Introducere: plotting
Introducere: ns-3: structura, build, rulat exemple cu plot si pcap tracing (wifi-tcp?)
Capacitatea mediului WiFi - cea ideala
Capacitatea mediului WiFi - downlink vs uplink
Modele de propagare WiFi: Friis, LogDistancePropagationLossModel, ThreeLogDistancePropagationLossModel , TwoRayGroundPropagationLossModel cu trafic UDP vs. TCP si cu/fara RTS/CTS
Carrier sense fizic (EnergyDetectionThreshold) vs virtual (RX sensitivity)
DCF / contention window
DCF / contention window (cont.)
Jain Fairness
MCS multiple si rate adaption cu distanta (e unul din exemplele din ns-3)
WiFi in Linux: setup hostapd, wpa_supplicant, iw, modul monitor si tcpdump - analizat radio tap header
WiFi in Linux 2: monitorizare PHY cu USRP?
//Din documentatia ns-3: https://www.nsnam.org/doxygen/classns3_1_1_wifi_mac.html
//https://www.nsnam.org/docs/release/3.5/manual/manual_59.html
//https://mehmetalierturk.com/2014/01/07/how-to-set-edca-parameters-in-ns3-802-11/
void ns3::WifiMac::ConfigureDcf ( Ptr< Txop > dcf,
uint32_t cwmin,
uint32_t cwmax,
bool isDsss,
AcIndex ac
)
NqosWifiMacHelper wifiMacHelper = NqosWifiMacHelper::Default ();
Ssid ssid = Ssid ("ns-3-ssid");
wifiMacHelper.SetType ("ns3::NqstaWifiMac", "Ssid", SsidValue (ssid), "ActiveProbing", BooleanValue (false));
wifiMacHelper.SetDcaParameters ("MinCw", UintegerValue (20), "Aifsn", UintegerValue (3));
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:
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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
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
