Hi all: The following is just a "word of warning" about IPv6 causing initial connect slowness in Kernel 2.6. Target audience: packagers of kernel 2.6 in Fedora Core 2 (maybe provide a work around or configurable shut off mechanism) or any kernel hackers or someone with additional familiarity. I'm writing this purely out of my personal experience and hope that it might be helpful for those on this list. Without disabling IPv6 in /etc/modprobe.conf with "alias net-pf-10 off", in certain environments that evidently do not support "it"--"it" being quite a nebulous definition since I am far from understanding any piece of IPv6--initial network connections will be obnoxiously slow, both DNS lookups and simple "telnet www.google.com 80" tests. The following threads provide some additional background information using Mandrake 10+ with Kernel 2.6: http://www.linuxquestions.org/questions/showthread.php?s=&threadid=151050&perpage=15&pagenumber=3 http://www.linuxquestions.org/questions/showthread.php?s=&threadid=158683 And fedora test list (the second gives netstat, interface, route information): http://www.redhat.com/archives/fedora-test-list/2004-March/msg00350.html http://www.redhat.com/archives/fedora-test-list/2004-March/msg00349.html Some websites that normally take 3 to 4 seconds to download, take up to 20 seconds under 2.6 with IPv6 enabled. Disabling it causes dramatic speed ups. The intriguing thing is that this problem doesn't occur in all network topologies. On my ADSL at home using Fedora Core 1 as a gateway, I have no problems at all with IPv6 running. However, in my office (same machine cause it's a laptop) it's slower than dog going through an Intel NetStructure VPN box. I could see Redhat, OSDL, et al. having a difficult time replicating and finding this since they most likely have a more homogenous network (vendor?) topology: Linux based servers, gateways, etc. My current system is an IBM T30 laptop running the following kernels under Redhat 9 (sorry i'm not using fc2-test outside of chroot environments yet, please forgive me..): Speed Rating (using feels-good(tm) benchmark) kernel-2.4.20-28.9 (distro) nominal kernel-2.4.24-1.ll.rh90.ccrma nominal kernel-2.6.2-1.156 (arjan) slow with IPv6; nominal without kernel-2.4.20-30.9 (dag) nominal kernel-2.6.5-1.332 (arjan) slow only on DNS with IPv6; nominal without (had to use links because my mouse and /udev stuff doesn't work yet) I will be installing fc2-test on another partition quite soon so I can test again with my laptop under the latest environment using the tools mentioned in the second thread on the fedora-test list. Sorry if I piss anyone off for mentioning running on an old distribution and/or if this off-topic. I hope this email will be useful to those who've yet seen the issue and might see it pop up again. take care, -- -jeff PS. Disclaimer: I'm just joining the list. There's a bunch of lists, and I've tried to do a preliminary search (http://www.google.com/search?q=site%3Aredhat.com%20kernel%202.6%20network%20slow) to see if this has been discussed; I apologize for any redundancy if one exists.
