Date: Tue, 28 Jan 1997 15:32:11 -0500 From: Brian Burton <brian@burton-computer.com> To: Steve <shovey@buffnet.net> Cc: Terry Lambert <terry@lambert.org>, robert@nanguo.chalmers.com.au, freebsd-questions@freebsd.org, freebsd-isp@freebsd.org Subject: Re: progress report on connection problems Message-ID: <32EE624B.773C2448@burton-computer.com> References: <Pine.BSI.3.95.970128140035.754B-100000@buffnet11.buffnet.net>
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Steve wrote:
> Yup - It was with users - only some - same problem as the other guy has..
> They would connect to the news server, and not be able to pull headers -
> or to the web server, and get the text but not the graphics. It would
> stall.
>
> The bandaide I put on it was to number all freebsd boxes on class C's
> other than those of my annexes, forcing the packets thru my cisco.
> Everything cleared.
Since there has been a great deal of discussion of tcp connections
hanging
when passing through annexes, I thought I would bring up the problem
that I am
having. The symptoms are *very* similar but the hardware is different.
Perhaps my problem will shed some light on the other people's problem.
I am running 2.1.6-stable connected to the Internet via an Ascend
Pipeline 50
router on my end and a Livinsgton Portmaster (unknown model) at my ISP
over
two ISDN b-channels. My ISP routes my traffic through a CISCO router
(unknown
model) to UUNET and then to the Internet.
The symptom that I encounter is as follows:
* Client on my side opens ftp connection to certain sites.
* Client begins file transfer and connection seems to hang after
some data has already been transferred.
The sure way to reproduce the problem is to ftp to ftp.caldera.com, cd
to
pub/mirrors/redhat/updates/i386 and type dir. Only about half of the
directory listing makes it through.
In addition, sup fails every night and I was unable to install FreeBSD
using
FTP because of this problem. I have also seen the same lock ups as have
been
described by others including NNTP headers and image transfers for web
pages.
The problem happens regardless of the tcp_extensions setting in
sysconfig.
Also, I have seen the exact same problem with Windoze 95 clients. I
also saw
the problem with linux 2.x kernels but not with linux 1.2.13!
What happens can be seen from the tcpdump output included below: The
Livingston/Ascend never manage to pass the packet containing octets
2485-3945
down to my network. My FreeBSD box keeps asking for a retransmission.
No
matter how many times caldera retransmits, the bytes never make it
through.
It appears from the Pipeline's stats that the Pipeline is rejecting the
packet
as having an invalid header. So I suspect that the Livingston is
corrupting
them, but I do not know that for sure yet.
If anyone has any ideas or suggestions I'd be happy to hear them.
++Brian
PS - I used caldera.com as an example of a site that I have trouble
communicating with. I am not claiming that this is their fault!
They
are simply an innocent bystander.
Here is an excerpt from the tcpdump of my side of a hung ftp to caldera.
15:25:16.874058 caldera.com.ftp-data >
bcc01.burton-computer.com.40001: S 4117168473:4117168473(0) win 512 <mss
1460> [tos 0x8]
15:25:16.874257 bcc01.burton-computer.com.40001 >
caldera.com.ftp-data: S 3890833409:3890833409(0) ack 4117168474 win
17520 <mss 1460> (DF)
15:25:17.025729 caldera.com.ftp-data >
bcc01.burton-computer.com.40001: . ack 1 win 31744 [tos 0x8]
15:25:19.873299 caldera.com.ftp-data >
bcc01.burton-computer.com.40001: P 1:1025(1024) ack 1 win 31744 (DF)
[tos 0x8]
15:25:19.921828 bcc01.burton-computer.com.40001 >
caldera.com.ftp-data: . ack 1025 win 17520 (DF) [tos 0x8]
15:25:19.969787 caldera.com.ftp-data >
bcc01.burton-computer.com.40001: P 1025:2485(1460) ack 1 win 31744 (DF)
[tos 0x8]
15:25:20.121842 bcc01.burton-computer.com.40001 >
caldera.com.ftp-data: . ack 2485 win 17520 (DF) [tos 0x8]
15:25:20.313058 caldera.com.ftp-data >
bcc01.burton-computer.com.40001: P 3945:4450(505) ack 1 win 31744 (DF)
[tos 0x8]
15:25:20.313167 bcc01.burton-computer.com.40001 >
caldera.com.ftp-data: . ack 2485 win 17520 (DF) [tos 0x8]
15:25:20.497450 caldera.com.ftp-data >
bcc01.burton-computer.com.40001: F 4450:4450(0) ack 1 win 31744 [tos
0x8]
15:25:20.497542 bcc01.burton-computer.com.40001 >
caldera.com.ftp-data: . ack 2485 win 17520 (DF) [tos 0x8]
15:26:33.252421 bcc01.burton-computer.com.40001 >
caldera.com.ftp-data: F 1:1(0) ack 2485 win 17520 (DF) [tos 0x8]
15:26:33.443142 caldera.com.ftp-data >
bcc01.burton-computer.com.40001: . ack 2 win 31744 [tos 0x8]
Here is an excerpt from my ISP's side of the failed ftp.
20:27:16.862191 caldera.com.20 > bcc01.burton-computer.com.40001: S
4117168473:4117168473(0) win 512 <mss 1460> [tos 0x8]
20:27:16.889774 bcc01.burton-computer.com.40001 > caldera.com.20: S
3890833409:3890833409(0) ack 4117168474 win 17520 <mss 1460> (DF)
20:27:17.014076 caldera.com.20 > bcc01.burton-computer.com.40001: .
ack 1 win 31744 [tos 0x8]
20:27:19.793237 caldera.com.20 > bcc01.burton-computer.com.40001: P
1:1025(1024) ack 1 win 31744 (DF) [tos 0x8]
20:27:19.825641 caldera.com.20 > bcc01.burton-computer.com.40001: P
1025:2485(1460) ack 1 win 31744 (DF) [tos 0x8]
20:27:19.937915 bcc01.burton-computer.com.40001 > caldera.com.20: .
ack 1025 win 17520 (DF) [tos 0x8]
20:27:20.140595 bcc01.burton-computer.com.40001 > caldera.com.20: .
ack 2485 win 17520 (DF) [tos 0x8]
20:27:20.170151 caldera.com.20 > bcc01.burton-computer.com.40001: P
2485:3945(1460) ack 1 win 31744 [tos 0x8]
20:27:20.173851 caldera.com.20 > bcc01.burton-computer.com.40001: P
3945:4450(505) ack 1 win 31744 (DF) [tos 0x8]
20:27:20.329662 bcc01.burton-computer.com.40001 > caldera.com.20: .
ack 2485 win 17520 (DF) [tos 0x8]
20:27:20.477486 caldera.com.20 > bcc01.burton-computer.com.40001: F
4450:4450(0) ack 1 win 31744 [tos 0x8]
20:27:20.516980 bcc01.burton-computer.com.40001 > caldera.com.20: .
ack 2485 win 17520 (DF) [tos 0x8]
20:27:21.956979 caldera.com.20 > bcc01.burton-computer.com.40001: P
2485:3945(1460) ack 1 win 31744 [tos 0x8]
20:27:25.612874 caldera.com.20 > bcc01.burton-computer.com.40001: P
2485:3945(1460) ack 1 win 31744 [tos 0x8]
20:27:32.965838 caldera.com.20 > bcc01.burton-computer.com.40001: P
2485:3945(1460) ack 1 win 31744 [tos 0x8]
20:27:47.853712 caldera.com.20 > bcc01.burton-computer.com.40001: P
2485:3945(1460) ack 1 win 31744 [tos 0x8]
20:28:16.896253 caldera.com.20 > bcc01.burton-computer.com.40001: P
2485:3945(1460) ack 1 win 31744 [tos 0x8]
20:28:33.290671 bcc01.burton-computer.com.40001 > caldera.com.20: F
1:1(0) ack 2485 win 17520 (DF) [tos 0x8]
20:28:33.451976 caldera.com.20 > bcc01.burton-computer.com.40001: .
ack 2 win 31744 [tos 0x8]
--
Brian Burton Burton Computer Corp.
brian@burton-computer.com 14315 National Highway
Suite 340
"This space intentionally left blank." La Vale, MD 21502
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