Sowmini.Varadhan at Sun.COM writes: > Actually I don't think Jim Carlson was advocationg on keeping/losing > the tunable itself
Yep. And if asked, I'd say I'd like to see the tunable removed. It's silly. >- he was only commenting on "64" being an inadequate > default. Do "others" provide a knob for this (not that I am aware of)? I like your idea to do some light optimization here, but I'm not sure it's worth the bother. The only case I think you can safely optimize is TCP. You know that there can't be any sane tunnel information on top of that (though some do tunnel over TCP), so including only the bare minimum for ICMP errors returned in response to TCP traffic those would work. But, unfortunately, this case seems uninteresting, because most TCP errors (e.g., port unreachable) are delivered by TCP itself, and not punted to ICMP. Maybe it might work for the long-deprecated source quench and the occasional network unreachable, but that'd be about it. With UDP and SCTP and random IP protocols, you don't know if there's other stuff on top, so including up to 576 seems to be the right choice. And I'm not buying any "performance" argument here. We're talking about the delivery of errors. Applications aren't built to deliver bulk data via error reports. If performance (or perhaps more accurately DoS risk) is really a concern, then we should just throttle the rate at which we send any messages at all, rather than trying to trim down the byte count to save a couple of cycles. That optimization needs to be made in the right place, and being capable of sending zillions of uselessly tiny ICMP errors per second is not something to strive for. So, yes, I think the default should be larger, but I'm really unsure that there should be a tunable here. It feels like a manual choke on a gasoline engine or a fine-tune adjust knob on a TV; when did you last have to mess with one of those? -- James Carlson, Solaris Networking <james.d.carlson at sun.com> Sun Microsystems / 35 Network Drive 71.232W Vox +1 781 442 2084 MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677
