Date: Sat, 9 Aug 2014 21:51:55 +0200 From: Michael Tuexen <Michael.Tuexen@lurchi.franken.de> To: John-Mark Gurney <jmg@funkthat.com> Cc: freebsd-net@freebsd.org, Niu Zhixiong <kaiaixi@gmail.com>, Bill Yuan <bycn82@gmail.com> Subject: Re: A problem on TCP in High RTT Environment. Message-ID: <8AE1AC56-D52F-4F13-AAA3-BB96042B37DD@lurchi.franken.de> In-Reply-To: <20140809184232.GF83475@funkthat.com> References: <CAOENNMA_CiBDJc0kchzUbTcf_JBwTJPF=PdBAUB6FPo-KzYkeQ@mail.gmail.com> <20140809184232.GF83475@funkthat.com>
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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, >>=20 >> 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=3D400ms). >> Besides, the TCP is extremely slow. >>=20 >> ALL BW=3D20Mbps, DELAY=3D 0 ~ 200MS, Packet LOSS =3D 0 (by dummynet) >>=20 >> This is my parameters: >> FreeBSD vfreetest0 10.0-RELEASE FreeBSD 10.0-RELEASE #0: Thu Aug 7 >> 11:04:15 HKT 2014 >>=20 >> sysctl net.inet.tcp >=20 > [...] >=20 >> net.inet.tcp.recvbuf_auto: 0 >=20 > [...] >=20 >> net.inet.tcp.sendbuf_auto: 0 >=20 > Try enabling this... This should allow the buffer to grow large = enough > to deal w/ the higher latency... >=20 > 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... Best regards Michael >=20 > If you use netstat -a, you should be able to see the send-q on the > sender grow as necessary... >=20 > --=20 > John-Mark Gurney Voice: +1 415 225 5579 >=20 > "All that I will do, has been done, All that I have, has not." > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" >=20
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