3. Wireless Internet-oriented Infrastructures & Protocols Flashcards
Definition: Wireless LAN & architecture
Wireless communication based on radio as transport medium -> Cell based architecture: basis module is a radio cell which covers a circular area that connected devices are able to use -> WLAN radio cell can be add-on for already existing cable-based networks
WLAN bandwidth depends on…? (4)
chose standard, distance between client & access point and construction/quantity of walls
Definition: Beacon Frame & how does it work?
Information and management packages with identification data, which base stations send out regularly, to inform about their presence and which mobile devices can use for orientation. WLAN base stations or access points send out beacons to offer WLAN clients their connectivity.
–> A Wireless LAN client sends a probe request. The Access Point answers with a probe response. If there is an agreement, the Wireless LAN client starts the communication over the Access Point.
Components of WLAN (802.11b)
Access Point (AP) = sender & receiver station that allows the connecting of many stations --- Stations = End-systems that establish a wireless connection e.g. by using AP (e.g. laptop)
WLAN – Infrastructure
Ad-hoc Network = devices on the wireless network directly connect to each other -> don’t require a centralized AP (e.g. airdrop)
WLAN – State-of-the-art Encryption
We only look at methods that use pre-shared key (PSK)
- –>WEP (Wireless Equivalent Privacy) encryption methods outdated & hence insecure
- –>Wi-Fi Protected Access (WPA) WPA (outdated) & WPA2 (now: includes 802.11i to its full extent and also the Advanced Encryption Standard (AES))
Key Reinstallation Attacks (KRACKs)
attack against 4-way handshake of WPA2 (doesn’t leak the encryption key, but sensitive info like usernames, passwords…)
WLAN – Mobility Restrictions
No existing standard for “handover” or “roaming” between AP/different providers of AP &
Change of AP leads to connection interrupt & new connection/authentication
WLAN – Roaming (how does it work?)
By combination of several AP a distribution system is growing -> Every AP covers one radio cell -> Upon leaving a radio cell the station starts scanning for other existing AP & tries to connect -> AP that was used before will be informed
WLAN – Roaming (architecture)
BASIC SERVICE SET (BSS): group of stations which use the same radio frequency
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ACCESS POINT (AP): station which is integrated into the radio as well as the fixed local area network (distribution system)
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PORTAL: transfer into another network
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DISTRIBUTION SYSTEMS: connection of different cells for building a larger network (ESS: extended service set)
Routing in TCP/IP & mobility problem
routing of data packets in TCP/IP takes place from Partner A to Partner B and vice versa —> separate IP addresses in the office and at home, DHCP for dynamic IP address assignment but continuous accessibility via one IP is not guaranteed
-> MOBILITY PROBLEM: when partner B changes network
Mobility Solutions for Routing in TCP/IP (2)
BINDING UPDATE: Redirection of first package via home address to mobile device & new route with remaining packets (problems: possible attack with illegitimate BU: Capture the route & redirect the TCP/IP session, observation of user movements through BU)
Radio Access Network (RAN)
part of mobile telecommunication system
provides connection between device & core network
examples: - GRAN (GSM radio access network) - GERAN (same as GRAN but specifying inclusion of EDGE) - UTRAN (UMTS RAN)
Name Classic Mobile Communication Services (3)
- Voice/Fax Service
- 2. Short Message Service (SMS)
- 3. Mobile Data Services
Voice/Fax Service
(Classic Mobile Communication Services) regular telephone service & emergency call, speech signals are digitally coded using a bidirectional (talk into both directions), symmetric, full-duplex (send & receive messages at same time) point-to-point connection
