On So, 15.07.2012, 09:16, Eric Dumazet wrote: > On Sun, 2012-07-15 at 01:43 +0200, Piotr Sawuk wrote: > >> oh, and again I recommend the really short although outdated thesis >> >> [1] https://sacerdoti.org/tcphealth/tcphealth-paper.pdf > > A thesis saying SACK are not useful is highly suspect. > > Instead of finding why they behave not so good and fix the bugs, just > say "SACK addition to TCP is not critical" the actual quotation is "We also found that the number of unnecessary duplicate packets were quite small potentially indicating that the SACK addition to TCP is not critical." > > Really ?
no, not really. he he actually said that SACK has been made mostly obsolete by "Linux 2.2 implements fast retransmits for up to two packet gaps, thus reducing the need for course grained timeouts due to the lack of SACK." and he was a bit more careful and admitted that further tests with tcphealth are needed to check if SACK really makes that big a difference. he admitted "It could be that SACK's advantage lies in other areas such as very large downloads or when using slow and unreliable network links." all these things could be checked again nowadays, with larger files available and wlan-users and higher traffic -- just find something without SACK... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
