Re: [Ethereal-users] duplicate sequence numbers???

[julien.leproust@xxxxxxxx]

oumer@xxxxxxxxxx a écrit :
> Hi,
>
> Here are few lines from tracing an hTTP connection. What I dont understand is
> there are some places where multiple packets have the same sequence number
> (sometime differening in that one has no data, just an ACK while the other
> duplicate will have a payload, OR in some other cases, the duplicated packets
> are acking different seq numbers.)
>
> Can anyone tell me what is wrong, or what I am missing?

I haven't looked at the full trace, but that seems completely normal.

The sequence number is the number of bytes you have already sent, 
including the payload of the current packet. That's why a packet with no 
payload, only acking, has the same sequence number as the previous one.

The acked sequence number is the number of bytes you have successfully 
received. That's why it is the same in two consecutive packets sent if 
nothing arrived in the reverse stream in the same time.

The sequence number and the acked sequence number refer to two different 
stream, they are completely independent. You increment your sequence 
numbers of the amount of data you send, and you ack the sequence numbers 
you receive. You perfectly can ack data without sending any payload, and 
send data without having received anything, so nothing more to ack.

hth,

--
Julien