Re: Re: Re: Re: Re: Re: Re: limited network bandwidth with 3.2.x kernels

Eric Dumazet
2012-02-15T13:49:49Z

Le mercredi 15 février 2012 à 05:44 -0800, alekcejk@googlemail.com a
écrit :
> В сообщении от Среда 15 февраля 2012 05:43:13 вы написали:
> > OK thanks, nothing seems wrong on receiver side.
> >
> > Could you try to force ECN enabled flows and send tcpdump, to check if
> > we receive retransmits ?
> >
> > echo 1 >/proc/sys/net/ipv4/tcp_ecn
> 2 was there before I did it.
>
>
> > And check tcp can engage ECN : tcpdump SYN/SYNACK should look like:
> >
> > 05:41:17.943538 IP 192.168.1.97.45986 > 68.232.35.119.80: Flags [SEW],
> > seq 2109565072, win 14600, options [mss 1460,sackOK,TS val 8295492 ecr
> > 0,nop,wscale 6], length 0
> >
> > 05:41:17.980619 IP 68.232.35.119.80 > 192.168.1.97.45986: Flags [S.E],
> > seq 2519424885, ack 2109565073, win 14600, options [mss
> > 1452,nop,nop,sackOK,nop,wscale 6], length 0
>
> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
> listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
> 15:21:20.799077 IP AA.BB.CC.XY.55374 > 213.83.42.56.21: Flags [SEW], seq 1233000896, win 14600, options [mss 1460,sackOK,TS val 764819 ecr 0,nop,wscale 4], length 0
> 15:21:20.853575 IP 213.83.42.56.21 > AA.BB.CC.XY.55374: Flags [S.], seq 3046667726, ack 1233000897, win 5792, options [mss 1460,sackOK,TS val 3782118833 ecr 764819,nop,wscale 7], length
> 0

> 15:21:21.450884 IP AA.BB.CC.XY.53691 > 213.83.42.56.36139: Flags [SEW], seq 2740127335, win 14600, options [mss 1460,sackOK,TS val 765471 ecr 0,nop,wscale 4], length 0
> 15:21:21.505467 IP 213.83.42.56.36139 > AA.BB.CC.XY.53691: Flags [S.], seq 3050262605, ack 2740127336, win 5792, options [mss 1460,sackOK,TS val 3782119106 ecr 765471,nop,wscale 7],
> length 0

Unfortunately remote server doesnt negotiate ECN (we dont see E flag in
the SYNACK frame)

Try to find another one, and check SYNACK looks like : Flags [S.E]