Ethernet Jumbo Frames

Has anyone on this list ever been given a requirement to implement
support for ethernet frames larger than the standard MTU of 1500?  ...

... for normal 10/100 Ethernet?   ... not gigabit.

The application is to support certain encapsulation protocols without
imposing smaller than 1500 byte MTU restrictions on the innermost
protocol.

I have been tasked to investigate this for a system based on PPC405EP.
Can it be done using the IBM EMAC, Linux drivers, etc?

Regards,

Darcy

We've done it for our 2.4 based kernel that runs on a Freescale MPC8270.
10/100/1000 doesn't really make any difference. For us the trick was to
support receving jumbo frames in multiple RX BufDescriptors (because our
MPC8270 FCC eth driver pre-allocates 2k buffers per RX BD).
For transmitting hardly any changes were necessary.

From linux (driver) standpoint there should be no problems,
the question is whether your ethernet MAC (IBM EMAC) properly supports it.

hth,
N. van Bolhuis.



Darcy Watkins wrote:

Has anyone on this list ever been given a requirement to implement
support for ethernet frames larger than the standard MTU of 1500?  ...

... for normal 10/100 Ethernet?   ... not gigabit.

The application is to support certain encapsulation protocols without
imposing smaller than 1500 byte MTU restrictions on the innermost
protocol.

I have been tasked to investigate this for a system based on PPC405EP.
Can it be done using the IBM EMAC, Linux drivers, etc?

Regards,

Darcy

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Sure, it can be done.  The Xilinx 10/100 Ethernet drivers have jumbo
frame support in MontaVista/WindRiver Linux.  As long as both ends are
talking jumbo frames, works just fine.

-Rick

-----Original Message-----
From: <redacted>
[mailto:linuxppc-embedded-bounces+moleres=3Dxilinx.com@ozlabs.org] On
Behalf Of Darcy Watkins
Sent: Monday, March 31, 2008 2:48 PM
To: LinuxPPC-Embedded
Subject: Ethernet Jumbo Frames

Has anyone on this list ever been given a requirement to implement
support for ethernet frames larger than the standard MTU of 1500?  ...

... for normal 10/100 Ethernet?   ... not gigabit.

The application is to support certain encapsulation protocols without
imposing smaller than 1500 byte MTU restrictions on the innermost
protocol.

I have been tasked to investigate this for a system based on PPC405EP.
Can it be done using the IBM EMAC, Linux drivers, etc?

Regards,

Darcy

_______________________________________________
Linuxppc-embedded mailing list
Linuxppc-embedded@ozlabs.org
https://ozlabs.org/mailman/listinfo/linuxppc-embedded

Thanks for the comments...

I have hacked the IBM EMAC driver (Xenomai-2.3.0 Real Time Linux
2.6.19.2) and got jumbo frames to pass back and forth between two such
embedded boards.  Checked it using ping, iperf and httpd / wget file
transfer with md5sum check.

Still have to clean things up a bit and do some more tests before I can
share it as a patch.

Regards,

Darcy



-----Original Message-----
Sure, it can be done.  The Xilinx 10/100 Ethernet drivers have jumbo
frame support in MontaVista/WindRiver Linux.  As long as both ends are
talking jumbo frames, works just fine.

-Rick

-----Original Message-----
We've done it for our 2.4 based kernel that runs on a Freescale MPC8270.
10/100/1000 doesn't really make any difference. For us the trick was to
support receving jumbo frames in multiple RX BufDescriptors (because our
MPC8270 FCC eth driver pre-allocates 2k buffers per RX BD).
For transmitting hardly any changes were necessary.

 From linux (driver) standpoint there should be no problems,
the question is whether your ethernet MAC (IBM EMAC) properly supports
it.

hth,
N. van Bolhuis.