digraph BWE_DataFlow {
    rankdir=LR;
    node [shape=box, style=rounded];

    // External inputs/outputs
    TWCC [label="TWCC Feedback\n(from remote)", shape=ellipse, style=filled, fillcolor=lightblue];
    Application [label="Application", shape=ellipse, style=filled, fillcolor=lightblue];
    Network [label="Network\n(packets out)", shape=ellipse, style=filled, fillcolor=lightblue];

    // Main orchestrator
    SSBE [label="SendSide\nBandwidth\nEstimator", style="filled,rounded", fillcolor=gold];

    // Delay-based path
    DC [label="Delay\nController", style=filled, fillcolor=lightcoral];
    AGA [label="Arrival Group\nAccumulator", style=filled, fillcolor=lightyellow];
    TE [label="Trendline\nEstimator", style=filled, fillcolor=lightyellow];
    RC [label="Rate Control\n(AIMD)", style=filled, fillcolor=lightyellow];

    // Throughput measurement
    ABE [label="Acked Bitrate\nEstimator", style=filled, fillcolor=lightcyan];

    // Loss-based path
    LC [label="Loss\nController", style=filled, fillcolor=lightpink];

    // Probe system
    PC [label="Probe\nControl", style=filled, fillcolor=plum];
    PE [label="Probe\nEstimator", style=filled, fillcolor=plum];

    // ALR system
    ALR [label="ALR\nDetector", style=filled, fillcolor=wheat];
    LCE [label="Link Capacity\nEstimator", style=filled, fillcolor=wheat];

    // Pacer system
    Pacer [label="Pacer\n(LeakyBucket +\nProbeClusterState)", style=filled, fillcolor=palegreen];
    PacerCtrl [label="Pacer\nControl", style=filled, fillcolor=palegreen];

    // Data flows
    TWCC -> SSBE [label="TwccSendRecord[]"];
    TWCC -> ABE [label="acked packets"];

    SSBE -> Application [label="bandwidth estimate", color=blue, penwidth=2];
    SSBE -> PacerCtrl [label="estimate"];

    // Delay controller internal flow
    DC -> AGA [label="acked packets"];
    AGA -> TE [label="InterGroupDelayDelta"];
    TE -> RC [label="BandwidthUsage\n(overuse/normal/underuse)"];
    RC -> DC [label="estimated bitrate"];

    // Delay controller to main
    DC -> SSBE [label="delay estimate", color=red, penwidth=2];

    // Acked bitrate flows
    ABE -> DC [label="instantaneous\nbitrate"];
    ABE -> LC [label="instantaneous\nbitrate"];

    // Loss controller
    LC -> SSBE [label="loss estimate", color=red, penwidth=2];
    TWCC -> LC [label="packet results"];

    // Probe system flows
    PC -> SSBE [label="ProbeClusterConfig"];
    SSBE -> PE [label="start probe\n(ProbeClusterConfig)", color=purple];
    SSBE -> Pacer [label="start probe\n(ProbeClusterConfig)", color=purple];
    Pacer -> SSBE [label="probe complete\n(cluster_id)", color=purple];
    TWCC -> PE [label="TwccSendRecord[]\n(filtered by cluster)", color=purple];
    PE -> SSBE [label="ProbeResult", color=purple, penwidth=2];
    SSBE -> DC [label="probe result"];

    // ALR system flows
    ALR -> PC [label="ALR state\n(start time)"];
    ALR -> LC [label="ALR state\n(start time)"];
    SSBE -> ALR [label="media sent"];
    PE -> LCE [label="ALR probe results", color=orange];
    LCE -> LC [label="capacity estimate", color=orange, penwidth=2];

    // Pacer control
    PacerCtrl -> Pacer [label="pacing_rate\npadding_rate"];

    // Pacer output
    Pacer -> Network [label="paced packets\n(with cluster ID)", color=blue, penwidth=2];

    // Grouping for visual clarity
    subgraph cluster_delay {
        label="Delay-Based Estimation";
        style=dashed;
        color=darkred;
        DC; AGA; TE; RC;
    }

    subgraph cluster_probe {
        label="Probe System";
        style=dashed;
        color=purple;
        PC; PE;
    }

    subgraph cluster_pacer {
        label="Pacing System";
        style=dashed;
        color=darkgreen;
        Pacer; PacerCtrl;
    }

    subgraph cluster_alr {
        label="ALR System";
        style=dashed;
        color=orange;
        ALR; LCE;
    }
}