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WEP (Wireless Equivalent Privacy) encryption methods outdated & hence insecure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Wi-Fi Protected Access (WPA) WPA (outdated) & WPA2 (now: includes 802.11i to its full extent and also the Advanced Encryption Standard (AES))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
Short Message Service (SMS)
(Classic Mobile Communication Services)
- allows to send & receive short messages
- types: point-to-point SMS (single addressee) / point-to-multiple SMS/ Cell broadcast SMS (all users in cell are adressees)
- messages are sent to an SMS service center (SMSC) & are processed in a store-and-forward mode (messages that cannot be relayed will be stored & send later)
Mobile Data Services
(Classic Mobile Communication Services)
– MODEM in analogue mobile networks – CSD in GSM networks – HSCSD in GSM networks – GPRS as first packet-based data service – EDGE
Mobile Data Services: GPRS – advantages/disadvantages of packet-oriented (GPRS) over circuit switched connections(CSD&HSCSD)
DISADVANTAGE: - existing GSM infrastructure must be upgraded (high investments) - new push services require new security concepts
Name Mobile Multimedia Services (4)
Multimedia Messaging Service (MMS), Wireless Application Protocol (WAP), i-mode, IP Multimedia Subsystem
Multimedia Messaging Service (MMS)
message service especially for the transmission of media e.g. images, videos, or sounds –> too expensive, people rather sent pictures attached to an E-mail
(In addition to SMS service center (SMSC), a Multimedia Message Service Centre (MMSC) is necessary to handle the multimedia content of the messages)
Wireless Application Protocol (WAP) - Why didn’t use internet protocols, but protocol family to provide internet contents on mobile devices?
WAP-Forum is a non-profit organization with the objective to build up an open standard (protocol) for wireless data-communication. -> typical scarce resource, when you are a client: bandwidth was too small -> So, what WAP needed to offer, was a modification of these protocols that they could work with these smaller bandwidths
(-> to make Internet content available for the slower transmission rates and longer response times in mobile communications and for the small displays of mobile phones)
i-mode
Japanese service for mobile internet access -> standard based on packet-based data transmission (“Always-online”-Function BUT requires special i-mode device)
- > focus on entertainment-services (e.g. in order to bridge waiting time)
- > convenient accounting via phone-bill
- > automatically integrated push e-mail
IP Multimedia Subsystem
architectural framework for delivering Internet Protocol (IP) multimedia services - idea: Internet Protocol (IP) realized as service based on 2.5G/3G mobile networks
Definition IP-based Mobile Services (IMS) & name services
Architectural framework for delivering Internet Protocol (IP) multimedia services
- > Push E-mail Services
- > VoIP e.g. Skype
- > Rich Communication Services – enhanced (RCS-e/joyn)
- > Mobile IPTV (again TV, but now based on IP basics)
- other IP based mobile services:
- > Instant Messaging
- > Online Games
- > Automotive Communication
Push Email Services
“Always-on” technology for transmitting new emails by “pushing” them to a mobile device, once they arrive, providing seamless over-the-air synchronization -> need special server software
Voice over IP (VoIP) - Definition, Application Scenarios, Security problems
packet-oriented telephony technology, using Internet protocols for transmitting the speech data (e.g. Skype)
- -> application scenarios: Internet-based (communication between Internet User into other communication network, like phone) & Intranet-based (communication with users in same network)
- -> security problems: billing, VoIP terminals are target for potential attacks, possible to eavesdrop communication
Rich Communication Services – enhanced (RCS-e/joyn):
Mobile Network Operators (MNOs) with a means of transitioning voice and messaging services into an all-IP
and LTE world
–> “Enhanced Phonebook”: automatic update of contacts, social presence information (status)
- “Enhanced Messaging”: 1-to-1 and group chat, file transfer, send location data
- “Enriched Calls”: e.g. video calls
