Problem with Intel 82579 and jumbo frames with MOD54415

[jaypdx]

I've been working with a MOD54415 and the EFFS-HTTP demo project. I was having a problem where I could transfer small files from the Netburner to my laptop but anything over around 1000 bytes would fail. My development setup is a Thinkpad T530 (which has an 82579LM network adapter) plugged into a Dell gigabit switch along with the MOD54415. The symptom was when I tried to open a large file with a browser it would just say 'Waiting for 192.168.1.73...' and sit there forever. Wireshark was showing some strange errors ([TCP Previous segment not captured]). When I disabled the jumbo frame support on my adapter the problem disappeared. A quick web search turned up a variety of problem related to these chips and jumbo frames. I'm running driver version 11.15.16.0, which is pretty old... I'll try the latest version and see if it fixes it.

Hopefully this will save someone else some some time in the future.

[jaypdx]

Even with the latest Intel Drivers (12.10.29.0 - which, amazingly, installed without requiring a reboot), I see the same problem. Things still work fine with jumbo packets disabled.

[sblair]

In theory jumbo frames are great. In practice, they are a mess.

For jumbo frames to work it requires every piece of hardware in the chain to support them. So if your switch doesn't support jumbo frames, it will just drop them.

I normally only see Jumbo Frame support on GbE adapters. I would be surprised if the Netburner supports jumbo frames.

[dciliske]

We definitely don't, though in theory it's possible. Here's how it would be done:

1. Change ETHER_BUFFER_SIZE to something like 9K or 15K.
2. Watch in horror as you are completely out of memory.

-Dan