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Networking
Module Nine
| Question | Answer |
|---|---|
| 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
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