Moving past TCP in the data center, part 1 [LWN.net]

Moving past TCP in the data center, part 1

Posted Nov 2, 2022 12:36 UTC (Wed) by paulj (subscriber, #341)
In reply to: Moving past TCP in the data center, part 1 by Cyberax
Parent article: Moving past TCP in the data center, part 1

Sending back-to-back frames - at a low enough level to ensure no other station could try send in-between - was a trick SGI used in IRIX NFS to get performance - I think I remember reading this in comments on LWN before, perhaps in a reply to you mentioning the same thing before. :)

NFS was of course RPC over UDP based too.

to post comments

Moving past TCP in the data center, part 1

Posted Nov 2, 2022 21:12 UTC (Wed) by amarao (guest, #87073) [Link] (2 responses)

I remember time people said that udp for NFS is back and we should switch to tcp. Had something changed?

Moving past TCP in the data center, part 1

Posted Nov 2, 2022 21:32 UTC (Wed) by joib (subscriber, #8541) [Link]

https://www.man7.org/linux/man-pages/man5/nfs.5.html#TRAN... has a discussion about the pitfalls of NFS over udp.

Should also be noted that current Linux kernels actually no longer support NFS over UDP.

Moving past TCP in the data center, part 1

Posted Nov 3, 2022 9:52 UTC (Thu) by paulj (subscriber, #341) [Link]

NFS has switched to TCP since /ages/ ago. However, in the beginning (and for quite a while) NFS ran its RPC protocol over UDP. Just, without any real flow-control, and poor loss handling. TCP provides flow-control and better loss-handling - though, still not great, (because of the impedance mismatch of TCP knowing only about the data as a byte-stream, and not being able to take the app. message boundaries into consideration), as per this talk.