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// 服务器到接入交换机 (边缘链路)
PointToPointHelper NodeToSW;
NodeToSW.SetDeviceAttribute("DataRate", StringValue("10Gbps"));
NodeToSW.SetChannelAttribute("Delay", StringValue("200ns"));

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// 汇聚到核心交换机 (上行链路)
PointToPointHelper SWToSW_50ns;
SWToSW_50ns.SetDeviceAttribute("DataRate", StringValue("40Gbps"));
SWToSW_50ns.SetChannelAttribute("Delay", StringValue("50ns"));
SWToSW_50ns.SetQueue("ns3::DropTailQueue", "MaxSize", 
                     StringValue(std::to_string(Corequeuesize) + "p"));

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// 创建 Pod 节点
NodeContainer pod0, pod1, pod2, pod3, core;
pod0.Create(8);  // 4 服务器 + 4 交换机
// ...

// 安装 TCP/IP 协议栈
InternetStackHelper stack;
stack.Install(pod0);
stack.Install(pod1);
stack.Install(pod2);
stack.Install(pod3);
stack.Install(core);

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// Pod 0 内部连接示例
pod0_dev  = NodeToSW.Install(pod0.Get(0), pod0.Get(4)); // Server0 → AccessSW4
pod0_dev2 = NodeToSW.Install(pod0.Get(1), pod0.Get(4)); // Server1 → AccessSW4
pod0_dev5 = SWToSW_50ns.Install(pod0.Get(4), pod0.Get(6)); // AccessSW4 → AggrSW6
pod0_dev6 = SWToSW_70ns.Install(pod0.Get(4), pod0.Get(7)); // AccessSW4 → AggrSW7

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// 核心层连接示例
core_dev  = SWToSW_50ns.Install(pod0.Get(6), core.Get(0)); // Pod0.AggrSW6 → Core0
core_dev2 = SWToSW_50ns.Install(pod1.Get(6), core.Get(0)); // Pod1.AggrSW6 → Core0

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// Pod 0 的 IP 分配
address.SetBase("10.0.0.0","255.255.255.252");  // Server0-AccessSW4
pod0_Iface = address.Assign(pod0_dev);
address.SetBase("10.0.1.0","255.255.255.252");  // Server1-AccessSW4
pod0_Iface2 = address.Assign(pod0_dev2);
// ...

// 核心层的 IP 分配
address.SetBase("10.10.0.0","255.255.255.252");   // Pod0.AggrSW6-Core0
core_Iface = address.Assign(core_dev);

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// 启用 ECMP
Config::SetDefault("ns3::Ipv4GlobalRouting::RandomEcmpRouting", BooleanValue(true));

// 填充路由表
Ipv4GlobalRoutingHelper::PopulateRoutingTables();

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// UDP Echo 服务器 (Pod0.Server0)
UdpEchoServerHelper echoServer(9);
ApplicationContainer serverApps = echoServer.Install(pod0.Get(0));
serverApps.Start(Seconds(1.0));
serverApps.Stop(Seconds(10.0));

// UDP Echo 客户端 (Pod1.Server0)
UdpEchoClientHelper echoClient(pod0_Iface.GetAddress(0), 9);
echoClient.SetAttribute("MaxPackets", UintegerValue(1));
echoClient.SetAttribute("PacketSize", UintegerValue(1024));
ApplicationContainer clientApps = echoClient.Install(pod1.Get(0));
clientApps.Start(Seconds(2.0));

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// TCP BulkSend 发送端 (Pod3.Server0)
BulkSendHelper source("ns3::TcpSocketFactory", 
                      InetSocketAddress(pod2_Iface.GetAddress(0), 80));
source.SetAttribute("MaxBytes", UintegerValue(1000000)); // 1 MB
ApplicationContainer sourceApps = source.Install(pod3.Get(0));
sourceApps.Start(Seconds(1.5));

// TCP PacketSink 接收端 (Pod2.Server0)
PacketSinkHelper sink("ns3::TcpSocketFactory", 
                      InetSocketAddress(Ipv4Address::GetAny(), 80));
ApplicationContainer sinkApp = sink.Install(pod2.Get(0));
sinkApp.Start(Seconds(1.0));

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// PCAP 数据包捕获
NodeToSW.EnablePcapAll("DCN_FatTree_CSMA_Pcap");

// FlowMonitor 统计
FlowMonitorHelper flowmonHelper;
flowmonHelper.InstallAll();

// NetAnim 动画
AnimationInterface anim("animation.xml");
anim.SetConstantPosition(pod0.Get(0), 1.0, 20.0);  // 设置节点位置

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Corequeuesize = 8;   // 核心层: 8 个数据包
Leafqueuesize = 4;   // 接入/汇聚层: 4 个数据包

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// 在代码中添加
LogComponentEnable("Ipv4GlobalRouting", LOG_LEVEL_LOGIC);
LogComponentEnable("TcpSocketBase", LOG_LEVEL_INFO);

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// 多个服务器同时向一个服务器发送数据
for (int i = 0; i < 4; i++) {
    BulkSendHelper source("ns3::TcpSocketFactory", 
                          InetSocketAddress(pod0_Iface.GetAddress(0), 80));
    source.SetAttribute("MaxBytes", UintegerValue(100000));
    ApplicationContainer app = source.Install(pod1.Get(i));
    app.Start(Seconds(1.0));
}

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// 所有服务器互相通信
for (int src_pod = 0; src_pod < 4; src_pod++) {
    for (int dst_pod = 0; dst_pod < 4; dst_pod++) {
        if (src_pod != dst_pod) {
            // 创建从 src_pod 到 dst_pod 的流量
        }
    }
}

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// k=8 Fat-Tree
// 64 台服务器, 80 个交换机
int k = 8;
int num_pods = k;
int servers_per_pod = (k * k) / 4;
int switches_per_pod = k;
int core_switches = (k * k) / 4;

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// 使用 DCTCP
Config::SetDefault("ns3::TcpL4Protocol::SocketType", 
                   StringValue("ns3::TcpDctcp"));

// 启用 ECN
Config::SetDefault("ns3::TcpSocketBase::UseEcn", 
                   StringValue("On"));

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// 使用 PrioQueue 替代 DropTailQueue
SWToSW_50ns.SetQueue("ns3::PrioQueue", 
                     "MaxSize", StringValue("8p"),
                     "NumBands", UintegerValue(4));

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// 在仿真中途断开一条链路
Simulator::Schedule(Seconds(5.0), &DisableLink, pod0_dev5);

void DisableLink(NetDeviceContainer& dev) {
    dev.Get(0)->SetDown();
    dev.Get(1)->SetDown();
}

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// 替换全局路由为自定义路由
Ipv4StaticRoutingHelper staticRouting;
Ipv4ListRoutingHelper list;
list.Add(staticRouting, 0);

// 手动添加路由规则
Ptr<Ipv4StaticRouting> routing = staticRouting.GetStaticRouting(node->GetObject<Ipv4>());
routing->AddNetworkRouteTo(Ipv4Address("10.1.0.0"), 
                           Ipv4Mask("255.255.0.0"),
                           Ipv4Address("10.0.4.2"), 1);

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// RED (Random Early Detection)
SWToSW_50ns.SetQueue("ns3::RedQueue",
                     "MinTh", DoubleValue(5),
                     "MaxTh", DoubleValue(15));

// CoDel (Controlled Delay)
SWToSW_50ns.SetQueue("ns3::CoDelQueue",
                     "Target", TimeValue(MilliSeconds(5)),
                     "Interval", TimeValue(MilliSeconds(100)));

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// 增大 TCP 窗口大小
Config::SetDefault("ns3::TcpSocket::RcvBufSize", UintegerValue(1 << 21));
Config::SetDefault("ns3::TcpSocket::SndBufSize", UintegerValue(1 << 21));

// 使用 TCP CUBIC
Config::SetDefault("ns3::TcpL4Protocol::SocketType",
                   StringValue("ns3::TcpCubic"));

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// 自定义流量分析回调
void PacketSinkRxCallback(Ptr<const Packet> packet, const Address& from) {
    std::cout << "Received packet of size " << packet->GetSize() 
              << " from " << InetSocketAddress::ConvertFrom(from).GetIpv4() 
              << std::endl;
}

// 连接回调
Config::ConnectWithoutContext("/NodeList/*/ApplicationList/*/$ns3::PacketSink/Rx",
                              MakeCallback(&PacketSinkRxCallback));