How to find out when an ACK for a particular packet is received
HI,
I captured some packets through wireshark while uploading a file to a server.
Here is the captured file :
tcp-gaia.txt
I am using the following filter to see only the packet between the source and destination server :
ip.addr == 128.119.245.12 && tcp.port == 80
Consider the packet no. 17 it is the one containing POST
I have some questions related to it :
1) Why does this contains an ACK ?
As per what i understand an ACK is sent to a response but here i am sending data the 172....ip is my machines ip...
2) Also i see all the packets containing ACK . why is this so ?
3) How do i find out when was an ACK for a particular segment say the packet no. 17 received ?
Thanks
I captured some packets through wireshark while uploading a file to a server.
Here is the captured file :
tcp-gaia.txt
I am using the following filter to see only the packet between the source and destination server :
ip.addr == 128.119.245.12 && tcp.port == 80
Consider the packet no. 17 it is the one containing POST
I have some questions related to it :
1) Why does this contains an ACK ?
As per what i understand an ACK is sent to a response but here i am sending data the 172....ip is my machines ip...
2) Also i see all the packets containing ACK . why is this so ?
3) How do i find out when was an ACK for a particular segment say the packet no. 17 received ?
Thanks
SOLUTION
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ASKER
Hi,
I will read up that doc..
But consider packet no. 17, 18, 19 they are just carrying data from my computer to the server.
Now what i expect is that there should be a response to each of them from server side confirming that the packet has been recieved properly.
And this must be a packet from the server to my machine. where can i spot this packet in the capture above ?
I will read up that doc..
But consider packet no. 17, 18, 19 they are just carrying data from my computer to the server.
Now what i expect is that there should be a response to each of them from server side confirming that the packet has been recieved properly.
And this must be a packet from the server to my machine. where can i spot this packet in the capture above ?
ASKER
So basically the ACK packet will have Seq number and ACK number interchanged ?
ALso do i have to manually see this ? IS there a shortcut or tool in wireshark thru which i can just select a packet and ask for its ACK ?
Thanks
ALso do i have to manually see this ? IS there a shortcut or tool in wireshark thru which i can just select a packet and ask for its ACK ?
Thanks
Pretty much. I am not aware of such shortcut; always done it manually. What you can do is right click and follow TCP stream.
ASKER CERTIFIED SOLUTION
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ASKER
Hi,
That was good explanation. However i am confused about one thing.
Like SIM50 mentioned Packet 29 is sending ACK for packet 24,
But if i see the next sequence number for 24 it is - 91861149 and packet 30 is the one having ACK of this number
So as per what you have said packet 30 should be the one that has send ACK for packet 24 and not 29.
Please correct me..
That was good explanation. However i am confused about one thing.
Like SIM50 mentioned Packet 29 is sending ACK for packet 24,
But if i see the next sequence number for 24 it is - 91861149 and packet 30 is the one having ACK of this number
So as per what you have said packet 30 should be the one that has send ACK for packet 24 and not 29.
Please correct me..
SOLUTION
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BillBach, thank you for correcting me.
No worries. I got hung up on reading Alice, too.
Look at sequence and ACK numbers.
PS. Love Alice in Wonderland.