Does setting TCP_NODELAY affect the behaviour of both ends of the socket?

Question

I've always assumed that Nagle's algorithm affected the socket in both directions, and that setting TCP_NODELAY somehow informed the remote end also to switch off Nagle.

Is that right, or does setting TCP_NODELAY only affect the behaviour of the end that calls it?

Answer 1

TCP_NODELAY affect sending TCP segments only on the host that sets this option on its socket. That is, the peer's sending algorithm is not affected.