OmniPeek Support

NFS and fragmentation

jhally
Posts: 1
Joined: Mon Mar 10, 2008 10:09 am

NFS and fragmentation

Postby jhally » Mon Mar 10, 2008 10:15 am

Hello All,

I need a sanity check. We have a non routed VLAN used for NFS servers/hosts. I notice that there is huge amounts of fragmentation going on even though there are no hops between the servers and hosts, they're all residing on the same network segment/vlan. I want to say that this is common for NFS but something just doesn't feel right.

MSS on the hosts is 1500, while I've been told that it is also 1500 on the nfs servers as well. would the mount options (8k, udp, read/write) be the 'culprit' causing the fragmentation?

thanks!

DJWP
Posts: 682
Joined: Tue Oct 30, 2007 11:42 am

Postby DJWP » Mon Mar 10, 2008 12:48 pm

Right away, we can think of one main cause of this. NFS mount will allow UDP to transmit a max frame size of 8000. If you are capturing these frames using a standard GB ethernet interface, then those frames will be fragmented because most adapters cannot handle jumbo frames. Try matching the MSS of your mount to the size on the VLAN (1500) and you may see less fragmentation.


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