nagle

One of the few legit cases for turning off the Nagle algorithm is for a FPS game running over the net.

As is well known, the interaction between delayed ACKs and the Nagle algorithm is awful.

TCP sends successive data elements together, at least as part of the Nagle algorithm.

The bad interaction between the Nagle Algorithm and Delayed ACK still irks me.

It still bothers me that the Nagle algorithm (which I called tinygram prevention) and delayed ACKs interact so badly.

In fact my own UDP protocol does something similar to Nagle as well.

If you turn off the Nagle algorithm and then rapidly send single bytes to a socket, each byte will go out as a separate packet.

Apache disables Nagle by default, which is what you want for small static files, but I'd love to see data showing that Nagle is actually a significant performance issue for a realistic load.

What's this 200ms delay (I kid you not, forgot Nagle once!)?

Using a proxy like nginx or varnish to serve static files (and even dynamic data) if you have the proper KeepAlive and Nagle bits flipped can save you a lot of server resources at the application layer.

The second half of the problem is delayed acks, but this is not mentioned in the article, instead it goes on saying > [...] but Nagle is not relevant to the modern Internet [...] which is indeed popular belief, but a very superficial analysis that holds no water if you study it further.

> When everything is working perfectly and there is no packet loss (assuming Nagle is disabled), UDP and TCP will perform approximately equivalently; data gets through immediately, it's delivered to the application, there's no need to retransmit.

The article has a section "Sender SWS Avoidance and Nagle's Algorithm" and claims that they're related.

I can be reached at "nagle@animats.com" if needed.

The tinygram problem, which is addressed by Nagle's Algorithm, occurs when the pipe is almost empty and the writing end is making tiny writes.

Nagle's algorithm makes a lot of sense in a lot of situations.

Nagle's algorithm does not have any delay or timer build in.