RE: [RPRWG] RE: [IPORPR] payload length and padding and stuff
Dan -
I think that you will find the 802.1D standard requires conformant
Bridges to discard frames that exceed the max frame size for the
destination LAN:
"7.7.1 Enforcing topology
restriction
Each Port is selected as a
potential transmission Port if, and only if
a) The Port on which the frame was received was in a forwarding state
(8.4), and
b) The Port considered for transmission is in a forwarding state,
and
c) The Port considered for transmission is not the same as the Port on
which the frame was received,
and
d) The size of the mac_service_data_unit conveyed by the frame does not
exceed the maximum size of
mac_service_data_unit supported by the LAN to which the Port considered
for transmission is
attached.
For each Port not selected as a potential transmission Port, the frame
shall be discarded."
Regards,
Tony
At 18:25 04/12/2002 +0200, Romascanu, Dan (Dan) wrote:
Nader,
There are actually two different layers here.
802.3 MACs and PHYs MUST support a max frame length of 1522. You may find
implementations that are both standard compliant and support jumbo sizes
as proprietary extensions.
I think that 802.1 bridges do not have such a limitation within the
standard. As you mention, they can be configured to support larger frame
sizes. Actually some of the non-Ethernet 802 technologies already support
larger frame sizes.
Dan
> -----Original Message-----
> From: Nader Vijeh
[mailto:nader@xxxxxxxxxxxxxx]
> Sent: Wednesday, December 04, 2002 6:10 PM
> To: Romascanu, Dan (Dan)
> Cc: iporpr@xxxxxxxx; stds-802-17@xxxxxxxx
> Subject: RE: [RPRWG] RE: [IPORPR] payload length and padding and
stuff
>
>
> Dan,
>
> Thank you for the correction. Jumbo frames are not supported
> by the 802.3
> standard.
> There are Ethernet switches on the market that support jumbo
> frames in a
> proprietary manner. Of course these will not interoperate
> with standard
> compliant 802.1 bridges. As I pointed out in the rest of the
> message, even
> if jumbo frames are supported, max frame size "needs to be
> configurable to
> be lower, in order to comply with transparent bridging
requirements".
>
> Nader
>
> -----Original Message-----
> From: Romascanu, Dan (Dan)
[mailto:dromasca@xxxxxxxxx]
> Sent: Wednesday, December 04, 2002 12:45 AM
> To: Nader Vijeh; Necdet Uzun; Anoop Ghanwani
> Cc: Frank Kastenholz; iporpr@xxxxxxxx; stds-802-17@xxxxxxxx
> Subject: RE: [RPRWG] RE: [IPORPR] payload length and padding and
stuff
>
>
> >
> > The max frame size may be extended beyond 802.3 1522 bytes
> > limit as there is
> > precedence in 802.3 community.
>
> Nader,
>
> I am not sure what you exactly mean. If you refer to what is
> popularly known
> as 'Jumbo frames', they are not supported by the IEEE 802.3
> standards.
>
> Dan
>
Regards,
Tony