[nsd-users] How does NSD use TFO (TCP Fast Open)?

Anand Buddhdev anandb at ripe.net
Wed Jun 3 13:28:10 UTC 2020

Hi NSD developers,

I see that NSD can be configured with --enable-tcp-fastopen. However, 
the documentation doesn't say which parts of NSD use TFO.

Does NSD use TFO as a client, when requesting XFR from a server?

Does NSD generate and provide TFO cookies to clients that request them?

Or does NSD do both of the above?

Is there any downside to enabling TFO? If not, why isn't it enabled by 


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