[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Thu, 08 Aug 2013 15:34:41 -0400
From: Dong Fang <yp.fangdong@...il.com>
To: netdev@...r.kernel.org, Dong Fang <yp.fangdong@...il.com>
Subject: Re: some questions of tcp congestion window
On 08/08/2013 03:26 PM, Dong Fang wrote:
> hi, all
>
> I'am reading the tcp/ip network source code(kernel 3.10), i was
> fogged by the congestion window. so, i want to confirm something
> about it:
>
> Note: sack is disable. and A is sender, B is receiver.
>
> 1. at time t, the number of packets in flight is 100. like this:
> u, u+1, u+2, ..., u+99
> and suppose u is lost and all other packets are not. so bwtween
> t:t+RTT we would have retransmitted u and received 99 dupack.
> all of this dupack's ack == u, right?
>
> when A recieved 3 dupack, it changed to TCP_CA_Recovery state.
> in this state, the congestion window won't grow any more.
> then, A retransmit U packet. after that, if A receive a new ack,
> acked all the packets in flight, so the sock state is changed
> to TCP_CA_Open. right?
>
> 2. at time t, the number of packets in flight is 100, like this:
> u, u+1, u+2, ..., u+99
> and suppose u and u+5 is lost and all other packets are not.
> between t:t+RTT, we should have retransmitted u and received 99
> dupack, all of this dupack's ack == u, right?
>
> when A recieved 3 dupack, it changed to Recovery state, then
> retransmit U packet, after that, if A receive a new ack,
> this ack is only acked for u+5, at this time, current sshresh =
> cwnd/2 + 5(the first 5 packets was acked), but cwnd > sshresh.
> so A won't send any packets to B, and B won't send any ack to
> A too, because B have beed send 99 dupack and 1 new ack, it
> have done its work, right? the only way to let B send ack to
> A is, the retransmit timeout of u+5 packet.
>
> when A was retransmit u+5 packet to B, then B send packet ack
> for u+100 to A, this time, the A's cwnd == sshresh << 1, enter
> CA progress, right?
can anybody help me? :)
--
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
Powered by blists - more mailing lists