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RE: RUNT Packets


We are writing a standard and need to keep focused on what is in scope for
the standard to define.

The MAC defined in 802.3 doesn't forward a packet to the host until it has
checked. Of course, some implementations may start forwarding the packet
earlier, but providing some mechanism to cause discard of an errored frame
that the MAC has started to forward is an implementation issue for those
MACs and not an 802.3 issue.  

The MAC defined in 802.3 also does not take any action with an undersized
frame other than discard it. It does not do any counter update for an
undersized frame. We haven't changed this aspect of the MAC definition. It
has been this way always. Of course, an implementation or an IETF management
standard such as RMON is always free to add additional managed objects that
cover items we did not put in the 802.3 MAC decision. In that case, it is up
to the implementor or the IETF folks to define the way that object works.
The alternative is for someone to propose adding the object to 802.3

I do not see why we are continuing to discuss this subject. Are you
proposing some action for 802.3ae?


-----Original Message-----
From: Louis Lin [mailto:louislin@xxxxxxxx]
Sent: Thursday, November 16, 2000 2:20 PM
Cc: stds-802-3-hssg@xxxxxxxx
Subject: Re: RUNT Packets


I have to disagree with your statement of "The MAC silently discards packets
that are shorter than the minimum". When MAC is receiving a packet and
forwarding the packet data to the host. If the the EOP comes before 64th
MAC needs to inform host to discard the packet and that packet needed to be
counted in RMON. Otherwise we will see packets disappear(packet counts
mis-match) if they are shortened by what ever reasons.

Standard doesn't need to say anything about it, but saying "The MAC silently
discards packets that are shorter than the minimum"  is not good. And I
believe most MACs in the market count undersized packets.

Of course, most undersized packets don't come with good CRC. But we can't
make this kind of assumption.



Shimon Muller wrote:

> > The important point is that runts are not counted by MACs.
> > The MAC silently discards packets that are shorter than the minimum.
> > It has no counter for them.
> Pat is absolutely correct.
> > Unless someone is proposing creating a new runt MIB object, runts do not
> > apply to 10 Gig Ethernet because we do not have repeaters.
> I do not believe we should create such an object.
> Just ignore the "shortened" frame. This is not something that is expected
> to happen very often. And if it does, there are going to be other errors
> that will give you plenty of indication that something is broken.
>                                                 Shimon.