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187 lines
6.7 KiB
Markdown
187 lines
6.7 KiB
Markdown
---
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title: "09-wireless-networking"
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tags:
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- lecture
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- cosc301
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---
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IEEE 802 Standards
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- 802.1: Bridging and Management, e.g. 802.1X
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- 802.3: Ethernet
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- 802.11: Wireless (WiFi)
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- 802.11b, 802.11a, .11d, .11g, …, .11aj, .11ay
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- 802.16 Broadband Wireless MAN (WiMAX)
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- 802.15.4: Zigbee, wireless sensor networks
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- 802.15.1: bluetooth, 802.15.6: WBAN
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- http://standards.ieee.org/getieee802/
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802.11 Family
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- 802.11b
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- 11Mbps, 2.4GHz, Kick-started Wi-Fi technology, ~30m indoors.
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- 802.11a
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- 54Mbps, 5GHz, technically superior to 11g, gradually common.
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- 802.11g
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- 54Mbps, 2.4GHz, still very common. Compatible with 11b.
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- 802.11n
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- 540Mbps (typ. 200Mbps), 2.4+5GHz, current choice
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- Max speed hard to determine, ~50m indoor, MIMO
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- Supports a/b/g or ‘Greenfield’ (exclusive).
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- Also supports extensions for priority, multimedia
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- 802.11aj -- 15Gbps, mmWave
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- 802.11ay -- 20Gbps, mmWave
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> [!INFO] millimeter wave still not popular but very fast. might be dangerous to human health. very short range
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> wifi has different frequency band in different countries. same frequency band but different "sub freqs" - channel
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Operation Modes of 802.11
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- Independent or ad-hoc mode
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- 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
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- ZeroConf protocols to manage IP addresses etc.
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- Infrastructure or managed mode
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- Requires an access point (AP) to function
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- Higher network layers such as data link and IP are configured using the same methods as any wired Ethernet. Most commonly DHCP is used
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- Further security measures may be employed to manage security risks associated with wireless
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> [!INFO] more bandwidth = higher speed but less range
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Ad Hoc mode
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> [!INFO] e.g., peer to peer directly between laptops. e.g., airdrop, bluetooth, android wifi direct
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> can set up computer to copmuter network.
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> you can make any host an access point. and set it up as a server to route traffic to the internet. but this would be a slow AP
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> dont need configuration. i.e., no DHCP nor DNS
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Infrastructure mode
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> [!INFO] AP includes services like DHCP and DNS
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> eventually connects to wired network
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> [!INFO] Infrasrtucture mode can have multiple APs connected together
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Basic terminology
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- AP: Access Point
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- STA: Station/devices
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- BSS: Basic Service Set
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- A group of stations that communicate with each other via an access point.
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- ESS: Extended Service Set
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- Multiple BSSs can be linked using a distribution system to create an Extended Service Set
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- SSID: Service Set Identifier
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- The MAC address of an AP
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- ESSID: Extended Service Set Identifier
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- The name of the network
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> [!INFO] if there is only on AP it is BSS
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> if there are more than one AP it is ESS
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> each AP in a ESS can have a different configuration
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Wireless Distribution System (WDS)
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- Backbone of multiple APs, and the inter-AP communication. Usually Ethernet, may be wireless.
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- 802.11F defines the Inter Access-Point Protocol (IAPP)
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> [!INFO] used for ESS. connected APs togehter
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> do handover, access control etc
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Signal Strength
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- Signal Level: Strength of the received signal
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- Noise Level: Strength of the noise
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- Link Quality: Signal to Noise Ratio (SNR) (10:1 is a good ratio) (1:1 is a bad ratio)
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- Transmit Power: How loud we speak
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- Receive Sensitivity: How well we can hear
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- Decibel: 10*log10(P/P0), which shows the ratio of power of one signal over another.
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> [!INFO]
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Finding a Network
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- Passive scanning listens for AP beacons
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- Listens on each channel for a certain dwell time
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- Won’t detect closed/hidden networks
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- Active scanning sends Probe Requests
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- On each channel
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- Requests a particular ESSID or “any”
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- Produces a scan report with discovered ESSIDs
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> [!INFO] active scanning is most only hacker trying to access other peoples wifi
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> most laptops use passive scanning
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> drive by, tries to scan all wifi networks (including hidden), and identify possible weak ones
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> if you dont become a target no one will try to hack you
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> dont "boast" about what you have
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Security of WiFi
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- MAC Filter List
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- Not a security protocol
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- Access Control by (changeable) MAC address
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- ACLs can be stored centrally using RADIUS
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- WEP (Wired Equivalent Privacy)
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- Minimal protection
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- Not secure due to short key length
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- Pre-Shared Key (PSK)
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> [!INFO] MAC can be forged. not secure
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> WEP not secure, key is too short
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WPA
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- Wi-Fi Protected Access
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- Subset of 802.11i that was released when WEP flaws became a barrier to adoption
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- WPA Personal
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- WEP with short-lived changing keys
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- Temporal Key Integrity Protocol (TKIP)
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- Different key per user/session/packet
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- Performance cost if not done in hardware
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> WPA/WPA2 is common
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WPA Enterprise
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- WPA Enterprise
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- 802.1X for user authentication
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- “Port” based authentication framework
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- Extensible Authentication Protocol (EAP)
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- Requires RADIUS backend
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- 802.11i—WiFi Alliance calls it WPA2
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- Advanced Encryption Standard (AES) cryptography
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>[!INFO] WPA enterprise everyone has their own account. this way you can hold people acountable is their accound is hacked. we know which accound had access
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> [!QUESTION] what is RADIUS backend
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Security Issues
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- Bandwidth stealing
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- You are responsible for their actions
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- Access to wired network
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- and other wireless nodes
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- ARP Poisoning
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- Man-in-the-middle attacks
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- AP Spoofing
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> [!INFO] ARP poisoning, once you connect to the wifi someone else can pretend to be the router. respond to ARP requets before AP, and route request through their own computer
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Uses of Wireless
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- When cables are a hassle/liability ✔
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- Transient networks ✔
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- Hotspots✔
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- Backup links ✔
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- Reliability ✗
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- Security (can be managed) ✗
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- Speed ✗
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Channel Layout
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- 13 channels (1, 2, …, 13)
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- Hex-pattern layout for non-overlapping channels
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- But don’t forget that space is 3D
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- Limit number of nodes to about 30 per AP
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Antenna Types
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- Omni-directional
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- Diversity antennas
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- High-gain Omni
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Antenna Types
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- Directional
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- Panel, Yagi, Parabolic
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- Shown is a Wave-Guide “cantenna”
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- Trade off polar coverage for distance
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- dBi is used to measure the gain: 10*log10(PD/PO), PD is the power for directional, PO is the power for standard omnidirectional.
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