Date: Wed, 08 Apr 2015 00:10:51 +0200 From: Marek Salwerowicz <marek_sal@wp.pl> To: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: RTT and TCP Window size doubts, bandwidth issues Message-ID: <552455EB.7080609@wp.pl>
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Hi list, I am trying to find correct setup of sysctl's for following machines (VMs under Vmware Workstation 8) to test large TCP window size: There are 2 boxes, each of them has following setup: - % uname -a FreeBSD freeA 10.1-RELEASE-p6 FreeBSD 10.1-RELEASE-p6 #0: Tue Feb 24 19:00:21 UTC 2015 root@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64 - 4GB of RAM - 1 NIC without any modifications, iperf reports bandwidth speed ~1Gbit/s between hosts: server-side: # iperf -s ------------------------------------------------------------ Server listening on TCP port 5001 TCP window size: 64.0 KByte (default) ------------------------------------------------------------ client-side: # iperf -c 192.168.108.140 ------------------------------------------------------------ Client connecting to 192.168.108.140, TCP port 5001 TCP window size: 32.5 KByte (default) ------------------------------------------------------------ [ 3] local 192.168.108.141 port 35282 connected with 192.168.108.140 port 5001 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.0 sec 1.46 GBytes 1.25 Gbits/sec I want to simulate (using dummynet) link between hosts with bandwidth 400mbit/s and latency ~20ms. In order to do that, I create the ipfw pipe on one box: IPFW="ipfw -q" $IPFW pipe 1 config bw 400Mbit/s delay 10ms $IPFW add 1500 pipe 1 ip from any to any after running ipfw, bandwidth with default kernel sysctl becomes lower: client-side: ------------------------------------------------------------ Client connecting to 192.168.108.140, TCP port 5001 TCP window size: 32.5 KByte (default) ------------------------------------------------------------ [ 3] local 192.168.108.141 port 35340 connected with 192.168.108.140 port 5001 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.1 sec 12.5 MBytes 10.4 Mbits/sec I'd like to achieve bandwidth ~400Mbit/s. I've modified following sysctl's (both on client- and server-side): kern.ipc.maxsockbuf=33554432 # (default 2097152) net.inet.tcp.sendbuf_max=33554432 # (default 2097152) net.inet.tcp.recvbuf_max=33554432 # (default 2097152) net.inet.tcp.cc.algorithm=htcp # (default newreno) #enabled in /boot/loader.conf also net.inet.tcp.cc.htcp.adaptive_backoff=1 # (default 0 ; disabled) net.inet.tcp.cc.htcp.rtt_scaling=1 # (default 0 ; disabled) net.inet.tcp.mssdflt=1460 # (default 536) net.inet.tcp.minmss=1300 # (default 216) net.inet.tcp.rfc1323=1 # (default 1) net.inet.tcp.rfc3390=1 # (default 1) net.inet.tcp.sendspace=8388608 # (default 32768) net.inet.tcp.recvspace=8388608 # (default 65536) net.inet.tcp.sendbuf_inc=32768 # (default 8192 ) net.inet.tcp.recvbuf_inc=65536 # (default 16384) But the results are not really good as I expected: server-side: # iperf -s ------------------------------------------------------------ Server listening on TCP port 5001 TCP window size: 8.00 MByte (default) ------------------------------------------------------------ client-side: # iperf -c 192.168.108.140 ------------------------------------------------------------ Client connecting to 192.168.108.140, TCP port 5001 TCP window size: 8.00 MByte (default) ------------------------------------------------------------ [ 3] local 192.168.108.141 port 21894 connected with 192.168.108.140 port 5001 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.1 sec 24.2 MBytes 20.2 Mbits/sec I was trying to follow the articles: - http://www.psc.edu/index.php/networking/641-tcp-tune - https://fasterdata.es.net/host-tuning/freebsd/ But can't really figure out what / how should be tuned in order to achieve good results. If anyone could find some time and give me some hints, I'd be pleased! Cheers Marekhome | help
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