[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date: Thu, 08 Aug 2013 15:26:21 -0400
From: Dong Fang <yp.fangdong@...il.com>
To: netdev@...r.kernel.org
Subject: some questions of tcp congestion window
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?
--
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