At 10:17 AM 3/12/2004, you wrote:
>farr_at_metservice.com wrote:
>>At 08:23 AM 3/12/2004, you wrote:
>
>[...]
>
>>>>Perhaps you can help ... the following 3 steps happen really fast
>>>>(within 3ms or so) according to ethereal
>>>>STOR filename
>>>>150 Accepted data connection
>>>>two packets of data going to server and being acked straight away, the
>>>>last packet is the last packet of data for that file.
>>>>tcp control packet sent to server
>>>>tcp control packet recieved form server
>>>>tcp control packet sent to server
>>>>now we get a long pause of any where from 120ms to 200ms then a message
>>>>from the client box port (which seems to be the same for each file in
>>>>the transfer set) to ftp on the server ... it looks like this in ethereal
>>>>3044 > ftp [ACK] Seq=327186750 Ack=2387512526 Win=63626 Len=0 (60 bytes
>>>>of control data)
>>>>Response 226-32456.2 Mbytes of free disk space
>>>>etc with everything going really fast again
>>>>So it looks like there is a packet being sent to the server that is
>>>>being ignored ... and this is causing a delay between the end of one
>>>>file and the start of the next.
>>>
>>>Can you post the actual ethereal output?
>>It is attached as a libpcap file. If that is not enough I will send it
>>directly to you ...
>
>It looks like the delay you see is due to TCP's delayed ACK feature. It's
>hard to be certain from the output, but the timing seems to fit. The
>delayed ACK feature holds a pending ACK segment in the hope that some data
>will arrive within some amount of time (typically 50 - 200 ms) which it
>can piggyback the ACK on top of. If that doesn't happen the ACK will be
>sent when the timer expires.
>
>I don't know if there's a standard way to turn that off, but your OS may
>have some mechanism to do so if you really want to (it probably will turn
>it off for the whole system though).
>
>At any rate, this looks like a TCP issue to me rather than a curl issue.

Looks like you are right there. At least we know what the problem is now,
thanks.

Mike
Received on 2004-03-11