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diff --git a/usth/ICT3.16/labworks/4.md b/usth/ICT3.16/labworks/4.md new file mode 100644 index 0000000..346daf9 --- /dev/null +++ b/usth/ICT3.16/labworks/4.md @@ -0,0 +1,156 @@ +# Network Simulation: Labwork 4 +The code presented in this report is a heavily modified version of the ns-3 +tutorial `third`. + +## Wireless Network Topology +Consider a Wi-Fi network topology of 3 nodes (1 access point AP and 2 stations +STA1 and STA2) using wireless channel. The AP is connected to an echo server S +via LAN channel: + +```c++ +NodeContainer p2pNodes; +p2pNodes.Create (2); // AP and S +NodeContainer wifiApNode = p2pNodes.Get (0); + +PointToPointHelper pointToPoint; // LAN channel +pointToPoint.SetDeviceAttribute ("DataRate", StringValue ("5Mbps")); +pointToPoint.SetChannelAttribute ("Delay", StringValue ("2ms")); +NetDeviceContainer p2pDevices = pointToPoint.Install (p2pNodes); + +NodeContainer wifiStaNodes; +wifiStaNodes.Create (2); // STA 1 and STA2 + +YansWifiChannelHelper channel = YansWifiChannelHelper::Default (); +YansWifiPhyHelper phy = YansWifiPhyHelper::Default (); +phy.SetChannel (channel.Create ()); + +WifiHelper wifi; +wifi.SetRemoteStationManager ("ns3::AarfWifiManager"); + +WifiMacHelper mac; +Ssid ssid = Ssid ("ns-3-ssid"); +mac.SetType ("ns3::StaWifiMac", + "Ssid", SsidValue (ssid), + "ActiveProbing", BooleanValue (false)); +NetDeviceContainer staDevices = wifi.Install (phy, mac, wifiStaNodes); + +mac.SetType ("ns3::ApWifiMac", "Ssid", SsidValue (ssid)); +NetDeviceContainer apDevices = wifi.Install (phy, mac, wifiApNode); + +MobilityHelper mobility; +mobility.SetPositionAllocator ("ns3::GridPositionAllocator", + "MinX", DoubleValue (0.0), + "MinY", DoubleValue (0.0), + "DeltaX", DoubleValue (5.0), + "DeltaY", DoubleValue (10.0), + "GridWidth", UintegerValue (3), + "LayoutType", StringValue ("RowFirst")); + +mobility.SetMobilityModel ("ns3::ConstantPositionMobilityModel"); +mobility.Install (wifiStaNodes); +mobility.Install (wifiApNode); +``` + +## Echo Server +Implement scenario of STA1 is a client that sends 100 packets within 10 s to S. + +```c++ +InternetStackHelper stack; +stack.Install (p2pNodes); +stack.Install (wifiStaNodes); + +Ipv4AddressHelper address; +address.SetBase ("10.1.2.0", "255.255.255.0"); +Ipv4InterfaceContainer p2pInterfaces; +p2pInterfaces = address.Assign (p2pDevices); + +address.SetBase ("10.1.1.0", "255.255.255.0"); +address.Assign (staDevices); +address.Assign (apDevices); + +UdpEchoServerHelper echoServer (9); + +ApplicationContainer serverApps = echoServer.Install (p2pNodes.Get (1)); +serverApps.Start (Seconds (1.0)); +serverApps.Stop (Seconds (12.0)); + +UdpEchoClientHelper echoClient (p2pInterfaces.GetAddress (1), 9); +echoClient.SetAttribute ("MaxPackets", UintegerValue (100)); +echoClient.SetAttribute ("Interval", TimeValue (MilliSeconds (100))); +echoClient.SetAttribute ("PacketSize", UintegerValue (1024)); + +ApplicationContainer clientApps = echoClient.Install (wifiStaNodes.Get (0)); +clientApps.Start (Seconds (2.0)); +clientApps.Stop (Seconds (12.0)); + +Ipv4GlobalRoutingHelper::PopulateRoutingTables (); +Simulator::Stop (Seconds (12.0)); +``` + +Capture the pcap trace from the access point, where all traffic in our setup +has to go through, and run the simulation: + +```c++ +phy.EnablePcap ("third", apDevices.Get (0)); +``` + +The TCP dumped trace is attached as `third-0-1-station`. There is not much +to be deduced from it other than that the latency across Wi-Fi is now in +the order of milliseconds, i.e. tens of times worse than on a typical +Ethernet configuration. As expected, there is not any drop due to queuing +since we set the interval to 100 ms. + +In addition, there is Beacon frames (which if I understand correctly +is to discover devices and keep updated about their stati). By default +they are 100 time units or 102.4 ms a part, which explains how the packet +delivery seems to alternate with the Beacon and Acknowledgement frames. + +## Mobile Stations +Let the two STAs move in a random direction and speed respecting +to RandomWalk mode: + +```c++ +mobility.SetMobilityModel ("ns3::RandomWalk2dMobilityModel", "Bounds", + RectangleValue (Rectangle (-50, 50, -50, 50))); +mobility.Install (wifiStaNodes); +``` + +The TCP dumped trace is attached as `third-0-1-mobile`. To my surprise, +there exists only minor differences in delay of the first few packets, +and the mobile model actually has lower latency: + +```diff +--- third-0-1-station 2021-03-24 22:50:45.137239064 +0700 ++++ third-0-1-mobile 2021-03-24 22:46:33.867879542 +0700 +@@ -25,18 +25,18 @@ + 1.728436 Beacon (ns-3-ssid) [6.0* 9.0 12.0* 18.0 24.0* 36.0 48.0 54.0 Mbit] ESS + 1.830836 Beacon (ns-3-ssid) [6.0* 9.0 12.0* 18.0 24.0* 36.0 48.0 54.0 Mbit] ESS + 1.933236 Beacon (ns-3-ssid) [6.0* 9.0 12.0* 18.0 24.0* 36.0 48.0 54.0 Mbit] ESS +-2.006146 ARP, Request who-has 10.1.1.3 (ff:ff:ff:ff:ff:ff) tell 10.1.1.1, length 32 +-2.006162 Acknowledgment RA:00:00:00:00:00:03 +-2.006240 ARP, Request who-has 10.1.1.3 (ff:ff:ff:ff:ff:ff) tell 10.1.1.1, length 32 +-2.006449 ARP, Reply 10.1.1.3 is-at 00:00:00:00:00:05, length 32 +-2.006621 Acknowledgment RA:00:00:00:00:00:05 +-2.008131 IP 10.1.1.1.49153 > 10.1.2.2.9: UDP, length 1024 +-2.008147 Acknowledgment RA:00:00:00:00:00:03 +-2.021537 ARP, Request who-has 10.1.1.1 (ff:ff:ff:ff:ff:ff) tell 10.1.1.3, length 32 +-2.021795 ARP, Reply 10.1.1.1 is-at 00:00:00:00:00:03, length 32 +-2.021811 Acknowledgment RA:00:00:00:00:00:03 +-2.021961 IP 10.1.2.2.9 > 10.1.1.1.49153: UDP, length 1024 +-2.023498 Acknowledgment RA:00:00:00:00:00:05 ++2.002146 ARP, Request who-has 10.1.1.3 (ff:ff:ff:ff:ff:ff) tell 10.1.1.1, length 32 ++2.002162 Acknowledgment RA:00:00:00:00:00:03 ++2.002240 ARP, Request who-has 10.1.1.3 (ff:ff:ff:ff:ff:ff) tell 10.1.1.1, length 32 ++2.002449 ARP, Reply 10.1.1.3 is-at 00:00:00:00:00:05, length 32 ++2.002621 Acknowledgment RA:00:00:00:00:00:05 ++2.004131 IP 10.1.1.1.49153 > 10.1.2.2.9: UDP, length 1024 ++2.004147 Acknowledgment RA:00:00:00:00:00:03 ++2.014537 ARP, Request who-has 10.1.1.1 (ff:ff:ff:ff:ff:ff) tell 10.1.1.3, length 32 ++2.014795 ARP, Reply 10.1.1.1 is-at 00:00:00:00:00:03, length 32 ++2.014811 Acknowledgment RA:00:00:00:00:00:03 ++2.014961 IP 10.1.2.2.9 > 10.1.1.1.49153: UDP, length 1024 ++2.016498 Acknowledgment RA:00:00:00:00:00:05 + 2.035636 Beacon (ns-3-ssid) [6.0* 9.0 12.0* 18.0 24.0* 36.0 48.0 54.0 Mbit] ESS + 2.101510 IP 10.1.1.1.49153 > 10.1.2.2.9: UDP, length 1024 + 2.101526 Acknowledgment RA:00:00:00:00:00:03 +``` |