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slowdown nt <-> linux

To: netdev@xxxxxxxxxxx
Subject: slowdown nt <-> linux
From: Francois Romieu <romieu@xxxxxxxxxx>
Date: Thu, 8 Feb 2001 17:05:02 +0100
Sender: owner-netdev@xxxxxxxxxxx
Hi,

  I've got some strange bahaviours between an NT server and a Linux box.
Say:
1 - Linux 1     -> NT client 1: fast (ftp, smb)
2 - NT server 1 -> NT client 1: fast (ftp, smb)
3 - NT server 1 -> NT server 2: fast (ftp, smb)
4 - Linux 1     -> NT server 1: slow as hell (ftp, smb)
fast = some Mo/s on a 100Mb/s link.
slow = 50-100 ko/s on the same link.
Everybody is on the same switch. Linux is 2.2.18pre15. WFIW NT has SP6 applied.
I tcpdump a smb transfer (4) and I'm frankly confused:
[...]
14:53:52.356875 NT.1881 > gw-rdc-1.netbios-ssn: P 8857:8921(64) ack 89256 win 
8760 (DF) [tos 0x20]
14:53:52.360751 gw-rdc-1.netbios-ssn > NT.1881: P 89256:90716(1460) ack 8921 
win 32120 (DF) [tos 0x10]
14:53:52.360791 gw-rdc-1.netbios-ssn > NT.1881: P 90716:92176(1460) ack 8921 
win 32120 (DF) [tos 0x10]
14:53:52.360812 gw-rdc-1.netbios-ssn > NT.1881: P 92176:93636(1460) ack 8921 
win 32120 (DF) [tos 0x10]
14:53:52.360830 gw-rdc-1.netbios-ssn > NT.1881: . 93636:95096(1460) ack 8921 
win 32120 (DF) [tos 0x10]
                                                  ^^^^^
14:53:52.360854 gw-rdc-1.netbios-ssn > NT.1881: . 95096:96556(1460) ack 8921 
win 32120 (DF) [tos 0x10]
14:53:52.360874 gw-rdc-1.netbios-ssn > NT.1881: P 96556:97511(955) ack 8921 win 
32120 (DF) [tos 0x10 ]
14:53:52.356875 NT.1881 > gw-rdc-1.netbios-ssn: . ack 92176 win 8760 (DF) [tos 
0x20]
14:53:52.356875 NT.1881 > gw-rdc-1.netbios-ssn: . ack 93636 win 8760 (DF) [tos 
0x20]
                                                      ^^^^^
14:53:52.356875 NT.1881 > gw-rdc-1.netbios-ssn: . ack 93636 win 8760 (DF) [tos 
0x20]
                                                      ^^^^^
Two acks with the same timestamp (+/-10ms slot I guess, no ?).

14:53:52.556900 gw-rdc-1.netbios-ssn > NT.1881: . 93636:95096(1460) ack 8921 
win 32120 (DF) [tos 0x10]
14:53:52.556877 NT.1881 > gw-rdc-1.netbios-ssn: . ack 97511 win 8760 (DF) [tos 
0x20]
14:53:52.556877 NT.1881 > gw-rdc-1.netbios-ssn: P 8921:8985(64) ack 97511 win 
8760 (DF) [tos 0x20]
14:53:52.558006 gw-rdc-1.netbios-ssn > NT.1881: P 97511:98971(1460) ack 8985 
win 32120 (DF) [tos 0x10]

At a normal speed (1), I never see this kind of ack sequences. What do they 
mean ?

-- 
Ueimor

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