[e2e] TCP/TCPDUMP/Why do I see such a thing happening ?

[Kalyan]

Group,


Something about the following chunk of tcpdump is worrying me !!
I see that for a connection:

My Host-IP: 111.111.11.111
Destination Host-IP: 222.22.222.222

1048542208.980726 222.22.222.222.80 > 111.111.11.111.1326: . 
53684:55132(1448) ack 2514 win 64651
1048542208.980726 222.22.222.222.80 > 111.111.11.111.1326: . 
55132:56580(1448) ack 2514 win 64651
1048542208.980726 222.22.222.222.80 > 111.111.11.111.1326: . 
56580:58028(1448) ack 2514 win 64651


1048542208.980726 111.111.11.111.1326 > 222.22.222.222.80: . ack 
55132 win 63712
1048542208.980726 222.22.222.222.80 > 111.111.11.111.1326: . 
58028:59476(1448) ack 2514 win 64651


1048542208.980726 111.111.11.111.1326 > 222.22.222.222.80: . ack 
55132 win 63712
1048542208.990726 222.22.222.222.80 > 111.111.11.111.1326: . 
59476:60924(1448) ack 2514 win 64651
...
...
...
>>I see the ack for 55132 28 times in total<<
...
...
...
1048542209.180726 111.111.11.111.1326 > 222.22.222.222.80: . ack 
55132 win 63712
1048542209.180726 222.22.222.222.80 > 111.111.11.111.1326: . ack 
2514 win 64651


>>why P is set in the below transfer<<


1048542209.180726 222.22.222.222.80 > 111.111.11.111.1326: P 
94228:95295(1067) ack 2514 win 64651


>>then something strange happens below<<

1048542209.180726 111.111.11.111.1326 > 222.22.222.222.80: . ack 
55132 win 63712
1048542209.180726 222.22.222.222.80 > 111.111.11.111.1326: . 
56568:56580(12) ack 2514 win 64651

>>why transfer 56568:56580, (Out-of-order ??) when asked for 
>>55132:56568 above and why only 55132:56568<<


1048542209.180726 111.111.11.111.1326 > 222.22.222.222.80: . ack 
55132 win 63712


1048542209.190726 222.22.222.222.80 > 111.111.11.111.1326: . 
55132:56568(1436) ack 2514 win 64651


>>alright!! finally transferred 55132:56568<<


1048542209.190726 222.22.222.222.80 > 111.111.11.111.1326: . ack 
2514 win 64651


1048542209.190726 111.111.11.111.1326 > 222.22.222.222.80: . ack 
95295 win 30408


1048542209.230726 111.111.11.111.1326 > 222.22.222.222.80: . ack 
95295 win 60816

...
...


Am I missing something or is it just that I don't understand 
TCP:

* Why did the sender send 28 acks ?
* Why send 56568:56580 when asked for 55132:56568 ? -- Is it 
Out-of-order or is there something wrong ?


Thanks,
¬Kalyan C
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