Re: TCP Initial Window 10 MFC (was: Re: svn commit: r252789 - stable/9/sys/netinet)
Hi, On Aug 14, 2013, at 10:36, Lawrence Stewart lstew...@freebsd.org wrote: I don't think this change should have been MFCed, at least not in its current form. FYI, Google's own data as presented in the HTTPBIS working group of the recent Berlin IETF shows that 10 is too high for ~25% of their web connections: see slide 2 of http://www.ietf.org/proceedings/87/slides/slides-87-httpbis-5.pdf (That slide shows a CDF of CWND values the server used at the end of a web transaction.) Lars signature.asc Description: Message signed with OpenPGP using GPGMail
Re: TCP Initial Window 10 MFC (was: Re: svn commit: r252789 - stable/9/sys/netinet)
Oh: The other interesting bit is that Chrome defaulted to telling the server to use IW32 if it had no cached value... I think Google are still heavily tweaking the mechanisms. Lars On Aug 14, 2013, at 16:46, Eggert, Lars l...@netapp.com wrote: Hi, On Aug 14, 2013, at 10:36, Lawrence Stewart lstew...@freebsd.org wrote: I don't think this change should have been MFCed, at least not in its current form. FYI, Google's own data as presented in the HTTPBIS working group of the recent Berlin IETF shows that 10 is too high for ~25% of their web connections: see slide 2 of http://www.ietf.org/proceedings/87/slides/slides-87-httpbis-5.pdf (That slide shows a CDF of CWND values the server used at the end of a web transaction.) Lars signature.asc Description: Message signed with OpenPGP using GPGMail
TCP Initial Window 10 MFC (was: Re: svn commit: r252789 - stable/9/sys/netinet)
Hi Andre, [RE team is BCCed so they're aware of this discussion] On 07/06/13 00:58, Andre Oppermann wrote: Author: andre Date: Fri Jul 5 14:58:24 2013 New Revision: 252789 URL: http://svnweb.freebsd.org/changeset/base/252789 Log: MFC r242266: Increase the initial CWND to 10 segments as defined in IETF TCPM draft-ietf-tcpm-initcwnd-05. It explains why the increased initial window improves the overall performance of many web services without risking congestion collapse. As long as it remains a draft it is placed under a sysctl marking it as experimental: net.inet.tcp.experimental.initcwnd10 = 1 When it becomes an official RFC soon the sysctl will be changed to the RFC number and moved to net.inet.tcp. This implementation differs from the RFC draft in that it is a bit more conservative in the case of packet loss on SYN or SYN|ACK because we haven't reduced the default RTO to 1 second yet. Also the restart window isn't yet increased as allowed. Both will be adjusted with upcoming changes. Is is enabled by default. In Linux it is enabled since kernel 3.0. I haven't been fully alert to FreeBSD happenings this year so apologies for bringing this up so long after the MFC. I don't think this change should have been MFCed, at least not in its current form. Enabling the switch to IW=10 on a stable branch is inappropriate IMO. I also think the net.inet.tcp.experimental sysctl branch is poorly named as per the important discussion we had back in February [1]. I would really prefer we didn't get stuck having to keep it around by making a stable release with it being present. I think this commit should be backed out of stable/9 and more importantly, 9.2-RELEASE. As an aside, I am intending to follow up to the Feb discussion with a patch that implements the basic infrastructure I proposed so that we can continue that discussion. Thoughts? Cheers, Lawrence [1] http://lists.freebsd.org/pipermail/freebsd-net/2013-February/034698.html ___ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to freebsd-net-unsubscr...@freebsd.org
