RE: RUNT Packets
Bob,
The important point is that runts are not counted by MACs. The MIB
definition that Geoff provided is for aRunts which is a _repeater_ MIB
object. The MAC silently discards packets that are shorter than the minimum.
It has no counter for them. The counter update process,
LayerMgmtReceiveCounters, only runs when a packet that meets minimum packet
size is received. (See 4.2.9 for the MAC receiver and Table 30-1 for a
listing of MIB objects.)
Unless someone is proposing creating a new runt MIB object, runts do not
apply to 10 Gig Ethernet because we do not have repeaters.
Regards,
Pat
-----Original Message-----
From: Grow, Bob [mailto:bob.grow@xxxxxxxxx]
Sent: Wednesday, November 15, 2000 3:22 PM
To: stds-802-3-hssg@xxxxxxxx
Subject: RE: RUNT Packets
Pat:
I probably over simplified the 10 Gb/s explanation of runts, my appologies
to those confused by it. Those that want the precise answer can read the
MIB definition that Geoff Thompson posted from the standard.
I was only addressing the noise hit causing detection of an end delimiter,
and transmitting a smaller than minimum frame (a protocol error). Many see
a high runt count as reason to suspect a device is transgressing protocol by
transmitting the runts.
In my haste to get the first draft of clause 46 out, any noise hit yielding
one (or more) control characters at the RS would terminate the frame,
including those noise hits converted to Error by the PCS. The change agreed
to in Tampa was to exclude Error control characters from terminating the
frame, thus significantly reducing the number of noise hits that will result
in counting a runt packet. This basically places the burden of deliminating
the frame on the PCS without the RS changing that determination.
--Bob Grow
-----Original Message-----
From: THALER,PAT (A-Roseville,ex1) [mailto:pat_thaler@xxxxxxxxxxx]
Sent: Wednesday, November 15, 2000 1:52 PM
To: Grow, Bob; 'James Colin'; stds-802-3-hssg@xxxxxxxx
Subject: RE: RUNT Packets
Bob,
I do not understand your point. At lower speeds, there are four possible
causes of a runt -
A noise hit causes a short event on a segment which arrives at a repeater,
since ther repeater never transmits less than a minimum size fragment it
sends a runt.
A collision fragment
A noise hit that causes an end delimiter to be detected in error.
Someone transmitted a frame smaller than the minimum frame size. (Is this
the protocol error you referred to?)
Therefore, at the lower speeds, runts can be caused by noise, the normal
operation of CSMA/CD or transmission shorter than the minimum. For full
duplex they are only caused by noise or transmission shorter than minimum.
Pat
-----Original Message-----
From: Grow, Bob [mailto:bob.grow@xxxxxxxxx]
Sent: Tuesday, November 14, 2000 10:52 AM
To: 'James Colin'; stds-802-3-hssg@xxxxxxxx
Subject: RE: RUNT Packets
A minimum frame size was established at 10 Mb/s to assure that collisions
were detected. Shorter "runt" frames are an error and are commonly counted
and monitored in management databases. In the desire to maintain
consistency over all speeds of ethernet, we should attempt to preserve
similar error properties. If the RS turns an error created by transmission
noise into a protocol error (e.g., runt frame) we are violating the
objective to make things look the same.
--Bob Grow
-----Original Message-----
From: James Colin [mailto:james_colin_j@xxxxxxxxx]
Sent: Tuesday, November 14, 2000 2:50 AM
To: stds-802-3-hssg@xxxxxxxx
Subject: RUNT Packets
Louis, Bob
Can you explain the term "runt packets"?
Thank you,
James
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