I have a mid sized network, around 80 users. Most of these users are using windows clients, with a few macs. There are 3 Linux servers, 2 for file services (samba and netatalk), and one as domain controller (Samba) and email (cyrus / postfix). There is also a windows server used for Sage.
We have recently started to notice periodic delays in network traffic. I am not aware of any changes to the network at the time when this problem started - it has been fine for 18 months or so. This has been noticed as follows:
1. remote ssh into Linux server - typing gets momentarily delayed, for about 5-10 seconds, then resumes. This occurs randomly, but typically every minute or so.
2. Remote desktop (to a windows client), freezes, and occasionally drops out.
3. File access to samba shares sometimes takes a very long time, or times out. Then a retry works almost instantly.
4. There is also a DOS (runs in XP command window) based database, whose files reside on a samba share. When scrolling through records, this occasionally freezes, then resumes.
The delay periods are all fairly consistent - ie, they affect the above for roughly the same periods. I have monitored tcpdump from the Linux server whilst accessing the database, and can see server responses from samba to the DOS client, immediately before a delay occurs.
I am certain the servers are not responsible, since it affects services on different machines, and can see samba packets from the server at the right time. Also, I've monitored the broadband traffic, and can see nothing unusual.
The network has gigabit connections from the servers to 3 stacked switches. Fibre between buildings - although the problem affects all buildings. Clients are typically on 100M connections.
the windows clients are all running NOD32 AV. RKhunter and chkrootkit are run on the servers overnight, and show nothing. I'm not sure what else to look for. I've monitored the servers with wireshark, and they look normal.
Any ideas would be welcome, please.
Stuart Bailey BSc (hons) CEng CITP MBCS LinuSoft (Managing Director) Linux Specialist & Software Developer ~~~~~~~~~~~~~~~~~~~~~~~ Phone: (0845) 658 3563 Direct: +44 (0) 1953 878162 Fax: +44 (0) 1603 858583 ~~~~~~~~~~~~~~~~~~~~~~~ http://www.linusoft.co.uk
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