I have the following capture made via wireshark. For e.g. in line 96 it send the post request then it get OK ack in line 98. Again in line 99 it keep sending the same thing. I have check my application is only sending it ones. What could be going on at the network layer? I dont see the repetition at the application layer. Because if its a bug in my app then it should be always repeating it. But it happens only sometimes. Just to add on those without problem I notice this [ACK] Seq=1. The value is always 1 for the Seq and with those there is not repetition?
asked 21 Oct '15, 10:02 newbie14 edited 21 Oct '15, 10:19 |
One Answer:
Maybe someone has another idea, but it seems as though the ACKs do different things.
ACKs are also sent when a packet has not arrived to signal a need to resend. In that case, the This is called fast recovery and fast retransmit. It is part of TCP's error recovery mechanism. Different purposes of ACKs:
Sometimes the packets also cross on the layer (an ACK being sent to retransmit while the other packet is in transit). In your case, have you considered posting the code at some Programmer's site (or here, if need be). Maybe it sends the data several times in some corner cases... answered 21 Oct '15, 10:40 user1234 edited 01 Nov '15, 10:07 @user1234 I dont quite get you on the ack and seq=3068. If you say data have not arrived then why does the the other send 98 375.244932864 ...12 ...23 HTTP/XML 714 HTTP/1.1 200 OK to say that is has received the data. But I notice the seq is not 1 but all those with normal flow the seq=1. How to diagnose based on the sequence 1? (21 Oct '15, 11:05) newbie14 That '200 OK' is the application layer talking. We're talking about retransmission at the transport layer. Dig out your OSI model book to get the difference. (21 Oct '15, 22:46) Jaap ♦ My confusion is that why the application layer is sending the OK. It can only send if the earlier packet have reached meaning the packet send succesfully so why there is a retransmission then? (22 Oct '15, 19:58) newbie14 @newbie14: Yes, you were right. In this case (different ack/seq-numbers), the ACKs should acknowledge different data packets. So from the trace it seems as though the application is asked three times and responds three times. (12 May '16, 03:39) user1234 |
Could you provide us a trace at public accessible place?
I dont get you what trace do you need please ?
The pcap file, from which you get the txt output.
The problem it has all the ip address which I could not disclosed. But what is your say on the fast retransmit?
Use TraceWrangler, available from www.tracewrangler.com, to anonymize the IP addresses.