Jumbo frames questions

[MichaelD]

I searched and found a lot of posts containing the words "jumbo frames" but not much data to answer my questions. I'm lacking in understanding Jumbo Frames and how/when/if to use them and the benefits of doing so.

I have a SOHO switch at the house USR997716. and it supports Jumbo Frames (feature is off by default). The online specs don't show Jumbo frames but it's there in the menu and can be turned on/off.

The PCs in my sig both have Gigabit NICs as does my NAS. But I have two network printers plugged into the switch as well; one only connects at 10MB/s (no idea why). I also have a WAP plugged into the switch and it's link is only 100MB/s, not gigabit.

I don't want to break anything/kill network access.

Should I turn on Jumbo Frames? Do I need to set anything up on the PCs? Will the printers be OK?

Thanks for the help.

 

[VirtualLarry]

My understanding is that you can only enable jumbo frames if EVERYTHING on the network supports them. Which means you cannot enable them if you have a 10/100 router sharing internet access connected to your gigabit switch.

 

[MichaelD]

Thanks, VirtualLarry. What you've described is exactly how I have it setup. I have no idea if the onboard NiCs in my PCs or any of the printers would support jumbo frames.

 

[JackMDS]

It usually Not a big lose. On regular peer-to-peer with regular hardware the difference between with Jumbo frames and without is nothing to write home about.

On the other hand if you optimize the computers' TCP/IP stack according to your Internet connection and double the RCwin parameter you would get better Giga.

Originally posted by: MichaelD
I have no idea if the onboard NiCs in my PCs or any of the printers would support jumbo frames.

NICs Jumbo frames setting is done through adjusting the MTU value (the classical is MTU value of 9000). Look at the Drivers setting in the card's properties you might see there and entry that would tell you whether it can be adjust to Jumbo Frames.

 

[MichaelD]

Thanks very much, JackMDS. I will check my onboard NiC's settings.

For my printers, which have no way to adjust MTU values, would jumbo frames hurt anything? Data corruption, etc?

Well, what do you know! There's a Jumbo Frames setting...at least on this (my "gaming box") PC.

Which one of those "K" sizes would I choose, Jack?

 

[spidey07]

The biggest one supported by your switch. Jumbo frames won't harm TCP connections on your local LAN and it's not possible for data to be corrupt because of a frame checksum.

Just turn them on and make them the same size supported by the switch or smaller.

 

[MichaelD]

Thanks, Spidey07; it's good to know my data won't be corrupt b/c of the JF's. I'm not sure what size the switch supports...gotta break out the CD that came with it and look at the documentation. Is there a "common size" for Jumbo Frames?

 

[JackMDS]

Originally posted by: MichaelDIs there a "common size" for Jumbo Frames?

Many switches that support Jumbo frames usually go up to 9000 (9K).

If you switch support it use the 7K entry on your NIC.

 

[cmetz]

MichaelD et al, the de facto standard is 9000 bytes. (6 x 1500) Many other values are around, but 9000 is becoming the most common in my experience.

You need every station in a L2 domain to use the same MTU, or systems have problems talking. Ethernet has no L2 way to negotiate or adapt MTU between stations. In the long run, as speeds keep going up, we're just going to have to move to a higher MTU - the PPS rates caused by a MTU of 1500 are killing us at higher speeds. So I would strongly recommend that you buy new gear with jumbo frame support where possible, as it will help when you want to use jumbo frames in the future and need all your gear to support it.

In the short run, jumbo frames are useful in carefully controlled circumstances. It's hard to use them in most SOHO networks today because most SOHO networks are one L2 network and it only takes one device that doesn't support them to make them unusable.

 

[Stangs55]

Found this thread and wanted to add a question to it....

All of my computers, switches, and WHS support jumbo packets...but I also have a 360, PS3, and Slingbox HD that I stream data to from my PC. Will enabling jumbo packets on that PC corrupt streaming of data to these devices?

And will my Macbook Pro wirelessly connected to this network have trouble talking to the PC if jumbo packets are enabled?

Thanks.

 

[JackMDS]

I have a bright idea. :light: Why Not to try and check?

If it does not help, or make the system worse, it takes a few minutes to change the components back to their original state.

In general, when using peer-to-peer Network based on client OS', Jumbu Frames either do Nothing, or might add very little "Speed".

While every One understands that putting Racing Car tires on his Sedan/SUV would do nothing for the cars, they think that using configurations that are suitable for heavy traffic Business Networks (the kind that Spidey attends to) would do something for their home networks.

 

[Stangs55]

Originally posted by: JackMDS
I have a bright idea. :light: Why Not to try and check?

If it does not help, or make the system worse, it takes a few minutes to change the components back to their original state.

In general, when using peer-to-peer Network based on client OS', Jumbu Frames either do Nothing, or might add very little "Speed".

While every One understands that putting Racing Car tires on his Sedan/SUV would do nothing for the cars, they think that using configurations that are suitable for heavy traffic Business Networks (the kind that Spidey attends to) would do something for their home networks.

Cranky much?

My bright response is that I don't have the switches that support jumbo frames yet. They're ordered and should arrive today. I was just asking a question to help plan out the network...also a bright idea.

And I don't give 2 craps about jumbo packets except for the fact that I have a 4 TB WHS that I backup to frequently...I was hoping to get some modest speed improvements in the process since the switches I ordered support jumbo frames anyways...

 

[TheKub]

Originally posted by: Stangs55
Cranky much?

Um, Im pretty sure he is just telling you that most home users will not see much (if any) network performance improvement. Also, you have nothing to loose but a little time setting it up, trying it out, and maybe undoing it if it doesnt work for you.

Everyones network is completely different than everyone elses, and sometimes giving absolute advice is difficult (if not impossible). You have been given the info you need and the advice to "try it".

 

[Emulex]

keep jumbo frames on the vlan segment for storage (iscsi,nfs) gigabit-only.

you can run standard 10/100 non jumbo for other devices on primary vlan.

the storage server can just have two nic's one running 10/100 and one for jumbo frames.

you may carefully consider flow control but it can really bite you.

ideally you do not want to have a vlan segment with more than 1 speed. causes alot of pressure on the switch.

smb and windows delayed ack / nagle can do some wonky stuff with mixed speeds like a server at gig-e and a pc at 100. if you see a saw-like choppy output from the gig-e server to the slower pc you probably know what i'm talking about.