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拓扑图：A和H通信，n8和n9、n10和n11在中间某个时刻开始产生背景流量
A和H之间通信60s，在20s到40s时，n8和n9开始通信，n10和n11开始通信。
瓶颈链路：router2和router4之间，链路带宽设置为10Mbps，router3和router5之间为10Mbps，n8与router2之间、n9与router4之间、n10与router3之间、n11与router5之间带宽为5Mbps。
1、代码及注释
/*
n8 n9
| |
router2(2)------router4(4)
/ \
/ \
A(0)----router1(1) router6(6)----H(7)
\ /
\ /
router3(3)------router5(5)
| |
n10 n11
(i)为程序中NodeContainer nodes中节点的顺序号
*/
#include <iostream>
#include <fstream>
#include <string>
#include <cassert>
#include <vector>
#include "ns3/core-module.h"
#include "ns3/network-module.h"
#include "ns3/csma-module.h"
#include "ns3/internet-module.h"
#include "ns3/point-to-point-module.h"
#include "ns3/applications-module.h"
#include "ns3/ipv4-global-routing-helper.h"
using namespace ns3;
NS_LOG_COMPONENT_DEFINE ("myFirstExample");
int
main (int argc, char * argv[])
{
/* uint16_t nodesNum = 12;
float dataRateAtoB = 100.0;//A——B
float dataRateGtoH = 100.0;//G——H
float dataRateBtoC = 100.0;
float dataRateBtoD = 100.0;
float dataRateGtoE = 100.0;
float dataRateGtoF = 100.0;
float dataRateNodetoaRouter = 100.0;
float dataRateR1toR3 = 5.0;
float dataRateR2toR4 = 5.0;
*/
/*使用可视化工具 PyViz*/
CommandLine cmd;
cmd.Parse (argc,argv);
//设置默认拥塞控制算法
Config::SetDefault("ns3::TcpL4Protocol::SocketType", StringValue("ns3::TcpReno"));
Config::SetDefault ("ns3::OnOffApplication::PacketSize", UintegerValue (1024)); //设置默认包的尺寸
Config::SetDefault ("ns3::OnOffApplication::DataRate", StringValue ("50Mb/s")); //设置默认发包速率
/*创建节点
1 client (lefts)
1 server (rights)
4 nodes to generate background flow
6 routers = 1 封装&转发 + 1解封&转发 + 4转发
*/
std::cout << "create nodes"<<std::endl;
NodeContainer left, right, routers, othernodes;
left.Create(1);
right.Create (1);
routers.Create (6);//多路径转发设备为1个路由
othernodes.Create(4);//产生背景流量
NodeContainer nodes = NodeContainer(left, routers,right, othernodes);
//各条边的节点组合,一共12条边
std::vector<NodeContainer> nodeAdjacencyList(12);
nodeAdjacencyList[0]=NodeContainer(nodes.Get(0),nodes.Get(1));//A(0)
nodeAdjacencyList[1]=NodeContainer(nodes.Get(1),nodes.Get(2));
nodeAdjacencyList[2]=NodeContainer(nodes.Get(1),nodes.Get(3));
nodeAdjacencyList[3]=NodeContainer(nodes.Get(2),nodes.Get(4));
nodeAdjacencyList[4]=NodeContainer(nodes.Get(3),nodes.Get(5));
nodeAdjacencyList[5]=NodeContainer(nodes.Get(4),nodes.Get(6));
nodeAdjacencyList[6]=NodeContainer(nodes.Get(5),nodes.Get(6));
nodeAdjacencyList[7]=NodeContainer(nodes.Get(6),nodes.Get(7)); //H(7)
nodeAdjacencyList[8]=NodeContainer(nodes.Get(2),nodes.Get(8));
nodeAdjacencyList[9]=NodeContainer(nodes.Get(4),nodes.Get(9));
nodeAdjacencyList[10]=NodeContainer(nodes.Get(3),nodes.Get(10));
nodeAdjacencyList[11]=NodeContainer(nodes.Get(5),nodes.Get(11));
/*配置信道*/
std::vector<PointToPointHelper> p2p(12);
//高速路段
for(int i = 0; i < 3; i ++){
p2p[i].SetDeviceAttribute ("DataRate", StringValue ("50Mbps"));//设置带宽
p2p[i].SetChannelAttribute ("Delay", StringValue ("5ms")); //设置时延
}
//瓶颈路段1
p2p[3].SetDeviceAttribute ("DataRate", StringValue ("10Mbps"));
p2p[3].SetChannelAttribute ("Delay", StringValue ("10ms"));
//瓶颈路段2
p2p[4].SetDeviceAttribute ("DataRate", StringValue ("10Mbps"));
p2p[4].SetChannelAttribute ("Delay", StringValue ("20ms"));
//高速路段
for(int i = 5; i < 8; i ++){
p2p[i].SetDeviceAttribute ("DataRate", StringValue ("50Mbps"));//设置带宽
p2p[i].SetChannelAttribute ("Delay", StringValue ("5ms")); //设置时延
}
//背景流量段
for(int i = 8; i < 12; i ++){//上次错误，此处的i写成了3
p2p[i].SetDeviceAttribute ("DataRate", StringValue ("5Mbps")); //背景流量段带宽可设置5,10,20
p2p[i].SetChannelAttribute ("Delay", StringValue ("5ms"));
}
std::vector<NetDeviceContainer> devices(12);
for(int i = 0; i < 12; i ++){
devices[i] = p2p[i].Install(nodeAdjacencyList[i]);
}
/*安装网络协议栈*/
InternetStackHelper stack;
stack.Install (nodes);//安装协议栈，tcp、udp、ip等
/*上面1句等价于下面4句
stack.install(left);
stack.install(right);
stack.install(routers);
stack.install(othernodes);
*/
//NS_LOG_INFO ("Assign IP address.");
Ipv4AddressHelper address;
std::vector<Ipv4InterfaceContainer> interfaces(12);
for(uint32_t i=0; i<12; i++)
{
std::ostringstream subset;
subset<<"10.1."<<i+1<<".0";
//n0:10.1.1.1 n1接口1:10.1.1.2 n1接口2:10.1.2.1 n2接口1:10.1.2.2 ...
address.SetBase(subset.str().c_str (),"255.255.255.0");//设置基地址（默认网关）、子网掩码
interfaces[i]=address.Assign(devices[i]);//把IP地址分配给网卡,ip地址分别是10.1.1.1和10.1.1.2，依次类推
}
//分配给A的IP地址为10.1.1.1 H的IP地址为10.1.8.2（A和H为多路径的两端）
/*接下来是建立通信的app和路由表的建立*/
// Create router nodes, initialize routing database and set up the routing
// tables in the nodes.
Ipv4GlobalRoutingHelper::PopulateRoutingTables ();//这里直接调用了ns3的路由实现，后期需要修改
/*在n7,n9,n11的8080端口建立SinkApplication
发数据 n0——n7 （背景流量 n8——n9 n10——n11）
sink接收TCP流数据
*/
//uint16_t servPort = 8080;
//PacketSinkHelper sinkHelper ("ns3::TcpSocketFactory", InetSocketAddress (Ipv4Address::GetAny (), servPort));
//ApplicationContainer sinkApp = sinkHelper.Install (n);
//sinkApp.Start (Seconds (0));
//sinkApp.Stop (Seconds (30.0));
//uint16_t serverSum = 3; //n7,n9,n11上安装serverApp,所以server一共3个
uint16_t servPort = 50000;
ApplicationContainer sinkApp;
Address sinkLocalAddress (InetSocketAddress (Ipv4Address::GetAny (), servPort)); //???
PacketSinkHelper sinkHelper ("ns3::TcpSocketFactory", sinkLocalAddress); //第二个参数为上一行中的Address
sinkApp.Add(sinkHelper.Install(nodeAdjacencyList[7].Get(1)));
sinkApp.Add(sinkHelper.Install (nodeAdjacencyList[9].Get(1)));
sinkApp.Add(sinkHelper.Install(nodeAdjacencyList[11].Get(1)));
sinkApp.Start (Seconds (0.0));
sinkApp.Stop (Seconds (60.0)); //应该为60s
/*在n0, n8, n10安装client*/
OnOffHelper clientHelper ("ns3::TcpSocketFactory", Address ());
//OnOffApplication类中的m_onTime和m_offTime分别为发送持续的时间和不发送持续的时间。如下表示一直发送。
clientHelper.SetAttribute ("OnTime", StringValue ("ns3::ConstantRandomVariable[Constant=1]"));
clientHelper.SetAttribute ("OffTime", StringValue ("ns3::ConstantRandomVariable[Constant=0]"));
ApplicationContainer clientApps1, clientApps2, clientApps3;
uint16_t port = 50000;
//n0->n7
AddressValue remoteAddress(InetSocketAddress (interfaces[7].GetAddress (1), port)); //目的地址
clientHelper.SetAttribute("Remote",remoteAddress);
clientApps1 = clientHelper.Install(nodeAdjacencyList[0].Get(0));
//n8->n9
remoteAddress=AddressValue(InetSocketAddress (interfaces[9].GetAddress (1), port));
clientHelper.SetAttribute("Remote",remoteAddress);
clientApps2 = clientHelper.Install(nodeAdjacencyList[8].Get(1));
//n10->n11
remoteAddress=AddressValue(InetSocketAddress (interfaces[11].GetAddress (1), port));
clientHelper.SetAttribute("Remote",remoteAddress);
clientApps3 = clientHelper.Install(nodeAdjacencyList[10].Get(1));
clientApps1.Start(Seconds(1.0));
clientApps1.Stop(Seconds (60.0)); //60s
clientApps2.Start(Seconds(20.0)); //20s
clientApps2.Stop(Seconds (40.0)); //40s
clientApps3.Start(Seconds(20.0)); //20s
clientApps3.Stop(Seconds (40.0)); //40s
//Ipv4GlobalRoutingHelper::PopulateRoutingTables ();
//嗅探,记录所有节点相关的数据包
for(uint32_t i=0; i<11; i++)
p2p[i].EnablePcapAll("mytest");
//在TCP连接时间内统计PacketSink收到的TCP包，计算吞吐量并打印
// Ptr<PacketSink>pktSink;
// std::cout << "Rx = " << PacketSink-> GetTotalRx() << "bytes("
// << pktSink->GetTotalRx()*8 / (stopTime - startTime) << "bps)," << endl;
std::cout << "last"<<std::endl;
Simulator::Run ();
std::cout << "lastlastlast"<<std::endl;
Simulator::Destroy ();
std::cout << "lastlast"<<std::endl;
return 0;
}2、分析生成的pcap包：
使用wireshark打开mytest-0-0.pcap，使用statistics——IO Graph（如图1），生成图2所示的IO Graph，可知不加背景流量时，链路利用率基本为100%，达到瓶颈可用带宽10Mbps，在20s时加入背景流量后，背景流量占据了一半的带宽，此时主路径占用带宽为5Mbps。
注意：Y轴Unit选择Bit/Tick.
应用Wireshark IO图形工具分析数据流，下面这篇文章讲解的非常好，不会使用Wireshark IO图形工具的可以学习一下：
http://blog.jobbole.com/70929/