On Thu, 25 Sep 2014, David Lang wrote:
well, even if you have a 10GE connection, you don't know how heavily it's going to be used.
No, but I will have a hunch. I don't need to *know*, I need to have a decent probability of being right.
what happens if the wrong hint is given? (either accidently or maliciously)
Then you get IW10 instead of IW4. Right now if I am correct, Google does IW10 all across the board.
The approach of starting slow and ramping up works well, except in the case where you have lots of very short connections. So I don't see a benefit of trying to hint slowness. There may be some value in hinting for faster ramp-ups, but what will that do to fairness with existing systems?
In my world, core network congestion isn't something that is permanent and continous, but an anomaly. So since the only port that should be congesting is my access port, I don't care about fairness. Also, we're not talking about starting off with a 1M TCP window to blast a huge chunk of data down the wire, we're talking about perhaps being a bit more agressive in increasing the window from a slightly higher initial level, let's say IW10 and instead of doubling, tripling window size, if the client hints they have a fast connection, and if the client says they have a slow connection, IW4 and increase 1.5x instead?
Use same mechanisms as today, but tweak them to be a bit more or less agressive depending on what the client has hinted.
I mean, why do we send MSS in TCP? Couldn't we just have a generic probing mechanism to test what MTU works? Well, that would be inefficient, so MSS helps. Same here.
But we have a number of companies who want to have things downloaded and used as quickly as possible, so if this sort of thing really does help, then I would expect that they would be experimenting with tweaking the TCP stack to ramp up faster (although, you would also be expecting outcrys about "how dare $bigcompany ignore the TCP defaults and be more agressive, that doesn't compete fairly with $normaltraffic)
Errr, google and IW10? So, already done!? -- Mikael Abrahamsson email: [email protected] _______________________________________________ Bloat mailing list [email protected] https://lists.bufferbloat.net/listinfo/bloat
