[PATCH][EMAC] allow rx of the maximum sized VLAN tagged packets

Eugene Surovegin ebs at ebshome.net
Tue Dec 14 05:02:33 EST 2004

On Mon, Dec 13, 2004 at 02:08:22PM +0100, Andriy Korud wrote:
> as I know from documentation and IBM's support when you program VTPID
> register, EMAC will receive only frames with programmed ID. Other frames
> will be received only if they do not exceed 1518 bytes.
> Can anybody please comment this?

I'm not sure I understand your question.

EMAC can process 1518-sized packets without any problems (1500 + 12 + 
2 + 4) even without this patch. These are normal (non-VLAN tagged 

With my patch EMAC will be able to receive 1522 sized frames which 
are VLAN-tagged with _any_ VLAN tag. Note VTPID contains L2 protocol 
id, _not_ VLAN/priority field itself. If frame is bigger than 1518 
but doesn't have 0x8100 right after the source MAC address, "Packet 
Too Long" error will be generated. 

Also, 440GX has an option to process jumbo frames, but this is 
completely different story.


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