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HTTP/3

HTTP/3 is built on a newer transport protocol called QUIC (Quick UDP Internet Connections). It is built on top of UDP

Why Was HTTP/3 Needed?​

HTTP/2 brought many improvements, but it still relied on TCP, which has some inherent problems:

  1. Head-of-Line Blocking at the Transport Level:
    • In HTTP/2, if one packet is lost, TCP forces the client to wait for the lost packet before continuing. This slows everything down.
  2. Connection Setup Time:
    • TCP connections require a "handshake" before data is sent, which adds delay.
  3. Inefficiency with Mobile Networks:
    • When switching networks (e.g., from Wi-Fi to mobile), TCP connections break and have to be re-established.

Key Features of HTTP/3:​

  1. No Head-of-Line Blocking:

    • In QUIC, if one packet is lost, only that packet is resent. Other data can keep flowing, improving speed and reliability.

  2. Faster Connections:

    • QUIC combines the handshake for both encryption (TLS) and transport into a single step. This reduces connection setup time.

  3. Seamless Connection Migration:

    • QUIC connections survive network changes (e.g., switching from Wi-Fi to mobile data), unlike TCP.

  4. Built-in Encryption:

    • QUIC has encryption (TLS 1.3) built into the protocol, making HTTP/3 more secure by default.

How HTTP/3 Works​

HTTP/1.1 and HTTP/2:​

  • Both use TCP, which guarantees that packets arrive in order. However, this can lead to delays because of packet retransmission.

HTTP/3:​

  • Uses UDP with QUIC.
  • QUIC manages retransmissions at the packet level but doesn't force all streams to wait if one packet is delayed. This avoids head-of-line blocking and makes data transfer faster.