RE: [RPRWG] RE: [IPORPR] payload length and padding and stuff
Tony,
You
are right, and I obviously stand corrected. My question would be - is the
reference mac_service_data_unit supported by the LAN configurable per port? If
the answer is yes, the implication would be that standard 802.1D bridges can be
configured to support these MAC and PHY implementations that accommodate larger
frame sizes ('jumbo frames') that some vendors built as proprietary extensions
to the 802.3 MAC and PHYs.
Regards,
Dan
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