alt Hacker News<waits for animats to show up>
Replies
e40 • yesterday at 11:46 PM
Came here thinking the same thing...
armitron • yesterday at 11:17 PM
Assuming he shows up, he'll still probably be trying to defend the indefensible..
Disabling Nagle's algorithm should be done as a matter of principle, there's simply no modern network configuration where it's beneficial.
OK, I suppose I should say something. I've already written on this before, and that was linked above.
You never want TCP_NODELAY off at the sending end, and delayed ACKs on at the receiving end. But there's no way to set that from one end. Hence the problem.
Is TCP_NODELAY off still necessary? Try sending one-byte TCP sends in a tight loop and see what it does to other traffic on the same path, for, say, a cellular link. Today's links may be able to tolerate the 40x extra traffic. It was originally put in as a protection device against badly behaved senders.
A delayed ACK should be thought of as a bet on the behavior of the listening application. If the listening application usually responds fast, within the ACK delay interval, the delayed ACK is coalesced into the reply and you save a packet. If the listening application does not respond immediately, a delayed ACK has to actually be sent, and nothing was gained by delaying it. It would be useful for TCP implementations to tally, for each socket, the number of delayed ACKs actually sent vs. the number coalesced. If many delayed ACKs are being sent, ACK delay should be turned off, rather than repeating a losing bet.
This should have been fixed forty years ago. But I was out of networking by the time this conflict appeared. I worked for an aerospace company, and they wanted to move all networking work from Palo Alto to Colorado Springs, Colorado. Colorado Springs was building a router based on the Zilog Z8000, purely for military applications. That turned out to be a dead end. The other people in networking in Palo Alto went off to form a startup to make a "PC LAN" (a forgotten 1980s concept), and for about six months, they led that industry. I ended up leaving and doing things for Autodesk, which worked out well.