Jumbo Frame - how do I implement it?

wasc · 14 Dec 2007 at 16:33

Hi all,

Some questions about JumboFrame.

1) I know I set the jumbo frame size in the properties for my NIC, but is that all I need to change, or do I also need to change the MTU in my windows registry???

2) If a device on my network doesn't support jumbo frames, will I lose connectivity to that device?

ANDARIAL · 15 Dec 2007 at 14:53

have a free bump.

I am interested to hear an answer too

wasc · 16 Dec 2007 at 14:56

ANDARIAL said:
have a free bump.
I am interested to hear an answer too

Thanks

Well, I did a lot of reading and in the end decided to just give it a go

I have 3 machines (all of which support jumbo frames) so I enabled jumbo frames on the nic's of all 3 machines and then ran a network speed test - was no different. In addition, I tried to connect to another machine which didn't have jumbo frames on and that still worked as well, so basically enabling it did nothing.

Therefore I used a program called "Dr TCP" to change the MTU size in windows (on all 3 machines) to 4088 as this is supposed to be a good value according to a number of websites. I also enabled the MTU size discovery option in DR TCP and tested again. This time transfering files between the machines was quicker, so performance is now up. Also connecting to machines without Jumbo frame support still worked

**BUT** I lost connectivity to the computer in my DMZ. Therefore I put a rule on my firewall which was "Allow ICMP Code 3 Type 4 from ANY to ANY"

This restored my connectivity to my machine in my DMZ so obviously firewall was blocking this data. So far no other side effects but will update if I find one. Still in the early days of testing so far. Oh, very important - your switch MUST support jumbo frames (my netgear switch did).

ANDARIAL · 16 Dec 2007 at 16:49

just read your post and had a `play` too

got a netgear switch that supports jumbo frames
main pc onboard enabled,dl pc enabled,server pc enabled
trouble with server pc although the card settings say jumbo enabled i cant connect to the net when enabled

gotta disable jumbo on that pc.all others `appear`to be a little bit faster(showing up to 50%) transfer rates where before it was only upto 30% ish

mandelbug · 17 Dec 2007 at 06:24

I have jumbo frames enabled on my Cisco network at work and the on-board Intel Ethernet controller on the BAD-AXE2 mobo doesnt run stable with it and keeps dropping the speed back down to 100Mbps. Certainly from Cisco side of things with regards to connecting to lower speed devices, PMTU discovery should do the job in that part of the intial connection requests max MTU size and both devices run at the lowest value. Max MTU size for jumbo frames is 9016 bytes. Unless you do a lot of big file transfers on a full Gigabit LAN you would not notice any difference in performance and if you only run a 100Mbps network you shouldnt be able to set it

ANDARIAL · 17 Dec 2007 at 20:14

update to my previous post after playing around and getting faster speeds for a few test folder transfers,it stopped playing ball.

now back to no jumbo frames and while slower it it stable and all m/c can access the net

cavemanoc · 4 Jul 2008 at 10:32

I'm playing around with this as I'm busy transferring a lot of stuff onto my new WHS box from my home machines and would like to speed up the connection. I have set up Jumbo Frames both cards (9016 ATM, might try the 4000 one as it seems to be more popular.) Made no difference - I'll try the Dr TCP suggested above and see if it helps - but I can't work out if my router supports it - it's a Belkin Gigabit Wireless cable router (the UK one) - where would I find the options for it in the router settings? Can't find any reference to it in the setup page (assumed it would be under LAN settings, but there's nothing of interest there?

Network is runing at about 22% - which I guess is about 22MB/s, I know the HDDs are limiting, but given that they're fairly new - should be capable of at least 40ish?

rick827 · 4 Jul 2008 at 10:46

when trying to optimise your throughput iperf and wireshark are your friends. As already noted, you need a switch which supports jumbo frames. If you're on windows try "ping -l 4000 -f" between your machines to see if a 4k packet is allowed

cavemanoc · 4 Jul 2008 at 15:18

Thanks for that - tried it and I get a request timeout for anything over the standard packet size

- Could it be that it's an option in the router settings somewhere that I haven't found or does it look like the router simply can't do it - seems strange given that it is a gigabit lan?

rick827 · 4 Jul 2008 at 15:30

cavemanoc said:
Thanks for that - tried it and I get a request timeout for anything over the standard packet size - Could it be that it's an option in the router settings somewhere that I haven't found or does it look like the router simply can't do it - seems strange given that it is a gigabit lan?

Depends on your network setup, but if they both plug into the same switch your router wont effect it - just the switch. To be sure you could try a cross over cable between the 2 PCs. Do they both definately report the correct MTU?