quartz/content/notes/09-wireless-networking.md

title	tags
09-wireless-networking	lecture cosc301

IEEE 802 Standards

• 802.1: Bridging and Management, e.g. 802.1X
• 802.3: Ethernet
• 802.11: Wireless (WiFi)
  • 802.11b, 802.11a, .11d, .11g, …, .11aj, .11ay
• 802.16 Broadband Wireless MAN (WiMAX)
• 802.15.4: Zigbee, wireless sensor networks
• 802.15.1: bluetooth, 802.15.6: WBAN
• http://standards.ieee.org/getieee802/

802.11 Family

• 802.11b
  • 11Mbps, 2.4GHz, Kick-started Wi-Fi technology, ~30m indoors.
• 802.11a
  • 54Mbps, 5GHz, technically superior to 11g, gradually common.
• 802.11g
  • 54Mbps, 2.4GHz, still very common. Compatible with 11b.
• 802.11n
  • 540Mbps (typ. 200Mbps), 2.4+5GHz, current choice
  • Max speed hard to determine, ~50m indoor, MIMO
  • Supports a/b/g or ‘Greenfield’ (exclusive).
  • Also supports extensions for priority, multimedia
• 802.11aj -- 15Gbps, mmWave
• 802.11ay -- 20Gbps, mmWave

Operation Modes of 802.11

• Independent or ad-hoc mode
  • Nodes in an ad-hoc network communicate without any need for network infrastructure such as an AP, or network level services such as DHCP, DNS
  • ZeroConf protocols to manage IP addresses etc.
• Infrastructure or managed mode
  • Requires an access point (AP) to function
  • Higher network layers such as data link and IP are configured using the same methods as any wired Ethernet. Most commonly DHCP is used
  • Further security measures may be employed to manage security risks associated with wireless

Ad Hoc mode

[!INFO]

Infrastructure mode

[!INFO]

Basic terminology

• AP: Access Point
• STA: Station/devices
• BSS: Basic Service Set
  • A group of stations that communicate with each other via an access point.
• ESS: Extended Service Set
  • Multiple BSSs can be linked using a distribution system to create an Extended Service Set
• SSID: Service Set Identifier
  • The MAC address of an AP
• ESSID: Extended Service Set Identifier
  • The name of the network

Wireless Distribution System (WDS)

• Backbone of multiple APs, and the inter-AP communication. Usually Ethernet, may be wireless.
• 802.11F defines the Inter Access-Point Protocol (IAPP)

Signal Strength

• Signal Level: Strength of the received signal
• Noise Level: Strength of the noise
• Link Quality: Signal to Noise Ratio (SNR)
• Transmit Power: How loud we speak
• Receive Sensitivity: How well we can hear
• Decibel: 10*log10(P/P0), which shows the ratio of power of one signal over another.

Finding a Network

• Passive scanning listens for AP beacons
  • Listens on each channel for a certain dwell time
  • Won’t detect closed/hidden networks
• Active scanning sends Probe Requests
  • On each channel
  • Requests a particular ESSID or “any”
  • Produces a scan report with discovered ESSIDs

Security of WiFi

• MAC Filter List
  • Not a security protocol
  • Access Control by (changeable) MAC address
  • ACLs can be stored centrally using RADIUS
• WEP (Wired Equivalent Privacy)
  • Minimal protection
  • Not secure due to short key length
  • Pre-Shared Key (PSK)

WPA

• Wi-Fi Protected Access
  • Subset of 802.11i that was released when WEP flaws became a barrier to adoption
• WPA Personal
  • WEP with short-lived changing keys
  • Temporal Key Integrity Protocol (TKIP)
  • Different key per user/session/packet
  • Performance cost if not done in hardware

WPA Enterprise

• WPA Enterprise
  • 802.1X for user authentication
    • “Port” based authentication framework
    • Extensible Authentication Protocol (EAP)
  • Requires RADIUS backend
• 802.11i—WiFi Alliance calls it WPA2
  • Advanced Encryption Standard (AES) cryptography

[!QUESTION] what is RADIUS backend

Security Issues

• Bandwidth stealing
  • You are responsible for their actions
• Access to wired network
  • and other wireless nodes
• ARP Poisoning
  • Man-in-the-middle attacks
• AP Spoofing

[!INFO]