Wireless Networking & Internet Flashcards
IEEE 802.11
A wireless ethernet networking standard.
Uses RF (Radio Frequency)
Uses spread spectrum radio waves.
Broadcasts/Receives one of two bands:
2.4GHz & 5GHz
WAP
Wireless Access Point:
Centrally connects wireless network nodes in the same way a hub connects wired Ethernet PCs.
Also act as switches & internet routers.
PoE
Power over Ethernet:
Ethernet cable that supplies power.
Supplied by a PoE-capable switch.
PoE Injector
Connects PoE-enabled network device to a non-PoE LAN switch port
Can extend a PoE connection up to 100m
CSMA/CA
Carrier Sense Multiple Access/Collision Avoidance:
Network multiple access method in which carrier sensing is used, but nodes attempt to avoid collisions by beginning transmission only after the channel is sensed to be “idle”.
Collision Avoidance
A wireless node listens in on the wireless medium to see if another node is currently broadcasting data. Waits a random amount of time before retrying.
RTS/CTS
Request to Send/Clear to Send:
Transmitting node sends an RTS frame to the receiving node after it determines the wireless medium is clear to use.
Receiving node responds with CTS frame; tells sending node that it’s okay to transmit
Data is sent, then transmitting node waits for an ACK from the receiving node before sending the next data packet.
Ad Hoc Mode
Each wireless network node is in direct contact with every other node in a decentralized free-for-all (no need for WAP).
Good for small groups of PCs sharing files/printers.
Good for temporary networks (study groups/meetings)
IBSS
Independent Basic Service Set:
2 or more wireless nodes communicating in ad hoc mode.
Infrastructure Mode
Devices connect using an access point (ex: router).
Better for networks that need to share dedicated resources such as internet connections and centralized databases.
Good for SOHO (Small office/Home office)
BSS
Basic Service Set:
A single WAP servicing a given area.
WMN
Wireless Mesh Network:
Hybrid wireless topology, where most of the nodes connect in a mesh network (includes wired machines).
Nodes act like routers, forwarding traffic for other nodes, but without wires.
Wireless Speed & Range Issues
Speed decreases as distance increases.
Maximum throughput is only really achieved at 25ft or less.
Dead spots
Increasing Wireless Range
You can install multiple WAPs to permit “roaming” between one WAPs coverage area and another’s.
Replace WAP with one that has greater signal strength/range.
Signal boosters.
Wireless Repeaters/Extenders
Frequency Band (or just Band)
A contiguous range of frequencies that is usually divided up into discrete slices (channels).
802.11a
Frequency Band: 5GHz
Max Range: 150ft
Max Speed: 54Mbps
8 Available Channels
Less prone to interference than 802.11b & g
802.11b
Frequency Band: 2.4GHz
Max Range: 300ft
Max Speed: 11Mbps
14 Available Channels (11 for US)
3 Non-overlapping Channels
802.11g
Frequency Band: 2.4GHz
Max Range: 300ft
Max Speed: 54Mbps
14 Available Channels (11 for US)
Backwards compatibility: 802.11b
Improved security enhancements.
3 Non-overlapping Channels
802.11n
Frequency Band: 2.4 & 5GHz
Max Range: 300ft
Max Speed: 100+Mbps
MIMO to increase range & speed.
Backwards compatibility: 802.11b & g
Same as 802.11g but adds 5GHz band.
802.11ac
Frequency Band: 5GHz
Max Range: 300+ft
Max Speed: 1Gbps
MU-MIMO
Backwards compatibility: all previous
Tethering/Hotspots
Using your smartphone to tether.
Tethering: Using a cellular device to bridge cellular network and Wi-Fi
Infrared Wireless Networking
IrDA Protocol (Infrared Data Association)
Max Speed: 4Mbps
Max Range: 1 meter
Links are direct line-of-sight
Anything that breaks the beam can disrupt.
Point-to-point (ad hoc only)
Half-duplex
Bluetooth
Creates small wireless networks preconfigured to do specific jobs. (PAN: Personal Area Network)
802.15 Network Standard
Bluetooth Speeds (by generation)
1st Gen: 1Mbps
2nd Gen: 3Mbps
3rd Gen: 24Mbps
4th Gen: Reduces cost & power consumption
Improves speed & security.
IP Connectivity
5th Gen: Option to increase speed at cost of range
Better IoT support
Bluetooth Broadcasting Method
Uses a broadcasting method that switches between any of the 79 frequencies available in the 2.45GHz range.
Hops frequencies 1600 times per second (highly resistant to interference)
Bluetooth Modes
Ad hoc = device-to-device
Infrastructure = Bluetooth access points
Backbones
Backbones span the major cities of the earth and interconnect at special locations called NAPs (Network Access Points)
Internet Tier 2
Tier 2 providers own smaller, regional networks and must pay the Tier 1 providers.
Most famous ISPs are Tier 2 providers
Internet Tier 3
Even more regional than Tier 2, and connect to Tier 2 providers.
Purpose of Interweaving Backbones
The key reason for interweaving backbones of the internet is to provide alternative pathways for data if one or more of the routers went down.
If backbone routers in a particular region go down, the other routers would update their list of good routes and attempt to reroute the connection.
TCP/IP
Provides basic software structures for communication on the internet.
Provides the addressing scheme for computers to communicate.
Provides the framework and common language for the internet.
Wide-open structure for creative purposes.
Dial-Up: 2 Requirements
Hardware to dial the ISP (modem/ISDN terminal adapter)
Software to govern the connection
Microsoft DUN: Dial-Up Networking
Dial-Up: Modems
Short for Modulator/Demodulator
Converts digital data into an analog telephone signal, and then back to digital data when reaching the other end of the connection.
Internal: PCI/PCIe
External: USB
Baud
Speed-based unit for phone lines.
1 Baud = 1 cycle per second
Max phone line speed: 2400 baud
14 bits in every baud
2400 x 14 = 33.6Kbps
Dial-Up Network Setup
ISP provides a dial-up telephone number/s
ISP provides a Username & Initial password
Network & Sharing > Set up new connection/network
PPP
Point-to-Point Protocol:
Streaming protocol developed for dial-up internet access.
ISDN
Integrated Services Digital Network: Phone companies switched to digital signals. Up to 64Kbps per line 2 Channels: B (Bearer) & D (Delta) Faster than modems (no dial-up tone) Must be within 18,000ft of central office Wall socket = RJ-45 TA (Terminal Adapter): Much like a modem
ISDN: B Channel
Bearer Channel:
Carries data & voice info at 64Kbps
Most ISDN providers allowed 2 B channels.
ISDN: D Channel
Delta Channel:
Carries setup & configuration info at 16Kbps
ISDN: BRI
Basic Rate Interface Setup:
Two B channels
One D channel
One physical line, but both B channels send 64Kbps
2 x 64 = 128Kbps
ISDN: PRI
Primary Rate Interface: 23 B Channels @ 64Kbps 1 D Channel @ 64Kbps 1.544Mbps Total Lines are called "T1" lines
DSL
Digital Subscriber Line:
Connections to ISPs use a standard telephone line with special equipment on each end to create always-on internet connections at speeds greater than dial-up.
Must be within 18,000ft range of central office.
Modem/receiver connects to the telephone line & PC.
Configure modem to settings provided by ISP.
DSL Speeds
Low-end: 3Mbps Download | 1Mbps Upload
High-end: Tens to hundreds of Mbps
ADSL vs. SDSL
Asymmetric DSL: Slower upload, faster download
Symmetric DSL: Same upload & download speeds
Can cost much more
Cable Internet
Upload Speeds: 5-35+Mbps
Download Speeds: 15-1000+Mbps
Available anywhere you can get cable TV.
Cable Internet Setup
RG-6 or RG-59 cable comes into your house.
Connects to a cable modem that connects to a router or NIC via ethernet.
Fiber Optics (FTTN)
Fiber-to-the-node:
Fiber connection runs from provider to a box somewhere in the neighborhood.
Box connects to home/office with coax or ethernet
Upload speed: 1-20Mbps (AT&T)
Download speed: 10-100Mbps (AT&T)
Fiber Optics (FTTP)
Fiber-to-the-premises:
Runs fiber the whole way from provider straight into home/office.
Once inside home/office, can use any standard cabline or wireless.
Download/Upload (AT&T): 100Mbps to 1Gbps
Download/Upload (Verizon): 50Mbps to 1Gbps
MAN
Metropolitan Area Network:
A network that covers a single city.
Line-of-Sight Wireless
A tower system that broadcasts Internet signal through the air as opposed to underground.
Addresses range issues by using high-powered, directional antennas and Ethernet bridge devices (up to 8+ miles)
Can use bands like 24GHz
Cellular Data Types
1G: Analog cell phone data service (cannot carry packetized data)
2G: GSM standard; encrypted phone convos, more efficient use of RF spectrum; data services (SMS)
3G: EV-DO - Up to 7.2Mbps (This is debatable apparently)
3.5G
4G/LTE - Up to 100Mbps (Also debatable apparently)
LTE
Long Term Evolution:
Theoretical speeds up to 1Gbps download & 100Mbps upload.
Synonymous with 4G.
Can readily replace wired network tech.
Efficient with mobile hotspots for remote areas.
WWAN & WLAN
Wireless Wide Area Network
Wireless Local Area Network
Satellite Internet
Data is beamed to a satellite dish on your house/office.
Receiver handles the flow of data.
Eventually sends through Ethernet to NIC
HughesNet: 25Mbps Download & 3Mbps Upload
Satellite Internet Setup
Professionally-installed dish with line-of-sight to satellite.
Coax cable runs from dish to satellite modem.
Satellite modem has RJ-45 connection.
(Can go directly into computer/router)
Satellite Internet Downsides
Satellite latency: Delay for signal to reach the satellite.
Can impede on gaming, voice, or video
Fowl weather can degrade signal
Operators must implement usage caps to keep the system from getting overloaded.
(HughesNet: Fair access policy)
NAT
Network Address Translation:
Presents an entire LAN of computers to the internet as a single machine.
Effectively hides all of your computers and makes them invisible to others on the internet.
Only a Public IP is visible (LAN uses private IPs)
Acts as a firewall, protecting the internal network from probing/malicious users.
DNAT or Pooled NAT
Dynamic Network Address Translation:
Allows a large connection of hosts to connect to the Internet with limited registered addresses.
Multiple public IPs are mapped and used with an internal or private IP.
Allows a user to connect a local computer/server/device to an external network with an unregistered private IP.
Basic Router Configuration
Router’s IP: Access to configuration
Username & Password
(Comes with default, can be changed in config)
Set static IP
Update router firmware
(Bad update can brick router)
UPnP
Universal Plug and Play:
Set of networking protocols that enables seamless interconnectivity between devices at the cost of somewhat lowered security.
Many networking devices use this to seek out, find, and connect to other UPnP devices.
Uses Internet Gateway Device Protocol
IoT
Internet of Things:
Smart devices are collectively known as IoT.
Home automation: thermostats, lights, refrigerators, digital assistants.
Z-Wave & Zigbee
Home Automation Protocols:
Competing technologies used for home automation.
Both use mesh network topology
Have hubs that act as network interconnect
Z-Wave: A proprietary standard (with open API)
Zigbee: Completely open standard
QoS
Quality of Service:
Tool to prioritize access to network resources
Enables you to ensure certain users/apps/services are prioritized when there isn’t enough bandwidth to go around.
Can limit bandwidth for certain types of data based on application protocol, IP address, or other features.
