Explain Jumbo Frames

[Jimkirk363]

Hi Guys im wondering if u can give me some advice to someone that knows very little on networking.

 

Would there be any advantage to enabling jumbo frames on my Synology ds215j NAS and if so what would the MTU also need to be set at?

Thanks.

[Vezzeract]

3 hours ago, jimkirk363 said:

Hi Guys im wondering if u can give me some advice to someone that knows very little on networking.

 

Would there be any advantage to enabling jumbo frames on my Synology ds215j NAS and if so what would the MTU also need to be set at?

Thanks.

If you are able to mantain this than try it out but if not stick with what is stable and you are comfortable with..

 

I am networking guy but I no little about prebuilt systems.

[mikat]

4 minutes ago, jimkirk363 said:

Hi Guys im wondering if u can give me some advice to someone that knows very little on networking.

 

Would there be any advantage to enabling jumbo frames on my Synology ds215j NAS and if so what would the MTU also need to be set at?

Thanks.

https://en.wikipedia.org/wiki/Jumbo_frame

MTU at 9000 for jumbo frames

and what performance are you getting from your nas right now?

[Jimkirk363]

At the moment i know it sounds weird.... Performance is all over the place.

 

Sometimes im getting as high as 80mb/s transfers, other times im down in the kbs,

 

Im using Cat 6 Belkin cables and its connected to a Killer network port.

[leadeater]

More often than anything else increasing the MTU size, enabling jumbo frames, on NAS storage systems does not increase network file copy performance. There are other things in the network stack that optimize them self to give the best performance possible, TCP window size etc.

 

Increasing MTU size on network block storage does give better performance i.e. iSCSI.

[beavo451]

4 hours ago, jimkirk363 said:

At the moment i know it sounds weird.... Performance is all over the place.

 

Sometimes im getting as high as 80mb/s transfers, other times im down in the kbs,

 

Im using Cat 6 Belkin cables and its connected to a Killer network port.

If you are transferring many files of varying sizes, it is normal for transfer speed to vary. Don't automatically assume that something is wrong and do something stupid (like the other guy that smashed his switch).

[Blake]

7 hours ago, jimkirk363 said:

Hi Guys im wondering if u can give me some advice to someone that knows very little on networking.

 

Would there be any advantage to enabling jumbo frames on my Synology ds215j NAS and if so what would the MTU also need to be set at?

Thanks.

Yes, but it depends on your network setup.

Normal Ethernet frames live on layer 2 of the OSI model, and adjusting the frame length means each frame can be larger, which is a good thing assuming you actually use the extra payload. if you don't you "should" still an improvement in efficiency. Normal frames get 1460 bytes of payload, jumbo frames get 8960, so when every frame has ~80 bytes of overhead you'd go from ~95% to ~99% effective use of each frame.

 

 

In saying this you would use this setting (MTU) to tune your network performance, for example, connections out to the internet, stick with the standard (or the one provided by your ISP), over an MPLS network you want to bump it up to 1600, on a storage/backup VLAN? bump it up as high as possible. Also Just because you enable jumbo frames, does not mean that you automatically use the extra payload, As it is bound to layer 2, you will find that it only handles node-to-node communications (so you need to go to every node/device in the end to end connection and enable jumbo frames to actually be able to use them). So configuring this on your NAS means when your NAS negotiates with the switch/router it is directly connected to both devices agree on frame size so if your switch/router only supports 1500 MTU, that will be the agreed frame size. Which bring me to another point, if the receiving device buffer fills, it sends a stop signal to the other device and will wait till the buffer is cleared before starting the transfer again, and jumbo (or super jumbo) frames will fill the buffer up a lot quicker.

 

I'm properly butchering the theory a little (or a lot), go grab http://www.amazon.com/CCNA-Routing-Switching-Study-Guide/dp/1118749618/ref=sr_1_3?s=books&ie=UTF8&qid=1458539609&sr=1-3 if you want to learn more. 

 

Also as to what you'd set the MTU to, it depends on the vendor, some want to ignore overhead, others not, others, just part of the overhead, but it can be anything over 1500.