Date: Mon, 29 Aug 2005 23:20:29 +0800 From: Huang wen hui <hwh@gddsn.org.cn> To: questions@freebsd.org Subject: Question about TCP packet. Message-ID: <431327BD.6030006@gddsn.org.cn>
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hi, I use FreeBSD(192.168.168.137) connect one embedded device(211.96.21.220). using tcpdump dump network traffic, found that I received 2 ack packets when sent data to embedded device. Does It mean one ack packet is not necessary and the embedded device's tcp stack is broken? thanks, --hwh #tcpdump -i fxp0 -s 0 -X host 192.168.168.137 16:58:08.443604 192.168.168.137.1693 > 211.96.21.220.9742: S 2684474362:2684474362(0) win 65535 <mss 1460,nop,nop,sackOK> (DF) 0x0000 4500 0030 a1ff 4000 8006 065a c0a8 a889 E..0..@....Z.... 0x0010 d360 15dc 069d 260e a001 d3fa 0000 0000 .`....&......... 0x0020 7002 ffff 9009 0000 0204 05b4 0101 0402 p............... 16:58:08.445076 211.96.21.220.9742 > 192.168.168.137.1693: S 874963524:874963524(0) ack 2684474363 win 1460 <mss 1460,nop,nop,nop,nop> (DF) 0x0000 4500 0030 35f8 4000 7d06 7561 d360 15dc E..05.@.}.ua.`.. 0x0010 c0a8 a889 260e 069d 3426 e244 a001 d3fb ....&...4&.D.... 0x0020 7012 05b4 76da 0000 0204 05b4 0101 0101 p...v........... 16:58:08.445277 192.168.168.137.1693 > 211.96.21.220.9742: . ack 1 win 65535 (DF) 0x0000 4500 0028 a200 4000 8006 0661 c0a8 a889 E..(..@....a.... 0x0010 d360 15dc 069d 260e a001 d3fb 3426 e245 .`....&.....4&.E 0x0020 5010 ffff a651 0000 0000 0000 0000 P....Q........ 16:58:08.448730 192.168.168.137.1693 > 211.96.21.220.9742: P 1:22(21) ack 1 win 65535 (DF) 0x0000 4500 003d a201 4000 8006 064b c0a8 a889 E..=..@....K.... 0x0010 d360 15dc 069d 260e a001 d3fb 3426 e245 .`....&.....4&.E 0x0020 5018 ffff bf19 0000 436f 6e6e 6563 7420 P.......Connect. 0x0030 546f 2054 4445 2d33 3234 4349 00 To.TDE-324CI. 16:58:08.450458 211.96.21.220.9742 > 192.168.168.137.1693: . ack 22 win 1439 (DF) 0x0000 4500 0028 35f9 4000 7d06 7568 d360 15dc E..(5.@.}.uh.`.. 0x0010 c0a8 a889 260e 069d 3426 e245 a001 d410 ....&...4&.E.... 0x0020 5010 059f a09d 0000 P....... 16:58:08.482349 211.96.21.220.9742 > 192.168.168.137.1693: . ack 22 win 1460 (DF) 0x0000 4500 0028 35fa 4000 7d06 7567 d360 15dc E..(5.@.}.ug.`.. 0x0010 c0a8 a889 260e 069d 3426 e245 a001 d410 ....&...4&.E.... 0x0020 5010 05b4 a088 0000 P....... 16:58:08.482868 211.96.21.220.9742 > 192.168.168.137.1693: P 1:26(25) ack 22 win 1460 (DF) 0x0000 4500 0041 35fb 4000 7d06 754d d360 15dc E..A5.@.}.uM.`.. 0x0010 c0a8 a889 260e 069d 3426 e245 a001 d410 ....&...4&.E.... 0x0020 5018 05b4 9017 0000 4441 5441 2052 4543 P.......DATA.REC 0x0030 4549 5645 2050 4153 5357 4f52 442e 2e2e EIVE.PASSWORD... 0x0040 00 . 16:58:08.484765 192.168.168.137.1693 > 211.96.21.220.9742: P 22:38(16) ack 26 win 65510 (DF) 0x0000 4500 0038 a202 4000 8006 064f c0a8 a889 E..8..@....O.... 0x0010 d360 15dc 069d 260e a001 d410 3426 e25e .`....&.....4&.^ 0x0020 5018 ffe6 0c88 0000 3132 3334 3536 0000 P.......123456.. 0x0030 0000 0000 0000 0000 ........ 16:58:08.486242 211.96.21.220.9742 > 192.168.168.137.1693: . ack 38 win 1444 (DF) 0x0000 4500 0028 35fc 4000 7d06 7565 d360 15dc E..(5.@.}.ue.`.. 0x0010 c0a8 a889 260e 069d 3426 e25e a001 d420 ....&...4&.^.... 0x0020 5010 05a4 a06f 0000 P....o.. 16:58:08.521405 211.96.21.220.9742 > 192.168.168.137.1693: . ack 38 win 1460 (DF) 0x0000 4500 0028 35fd 4000 7d06 7564 d360 15dc E..(5.@.}.ud.`.. 0x0010 c0a8 a889 260e 069d 3426 e25e a001 d420 ....&...4&.^.... 0x0020 5010 05b4 a05f 0000 P...._.. 16:58:08.521886 211.96.21.220.9742 > 192.168.168.137.1693: P 26:43(17) ack 38 win 1460 (DF) 0x0000 4500 0039 35fe 4000 7d06 7552 d360 15dc E..95.@.}.uR.`.. 0x0010 c0a8 a889 260e 069d 3426 e25e a001 d420 ....&...4&.^.... 0x0020 5018 05b4 771d 0000 434f 4e4e 4543 5420 P...w...CONNECT. 0x0030 4f4b 2141 444d 494e 00 OK!ADMIN. 16:58:08.523627 192.168.168.137.1693 > 211.96.21.220.9742: P 38:46(8) ack 43 win 65493 (DF) 0x0000 4500 0030 a203 4000 8006 0656 c0a8 a889 E..0..@....V.... 0x0010 d360 15dc 069d 260e a001 d420 3426 e26f .`....&.....4&.o 0x0020 5018 ffd5 a41c 0000 0000 0000 0100 0100 P............... 16:58:08.525169 211.96.21.220.9742 > 192.168.168.137.1693: . ack 46 win 1452 (DF) 0x0000 4500 0028 35ff 4000 7d06 7562 d360 15dc E..(5.@.}.ub.`.. 0x0010 c0a8 a889 260e 069d 3426 e26f a001 d428 ....&...4&.o...( 0x0020 5010 05ac a04e 0000 P....N.. 16:58:08.525589 211.96.21.220.9742 > 192.168.168.137.1693: . ack 46 win 1460 (DF) 0x0000 4500 0028 3600 4000 7d06 7561 d360 15dc E..(6.@.}.ua.`.. 0x0010 c0a8 a889 260e 069d 3426 e26f a001 d428 ....&...4&.o...( 0x0020 5010 05b4 a046 0000 P....F..
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