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Date: Tue, 14 Jul 2009 15:12:16 -0400 From: Yinglin Sun <yinglinsun@...pitt.edu> To: David Miller <davem@...emloft.net> Cc: netdev@...r.kernel.org Subject: Re: [TCP_CA_CWR] Causes for entering TCP_CA_CWR state with 0 retransmissions Hi David, I use the total number of retransmissions reported by tcp_info. The field name is tcpi_total_retrans. From the kernel source code, I found that this number is for both fast retransmit and timeout retransmissions. On the other hand, if fast retransmission happened, ca_state should be TCP_CA_Recovery or TCP_CA_Disorder, but it's TCP_CA_CWR. Thanks. Yinglin On Tue, Jul 14, 2009 at 2:42 PM, David Miller<davem@...emloft.net> wrote: > From: Yinglin Sun <yinglin.s@...il.com> > Date: Tue, 14 Jul 2009 14:38:07 -0400 > >> I have a question about tcp_ca_state "TCP_CA_CWR". Under what >> circumstances does it enter this state? >> I'm doing some experiments and have trace from tcp_info. From tcp_info >> trace, I found that many places show ca_state is 2 (TCP_CA_CWR). Under >> this state, the congestion window size decreases but the total number >> of retransmissions is still 0. > > What kind of "retransmissions"? I bet the counter you are looking > at is counting timeout based retransmissions, which means it isn't > including the most predominant type of retransmissions, which are > fast retransmissions which are triggered in response to ACKs. > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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