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?

Quoted 35 lines · Dong Fang

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.

Quoted 3 lines

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? :)