[c-nsp] DTS traffic shaping & voice queuing

[Clinton Work]

I have found clocking down a circuit provides much better shaping than
using a MQC traffic shaper. The problem with the software based shaper 
is that it doesn't smooth out bursts. Tokens (bytes) are put into
the bucket at 10ms intervals, but the entire bucket can be used up in 
the first 1ms  by a large burst. IP packets after the token is exhausted 
will be queued until token bucket is refreshed (in 9ms). If a downstream
device is policing traffic to the shaped rate with a small burst size
then the bursts will be dropped.

The software driver for a interface will smooth out bursts as packets 
are taken out of the queue and transmitted at a regular interval.

Token refresh rate (10 - 125ms).
http://www.cisco.com/en/US/tech/tk543/tk545/technologies_tech_note09186a00800a3a25.shtml#tokenrefreshrate

Rodney Dunn wrote:
> That's not really true.  I think of it this way.  If you have a T1
> you can only clock bits out on the wire at a T1 rate.  So the shaping
> is /*if you will*/ built in to the circuit.  Therefore to do QOS you
> just apply the queueing policy on the interface.