[c-nsp] Cat 6500 and QoS for lower bandwidth

[Grischa Stegemann]

Dear all

During the last weeks I have learned quite a lot about the QoS
mechanisms available on the Cat6500 platform.

Now I would like to confirm somehow whether I understand one thing
correctly:

As soon as I have a connection with less bandwidth than the interface
line rate connected to the Catalyst there is no way to achieve decent
QoS functionality involving class based and/or priority queueing
according to the low bandwidth available behind a
(Fast)Ethernet-interface, right?

One can use the PFC to globally police the output rate of the port. But
although it is possible to use different classes with different policies
here, one cannot do any flexible shaping/priority- or bandwidth-queueing
at this level.
The actual cos-based queueing will be done on port level and its
mechanism always works in relation to the actual port line rate (using
wrr bandwidth RATIOS).

Thus there is no way to achieve something like a shaping down to 5MBit/s
AND considering the dscp/cos-classes at the same time.

And it does not matter which queueing capabilities the linecard actually
provides. I tried this with 6348, 6548 and 6748 together with Sup720-3BXL.

Did I get this right or have I overlooked some (more or less obvious)
solution?

Regards,
Grischa