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\ihead{Netzwerktechnik}
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\ohead{http://kohnlehome.de/netz/wlan.pdf}
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\begin{document}

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Wireless LAN
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\section*{Standards}
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\begin{tabular}{l | r | r | r | r }
Standard & Name & Bandbreite & Frequenz & Jahr\\ \hline \hline
IEEE 802.11 & (Wi-Fi 1) & 2 Mbit/s & 2,4 GHz & 1997\\
IEEE 802.11b & (Wi-Fi 2) & 11 Mbit/s & 2,4 GHz & 1999\\
IEEE 802.11a & (Wi-Fi 3) & 54 Mbit/s & 5 GHz & 1999\\
IEEE 802.11g & (Wi-Fi 3) & 54 Mbit/s & 2,4 GHz & 2003\\ \hline
IEEE 802.11n & Wi-Fi 4 & 600 Mbit/s & 2,4 GHz / 5 GHz & 2009\\
IEEE 802.11ac & Wi-Fi 5 & 1,3 Gbit/s & 5 GHz & 2013\\ \hline
IEEE 802.11ax & Wi-Fi 6 & 5 Gbit/s & 2,4 GHz / 5 GHz & 2019\\
IEEE 802.11ax & Wi-Fi 6E & 5 Gbit/s & 6 GHz & 2020\\ \hline
IEEE 802.11be & Wi-Fi 7 & 46,1 Gbit/s  & 2,4 GHz / 5 GHz / 6 GHz & 2024
\end{tabular}

\section*{Geräte}
\begin{itemize}
\item 802.11 NIC
\item Access-Point (Autonomous / Controller-Based): verbindet 802.11 WLAN mit 802.3 Ethernet
\item Wireless-Router: Access-Point, Switch, Router, Modem
\item Antenne
\begin{itemize}
\item Omnidirectional
\item Directional
\item MIMO (Multiple Input Multiple Output): mehrere Sende- und Empfangsantennen
\end{itemize}
\end{itemize}

\section*{Topologien}
Siehe \href{http://kohnlehome.de/netz/wlan-topologien.pdf}{kohnlehome.de/netz/wlan-topologien.pdf}

\section*{Frame-Header}
\begin{itemize}
\item Frame Control: Protocol Version, frame Type, ...
\item Duration: Remaining time to receive next Frame
\item Address 1: Receiving Device or AP
\item Address 2: Transmitting Device or AP
\item Address 3: Destination MAC
\item Sequence Control: 
\item Address 4: only in Ad-Hoc-mode
\end{itemize}

\section*{CSMA/CA}
\begin{itemize}
\item half-duplex
\item wait till channel is idle
\item Client sends RTS (Ready To Send)
\item Client waits for CTS (Clear To Send)
\item All transimissions are acknowledged
\end{itemize}

\section*{Wireless Client and AP Association}
\begin{itemize}
\item Vorgang
\begin{itemize}
\item Discover a wireless AP
\item Authenticate with AP
\item Associate with AP
\end{itemize}
\item Modi
\begin{itemize}
\item Passive Mode: AP advertises SSID
\item Active Mode: Client must know SSID and sends Probe Request
\end{itemize}
\end{itemize}

\section*{CAPWAP (Control and Provisioning of Wireless Access Points)}
\begin{itemize}
\item WLC (Wireless LAN Controller) manages multiple APs and WLANs.
\item based on LWAPP (Lightweight Access Point Protocol)
\item UDP ports 5246 and 5247
\item Split MAC Architecture
\begin{itemize}
\item AP MAC Functions
\begin{itemize}
\item Beacons and probe responses
\item ACK and Retransmission
\item Frame queueing, prioritization
\item MAC layer data encryption and decryption
\end{itemize}
\item WLC MAC Functions
\begin{itemize}
\item Authentication
\item Association and re-association of roaming clients
\item Frame translation to other protocols
\item Termination of 802.11 traffic on a wired interface decryption
\end{itemize}
\end{itemize}
\item DTLS (Datagram Transport Layer Security) Encryption für control channel
\item FlexConnect: Verbindung WLC - AP über WAN
 \begin{itemize}
\item connected mode: WLC und AP haben Verbindung
\item standalone mode: AP hat Verbindung zu WLC verloren, kann aber trotzdem alleine arbeiten
\end{itemize}
\end{itemize}

\section*{Frequency Channel Saturation}
\begin{itemize}
\item DSSS (Direct-Sequence Spread Spectrum): Frequenzbereich wird ausgeweitet (802.11b)
\item FHSS (Frequency-Hopping Spread Spectrum): schnelles Wechseln zwischen Kanälen (802.11)
\item OFDM (Orthogonal Frequency-Division Multiplexing): mehrer Kanäle gleichzeitig nutzen (802.11a/g/n/ac)
\item OFDMA (Orthogonal Frequency-Division Multiaccess): (802.11ax)
\end{itemize}

\section*{Channels}
\begin{itemize}
\item 2,4 GHz: 13 Kanäle, non overlapping: 1, 6, 11
\item 5 GHz: 24 Kanäle
\end{itemize}

\section*{Wireless Security}
\subsection*{WLAN Threats}
\begin{itemize}
\item DoS Attacks
\item Rogue Access Points
\item Man-in-the-Middle Attack
\end{itemize}

\subsection*{Secure WLANs}
\begin{itemize}
\item SSID Cloaking
\item MAC Address Filtering
\item Authentication Methods
\begin{itemize}
\item Open system authentication
\item PSK (Shared key authentication)
\begin{itemize}
\item WEP
\item WPA (TKIP: Temporal Key Integrity Protocol)
\item WPA2 (AES: Advanced Encryption Standard, CCMP: Counter Cipher Mode with Block Chaining Message Authentication Code Protocol)
\item WPA3
\end{itemize}
\item AAA (Authentication, Authorization, and Accounting), RADIUS (Remote Authentication Dial-In User Service): 802.1X mit EAP (Extensible Authentication Protocol
\item Automatisch 
\begin{itemize}
\item WPS (Wi-Fi Protected Setup)
\item DPP (Device Provisioning Protocol), auch für IoT
\end{itemize}
\end{itemize}
\end{itemize}


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