Le 20/12/2011 13:35, Tom Austin a écrit :
> To the network gurus
> 
> We are currently experiencing some network slowdowns that we have not
> experienced in the past and I am trying to narrow down what is going on.
> 
> In the past one could expect 1/2 a second delay when loading images or
> other data.
> More recently we have seen 5+ minutes of delay.
> 
> Our applications make heavy use of images - one application loads (3)
> 5MB images at once.  This application is used by 3-5 people in the
> office at the same time.
> 
> We run a Windows 2003 SBS domain controller with a Linux based file
> server.  The file server is only that - a file server with Linux From
> Scratch so there is nothing else running on it.
> 
> So far I have looked at file locks and 'top' to try to see if anything
> stands out, but I am far from being a network administrator and am
> searching to find where the problem may lie.
> 
> What should I be looking at to help determine where the problem is
> originating from?
> 
> 
> Any help is greatly appreciated.

First consider each system which might be part of the problem (client &
server) and then the network.

Is the load on client higher than average ? (does it use swap ?)

Is the load on server higher than usual ? (does it use swap ?)

And now for the real problem, of the network:
* Is there any system which has been added or removed recently ?
 (for instance, one with the same Windows name as your server... maybe
someone copied the samba setting for another system... oops! the name
must be changed)
* Does any system reboot recently ?
* Is the DHCP server still running ?
(the last two are connected: if your client restarts without getting
DHCP info, it will be in a default network... which might be a bit
difficult to reach the normal network)

Check on the server the "ifconfig" statistic ("ifconfig -a")
          ...
          RX packets:121678837 errors:0 dropped:0 overruns:0 frame:0
          TX packets:230675697 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:9614830711 (9.6 GB)  TX bytes:333118590778 (333.1 GB)
          Interrupt:17

Are you with numbers instead of 0 ?

If you have manageable routers, did you check if someone is not eating
all the bandwidth with some "new" application (like "let's use skype !",
a torrent client is such fun, "I'm bored, so let's listen to
internet-radio", there is so many lovely video on youtube with dancing
cats... ). Hopefully the router can make a bit of graphs per port to
display the average traffic.

And with a bit of installation, put "Wireshark" on both client and
server, and make a capture in promiscious mode on both systems while
loading your image. Compare the captures, check the usage of bandwidth
for your application (are you 100% of packets, with lot of losts, or a
mere 0.01% in a storm of broadcast or other packets ? What is the
time-spacing of the packets for your application flow ?(need to isolate
the connection based on port number) ?

(Notice: you will have to install pcap driver on Windows for Wireshark
to capture... also, you need administrator right on both systems)


Did you check the cables ?

Any upgrade/update of systems ?

May be your office is now part of botnet, attacking some target in a
DDOS attack.

-- 
A good Manager will take you
through the forest, no mater what.
A Leader will take time to climb on a
Tree and say 'This is the wrong forest'.

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