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Evolution of Transport Layer Functionality

COMP211 Lectures

These notes are low-effort, due to catching up in this module. See the videos and slides for more detail.

You may want a protocol that is tailored to a specific scenario such as:

  • Long fat pipes (many in flight packets).
  • Wireless networks (noisy links with high bandwidth).
  • Long delay links (long RTT).
  • Data centre networks (latency sensitive).
  • Low priority TCP traffic.

To facilitate this you can implement transport-layer functions in the application layer, on top of UDP.

QUIC - Quick UDP Internet Connections (HTTP/3)

This is an application layer protocol on top of UDP:

  • Increases the performance of HTTP
  • Uses a slimmed HTTP/2 protocol and QUIC instead of TLS.

This protocol has the following features:

  • Error and Congestion Control - Similar to TCP
  • Connection Establishment - Reliability, congestion control, authentication, encryption and state all in one RTT.
    • Normally there would be two handshakes, one for TCP and one for TLS.
  • Multiple application-level streams can be multiplexed over a single QUIC connection.