[wplug] SMB connection slowing down

[Poyner, Brandon]

It's also possible the problem is tcp backoff.  The file services are
run over 139/tcp (netbios session service).  If you begin to lose
packets the transmission rate will be lowered.  If it continues to lose
packets the connection will continue to degrade.  You can use an
analyzer such as tcpdump to see if packets are being re-transmitted.  As
Nathan mentioned that can sometimes be caused by duplex mismatching, but
there are other possible reasons such as bad cabling or a weak WiFi
signal.  The ultimate book on TCP/IP is TCP/IP Illustrated Vol 2 by W.
Richard Stevens and Gary Wright.  I worked briefly with Gary and it's
spooky what he can tell you from a tcpdump.

Brandon Poyner
Network Engineer II
CCAC - College Office
412-237-3086


-----Original Message-----
From: Jason Jerome [mailto:jjerome2 at yahoo.com] 
Sent: Friday, July 16, 2004 12:59 PM
To: General user list
Subject: Re: [wplug] SMB connection slowing down



I had something similar to this a long time ago (so my knowledge is
limited).  In my case when the file neared completetion, it never
finished.  I eventuallly figured out it had to do with my Samba server,
something to do with the size of files and bandwidth.

It may be a dead end, but it couldn't hurt to check.



--- Alexandros Papadopoulos <apapadop at alumni.carnegiemellon.edu> wrote:
> I'm copying a 130MB file from an SMB-mounted partition on a remote
> NT4 
> server, to my linux box. The server has a 100MBit NIC, the linux box
> is 
> on a 11MBit wireless link. They're both practically on the same
> switch.
> 
> Ping from my linux box to the NT server reports:
> 7 packets transmitted, 7 received, 0% packet loss, time 6056ms
> rtt min/avg/max/mdev = 3.312/3.426/3.684/0.139 ms
> 
> Although right after issuing the cp command, a couple megabytes get 
> transferred quickly (the first 10MB take less than 30 seconds), it's 
> now 4,5 hours (four and a half HOURS) later, and it has transfered
> 97MB 
> of the file in question. With a back-of-envelope calculation, that 
> works out at roughly 6KB/sec, which is pathetic for a LAN.
> 
> I stopped and re-issued the command, while sniffing with Ethereal. I 
> singled out the TCP stream, and then graphed for throughput, which
> gave 
> about 250KB/s. It's slowing down as it goes.
> 
> I don't have the first idea how to troubleshoot this, any
> suggestions?
> 
> Thanks
> 
> -A
> _______________________________________________
> wplug mailing list
> wplug at wplug.org
> http://www.wplug.org/mailman/listinfo/wplug
> 


=====
http://jjerome.com/resume


		
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