If you can think of a better list to post this, please forward it... The following TCP bug has been measured to consume as much as 15% of Internet links. ISPs who run heavily congested links and/or satellite links will lose 15% of their bandwidth as we have due to this error by Sun. Please distribute this announcement to those running Solaris 2 as often as possible. Thanks, Hank Nussbacher IBM Israel -------------------------------------------------------------------- During the last few weeks we were conducting a survey of our internet communication performance. As a result of the survey we have discovered that your host is involved in a large portion of TCP/IP retransmissions. This phenomena significantly decreases the communication performance. If your host is a Sun running Solaris 2, than we think we know what is the source of the problem. It appears that Solaris 2 has a bug in the TCP/IP implementation, causing excessive retransmissions to occur. The following is an excerpt from the May 3rd Solaris 2 FAQ: ----------------------------------------------------------------------------- +5.49) Solaris 2.5 and Solaris 2.4 patch 101945-34+ have poor TCP performance over slow links. Solaris 2.5 and Solaris 2.4 kernel patch 101945-34 and later have a bug in their TCP retransmission algorithm that cause excessive retransmissions over slow links, Sun's bug ID is #1233827. A work around for this bug is running the following commands at system boot, e.g., by adding them to /etc/init.d/inetinit (values are in milliseconds): /usr/sbin/ndd -set /dev/tcp tcp_rexmit_interval_min 3000 /usr/sbin/ndd -set /dev/tcp tcp_rexmit_interval_initial 3000 ----------------------------------------------------------------------------- Please note that the above mentioned patch (101945-34) included a "fix" to the retransmission problem, but apparently, the fix is not good enough (see "http://www.sun.com/sunworldonline/common/cockcroft.letters.html" section: "How can I improve my Web server's http performance?"). To summarize, it seems that all Solaris 2 versions suffer from this problem! We recommend that you apply the above workaround until the problem is resolved in a future Sun release. Please note that the problem affects mainly your host and users accessing it over large latency links, such as satellite links (as we do), or over slow links (e.g. dialup lines) or a congested network . We will appreciate if you let us know how do you intend to proceed with this. Thanks for your cooperation, Oded Comay (comay@post.tau.ac.il) Operating Systems group Computing Center Tel Aviv University