Jumbo frames trash NIC

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ziddey

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I'm trying to setup simple jumbo frames on my home network. There will be one printer that is 100mbps, and a few wireless clients. Otherwise, all desktops support jumbo frames, and it is working well between two Realtek adapters.

The problem is with an Intel Pro/1000 MT adapter. I set it to 9014bytes (Alteon). Frames up to somewhere around 8000bytes work just fine. But if I try 9000 bytes, it knocks the NIC offline. It comes back on its own after a few minutes, and works fine as long as no 8000+ byte packets occur again.

With all adapters, if I exceed the mtu and specify -f, it shows that packet needs to be fragmented as it should. The Intel does not go down. This is good and normal.

If I don't specify -f, the Realteks will still respond to ICMP properly, obviously fragmenting automatically as it should. But it takes the Intel one offline for a few minutes.

What is happening?!
 
I know this is trivial, but have you made sure you're running the latest NIC drivers on both NICs? This sounds very much like a bug in something.
 
What switch do you have? Are you also using VLANS, QOS, etc. Try playing with them on the card, it might be a point that the MTU size isn't including these factors and therefore conflicts with the Realteks.

Just a thought and I might be completely wrong.
 
First, this isn't worth hassling with. Second, set MTU to 9000 and try again.
 
You won't see that big of a difference at all with jumbo frames. If anything, it may hinder performance.
 
Every time I've tried playing with Jumbo frames with all my equipment that officially support them, I've never seen a speed increase no matter the data I use to test with. I'm not sure of the point.
 
I'm sure your aware of this, but in theory increasing the MTU size increases the amount of data that is sent in a single packet, therefore reducing the amount of single packets, cpu usage and increasing throughput.

The problems come from how the data is handled. For example if an error is withing a packet, it is usually re-sent and reduces performance, which is a reason for only using Jumbo Frames if your network is rock solid.

Because Jumbo Frames are customizable it's easy to get wrong and miss configuration will see frame errors. It might not be apparent but there happening. And the reason its easy to get wrong, is because devices differ in how they calculate the packet size. Some will include the header within the size and others don't, so depending what you have in the header (QoS, VLANS, etc.) you'll be increasing the MTU by 4 bytes or even 22 bytes. Not to mention that some devices only support 4k, so all this can muddy the water.

The kicker in all this, its massively dependent on your NIC's, switches and other hardware that can course bottlenecks. So depending on your cards you might see no difference, poor performance or an increase in throughput (not speed of a packet). Not to mention the application and sizes of the data being sent. So its good to say, use it for special purposes, such as SAN's.

Personally I don't have a problem with someone playing with it at home or on a home network. Its all about learning, weather it gives an improvement or not. Just learn how to test it properly and capture traffic to see whats happening. It will also give you an insight into whats happening at this level and why some hardware is $1000 rather than 50 quid.

This might help, http://www.bitplumber.net/2009/03/how-to-configure-jumbo-frames/
 
Look jumbo frames sound cool at all from a geek perspective, but you have to know when it's really needed. Most common home networks? Forget it, there's no need. Jumbo frames only begin to show some performance increase when all network traffic is at 1Gbps and even then you would only notice it if you were doing massive data transfers on a continuous basis.

Streaming video on your home media server? No.
LAN party playing BF3 or whatever else you can think of? No.
A company backing up their data every night? Yes.
Hosting massive databases that have thousands of transactions written every few seconds? Yes.

We just began to enable jumbo frames at my place and that was after we installed some of our first 10 gig blades on our core switches. We still haven't really put them to the test though and I don't think it will happen for another year or so because our production databases are huge and we can't afford to be screwing around with them unless we're absolutely certain we can realize some increase in performance.
 
Hi,

You might want to look here:

Network receive problems with Jumbo Frames at 9014 on Intel PRO/1000 MT Dual Port Server Adapter.
http://social.technet.microsoft.com...N/thread/d6c23f54-d8f1-4ee2-8492-3aa4d5077c2c

I ran into the same problem again today, and found that with the load I was using, the work-around of maxing out the TX & RX buffers did not help, nor did using a lesser Jumbo Frame size of 4088.

You just cannot use these PCI card with Jumbo Frames on Windows 2008 I guess.

~ Jeff Byers ~
 
Unless all the MTU sizes are set exactly the same on all the cards and the switch, you're wasting your time. Even if they are, you're wasting your time.
 
criccio said:
Every time I've tried playing with Jumbo frames with all my equipment that officially support them, I've never seen a speed increase no matter the data I use to test with. I'm not sure of the point.
Click to expand...

Ditto. I'll try a transfer with 1500 and get say 35MBps. Then try 9000 and get 38MBps. Then try 9000 again and get 35MBps.....:mad:
 
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