bluetooth Mobile wireless standard, designed as a replacement for infrared
Bluetooth Standardized by Bluetooth Special Interest Group and IEEE 802.15 (WPAN)
Bluetooth Operates in the 2.4GHz frequency range and uses frequency hopping spread spectrum (FHSS)
V1/V1.1 achieves effective throughput of about 700Kbps
V2.0 achieves 2.1Mbps throughput
Bluetooth Creates a personal area network (PAN) called a Piconet
Simple Piconet has one master and one slave
V1/V1.1 Piconet one master, up to seven slaves
V2.0 Piconet one master, unlimited number of slaves
Multiple Piconets may combine to form a scatternet
A node may be a master in one Piconet and a slave in another scatternet
Slaves can participate in more than one scatternet
The geographic range of Bluetooth v2.0 is about: 30 Meters or (approximately 100 feet)
What is the best method of connection when initially configuring an access point? patch cable
IEEE 802.11 access oUse of WLAN technology to access the Internet oActual Internet connection is a WAN technology, not the 802.11 WLAN
What is a hot spot? places where wireless internet access is available to the public
Wireless Broadband Standardized by IEEE 802.16 (WiMAX)
Long distance, high throughput direct competing with DSL and broadband cable
Wireless Broadband theoretical throughput of up to 70Mbps
The frequency range of WiMAX is: 2 and 66GHz
The geographic range of 802.16a is about: 50 Kilometers or (approx. 30 miles)
Three types of satellite orbits GEO, MEO and LEO
Geosynchronous Earth Orbit (GEO) satellite remains in the same place above the earthq
Medium Earth Orbit (MEO) satellite orbits the earth
Low Earth Orbit satellite orbits the earth
Two types of satellite Internet access service Dial Return and Satellite Return
Satellites used by popular satellite ISPs usually have this type of orbit: Geosynchronous orbiting
Wireless Network Testers •Various tools that capture and examine wireless signals •Some tools may assess the quality of a wireless signal •Specialized instruments can assess the wireless network status oSpectrum Analyzer
Wireless networks unique security challenges War Driving, signal interception, etc.
MAC Filtering oParticipating nodes must have a registered MAC address oOffers a level of security but relatively easy to overcome
Wired Equivalent Privacy (WEP) o Optional encryption standard that establishes a shared 64/128-bit network key oSusceptible to discovery, which means weak security
WiFi Protected Access (WPA/WPA2/802.11i) oSeparates the authentication and encryption chores oAuthentication is based on EAP oWPA encryption is based on RC4
Narrowband signals concentrated into a single or narrow range of frequencies
Broadband signals spread across a wider frequency range
Spread spectrum signals spread across multiple frequencies
Created by: booaphi