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Laborator - subiecte de explorat
2h: Studiu & analiza PCAP
Un laborator in care capturam in modul monitor o asociere cu criptare WPA2 si o asociere in plain text. Setup-ul ar fi: AP → STA (Linux PC) + un alt PC cu iw monitor mode pornit. Scopul este:
- Analiza pachetelor de tip 802.11 ca aici: https://www.youtube.com/watch?v=ZXD_qg5dddM ; https://www.youtube.com/watch?v=Kn4hVq5vI3E
- Sa vada ca in beacon se face advertising la capabilitatile routerului (protocoale suportate, MCS-uri etc. - vezi asta: http://www.sharetechnote.com/html/WLAN_Beacon.html ) si ca in probe request STA isi declara capabilitatile
- Sa observe ca tot ce inseamna frame-uri de management (probe request, probe response assoc request blabla) se fac in format legacy la cel mai mic MCS suportat de AP si STA - motivele sunt evidente - nu vrem deloc sa pierdem/ratam aceste cadre
- Sa observe ca field-ul duration din beacone e 0 - beaconul folosește broadcast (fără SIFS+ACK)
- Sa vada ACK-urile de nivel wifi pentru fiecare cadru de management
- Sa analize duration-ul din pachete si sa observe ca e DIFS+SIFS+durata pachetului la cea mai mica modulatie
- Sa folosim cablu RF si 2 atenuatuare si sa observe scaderea SSI-ul sau antena si sa deplasam obiectele si sa observe scaderea SSI-ul si rate adaptionul de la MCS-uri
- FUN: configurat AP-ul sa foloseasca WEP encryption si sa foloseasca aircrack-ng
Curs echivalent: Pozele de aici: http://www.sharetechnote.com/html/WLAN_FrameStructure.html + poza asta: http://www.sharetechnote.com/image/WLAN_Stack_Overview.png
2h: wifi drivers Linux
Folosire hwsim de mac80211 sa se joace cu drivere? https://w1.fi/cgit/hostap/plain/tests/hwsim/example-setup.txt
4h: Studiu TCP+WiFi, wired+wireless
Review TCP: CW, AW, RTT, fast retr, throughput
- One hop wireless: AP→client
- plot MAC loss/delay/jitter vs PHY loss for fixed situations
- uniform loses
- bursty losses
- fixed rate, retries
- TCP/ICMP RTT vs MAC loss
- Application level RTT vs MAC loss
- Application level RTT vs AP bufferbloat
- Topology with one hop WiFi and one hop wired: simplest practical WiFi.
- download S→AP→Client
- vary loss on the wireless link
- vary delay on the wired link
- vary buffer in the AP
- monitor CW, RTT, throughput
2h: TCP mechanisms to combat loss
- what is in which OS? Linux/Windows/IOS
- SACK, TCP flavors
2h: Multiple downlink, uplink TCP clients
- increased efficiency?
- TCP acks are uplink - is there a problem?
- good link vs bad link, HOL blocking, fairness
