Networking Protocols: Unicast TCP, Raw UDP, and IP Multicast

In financial exchanges, high-frequency trading (HFT) platforms, and real-time media streaming, network protocol choice directly governs latency, throughput, and system architecture.

While standard web applications rely almost exclusively on TCP Unicast, market data feeds and high-speed telemetry use Raw UDP and IP Multicast (IGMP / PIM-SM).

1. Summary & Key Takeaways

• Unicast TCP: Provides reliable byte stream delivery and congestion control. However, packet drops trigger Head-of-Line Blocking and Retransmission Timeouts (RTO), stalling processing pipelines.
• Raw UDP: Connectionless, zero-handshake datagram protocol. Eliminates head-of-line blocking, but offers no native delivery or ordering guarantees.
• IP Multicast (IGMP / PIM-SM): A single packet published by a sender is duplicated by network hardware switches directly to all subscribed hosts in an IGMP multicast group (e.g. 239.255.0.1).
• Multicast Quirks & Duplicates: Dynamic Protocol Independent Multicast (PIM) tree re-convergence and IGMP snooping updates can cause temporary duplicate packets or out-of-order delivery that application layers must handle.

2. Interactive Protocol & Market Data Simulator

Use the interactive simulator below to test packet transmission under simulated network packet loss across TCP Unicast, Raw UDP, and IP Multicast!

3. Protocol Architecture Comparison

graph TD
    subgraph Unicast["Unicast TCP / UDP"]
    PUB1["Publisher"] -->|"Separate Packet per Client"| R1["Receiver 1"]
    PUB1 -->|"Duplicate Packet"| R2["Receiver 2"]
    PUB1 -->|"Duplicate Packet"| R3["Receiver 3"]
    end

    subgraph Multicast["IP Multicast (IGMP / PIM-SM)"]
    PUB2["Publisher"] -->|"Single Packet to Switch"| SW["Hardware Switch"]
    SW -->|"Hardware Packet Copy"| R4["Receiver 1"]
    SW -->|"Hardware Packet Copy"| R5["Receiver 2"]
    SW -->|"Hardware Packet Copy"| R6["Receiver 3"]
    end

4. Networking Protocol Matrix