[c-nsp] difference between OutDiscards and Overruns

[Martin T]

Peter,
ok, thanks! I see this on Gi port of
WS-C3750G-24TS-S1U(c3750-ipbasek9-mz.122-44.SE1.bin). Regarding this
QoS comment- you mean if one experiences this OutDiscards issue on a
router port, where QoS is applied, then packets with high QoS priority
will not be dropped as they have higher priority in outbound buffer?


regards,
martin

2011/7/20 Peter Rathlev <peter at rathlev.dk>:
> On Wed, 2011-07-20 at 18:33 +0300, Martin T wrote:
>> I see. So most likely Outdiscards happen in case of backplane puts
>> frames to bus, but interface outbound buffers are not able to accept
>> new frames because they are full?
>
> Yes. Exactly where the drop occurs depends very much on the specific
> hardware platform. On what device (and software) are you seeing this?
>
> Outdiscards, often called "buffer drops", are simply a result of the
> device trying to send more traffic out an interface than it can handle.
> For example trying to send 120 Mbps out a 100 Mbps interface. The
> interface buffers can store the excess traffic for some time, but when
> they run out the interface starts to drop.
>
> Keep in mind that these buffer drops are exactly what QoS is about:
> dropping certain packets so there's room for others. (Simplified
> version, since LLQ and EF is also about rearranging packets.)
>
> --
> Peter
>
>
>