increasing the ethernet MTU greater than 1500 (1502)

[kamal kc]

--- Richard A Steenbergen <ras at e-gerbil.net> wrote:

> On Fri, Jan 06, 2006 at 10:02:07AM -0800, John-Mark
> Gurney wrote:
> > Nope, for pre-gige, only 1500 MTU is supported... 
> This was extended
> > slightly to support vlan tagging, but I believe
> many of the drivers to
> > If you have a good gige card, you can go to 9000
> MTU and beyond...
> Technically speaking, the problem was not fixed by
> GigE or even 10GigE. 
> The wonderful folks over at the IEEE feel there is
> no need to bring us out 
> of the ethernet networking dark ages by defining any
> kind of standards for 
> anything > 1500 bytes. We're left with a bunch of
> vendors who are each 
> trying to do the right thing by picking random sizes
> ranging from 1518 
> (stock + 4 bytes for a single .1q tag) to 16384, but
> there are no real 
> standards, no mechanisms for ensuring
> interoperability, no protocols for 
> negotiating MTUs between networks, etc.
 Lots of newer FastE cards
> support jumbos or some kind 
> of mini jumbo too. There are still plenty of NICs
> and switches out there 
> with no or very half-ass jumbo support though.

thanks for providing the insight. I would try 
with GigE next time.

since it seems a bad option to try MTU larger than
1500 in 10/100 Mbps ethernet i tried another option to

solve my problem.

Now i don't add additional header(2 bytes) to
distinguish 
the packets that were processed. I rather tried for 
protocol mapping.

This is what i did,

i mapped the protocol (in the protocol field of the ip
header)

          0..56 to 138..194 if compressed
          0..56 to 195..251 if uncompressed 

with this simple protocol mapping i could only
compress
57 protocol data.

I guess the protocols 138 to 251 will not be used for 
couple of years. 
OR Is there any slighest possibility ????


thanks, 

kamal

 
   














		
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