[tcpm] Re: Discussion on whether the TCP four-wave mechanism can be simplified to three-wave mechanism

[Michael Tuexen <[e-mail]>]

> On 26. Aug 2024, at 09:24, Yoshifumi Nishida <[e-mail]> wrote:
> 
> Hi Yang,
> I think aggregating the 2nd packet (ACK for FIN) and the 3rd packet (FIN) is theoretically possible if you want to do it. 
That is correct. The following packetdrill script tests this:

+0.000 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0.000 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+0.000 bind(3, ..., ...) = 0
+0.000 listen(3, 1) = 0
+0.000 < S  0:0(0)       win 65535 <mss 1460,sackOK,eol,eol>
+0.000 > S. 0:0(0) ack 1 win 65535 <mss 1460,sackOK,eol,eol>
+0.050 <  . 1:1(0) ack 1 win 65535
+0.000 accept(3, ... ,...) = 4
+0.000 close (3) = 0
+0.000 close(4) = 0
+0.000 > F. 1:1(0) ack 1 win 65535
+0.050 < F. 1:1(0) ack 2 win 65535
+0.000 >  . 2:2(0) ack 2 win 65535

Best regards
Michael
> --
> Yoshi
> 
> 
> On Sun, Aug 25, 2024 at 1:02 AM [e-mail] <[e-mail]> wrote:
> I find the picture，When the server has no data to transmit, can the second and third waves be combined to reduce one wave? Because it has this delay mechanism, when there is data to be sent, it is sent, and there is no delay waiting. If something needs to be sent during the waiting period, can I do an ACK confirmation to send the merge?
> 
> 
> ---- Replied Message ----
> From Yoshifumi Nishida<[e-mail]> Date 08/25/2024 15:34 To [e-mail] Cc tcpm<[e-mail]> Subject Re: [tcpm] Discussion on whether the TCP four-wave mechanism can be simplified to three-wave mechanism Hi Yang,
> 
> OK. It seems to me that you're suggesting that when one peer sends the final FIN, it can terminate the connection without waiting for the FIN ACK.
> However, if this FIN hasn't arrived at the other end, the other end cannot know the peer has terminated the connection. 
> My concern here is that the other end would be suspended in this kind of situation.
> --
> Yoshi
> 
> On Sun, Aug 25, 2024 at 12:09 AM [e-mail] <[e-mail]> wrote:
> yes
> 
> 
> ---- Replied Message ----
> From Yoshifumi Nishida<[e-mail]> Date 08/25/2024 15:05 To [e-mail] Cc tcpm<[e-mail]> Subject Re: [tcpm] Discussion on whether the TCP four-wave mechanism can be simplified to three-wave mechanism Hi Yang,
> Are you referring to the 4 way close in TCP? and you want to make it 3 way?
> --
> Yoshi
> 
> On Fri, Aug 23, 2024 at 5:03 AM [e-mail] <[e-mail]> wrote:
> IEFT Hello, I am a Chinese computer major student, I have an idea is to study the TCP four wave mechanism, if one party still has data to pass, continue to open the connection. However, if both parties have no more data to transmit at a given moment, can it be possible to dispense with one wave, thus turning four waves into three? (Go straight back to the finally state at the end of the third time.) For example, is it feasible to go directly to the last step, that is, to change from the original four waves to three waves? Is there a theoretical basis for this assumption and the possibility of practical application?
>  Thank you, looking forward to reply!
>  I wish all the best!
> Yang Zhiyuan
> August 23, 2024
>  
> 
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