Chapter 20: Wireless Networking (A+ Study Notes)
A+
Study Notebook
You can find my complete study notes in Google Docs format below: https://docs.google.com/document/d/1zcKLWfsns1tqzmXtVRJbcd9NqfaEcjifgIo-oJIbEgc/edit?usp=sharing
References:
M. MEYERS, 2019. CompTIA A+ All-in-One Exam Guide. 10th ed.
Chapter 20: Wireless Networking
- Wi-fi
- RF (Radio Frequency)
- Wireless Network Card (NIC) / Or USB Adapter
- WAP (Wireless Access point) - central connection point for all wireless devices (just like ethernet and Hub)
- PoE (Power-over-Ethernet) - some WAPs support PoE which provides both power and Network connectivity at the same time. Power and network connection are both supplied by PoE-capable switch.
- How Wireless network operates:
- CSMA / CA (Carrier Sense Multiple Access/ Collision Avoidance) - A wireless node listens in on the wireless medium to see if another node is currently broadcasting data. If so, it waits a random amount of time before retrying. Request to Send/Clear to Send (RTS/CTS) protocol. With this protocol enabled, a transmitting node sends an RTS frame to the receiving node after it determines the wireless medium is clear to use. The receiving node responds with a CTS frame, telling the sending node that it’s okay to transmit. Then, once the data is sent, the transmitting node waits for an acknowledgment (ACK) from the receiving node before sending the next data packet.
- IEEE 802.11 (Wi-fi/ wifi)
- Ad-hoc Mode (all nodes connect with each other) - good for small networks
- If 2 or more wireless nodes operate in such way, then it is called as IBSS (Independent Basic Service Set)
- Infrastructure mode (connects multiple WAPs into wired network)
- Single WAP servicing a given area is called BSS (Basic Service Set)
- If single WAP extended by more WAPs it is called EBSS (Extended Basic Service Set)
- WMN (Wireless Mesh Network) - connects various WAPs, Ethernet etc. into single WMN.
- All nodes act as routers, forwarding traffic for other nodes, but without wires
- Wireless Security
- MAC address filtering - method which allows to limit access to your wireless network based on the physical, hard-wired address of the units wireless NIC.
- E.g. any data packets which contain MAC address not listed in the table - the connection will be rejected
- Authentication / Encryption and Security Protocols
- WEP (Wireless Equivalent Privacy Protocol)
- Idea is to secure data while in transit over the airwaves
- 40-bit encryption to scramble data packets (Sometimes 104-bit (even when advertised as 128-bit)
- Problem: Can be easily decrypted
- Problem: All WEP traffic is encrypted with the same key
- WPA (Wifi Protected Access Protocol)
- It uses TKIP (Temporal Key Integrity Protocol) which produces a new encrypted key for every sent packet
- Also EAP (Extensible Authentication Protocol) which checks key integrity
- WPA2 (also called IEEE 802.11i)
- Uses AES (Advanced Encryption Standard)
- WPA3
- Still in progress but should be able to encrypt users data even on public networks
- WPS (Wireless Protected Setup)
- Uses push button or password/code to connect faster
- Problem: Easy to decrypt 8-digit code
- SSID (Service Set Identifier / Network name)
- Change default network name, as it might include router/wap/switch model etc.
- Change Default password
- Don’t broadcast SSID (simply hide it)
- Antennas (you can pick appropriate antenna which broadcasts signal only into the direction where you require, rather than spreading behind the walls of your e.g. property)
- Polarization (how you position antenna e.g. vertically or horizontally to the device you use. Ideally and for max signal strength you want to have the same polarization on both)
- Omni directional - Sends signal in all directions. Signal is in a shape of a ball. The more signal the bigger the ball. e.g. on cars, or if placed in the center of the house - all house will receive the signal
- Dipole Antenna
- Patch
- Can direct signal only in one direction.
- Highly Directional
- Physical placement of WAP (as ports are not encrypted or password protected)
- Wireless Networking Standards
- IEEE 802.11
- Communicates over spread-spectrum radio waves. Which broadcasts data in small chunks over frequencies available within a certain frequency range
- Problem: interference
- Bands: wifi broadcasts and receives signal over: 5GHz vs 2.4 GHz
- Channels - contiguous range of frequencies that is usually divided up into discrete slices called channels
- Standards: 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac
- MIMO (Multiple input multiple output) - allows simultaneous connections
- MU-MIMO (Multiuser MIMO) - ability to broadcast multiple users simultaneously
- IrDA (Infrared Data Association Protocol)
- Works only in adhoc mode
- Operates at Half-duplex
- The only security feature is the distance at which it can operate
- Bluetooth
- Bluetooth uses all 79 frequencies available on 2.45-Ghz range.
- Bluetooth hops frequencies at 1600 times per second, making it highly resistant to interference.
- The faster and further device sends data - the more power it uses. That’s why devices are configured to specific Classes, which define maximum power usage in miliwatts (mW) and maximum distance:
Class 1 - 100mW | 100m
Class 2 - 2.5mW | 10m
Class 3 - 1 mW | 1m
- Cellular/ Mobile
- Setting up wifi:
- Ad-hoc mode (can be enabled in NIC’s Properties)
- Infrastructure Mode
- Most of the settings are done on the dedicated e.g. website. Website where you can set SSID, Mac filtering, Encryption, Channel, Band, etc.
- Enterprise
- To set up WPA2 you’ll need to enable authentication by using something called RADIUS server or TACACS+ protocols
- RADIUS (Remote Authentication Dial-In User Service)
- Partially encrypted and uses UDP
- TACACS+ (Terminal Access Controller Access-Control System Plus)
- Fully encrypted and uses TCP
- Both RADIUS and TACACS+ are protocols for authenticating network users and managing what resources they may access
- RFID (Radio Frequency Identification)
- NFC (Near Field Communication)
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