On 02/29/16 at 05:40P, Yongmin Cho wrote: > Thanks very much for the quick reply. > > I'm sorry, I didn't make patch file. > First, I wanted to discuss my opinion is right. > > Let me give you example, please check this. > > <- ACK (cumack = 1, sack[3-4], sack[6-7], sack[9-10]) > * here segment/byte 2, 5, and 8 are missing. > <- ACK (cumack = 1, sack[12-13], sack[15-16], sack[18-19]) > * here segment/bytes 11, 14 and 17 are also reported missing. > <- ACK (cumack = 1, sack[18-19], sack[21-24], sack[27, 28]) > * here segment/bytes 20 and 25, 26 are missing. (triggered fast > retransmission) > <- ACK.....(cumack = 1, sack[21-24], sack[27, 28], sack[32, 33]) > <- ACK.....(cumack = 1, sack[34-35], sack[37, 40], sack[42, 44]) > <- ACK.....(cumack = 1, sack[34-35], sack[37, 40], sack[42, 45]) > <- ACKs.....(many duplication acks, and new sacked blocks) > > In the fast recovery phase, the pipe is caculated like below, If the > net.inet.tcp.rfc6675_pipe is turned on. > pipe = snd_max - snd_una + sack_bytes_rexmit(1 MSS size) - > sacked_bytes(10 = 34-35, 37-40, 42-45 tcp_sack.c:390) > One segment is sended(sack_bytes_rexmit), when triggered fast > retransmission. > Because the snd_cwnd was set 1 mss size. (tcp_input.c:2609) > In the fast recovery phase, The sender can send data, > If this condition is right(awnd < tp->snd_ssthresh tcp_input.c:2568). > When in the network, It still has many in flight packets, > snd_max and snd_una will not be changed, and sack_bytes_rexmit is one MSS > size, and sacked_bytes is caculated by last ACK that has three SACK > blocks(34-35, 37-40, 42-45). > So, sometimes(In my test environment) the awnd(pipe) value can't go > down less than the snd_ssthresh, while receiving each ACKs > in fast recovery phase. > You know, If the awnd value can't go down less than the snd_ssthresh, > The sender can't send data that is included snd_holes. > > So, I think, the sacked_bytes should be caculated by all of sacked > blocks that is greater than snd_una, like below. > pipe = snd_max - snd_una + sack_bytes_rexmit - sacked_bytes(3-4, 6-7, > 9-10, 12-13, 15-16, 18-19, 21-24, 27-28, ...). > > But on current implementation, the sacked_bytes is caculated by three(or four) > sacked blocks that is in last ACK, like below. > pipe = snd_max - snd_una + sack_bytes_rexmit - sacked_bytes(34-35, > 37-40, 42-45 -> sacked blocks of last ACK). > > My opinion may not be right. Just I want to check implementation of > computing pipe.
Your opinion seems correct to me. If you can create a patch based on this, that'd be great. As I cannot spend time on this until next week. Cheers, Hiren
pgpQ2xc9yaNTt.pgp
Description: PGP signature
