Date: Sat, 9 Aug 2014 13:22:05 -0700 From: hiren panchasara <hiren.panchasara@gmail.com> To: Michael Tuexen <Michael.Tuexen@lurchi.franken.de> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, John-Mark Gurney <jmg@funkthat.com>, Niu Zhixiong <kaiaixi@gmail.com>, Bill Yuan <bycn82@gmail.com> Subject: Re: A problem on TCP in High RTT Environment. Message-ID: <CALCpEUHJ5X%2BhFShgeM4CBcyVaJaQf12WVPWj4b=-qAXSC_48SQ@mail.gmail.com> In-Reply-To: <8AE1AC56-D52F-4F13-AAA3-BB96042B37DD@lurchi.franken.de> References: <CAOENNMA_CiBDJc0kchzUbTcf_JBwTJPF=PdBAUB6FPo-KzYkeQ@mail.gmail.com> <20140809184232.GF83475@funkthat.com> <8AE1AC56-D52F-4F13-AAA3-BB96042B37DD@lurchi.franken.de>
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On Sat, Aug 9, 2014 at 12:51 PM, Michael Tuexen <Michael.Tuexen@lurchi.franken.de> wrote: > > On 09 Aug 2014, at 20:42, John-Mark Gurney <jmg@funkthat.com> wrote: > >> Niu Zhixiong wrote this message on Fri, Aug 08, 2014 at 20:34 +0800: >>> Dear all, >>> >>> Last month, I send problems related to FTP/TCP in a high RTT environment. >>> After that, I setup a simulation environment(Dummynet) to test TCP and SCTP >>> in high delay environment. After finishing the test, I can see TCP is >>> always slower than SCTP. But, I think it is not possible. (Plz see the >>> figure in the attachment). When the delay is 200ms(means RTT=400ms). >>> Besides, the TCP is extremely slow. >>> >>> ALL BW=20Mbps, DELAY= 0 ~ 200MS, Packet LOSS = 0 (by dummynet) >>> >>> This is my parameters: >>> FreeBSD vfreetest0 10.0-RELEASE FreeBSD 10.0-RELEASE #0: Thu Aug 7 >>> 11:04:15 HKT 2014 >>> >>> sysctl net.inet.tcp >> >> [...] >> >>> net.inet.tcp.recvbuf_auto: 0 >> >> [...] >> >>> net.inet.tcp.sendbuf_auto: 0 >> >> Try enabling this... This should allow the buffer to grow large enough >> to deal w/ the higher latency... >> >> Also, make sure your program isn't setting the recv buffer size as that >> will disable the auto growing... > I think the program sets the buffer to 2MB, which it also does for SCTP. > So having both statically at the same size makes sense for the comparison. > I remember that there was a bug in the combination of LRO and delayed ACK, > which was fixed, but I don't remember it was fixed before 10.0... If you are thinking of r256920, I believe it did make it into 10.0R. cheers, Hiren
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