Any downside to Jumbo Frames??

One downside is that there is still a lot of gear out there that doesn't support Jumbo frames. Turning them on by default could make it hard to provision/setup the NAS. Also, since jumbo frames are not part of the ethernet standard, the size limit for jumbo frames varies (my laptop for instance is limited to 4088 bytes, other devices go to 9000).

I ran across this post in my googling... (a reply on http://www.codinghorror.com/blog/2009/0 ... rames.html)

I participated in the IEEE 802.3 committee for a while. IEEE never standardized a larger frame size for two reasons that I know of: 1. The end stations can negotiate the frame size, but there was no backwards-compatible way to ensure that all L2 bridges between them can handle it. Even if you send a jumbo frame successfully, you can still run into a problem later if the network topology changes and your packets begin taking a different path through the network. 2. The CRC32 at the end of the packet becomes weaker after around 4 KBytes of data. It can no longer guarantee that single bit errors will be caught, and the multibit error detection becomes weaker as well. One is free to enable it, and it does improve the performance, but the situation is unlikely to ever get better in terms of standard interoperability. It will always be an option to be enabled manually. Also a number of years ago,. jumbo frames provided a much bigger boost. Going from 1.5K to 9K regularly doubled performance or more. What has happened since is smarter ethernet NICs: they routinely coalesce interrupts, steer packets from the same flow to the same CPU, and sometimes even reassemble the payload of the 1.5K frames back into larger units. The resistance to standardizing jumbo frames resulted in increased innovation elsewhere to compensate.

Thank you Stephen !

Suggest you turn them off. They can be more trouble than they are worth, esp in a mixed network.
I used to use them all the time, but my rates are faster with them off.
I have NASs, PCs, Switches, Media Streamers, Sonos, Access Points and more.

victorhortaliveson wrote:
Suggest you turn them off. They can be more trouble than they are worth, esp in a mixed network. I used to use them all the time, but my rates are faster with them off. I have NASs, PCs, Switches, Media Streamers, Sonos, Access Points and more.

I leave them off also. The overhead reduction on the network is negligible (about 1%), any performance gain you see is due to the reducing the CPU load in the clients.

StephenB wrote:
I leave them off also. The overhead reduction on the network is negligible (about 1%), any performance gain you see is due to the reducing the CPU load in the clients.

Here it lifts performance (NV) from 8 MB/s to (up to) 36 MB/s. MacBookPro 2.4 GHz.

ard wrote:
StephenB wrote: I leave them off also. The overhead reduction on the network is negligible (about 1%), any performance gain you see is due to the reducing the CPU load in the clients. Here it lifts performance (NV) from 8 MB/s to (up to) 36 MB/s. MacBookPro 2.4 GHz.

The gain is due to reducing the CPU load, not because the network itself runs more efficiently. Often NIC drivers have other ways to reduce the CPU load (though mileage certainly varies on how well those ways work).

In my case I am not seeing any real performance gain, so I leave them off. No point in worrying about fragmentation and packet loss over 100 mbit, wireless, and WAN connections, if I don't see any much gain anyway.