Late TCP-acks? Uplink problems? (2mbps)

24/03/2006, 10h16

Hey,

I have a question about a tcp behaviour of a ftp download. The client
computer is a win2000 machine. (the downlink speed is about 2mbps, rtt
around 100ms)

In the beginning you see what is expected: every 2 packets a ack is
sended.

33 0.741066 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
34 0.741066 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
35 0.741066 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=27745 Win=93440 Len=0
36 0.751080 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
37 0.751080 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=29165 Win=93440 Len=0
38 0.751080 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
39 0.761095 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
40 0.761095 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=32005 Win=93440 Len=0
41 0.761095 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 764 bytes
42 0.811167 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
43 0.821181 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=34189 Win=93440 Len=0
44 0.821181 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
45 0.821181 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
46 0.821181 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=37029 Win=93440 Len=0
47 0.841210 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
48 0.851224 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
49 0.851224 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=39869 Win=93440 Len=0

But after a while the client doens't send acks anymore every 2 packets.
It looks like the clients waits and then send a bulk of acks. Is that
my network card that cannot follow the uplink ip traffic?

324 1.672405 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
325 1.672405 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
326 1.672405 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=274925 Win=93440 Len=0
327 1.672405 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
328 1.672405 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=276345 Win=93440 Len=0
329 1.682419 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
330 1.682419 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 764 bytes
331 1.682419 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=278529 Win=93440 Len=0
332 1.692434 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
333 1.692434 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
334 1.702448 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
335 1.702448 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
336 1.712463 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
337 1.712463 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
338 1.722477 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
339 1.732491 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
340 1.732491 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
341 1.732491 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
342 1.742506 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=281369 Win=93440 Len=0
343 1.742506 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=284209 Win=93440 Len=0
344 1.742506 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
345 1.742506 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=285629 Win=93440 Len=0
346 1.752520 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=288469 Win=93440 Len=0
347 1.752520 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 764 bytes
348 1.752520 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=289889 Win=93440 Len=0
349 1.752520 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=292729 Win=93440 Len=0
350 1.752520 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=294149 Win=93440 Len=0
351 1.752520 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
352 1.752520 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=296333 Win=93440 Len=0
353 1.752520 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
354 1.762535 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes

When is the timestamp of ethereal taken? Is that when the segment is
leaving the tcp-ip stack? Or when it is transmitted?

Thanks a lot!

If you want, i can provide the ethereal logfile.

Bert

A bigger example:

528 2.263255 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
529 2.263255 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
530 2.273269 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=448049 Win=93440 Len=0
531 2.273269 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
532 2.273269 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=449469 Win=93440 Len=0
533 2.283283 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
534 2.283283 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
535 2.293298 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
536 2.293298 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
537 2.293298 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
538 2.303312 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
539 2.313327 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 764 bytes
540 2.313327 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
541 2.313327 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
542 2.323341 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
543 2.333355 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
544 2.333355 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=452309 Win=93440 Len=0
545 2.333355 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=453729 Win=93440 Len=0
546 2.333355 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=456569 Win=93440 Len=0
547 2.333355 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=457989 Win=93440 Len=0
548 2.333355 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=460173 Win=93440 Len=0
549 2.343370 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
550 2.343370 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=463013 Win=93440 Len=0
551 2.343370 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=465853 Win=93440 Len=0
552 2.343370 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
553 2.343370 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=467273 Win=93440 Len=0
554 2.343370 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
555 2.353384 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
556 2.353384 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=470113 Win=93440 Len=0
557 2.353384 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
558 2.353384 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=471533 Win=93440 Len=0
559 2.363399 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
560 2.363399 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
561 2.363399 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=474373 Win=93440 Len=0
562 2.373413 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 764 bytes
563 2.373413 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
564 2.383427 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
565 2.383427 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
566 2.393442 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
567 2.393442 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
568 2.403456 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
569 2.403456 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
570 2.413471 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
571 2.413471 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
572 2.423485 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
573 2.433499 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
574 2.433499 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 764 bytes
575 2.433499 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
576 2.443514 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=476557 Win=93440 Len=0
577 2.443514 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=479397 Win=93440 Len=0
578 2.443514 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=480817 Win=93440 Len=0
579 2.443514 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=483657 Win=93440 Len=0
580 2.443514 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
581 2.443514 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=485077 Win=93440 Len=0
582 2.443514 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=487917 Win=93440 Len=0
583 2.443514 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
584 2.443514 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=489337 Win=93440 Len=0
585 2.443514 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=491521 Win=93440 Len=0
586 2.453528 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
587 2.453528 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
588 2.463543 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
589 2.463543 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
590 2.473557 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
591 2.473557 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
592 2.483571 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
593 2.483571 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
594 2.493586 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 764 bytes
595 2.493586 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
596 2.503600 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
597 2.503600 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
598 2.513615 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
599 2.513615 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
600 2.523629 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
601 2.533643 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
602 2.533643 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
603 2.543658 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
604 2.543658 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
605 2.543658 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=494361 Win=93440 Len=0
606 2.543658 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=497201 Win=93440 Len=0
607 2.553672 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=498621 Win=93440 Len=0
608 2.553672 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=501461 Win=93440 Len=0
609 2.553672 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
610 2.553672 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=502881 Win=93440 Len=0
611 2.553672 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=505721 Win=93440 Len=0
612 2.553672 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 764 bytes
613 2.553672 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=507141 Win=93440 Len=0
614 2.553672 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=509325 Win=93440 Len=0
615 2.553672 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=512165 Win=93440 Len=0
616 2.553672 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
617 2.553672 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=515005 Win=93440 Len=0
618 2.563687 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=516425 Win=93440 Len=0
619 2.563687 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=519265 Win=93440 Len=0
620 2.563687 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=520685 Win=93440 Len=0
621 2.563687 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
622 2.563687 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=523525 Win=93440 Len=0
623 2.563687 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=525709 Win=93440 Len=0
624 2.563687 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
625 2.563687 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=528549 Win=93440 Len=0
626 2.563687 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
627 2.563687 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=529969 Win=93440 Len=0
628 2.573701 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
629 2.573701 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
630 2.573701 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=532809 Win=93440 Len=0
631 2.583715 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
632 2.583715 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=534229 Win=93440 Len=0
633 2.583715 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
634 2.593730 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
635 2.593730 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=537069 Win=93440 Len=0
636 2.593730 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
637 2.603744 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
638 2.603744 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 764 bytes
639 2.613759 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
640 2.613759 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
641 2.623773 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
642 2.623773 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
643 2.633787 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
644 2.633787 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
645 2.643802 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
646 2.643802 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
647 2.653816 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=538489 Win=93440 Len=0
648 2.653816 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=540673 Win=93440 Len=0
649 2.653816 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=543513 Win=93440 Len=0
650 2.653816 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
651 2.653816 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=546353 Win=93440 Len=0
652 2.653816 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=547773 Win=93440 Len=0
653 2.653816 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=550613 Win=93440 Len=0
654 2.653816 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
655 2.653816 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=552033 Win=93440 Len=0
656 2.653816 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=554873 Win=93440 Len=0
657 2.663831 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
658 2.663831 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=556293 Win=93440 Len=0
659 2.663831 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 764 bytes
660 2.663831 10.251.0.12 10.11.0.4 FTP-DATA
FTP Data: 1420 bytes
661 2.663831 10.11.0.4 10.251.0.12 TCP
1796 > 49328 [ACK] Seq=1 Ack=558477 Win=93440 Len=0

24/03/2006, 22h37

The situation may result from large RTT. Initially TCP is in slow-start
and congestion window is small, so you see ACK per two data packets.
But later on, the window opens up and the sender can quickly send a
window of data out, but because of large RTT, you don't see ACK so
much.

Joy

24/03/2006, 10h16	#1
bert.verneffe@gmail.com Messages: n/a Hébergeur:	Late TCP-acks? Uplink problems? (2mbps) Hey, I have a question about a tcp behaviour of a ftp download. The client computer is a win2000 machine. (the downlink speed is about 2mbps, rtt around 100ms) In the beginning you see what is expected: every 2 packets a ack is sended. 33 0.741066 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 34 0.741066 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 35 0.741066 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=27745 Win=93440 Len=0 36 0.751080 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 37 0.751080 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=29165 Win=93440 Len=0 38 0.751080 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 39 0.761095 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 40 0.761095 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=32005 Win=93440 Len=0 41 0.761095 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 764 bytes 42 0.811167 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 43 0.821181 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=34189 Win=93440 Len=0 44 0.821181 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 45 0.821181 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 46 0.821181 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=37029 Win=93440 Len=0 47 0.841210 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 48 0.851224 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 49 0.851224 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=39869 Win=93440 Len=0 But after a while the client doens't send acks anymore every 2 packets. It looks like the clients waits and then send a bulk of acks. Is that my network card that cannot follow the uplink ip traffic? 324 1.672405 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 325 1.672405 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 326 1.672405 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=274925 Win=93440 Len=0 327 1.672405 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 328 1.672405 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=276345 Win=93440 Len=0 329 1.682419 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 330 1.682419 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 764 bytes 331 1.682419 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=278529 Win=93440 Len=0 332 1.692434 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 333 1.692434 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 334 1.702448 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 335 1.702448 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 336 1.712463 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 337 1.712463 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 338 1.722477 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 339 1.732491 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 340 1.732491 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 341 1.732491 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 342 1.742506 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=281369 Win=93440 Len=0 343 1.742506 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=284209 Win=93440 Len=0 344 1.742506 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 345 1.742506 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=285629 Win=93440 Len=0 346 1.752520 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=288469 Win=93440 Len=0 347 1.752520 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 764 bytes 348 1.752520 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=289889 Win=93440 Len=0 349 1.752520 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=292729 Win=93440 Len=0 350 1.752520 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=294149 Win=93440 Len=0 351 1.752520 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 352 1.752520 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=296333 Win=93440 Len=0 353 1.752520 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 354 1.762535 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes When is the timestamp of ethereal taken? Is that when the segment is leaving the tcp-ip stack? Or when it is transmitted? Thanks a lot! If you want, i can provide the ethereal logfile. Bert A bigger example: 528 2.263255 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 529 2.263255 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 530 2.273269 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=448049 Win=93440 Len=0 531 2.273269 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 532 2.273269 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=449469 Win=93440 Len=0 533 2.283283 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 534 2.283283 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 535 2.293298 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 536 2.293298 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 537 2.293298 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 538 2.303312 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 539 2.313327 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 764 bytes 540 2.313327 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 541 2.313327 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 542 2.323341 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 543 2.333355 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 544 2.333355 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=452309 Win=93440 Len=0 545 2.333355 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=453729 Win=93440 Len=0 546 2.333355 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=456569 Win=93440 Len=0 547 2.333355 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=457989 Win=93440 Len=0 548 2.333355 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=460173 Win=93440 Len=0 549 2.343370 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 550 2.343370 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=463013 Win=93440 Len=0 551 2.343370 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=465853 Win=93440 Len=0 552 2.343370 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 553 2.343370 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=467273 Win=93440 Len=0 554 2.343370 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 555 2.353384 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 556 2.353384 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=470113 Win=93440 Len=0 557 2.353384 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 558 2.353384 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=471533 Win=93440 Len=0 559 2.363399 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 560 2.363399 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 561 2.363399 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=474373 Win=93440 Len=0 562 2.373413 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 764 bytes 563 2.373413 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 564 2.383427 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 565 2.383427 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 566 2.393442 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 567 2.393442 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 568 2.403456 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 569 2.403456 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 570 2.413471 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 571 2.413471 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 572 2.423485 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 573 2.433499 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 574 2.433499 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 764 bytes 575 2.433499 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 576 2.443514 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=476557 Win=93440 Len=0 577 2.443514 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=479397 Win=93440 Len=0 578 2.443514 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=480817 Win=93440 Len=0 579 2.443514 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=483657 Win=93440 Len=0 580 2.443514 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 581 2.443514 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=485077 Win=93440 Len=0 582 2.443514 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=487917 Win=93440 Len=0 583 2.443514 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 584 2.443514 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=489337 Win=93440 Len=0 585 2.443514 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=491521 Win=93440 Len=0 586 2.453528 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 587 2.453528 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 588 2.463543 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 589 2.463543 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 590 2.473557 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 591 2.473557 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 592 2.483571 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 593 2.483571 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 594 2.493586 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 764 bytes 595 2.493586 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 596 2.503600 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 597 2.503600 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 598 2.513615 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 599 2.513615 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 600 2.523629 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 601 2.533643 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 602 2.533643 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 603 2.543658 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 604 2.543658 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 605 2.543658 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=494361 Win=93440 Len=0 606 2.543658 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=497201 Win=93440 Len=0 607 2.553672 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=498621 Win=93440 Len=0 608 2.553672 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=501461 Win=93440 Len=0 609 2.553672 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 610 2.553672 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=502881 Win=93440 Len=0 611 2.553672 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=505721 Win=93440 Len=0 612 2.553672 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 764 bytes 613 2.553672 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=507141 Win=93440 Len=0 614 2.553672 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=509325 Win=93440 Len=0 615 2.553672 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=512165 Win=93440 Len=0 616 2.553672 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 617 2.553672 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=515005 Win=93440 Len=0 618 2.563687 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=516425 Win=93440 Len=0 619 2.563687 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=519265 Win=93440 Len=0 620 2.563687 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=520685 Win=93440 Len=0 621 2.563687 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 622 2.563687 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=523525 Win=93440 Len=0 623 2.563687 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=525709 Win=93440 Len=0 624 2.563687 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 625 2.563687 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=528549 Win=93440 Len=0 626 2.563687 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 627 2.563687 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=529969 Win=93440 Len=0 628 2.573701 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 629 2.573701 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 630 2.573701 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=532809 Win=93440 Len=0 631 2.583715 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 632 2.583715 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=534229 Win=93440 Len=0 633 2.583715 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 634 2.593730 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 635 2.593730 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=537069 Win=93440 Len=0 636 2.593730 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 637 2.603744 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 638 2.603744 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 764 bytes 639 2.613759 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 640 2.613759 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 641 2.623773 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 642 2.623773 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 643 2.633787 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 644 2.633787 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 645 2.643802 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 646 2.643802 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 647 2.653816 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=538489 Win=93440 Len=0 648 2.653816 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=540673 Win=93440 Len=0 649 2.653816 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=543513 Win=93440 Len=0 650 2.653816 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 651 2.653816 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=546353 Win=93440 Len=0 652 2.653816 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=547773 Win=93440 Len=0 653 2.653816 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=550613 Win=93440 Len=0 654 2.653816 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 655 2.653816 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=552033 Win=93440 Len=0 656 2.653816 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=554873 Win=93440 Len=0 657 2.663831 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 658 2.663831 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=556293 Win=93440 Len=0 659 2.663831 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 764 bytes 660 2.663831 10.251.0.12 10.11.0.4 FTP-DATA FTP Data: 1420 bytes 661 2.663831 10.11.0.4 10.251.0.12 TCP 1796 > 49328 [ACK] Seq=1 Ack=558477 Win=93440 Len=0

24/03/2006, 22h37	#2
cxiong Messages: n/a Hébergeur:	Re: Late TCP-acks? Uplink problems? (2mbps) The situation may result from large RTT. Initially TCP is in slow-start and congestion window is small, so you see ACK per two data packets. But later on, the window opens up and the sender can quickly send a window of data out, but because of large RTT, you don't see ACK so much. Joy

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