Netflix documentary The Playlist about Spotify, they present one of the technical breakthroughs that they created their own TCP implementation to reduce the latency from first click to playing the song to less than 250ms.

I don't find any resources on the Internet explaining what they did, but I found this presentation that probably describes this: https://www.csc.kth.se/~gkreitz/spotify/kreitz-spotify_kth11.pdf

Slide 21/22

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But what does "Configure kernels to not follow the RFC 5681 SHOULD." actually mean?

  • 1
    In simple english... don't do what RFC's say you should do. (i.e. ignore global specifications and do whatever the [censored] you want.) Microsoft has done similar things for decades.
    – Ricky
    Jun 18, 2023 at 20:24

1 Answer 1


See RFC 5681, and RFC 2119 for the IETF usage of MAY, SHOULD, MUST.

  • I've looked at the RFC, but it's a bit beyond my expertise to really understand what it means and what exactly Spotify has done and how it has improved latency. Could you please explain it in layman's terms?
    – zirkelc
    Jun 18, 2023 at 18:24
  • @zirkelc I'm sorry, but it's literally on the slide in your question. I can't explain all TCP to you here. For starters: en.wikipedia.org/wiki/TCP_congestion_control
    – Zac67
    Jun 18, 2023 at 19:14

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