Using Jumbo packets in gigabit ethernet

Archived from groups: comp.dcom.lans.ethernet (More info?)

I have MV64360 Marvell board and I try to send Jumbo frames.
I configured the Port Serial Control Register to support Jumbo frames.
When I send block in length up to 1500 bytes it works, more then 1500
it does not work and I don't receive any error from the SW. Why?

Archived from groups: comp.dcom.lans.ethernet (More info?)

phn@icke-reklam.ipsec.nu wrote:

> Hany <hanymil@rafael.co.il> wrote:

>>I have MV64360 Marvell board and I try to send Jumbo frames.
>>I configured the Port Serial Control Register to support Jumbo frames.
>>When I send block in length up to 1500 bytes it works, more then 1500
>>it does not work and I don't receive any error from the SW. Why?

> The rest of your networking gear must also support and be configured for
> jumbo frames. If not they simply throw your frames away as "errors"

It is at least known that most network equipment will support
slightly over 1500, as it is needed to support vlan tagged frames.

If things really stop exactly at 1500, it is not likely in layer 2
equipment.

Try a cable directly between two such devices configured for
jumbo frames and see if it works that way.

-- glen

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <S--dnbI2rcWN_RPcRVn-jw@rogers.com>,
James Knott <james.knott@rogers.com> wrote:
:glen herrmannsfeldt wrote:

:> It is at least known that most network equipment will support
:> slightly over 1500, as it is needed to support vlan tagged frames.

:> If things really stop exactly at 1500, it is not likely in layer 2
:> equipment.


:According to what I've read in O'Reilly's Ethernet book, the maximum value
:is 1535 bytes, so any equipment complying with the 802.3 spec, should be
:able to handle that.

When '1500' is being used, the figure does not usually include
the preamble or CRC, and certainly not the intra-frame gap (IFG).
'1500' also may not include the source and destination MAC addresses.

'1535', though, includes everything except perhaps the IFG, and
might include VLAN tags: without the tags, the total length including
preamble, CRC, and IFG is 1540 octet-times if I recall properly.

--
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Tenser, said the Tensor.
Tension, apprehension,
And dissension have begun. -- Alfred Bester (tDM)